Molecules

Editorial

Jump to: Research, Review

3 pages, 881 KiB

Open AccessEditorial

Wastewater Treatment: Functional Materials and Advanced Technology

by Jingtao Bi and Guohui Dong

Molecules 2024, 29(9), 2150; https://doi.org/10.3390/molecules29092150 - 6 May 2024

Viewed by 1340

Abstract

With accelerated advancements in various industries, water pollution has emerged as a significant issue characterized by two features: (1) the rapid increase in population and corresponding demands, leading to a sharp rise in wastewater discharge, and (2) the development of new technologies, contributing [...] Read more.

With accelerated advancements in various industries, water pollution has emerged as a significant issue characterized by two features: (1) the rapid increase in population and corresponding demands, leading to a sharp rise in wastewater discharge, and (2) the development of new technologies, contributing to a significant increase in the variety of emerging contaminants, resulting in a more complex wastewater composition [...] Full article

(This article belongs to the Special Issue Wastewater Treatment: Functional Materials and Advanced Technology)

► Show Figures

Figure 1

Research

Jump to: Editorial, Review

16 pages, 3583 KiB

Open AccessArticle

Activation of Peracetic Acid by CoFe₂O₄ for Efficient Degradation of Ofloxacin: Reactive Species and Mechanism

by Rong Li, Xing Lu, Jinxiang Gao, Yifan Chen and Shunlong Pan

Molecules 2023, 28(23), 7906; https://doi.org/10.3390/molecules28237906 - 2 Dec 2023

Cited by 4 | Viewed by 1521

Abstract

Peroxyacetic acid (PAA)-based advanced oxidation processes (AOPs) have attracted much attention in wastewater treatment by reason of high selectivity, long half-life reactive oxygen species (ROS), and wider applicability. In this study, cobalt ferrite (CoFe₂O₄) was applied to activate PAA [...] Read more.

Peroxyacetic acid (PAA)-based advanced oxidation processes (AOPs) have attracted much attention in wastewater treatment by reason of high selectivity, long half-life reactive oxygen species (ROS), and wider applicability. In this study, cobalt ferrite (CoFe₂O₄) was applied to activate PAA for the removal of ofloxacin (OFX). The degradation of OFX could reach 83.0% via the CoFe₂O₄/PAA system under neutral conditions. The low concentration of co-existing anions and organic matter displayed negligible influence on OFX removal. The contributions of hydroxyl radicals (·OH), organic radicals (R-O·), and other reactive species to OFX degradation in CoFe₂O₄/PAA were systematically evaluated. Organic radicals (especially CH₃C(O)OO·) and singlet oxygen (¹O₂) were verified to be the main reactive species leading to OFX destruction. The Co(II)/Co(III) redox cycle occurring on the surface of CoFe₂O₄ played a significant role in PAA activation. The catalytic performance of CoFe₂O₄ remained above 80% after five cycles. Furthermore, the ecotoxicity of OFX was reduced after treatment with the CoFe₂O₄/PAA system. This study will facilitate further research and development of the CoFe₂O₄/PAA system as a new strategy for wastewater treatment. Full article

(This article belongs to the Special Issue Wastewater Treatment: Functional Materials and Advanced Technology)

► Show Figures

Figure 1

24 pages, 3636 KiB

Open AccessArticle

Adsorption of Chromium and Nickel Ions on Commercial Activated Carbon—An Analysis of Adsorption Kinetics and Statics

by Joanna Lach and Ewa Okoniewska

Molecules 2023, 28(21), 7413; https://doi.org/10.3390/molecules28217413 - 3 Nov 2023

Cited by 3 | Viewed by 1437

Abstract

The adsorption of nickel Ni(II) and chromium Cr(III) ions on the commercial activated carbons WG-12, F-300 and ROW 08, which differ in their pore structure and the chemical nature of their surfaces, were analyzed. The nickel ions Ni²⁺ were best adsorbed on [...] Read more.

The adsorption of nickel Ni(II) and chromium Cr(III) ions on the commercial activated carbons WG-12, F-300 and ROW 08, which differ in their pore structure and the chemical nature of their surfaces, were analyzed. The nickel ions Ni²⁺ were best adsorbed on the WG-12 activated carbon, which had the largest number of carboxyl and lactone groups on the surface of the activated carbons, and the largest specific surface area. Chromium, occurring in solutions with pH = 6 in the form of Cr(OH)²⁺ and Cr(OH)₂⁺ cations, was best adsorbed on the ROW 08 Supra activated carbon, which is characterized by the highest values of water extract. The precipitation of chromium hydroxide in the pores of the activated carbon was the mechanism responsible for the high adsorption of Cr(III) on this carbon. For the other sorbents, the amount of carboxyl and lactone groups determined the amount of Cr(III) and Ni(II) adsorption. The adsorption kinetics results were described with PFO, PSO, Elovich and intraparticle diffusion models. The highest correlation coefficients for both the Cr(III) and Ni(II) ions were obtained using the PSO model. Among the seven adsorption isotherm models, very high R² values were obtained for the Toth, Temkin, Langmuir and Jovanovic models. The Cr(III) ions were removed in slightly larger quantities than the Ni(II) ions. The capacities of the monolayer q_m (calculated from the Langmuir isotherm) ranged from 55.85 to 63.48 mg/g for the Cr(III), and from 40.29 to 51.70 mg/g for the Ni(II) ions (pH = 6). The adsorption efficiency of Cr(III) and Ni(II) cations from natural waters with different degrees of mineralization (spring, weakly and moderately mineralized) was only a few percent lower than that from deionized water. Full article

(This article belongs to the Special Issue Wastewater Treatment: Functional Materials and Advanced Technology)

► Show Figures

Graphical abstract

17 pages, 3380 KiB

Open AccessArticle

Design of a Novel Sericite–Phosphoric Acid Framework for Enhancement of Pb(II) Adsorption

by Han-Soo Kim and Hee-Jeong Choi

Molecules 2023, 28(21), 7395; https://doi.org/10.3390/molecules28217395 - 2 Nov 2023

Cited by 1 | Viewed by 1000

Abstract

In this study, phosphoric acid was used to attach anions to the weak interlayer structure of sericite, one of the clay minerals composed of a tetrahedral structure of silicate, to increase the adsorption capacity of cations. Natural sericite beads (NSB) and activated sericite [...] Read more.

In this study, phosphoric acid was used to attach anions to the weak interlayer structure of sericite, one of the clay minerals composed of a tetrahedral structure of silicate, to increase the adsorption capacity of cations. Natural sericite beads (NSB) and activated sericite beads with phosphoric acid (PSB) were prepared as beads in order to increase reusability and facilitate the separation of adsorbates and adsorbents. Using this, lead (Pb(II)) removal efficiency from an aqueous solution was comparatively analyzed. The pHpzc was 6.43 in NSB but lowered to 3.96 in PSB, confirming that more acidic functional groups were attached to the PSB surface. According to FT-IR analysis, P=O, P-O-C, P=OOH and P-O-P bonds appeared on the surface of the PSB adsorbent, and the peaks of carboxyl groups and OH-groups were large and broad. The maximum adsorption capacity of Langmuir was 52.08 mg/g for NSB and 163.93 mg/g for PSB. The adsorption process was close to physical adsorption for NSB and chemical adsorption for PSB, and both adsorbents were endothermic reactions in nature in that the higher the temperature, the higher the adsorption efficiency. The adsorption mechanism of Pb(II) to PSB was achieved by ion exchange, electrostatic interaction, hydrogen bonding, and complexation. The adsorption of Pb(II) using PSB was not significantly affected by the adsorption of competing ions and showed a high adsorption efficiency of 94% in reuse up to 6 times. This confirms the favorable feasibility of removing Pb(II) from industrial wastewater using PSB. Full article

(This article belongs to the Special Issue Wastewater Treatment: Functional Materials and Advanced Technology)

► Show Figures

Figure 1

16 pages, 3331 KiB

Open AccessArticle

Synthesis, Characterization, and Biosorption of Cu²⁺ and Pb²⁺ Ions from an Aqueous Solution Using Biochar Derived from Orange Peels

by Felicia Omolara Afolabi and Paul Musonge

Molecules 2023, 28(20), 7050; https://doi.org/10.3390/molecules28207050 - 12 Oct 2023

Cited by 5 | Viewed by 1512

Abstract

In this study, orange peel (OP) biochar was used as a bio-sorbent for the removal of copper and lead from wastewater in single and binary systems. The equilibrium and kinetic studies were conducted at a pH value of 5, which was the maximum [...] Read more.

In this study, orange peel (OP) biochar was used as a bio-sorbent for the removal of copper and lead from wastewater in single and binary systems. The equilibrium and kinetic studies were conducted at a pH value of 5, which was the maximum adsorption pH value for both metal ions. The equilibrium studies were investigated at a varying initial concentration (10–200 mg/L) with a constant dosage of 0.1 g, while the kinetic studies were conducted at a fixed initial concentration of 200 mg/L with a constant dosage of 1 g/L for both single and binary systems. The maximum adsorption capacity of the orange peel biochar was 28.06 mg/g, 26.83 mg/g, 30.12 mg/g and 27.71 mg/g for single Cu²⁺, binary Cu²⁺, single Pb²⁺ and binary Pb²⁺ systems, respectively. The Langmuir isotherm model fitted the experimental data, suggesting that adsorption occurred on a monolayer, while the pseudo-second-order model performed well with the kinetic data. The point of zero charge (pH_pzc) of the orange peel biochar was found to be 10.03, which revealed that the surface of the bio-sorbent contains basic groups. A Fourier infrared transform (FTIR) spectroscope and scanning electron microscope, coupled with energy dispersive x-ray (SEM-EDX) and x-ray diffraction analyses, were used to determine the functional groups, surface morphology, and inorganic elements present on the surface of the bio-sorbent, respectively. The results obtained have shown that orange peel biochar is efficient for the removal of Cu²⁺ and Pb²⁺ ions from an aqueous solution. Full article

(This article belongs to the Special Issue Wastewater Treatment: Functional Materials and Advanced Technology)

► Show Figures

Figure 1

20 pages, 18483 KiB

Open AccessArticle

Impact of Polymer Chain Rearrangements in the PA Structure of RO Membranes on Water Permeability and N-Nitrosamine Rejection

by Silvia Morović, Alegra Vezjak Fluksi, Sandra Babić and Krešimir Košutić

Molecules 2023, 28(16), 6124; https://doi.org/10.3390/molecules28166124 - 18 Aug 2023

Cited by 1 | Viewed by 1360

Abstract

The use of solvents is overall recognized as an efficient method to improve the water permeability of polyamide thin film composite membranes (PA-TFC). The objective of this work was to test the performance of the membranes after exposing them to n-propanol ( [...] Read more.

The use of solvents is overall recognized as an efficient method to improve the water permeability of polyamide thin film composite membranes (PA-TFC). The objective of this work was to test the performance of the membranes after exposing them to n-propanol (n-PrOH) to improve the permeability of the membranes while maintaining the rejection factor for small uncharged organic molecules, namely N-nitrosamines (NTRs). After the membranes were exposed to n-PrOH, the water permeability of the UTC73AC membrane increased by 98%, with minimal change in rejection. N-nitrosodiethylamine (NDEA) rejection decreased (3.4%), while N-nitrosodi-n-propylamine (NDPA) and N-nitrosodi-n-butylamine (NDBA) rejection increased by 0.9% and 2.8%, respectively. In contrast, for the BW30LE membrane, water permeability decreased (by 38.7%), while rejection factors increased by 14.5% for NDEA, 6.2% for NDPA, and 15.0% for NDBA. In addition, the morphology of the membrane surface before and after exposure to n-PrOH was analyzed. This result and the pore size distribution (PSD) curves obtained indicate that the rearrangement of polymer chains affects the network or aggregate pores in the PA layer, implying that a change in pore size or a change in pore size distribution could improve the permeability of water molecules, while the rejection factor for NTRs is not significantly affected. Full article

(This article belongs to the Special Issue Wastewater Treatment: Functional Materials and Advanced Technology)

► Show Figures

Figure 1

9 pages, 3502 KiB

Open AccessCommunication

Study on the Degradation of Methylene Blue by Cu-Doped SnSe

by Li Fan, Hongliang Zhu, Kaili Wang, Hao Liu, Weina Hu, Xin Xu and Shancheng Yan

Molecules 2023, 28(16), 5988; https://doi.org/10.3390/molecules28165988 - 10 Aug 2023

Cited by 5 | Viewed by 1487

Abstract

Treatment of organic wastewater is still a difficult problem to solve. In this paper, Cu-doped SnSe powder was synthesized by a convenient and efficient hydrothermal method. Meanwhile, the degradation effect of different doping concentrations of SnSe on methylene blue was investigated. It was [...] Read more.

Treatment of organic wastewater is still a difficult problem to solve. In this paper, Cu-doped SnSe powder was synthesized by a convenient and efficient hydrothermal method. Meanwhile, the degradation effect of different doping concentrations of SnSe on methylene blue was investigated. It was found that at low doping concentrations, the degradation effect on methylene blue was not obvious because Cu was dissolved in the lattice of the SnSe matrix at low concentrations. As the doping concentration increased, SnSe changed from a layered structure to a nanocluster structure with reduced particle size, and a mixed phase of SnSe and Cu₂SnSe₄ appeared. In fact, the degradation effect on methylene blue was significantly enhanced, and we found that the catalytic degradation effect on methylene blue was best at a doping concentration of 10 wt.%. Full article

(This article belongs to the Special Issue Wastewater Treatment: Functional Materials and Advanced Technology)

► Show Figures

Figure 1

18 pages, 3328 KiB

Open AccessArticle

Understanding the Mechanism for Adsorption of Pb(II) Ions by Cu-BTC Metal–Organic Frameworks

by Joanna N. Weyrich, John R. Mason, Ekaterina A. Bazilevskaya and Hongwei Yang

Molecules 2023, 28(14), 5443; https://doi.org/10.3390/molecules28145443 - 16 Jul 2023

Cited by 8 | Viewed by 2610

Abstract

With the growing population, industrialization, and agriculture, water contamination not only affects people but entire ecosystems. Metal–organic frameworks (MOFs), because of their large surface area and porosity, show great potential as adsorbents for removing pollutants, such as heavy metals, from contaminated water. The [...] Read more.

With the growing population, industrialization, and agriculture, water contamination not only affects people but entire ecosystems. Metal–organic frameworks (MOFs), because of their large surface area and porosity, show great potential as adsorbents for removing pollutants, such as heavy metals, from contaminated water. The current research aims at examining copper (II) benzene-1,3,5-tricarboxylate (Cu-BTC) MOFs and understanding the mechanism for their adsorption of Pb(II) from aqueous solution. The Cu-BTC samples were characterized using FTIR and XRD, and their surface area and porosity were determined based on N₂ adsorption isotherms. The concentration of Pb(II) in the solutions was measured using atomic absorption spectroscopy (AAS). Both kinetic and equilibrium adsorption data were collected and then analyzed using numerical models. The analyses led to the findings that the limiting steps in the adsorption of Pb(II) on Cu-BTC are (a) pore diffusion of Pb(II) and (b) the availability of the active sites on Cu-BTC MOFs. It was further revealed that the former step is more dominant in the adsorption of Pb(II) when the lead concentration is low. The latter step, which is directly proportional to the surface areas of the MOFs, affects the adsorption to a greater extent when the lead concentration is high. The results also show that adsorption of Pb(II) ions on Cu-BTC is mainly a multi-layer heterogeneous process. Full article

(This article belongs to the Special Issue Wastewater Treatment: Functional Materials and Advanced Technology)

► Show Figures

Figure 1

19 pages, 7695 KiB

Open AccessArticle

Controllable Synthesis of ZnO Nanoparticles with Improved Photocatalytic Performance for the Degradation of Rhodamine B under Ultraviolet Light Irradiation

by Xinyue Ren, Yien Du, Xinji Qu, Yumei Li, Luxi Yin, Kaixin Shen, Jingwen Zhang and Yufang Liu

Molecules 2023, 28(13), 5135; https://doi.org/10.3390/molecules28135135 - 30 Jun 2023

Cited by 6 | Viewed by 1558

Abstract

In this work, two-dimensional (2D) Zn-HMT (Zn(NO₃)₂(HMT)₂(H₂O)₂]_n) nanosheets were synthesized using a facile one-step chemical precipitation in the presence of Zn(NO₃)₂, hexamine (HMT), and anhydrous ethanol at [...] Read more.

In this work, two-dimensional (2D) Zn-HMT (Zn(NO₃)₂(HMT)₂(H₂O)₂]_n) nanosheets were synthesized using a facile one-step chemical precipitation in the presence of Zn(NO₃)₂, hexamine (HMT), and anhydrous ethanol at room temperature. Subsequently, hexagonal Tx-ZnO (Tx-ZnO refers to the zinc oxide (ZnO) nanoparticles) were synthesized by a high-temperature solid-phase method at different temperatures (x = 500, 550, 600, 650, 700, 750, and 800 °C) nanoparticles with different morphologies were synthesized by a high-temperature calcination approach using 2D Zn-HMT nanosheets as precursor. The crystal structure, morphology, specific surface areas, surface and interface properties, optical properties, and charge migration behaviors of the as-synthesized Tx-ZnO nanoparticles were characterized by powder X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), automatic specific surface and aperture analyzer, X-ray photoelectron spectroscopy (XPS), UV-visible spectrophotometer, photoluminescence (PL) spectra, and electrochemical impedance spectroscopy (EIS). The photocatalytic performances and stabilities of the as-synthesized typical Tx-ZnO nanoparticles with various morphologies were evaluated and compared with the commercial ZnO (CM-ZnO) nanoparticle. The T700-ZnO nanoparticle with spherical and irregular morphology exhibited the highest photocatalytic activity (99.12%) for the degradation of Rhodamine B (RhB), compared to T500-ZnO (92.32%), T600-ZnO (90.65%), T800-ZnO (44.04%), and the CM-ZnO (88.38%) nanoparticle, which can be attributed to the cooperative effects of higher crystallinity, bigger crystal size, the strongest separation efficiency, the lowest recombination rate, the fastest charge carrier transfer path, and the highest charge-transfer efficiency. The superior photocatalytic activity illustrated by the T700-ZnO nanoparticle makes it have potential application prospects for the treatment of organic wastewater. Full article

(This article belongs to the Special Issue Wastewater Treatment: Functional Materials and Advanced Technology)

► Show Figures

Figure 1

21 pages, 6339 KiB

Open AccessArticle

Structured LDH/Bentonite Composites for Chromium Removal and Recovery from Aqueous Solutions

by Mitra De Geest, Bart Michielsen, Radu-G. Ciocarlan, Pegie Cool and Elena M. Seftel

Molecules 2023, 28(12), 4879; https://doi.org/10.3390/molecules28124879 - 20 Jun 2023

Cited by 6 | Viewed by 1723

Abstract

This study focuses on chromium removal through adsorption and ion exchange using structured calcined layered double hydroxide (LDH) (MgAl)–bentonite composites. Firstly, the powders were structured into granulates to study the effect on Cr sorption kinetics to circumvent the limitations of working with powders [...] Read more.

This study focuses on chromium removal through adsorption and ion exchange using structured calcined layered double hydroxide (LDH) (MgAl)–bentonite composites. Firstly, the powders were structured into granulates to study the effect on Cr sorption kinetics to circumvent the limitations of working with powders in real-life applications. Secondly, the regeneration of the structured composites was optimized to enable multi-cycling operation, which is the key for their applicability beyond laboratory scale. Firstly, the LDH/bentonite ratio was optimized to obtain the best performance for the removal of Cr³⁺ and Cr⁶⁺ species. In powder form, the calcined adsorbent containing 80 wt% LDH and 20 wt% bentonite performed best with an adsorption capacity of 48 and 40 mg/g for Cr³⁺ and Cr⁶⁺, respectively. The desorption was optimized by studying the effect of the NaCl concentration and pH, with a 2 M NaCl solution without pH modification being optimal. The kinetic data of the adsorption and desorption steps were modelled, revealing a pseudo-second order model for both. This was also demonstrated using XRD and Raman measurements after the Cr³⁺ and Cr⁶⁺ adsorption tests, indicating successful uptake and revealing the adsorption mechanism. Finally, five consecutive adsorption–desorption cycles were performed, each showing nearly 100% adsorption and desorption. Full article

(This article belongs to the Special Issue Wastewater Treatment: Functional Materials and Advanced Technology)

► Show Figures

Graphical abstract

14 pages, 3771 KiB

Open AccessArticle

An Integrated Electrochemical System for Synergistic Cathodic Nitrate Reduction and Anodic Sulfite Oxidation

by Bing Cui, Shizhao Wang, Xiaofu Guo, Yingying Zhao and Sohrab Rohani

Molecules 2023, 28(12), 4666; https://doi.org/10.3390/molecules28124666 - 9 Jun 2023

Cited by 1 | Viewed by 1524

Abstract

Electrochemical reduction of nitrate has broad application prospects. However, in traditional electrochemical reduction of nitrate, the low value of oxygen produced by the anodic oxygen evolution reaction and the high overpotential limit its application. Seeking a more valuable and faster anodic reaction to [...] Read more.

Electrochemical reduction of nitrate has broad application prospects. However, in traditional electrochemical reduction of nitrate, the low value of oxygen produced by the anodic oxygen evolution reaction and the high overpotential limit its application. Seeking a more valuable and faster anodic reaction to form a cathode–anode integrated system with nitrate reaction can effectively accelerate the reaction rate of the cathode and anode, and improve the utilization of electrical energy. Sulfite, as a pollutant after wet desulfurization, has faster reaction kinetics in its oxidation reaction compared to the oxygen evolution reaction. Therefore, this study proposes an integrated cathodic nitrate reduction and anodic sulfite oxidation system. The effect of operating parameters (cathode potential, initial NO₃⁻–N concentration, and initial SO₃²⁻–S concentration) on the integrated system was studied. Under the optimal operating parameters, the nitrate reduction rate in the integrated system reached 93.26% within 1 h, and the sulfite oxidation rate reached 94.64%. Compared with the nitrate reduction rate (91.26%) and sulfite oxidation rate (53.33%) in the separate system, the integrated system had a significant synergistic effect. This work provides a reference for solving nitrate and sulfite pollution, and promotes the application and development of electrochemical cathode–anode integrated technology. Full article

(This article belongs to the Special Issue Wastewater Treatment: Functional Materials and Advanced Technology)

► Show Figures

Figure 1

17 pages, 5124 KiB

Open AccessArticle

Fe–Ni/MWCNTs Nano-Composites for Hexavalent Chromium Reduction in Aqueous Environment

by Zeyu Kang, Hui Gao, Xiaolong Ma, Xiaodong Jia and Dongsheng Wen

Molecules 2023, 28(11), 4412; https://doi.org/10.3390/molecules28114412 - 29 May 2023

Cited by 3 | Viewed by 1729

Abstract

A novel Cr (VI) removal material was designed and produced comprising multi-walled carbon nanotubes (MWCNTs) as a support with a high specific surface area and the loaded Fe–Ni bimetallic particles as catalytic reducing agents. Such a design permits the composite particle to perform [...] Read more.

A novel Cr (VI) removal material was designed and produced comprising multi-walled carbon nanotubes (MWCNTs) as a support with a high specific surface area and the loaded Fe–Ni bimetallic particles as catalytic reducing agents. Such a design permits the composite particle to perform the adsorption, reduction, and immobilisation of Cr (VI) quickly and efficiently. Due to MWCNTs’ physical adsorption, Cr (VI) in solution aggregates in the vicinity of the composite, and Fe rapidly reduces Cr (VI) to Cr (III) catalysed by Ni. The results demonstrated that the Fe–Ni/MWCNTs exhibits an adsorption capacity of 207 mg/g at pH = 6.4 for Cr (VI) and 256 mg/g at pH 4.8, which is about twice those reported for other materials under similar conditions. The formed Cr (III) is solidified to the surface by MWCNTs and remains stable for several months without secondary contamination. The reusability of the composites was proven by retaining at least 90% of the adsorption capacity for five instances of reutilization. Considering the facile synthesis process, low cost of raw material, and reusability of the formed Fe–Ni/MWCNTs, this work shows great potential for industrialisation. Full article

(This article belongs to the Special Issue Wastewater Treatment: Functional Materials and Advanced Technology)

► Show Figures

Figure 1

16 pages, 4213 KiB

Open AccessArticle

Ultrasound-Assisted Mineralization of 2,4-Dinitrotoluene in Industrial Wastewater Using Persulfate Coupled with Semiconductors

by Wen-Shing Chen and Min-Chih Hsu

Molecules 2023, 28(11), 4351; https://doi.org/10.3390/molecules28114351 - 25 May 2023

Cited by 3 | Viewed by 1321

Abstract

Oxidative degradation of 2,4-dinitrotoluenes in aqueous solution was executed using persulfate combined with semiconductors motivated by ultrasound (probe type, 20 kHz). Batch-mode experiments were performed to elucidate the effects of diverse operation variables on the sono-catalytic performance, including the ultrasonic power intensity, dosage [...] Read more.

Oxidative degradation of 2,4-dinitrotoluenes in aqueous solution was executed using persulfate combined with semiconductors motivated by ultrasound (probe type, 20 kHz). Batch-mode experiments were performed to elucidate the effects of diverse operation variables on the sono-catalytic performance, including the ultrasonic power intensity, dosage of persulfate anions, and semiconductors. Owing to pronounced scavenging behaviors caused by benzene, ethanol, and methanol, the chief oxidants were presumed to be sulfate radicals which originated from persulfate anions, motivated via either the ultrasound or sono-catalysis of semiconductors. With regard to semiconductors, the increment of 2,4-dinitrotoluene removal efficiency was inversely proportional to the band gap energy of semiconductors. Based on the outcomes indicated in a gas chromatograph–mass spectrometer, it was sensibly postulated that the preliminary step for 2,4-dinitrotoluene removal was denitrated into o-mononitrotoluene or p-mononitrotoluene, followed by decarboxylation to nitrobenzene. Subsequently, nitrobenzene was decomposed to hydroxycyclohexadienyl radicals and converted into 2-nitrophenol, 3-nitrophenol, and 4-nitrophenol individually. Nitrophenol compounds with the cleavage of nitro groups synthesized phenol, which was sequentially transformed into hydroquinone and p-benzoquinone. Full article

(This article belongs to the Special Issue Wastewater Treatment: Functional Materials and Advanced Technology)

► Show Figures

Figure 1

18 pages, 6871 KiB

Open AccessArticle

Ultrasonication-Tailored Graphene Oxide of Varying Sizes in Multiple-Equilibrium-Route-Enhanced Adsorption for Aqueous Removal of Acridine Orange

by Zhaoyang Han, Ling Sun, Yingying Chu, Jing Wang, Chenyu Wei, Yifang Liu, Qianlei Jiang, Changbao Han, Hui Yan and Xuemei Song

Molecules 2023, 28(10), 4179; https://doi.org/10.3390/molecules28104179 - 18 May 2023

Cited by 3 | Viewed by 1798

Abstract

Graphene oxide (GO) has shown remarkable performance in the multiple-equilibrium-route adsorption (MER) process, which is characterized by further activation of GO through an in-situ reduction process based on single-equilibrium-route adsorption (SER), generating new adsorption sites and achieving an adsorption capacity increase. However, the [...] Read more.

Graphene oxide (GO) has shown remarkable performance in the multiple-equilibrium-route adsorption (MER) process, which is characterized by further activation of GO through an in-situ reduction process based on single-equilibrium-route adsorption (SER), generating new adsorption sites and achieving an adsorption capacity increase. However, the effect of GO on MER adsorption in lateral size and thickness is still unclear. Here, GO sheets were sonicated for different lengths of time, and the adsorption of MER and SER was investigated at three temperatures to remove the typical cationic dye, acridine orange (AO). After sonication, we found that freshly prepared GO was greatly reduced in lateral size and thickness. In about 30 min, the thickness of GO decreased dramatically from several atomic layers to fewer atomic layers to a single atomic layer, which was completely stripped off; after that, the monolayer lateral size reduction dominated until it remained constant. Surface functional sites, such as hydroxyl groups, showed little change in the experiments. However, GO mainly reduces the C=O and C-O bonds in MER, except for the conjugated carbon backbone (C-C). The SER adsorption kinetics of all temperatures fitted the pseudo-first-order and pseudo-second-order models, yet room temperature preferred the latter. An overall adsorption enhancement appeared as sonication time, but the equilibrium capacity of SER GO generally increased with thickness and decreased with the single-layer lateral size, while MER GO conversed concerning the thickness. The escalated temperature facilitated the exfoliation of GO regarding the adsorption mechanism. Thus, the isotherm behaviors of the SER GO changed from the Freundlich model to Langmuir as size and temperature changed, while the MER GO were all of the Freundlich. A record capacity of ~4.3 g of AO per gram of GO was obtained from the MER adsorption with a sixty-minute ultrasonicated GO at 313.15 K. This work promises a cornerstone for MER adsorption with GO as an adsorbent. Full article

(This article belongs to the Special Issue Wastewater Treatment: Functional Materials and Advanced Technology)

► Show Figures

Graphical abstract

21 pages, 5835 KiB

Open AccessArticle

Thermo-Chemical Modification of Cellulose for the Adsorptive Removal of Titan Yellow from Wastewater

by Ubaid Ur Rahman, Muhammad Humayun, Abbas Khan, Saima Farooq, Muhammad Sadiq, Mohamed Bououdina and Nasrullah Shah

Molecules 2023, 28(9), 3955; https://doi.org/10.3390/molecules28093955 - 8 May 2023

Cited by 12 | Viewed by 1849

Abstract

This research work focuses on the isolation and thermo-chemical modification of cellulose and its application as an adsorbent for the removal of organic pollutants. The used cellulose was collected from a locally available plant (Olive Europa) commonly called Zaitoon. The stem [...] Read more.

This research work focuses on the isolation and thermo-chemical modification of cellulose and its application as an adsorbent for the removal of organic pollutants. The used cellulose was collected from a locally available plant (Olive Europa) commonly called Zaitoon. The stem branches of Zaitoon were collected and then kept in water for 40–45 days at room temperature to extract the cellulose fibers. These cellulose fibers were then kept in the Soxhlet apparatus for washing in n-hexane for 72 h. The purified cellulose was divided into three parts: one part was subjected to thermal activation (TAC), the second was modified chemically (CMC) with Benzyl Chloride, while the last one remained un-functionalized (UFC). All the three forms of cellulose were characterized via FTIR and SEM, then utilized for the removal of Titan Yellow (TY) dye from aqueous media via adsorption process by varying the contact time, temperature, concentration of dye and type, and dose of adsorbent. The adsorption efficiencies of all adsorbents were compared under different experimental variables. Thermally activated cellulose showed the best results for the removal of TY compared with other materials. The calculated removal percentage of TY was found to be 97.69, 94.83, 94.83, and 98% under equilibrium conditions of contact time, temperature, adsorbent dose, and TY concentration. Similarly, the uptake capacities of TAC under optimal experimental conditions were found to be 19.56, 18.96, 18.52, and 18.75 mg/g. Thermodynamic studies of TAC, CMC, and UFC showed that the values of ΔG are negative, while those of ΔH and ΔS are positive in all cases and at all temperatures. This indicates that the TY elimination process is endothermic and spontaneous with an entropy-driven nature. The obtained results indicate that the as-fabricated low-cost biomaterials can effectively remove dyes from wastewater through physicochemical interactions. The removal process was influenced by the nature of the adsorbent and the operating variables. Full article

(This article belongs to the Special Issue Wastewater Treatment: Functional Materials and Advanced Technology)

► Show Figures

Figure 1

16 pages, 3077 KiB

Open AccessArticle

Effect of Enhanced Hydrolytic Acidification Process on the Treatment of Azo Dye Wastewater

by Xuehui Xie, Yiting Qin, Shanshan Yang, Yao Sun, Haonan Mo, Hangmi Zheng, Na Liu and Qingyun Zhang

Molecules 2023, 28(9), 3930; https://doi.org/10.3390/molecules28093930 - 6 May 2023

Cited by 4 | Viewed by 1726

Abstract

The hydrolysis acidification process is an economical and effective method, but its efficiency is still low in treating azo dye wastewater. It is therefore crucial to find more suitable and efficient means or techniques to further strengthen the process of treating azo dye [...] Read more.

The hydrolysis acidification process is an economical and effective method, but its efficiency is still low in treating azo dye wastewater. It is therefore crucial to find more suitable and efficient means or techniques to further strengthen the process of treating azo dye wastewater by a hydrolytic acidification process. In this study, a hydrolytic acidification aerobic reactor was used to simulate the azo dye wastewater process. The change of wastewater quality during the reaction process was monitored, and the deep enhancement effect of single or composite biological intensification technology on the treatment of azo dye wastewater by the hydrolytic acidification process was also explored. Co-substrate strengthening and the addition of fructose co-substrate can significantly improve the efficiency of hydrolytic acidification. Compared with the experimental group without the addition of fructose, the decolorization ratio of wastewater was higher (93%) after adding fructose co-substrate. The immobilization technology was strengthened, and the immobilized functional bacteria DDMZ1 pellet was used to treat the simulated azo dye wastewater. The results showed that the composite technology experimental group with the additional fructose co-matrix had a better decolorization efficiency than the single immobilized bio-enhancement technology, with the highest decolorization ratio of 97%. As a composite biological intensification method, the fructose co-matrix composite with immobilized functional bacteria DDMZ1 technology can be applied to the treatment of azo dye wastewater. Full article

(This article belongs to the Special Issue Wastewater Treatment: Functional Materials and Advanced Technology)

► Show Figures

Figure 1

18 pages, 37428 KiB

Open AccessArticle

A Porous Geopolymer Containing Ti-Bearing Blast Furnace Slag: Synthesis, Characterization, and Adsorption-Photodegradation Studies towards Methylene Blue Removal under Visible Light Condition

by Yijian Cheng, Kun Wang, Peng Li, Hongwei Guo, Bingji Yan, Dong Chen and Wei Zhao

Molecules 2023, 28(9), 3673; https://doi.org/10.3390/molecules28093673 - 24 Apr 2023

Cited by 6 | Viewed by 1916

Abstract

A porous geopolymer with adsorption and photocatalytic degradation functions was successfully developed by utilizing Ti-bearing blast furnace slag (TBBFS) as the raw material. The prepared porous geopolymers were characterized by X-ray diffraction, scanning electron microscope, energy dispersive spectrometer, and Fourier transform infrared spectrum. [...] Read more.

A porous geopolymer with adsorption and photocatalytic degradation functions was successfully developed by utilizing Ti-bearing blast furnace slag (TBBFS) as the raw material. The prepared porous geopolymers were characterized by X-ray diffraction, scanning electron microscope, energy dispersive spectrometer, and Fourier transform infrared spectrum. Selective crystallization, water quenching, and natural cooling methods were employed to investigate the influences of these modifications on the applicability of TBBFS as a precursor for geopolymer synthesis. Water-quenched slag with amorphous content was prone to alkali dissolution, and the resulting geopolymer exhibited the highest adsorption capacity (97.18 mg/g) for methylene blue (MB) removal. Selective crystallization at 1400 °C generated a hybrid microstructure consisting of a non-cementitious CaTiO₃ crystallization phase and a cementitious amorphous fraction. The retention of CaTiO₃ in the final geopolymer enables a bifunctionality in adsorption–photodegradation. Particularly, the adsorption and photodegradation processes under various conditions were investigated. The superior removal efficiency for MB could be attributed to the synergistic effects between the geopolymer matrix and CaTiO₃, leading to an enhancement in the formation of hydroxyl radicals. The conversion of TBBFS into porous geopolymer offers an efficient and straightforward solution for slag utilization and dye removal. Full article

(This article belongs to the Special Issue Wastewater Treatment: Functional Materials and Advanced Technology)

► Show Figures

Figure 1

12 pages, 5009 KiB

Open AccessArticle

A Novel Non-Metallic Photocatalyst: Phosphorus-Doped Sulfur Quantum Dots

by Ziyi Liu, Chuanfu Shan, Guiyu Wei, Jianfeng Wen, Li Jiang, Guanghui Hu, Zhijie Fang, Tao Tang and Ming Li

Molecules 2023, 28(8), 3637; https://doi.org/10.3390/molecules28083637 - 21 Apr 2023

Cited by 4 | Viewed by 2161

Abstract

In this paper, a novel phosphorus-doped sulfur quantum dots (P-SQDs) material was prepared using a simple hydrothermal method. P-SQDs have a narrow particle size distribution as well as an excellent electron transfer rate and optical properties. Compositing P-SQDs with graphitic carbon nitride (g-C [...] Read more.

In this paper, a novel phosphorus-doped sulfur quantum dots (P-SQDs) material was prepared using a simple hydrothermal method. P-SQDs have a narrow particle size distribution as well as an excellent electron transfer rate and optical properties. Compositing P-SQDs with graphitic carbon nitride (g-C₃N₄) can be used for photocatalytic degradation of organic dyes under visible light. More active sites, a narrower band gap, and stronger photocurrent are obtained after introducing P-SQDs into g-C₃N₄, thus promoting its photocatalytic efficiency by as much as 3.9 times. The excellent photocatalytic activity and reusability of P-SQDs/g-C₃N₄ are prospective signs of its photocatalytic application under visible light. Full article

(This article belongs to the Special Issue Wastewater Treatment: Functional Materials and Advanced Technology)

► Show Figures

Figure 1

13 pages, 4079 KiB

Open AccessArticle

A Self-Cleaning TiO₂ Bacterial Cellulose Super-Hydrophilic Underwater Super-Oleophobic Composite Membrane for Efficient Oil–Water Separation

by Yawen Cui, Xudong Zheng, Tongtong Xu, Biao Ji, Jinfeng Mei and Zhongyu Li

Molecules 2023, 28(8), 3396; https://doi.org/10.3390/molecules28083396 - 12 Apr 2023

Cited by 5 | Viewed by 2397

Abstract

Due to the increasingly serious problem of offshore oil spills, research related to oil–water separation has attracted more and more attention. Here, we prepared a super-hydrophilic/underwater super-oleophobic membrane (hereinafter referred to as BTA) using poly-dopamine (PDA) to adhesive TiO₂ nanoparticles on the [...] Read more.

Due to the increasingly serious problem of offshore oil spills, research related to oil–water separation has attracted more and more attention. Here, we prepared a super-hydrophilic/underwater super-oleophobic membrane (hereinafter referred to as BTA) using poly-dopamine (PDA) to adhesive TiO₂ nanoparticles on the surface of bacterial cellulose, coated with sodium alienate by vacuum-assisted filtration technique. This demonstrates its excellent underwater super-oleophobic property. Its contact angle is about 153°. Remarkably, BTA has 99% separation efficiency. More importantly, BTA still showed excellent anti-pollution property under ultraviolet light after 20 cycles. BTA has the advantages of low cost, environmentally friendliness and good anti-fouling performance. We believe it can play an important role in dealing with problems related to oily wastewater. Full article

(This article belongs to the Special Issue Wastewater Treatment: Functional Materials and Advanced Technology)

► Show Figures

Figure 1

13 pages, 4032 KiB

Open AccessArticle

Synthesis of High Specific Surface Lithium-Ion Sieve Templated by Bacterial Cellulose for Selective Adsorption of Li⁺

by Xi Zhang, Xudong Zheng, Tongtong Xu, Yuzhe Zhang, Guomeng Li and Zhongyu Li

Molecules 2023, 28(7), 3191; https://doi.org/10.3390/molecules28073191 - 3 Apr 2023

Cited by 4 | Viewed by 2498

Abstract

In recent years, with the development of batteries, ceramics, glass and other industries, the demand for lithium has increased rapidly. Due to the rich lithium resources in seawater and salt-lake brine, the question of how to selectively adsorb and separate lithium ions from [...] Read more.

In recent years, with the development of batteries, ceramics, glass and other industries, the demand for lithium has increased rapidly. Due to the rich lithium resources in seawater and salt-lake brine, the question of how to selectively adsorb and separate lithium ions from such brine has attracted the attention and research of many scholars. The Li-ion sieve stands out from other methods thanks to its excellent special adsorption and separation performance. In this paper, mesoporous titanium dioxide and lithium hydroxide were prepared by hydrothermal reaction using bacterial cellulose as a biological template. After calcination at 600 °C, spinel lithium titanium oxide Li₂TiO₃ was formed. The precursor was eluted with HCl eluent to obtain H₂TiO₃. The lithium titanate were characterized by IR, SEM and X-ray diffraction. The adsorption properties of H₂TiO₃ were studied by adsorption pH, adsorption kinetics, adsorption isotherm and competitive adsorption. The results show that H₂TiO₃ has a single-layer chemical adsorption process, and has a good adsorption effect on lithium ions at pH 11.0, with a maximum adsorption capacity of 35.45 mg g⁻¹. The lithium-ion sieve can selectively adsorb Li⁺, and its partition coefficient is 2242.548 mL g⁻¹. It can be predicted that the lithium-ion sieve prepared by biological template will have broad application prospects. Full article

(This article belongs to the Special Issue Wastewater Treatment: Functional Materials and Advanced Technology)

► Show Figures

Figure 1

20 pages, 5550 KiB

Open AccessArticle

A Recyclable Magnetic Aminated Lignin Supported Zr-La Dual-Metal Hydroxide for Rapid Separation and Highly Efficient Sequestration of Phosphate

by Enmin Zong, Xuanren Wang, Lirong Zhang, Jiayao Yang and Xiaohuan Liu

Molecules 2023, 28(7), 2923; https://doi.org/10.3390/molecules28072923 - 24 Mar 2023

Cited by 4 | Viewed by 1517

Abstract

The application of lignin-based adsorbents in the efficient removal of phosphate from wastewater has attracted much attention and been intensively studied in recent years. However, most currently reported lignin-based adsorbents are difficult to recover and recycle. Herein, we have developed a recyclable, nanostructured [...] Read more.

The application of lignin-based adsorbents in the efficient removal of phosphate from wastewater has attracted much attention and been intensively studied in recent years. However, most currently reported lignin-based adsorbents are difficult to recover and recycle. Herein, we have developed a recyclable, nanostructured bio-adsorbent, poly(ethyleneimine) (PEI)-modified lignin (LG) integrated with Fe₃O₄ and Zr-La dual-metal hydroxide (LG-NH₂@Fe₃O₄@Zr-La), by the Mannich reaction followed by the chemical coprecipitation method. Multilayer adsorption existed on the surface of LG-NH₂@Fe₃O₄@Zr-La based on the isotherm fitting curve, and its adsorption capacity reached 57.8 mg P g⁻¹, exhibiting a higher phosphate uptake than most reported metallic oxide-based composites. The adsorption process was dominated by inner-sphere complexation of ligand-exchange and electrostatic interactions. Moreover, LG-NH₂@Fe₃O₄@Zr-La exhibited excellent selectivity against coexisting anions, and the adsorption was more efficient under acidic conditions. When the phosphate concentration was 2.0 mg P L⁻¹, the removal efficiency of phosphate reached 99.5% and the residual concentration was only 10 μg P L⁻¹, which meets the United States Environmental Protection Agency (USEPA) standard for eutrophication prevention. In addition, the LG-NH₂@Fe₃O₄@Zr-La displayed excellent reusability, maintaining 91.8% of removal efficiency after five cycles. Importantly, owing to the magnetic properties of the loaded Fe₃O₄, the resulting composite could be separated within 30 s under an external magnetic field. Thus, the separable and recyclable biobased magnetic adsorbent developed in this work exhibited promising application in phosphate capture from real sewage. This research study provides a new perspective for lignin valorization in lignocellulose biorefineries and establishes an approach for developing an economical and efficient bio-adsorbent for phosphate removal from wastewater. Full article

(This article belongs to the Special Issue Wastewater Treatment: Functional Materials and Advanced Technology)

► Show Figures

Figure 1

12 pages, 3927 KiB

Open AccessArticle

Study on Wastewater Demulsification Technology of Crude Oil in Xinjiang Oilfield

by Jingui Ma, Liqiang Ma, Yongdi Gao, Yue Qin, Zhihao Jiao, Ruibo Guo and Junwei Hou

Molecules 2023, 28(6), 2873; https://doi.org/10.3390/molecules28062873 - 22 Mar 2023

Viewed by 1507

Abstract

The Second Oil Production Plant of Xinjiang Oilfield produces a large amount of highly emulsified crude oil, which has a serious impact on the subsequent oil–water separation. At present, the concentration of demulsifier has increased to 2000 mg/L, but the demulsification effect is [...] Read more.

The Second Oil Production Plant of Xinjiang Oilfield produces a large amount of highly emulsified crude oil, which has a serious impact on the subsequent oil–water separation. At present, the concentration of demulsifier has increased to 2000 mg/L, but the demulsification effect is still poor. In this paper, the source and physical properties of highly emulsified crude oil are investigated firstly. The results show that highly emulsified crude oil is composed of three kinds of liquid: (1) conventional water flooding (WF); (2) chemical flooding (CF); (3) fracturing backflow fluid (FB). Among them, high zeta potential, low density difference, high viscosity, and small emulsion particles are responsible for the difficulty in the demulsification of the WF emulsion, while the high pH value is the reason why the CF emulsion is difficult to demulsify. Therefore, systematic experiments were implemented to investigate the optimal demulsification approach towards the three liquids above. As for the WF emulsion, it was necessary to raise the temperature to 70 °C and the concentration of the demulsifier to 200 mg/L. Moreover, it was only necessary to add 200 mg/L of demulsifier to break the CF emulsion after adjusting the pH value to 7, while no extra treatments were needed to break the FB emulsion. We hope this study can provide a new insight for the treatment of emulsions in the later stage of oilfield development. Full article

(This article belongs to the Special Issue Wastewater Treatment: Functional Materials and Advanced Technology)

► Show Figures

Figure 1

18 pages, 9058 KiB

Open AccessArticle

Rape Straw Supported FeS Nanoparticles with Encapsulated Structure as Peroxymonosulfate and Hydrogen Peroxide Activators for Enhanced Oxytetracycline Degradation

by Guiyin Wang, Yan Yang, Xiaoxun Xu, Shirong Zhang, Zhanbiao Yang, Zhang Cheng, Junren Xian, Ting Li, Yulin Pu, Wei Zhou, Gang Xiang and Zhien Pu

Molecules 2023, 28(6), 2771; https://doi.org/10.3390/molecules28062771 - 19 Mar 2023

Cited by 4 | Viewed by 2236

Abstract

Iron-based catalysts with high load content of iron sulfide (FeS) were commonly peroxymonosulfate (PMS) and hydrogen peroxide (H₂O₂) activators to degrade organic pollutants but limited catalytic efficiency and increased risk of ferrous ion leaching restricted their use. Meanwhile, various [...] Read more.

Iron-based catalysts with high load content of iron sulfide (FeS) were commonly peroxymonosulfate (PMS) and hydrogen peroxide (H₂O₂) activators to degrade organic pollutants but limited catalytic efficiency and increased risk of ferrous ion leaching restricted their use. Meanwhile, various biomass materials such as straw, peel, and branch have been extensively prepared into biochar for mechanical support for iron-based catalysts; however, the preparation process of biochar was energy-intensive. In this study, FeS nanoparticles modified rape straw composites (RS–FeS) encapsulated with ethylenediaminetetraacetic acid (RS–EDTA–FeS) were successfully presented by in-situ synthesis method for efficiently activating PMS and H₂O₂ to degrade oxytetracycline (OTC), which was economical and environmentally friendly. The results showed that the modified rape straw can remove OTC efficiently, and the addition of EDTA also significantly enhanced the stability and the reusability of the catalyst. In addition, EDTA also promoted the activation of H₂O₂ at neutral pH. The OTC degradation efficiency of the two catalysts by PMS was faster than that of H₂O₂, but H₂O₂ had a stronger ability to remove OTC than PMS. The highest OTC removal efficiency of RS–FeS and RS–EDTA–FeS were 87.51 and 81.15%. O₂^•– and ¹O₂ were the major reactive oxidative species (ROS) in the PMS system. Furthermore, compared with RS–FeS, the addition of EDTA inhabited the generation of O₂^•– in the PMS system. Instead, O₂^•– and ^•OH were the major ROS in the H₂O₂ system, but ¹O₂ was also identified in RS–FeS/H₂O₂ system. RS–EDTA–FeS showed a trend of rising first and then decreasing in recycle test. Instead, the removal rate of OTC by RS–FeS decreased significantly with the increase in reuse times. In the actual wastewater test, the TOC removal of two catalysts active by H₂O₂ was better than PMS, which was consistent with the test results of OTC, indicating that the two catalysts have application value in the removal of organic pollutants in actual wastewater. This study directly used plant materials as catalysts and omits the preparation process of biochar, greatly reduces the preparation cost and secondary pollution of catalysts, and provides theoretical support for the deepening of advanced oxidation technology. Full article

(This article belongs to the Special Issue Wastewater Treatment: Functional Materials and Advanced Technology)

► Show Figures

Figure 1

20 pages, 6492 KiB

Open AccessArticle

Adsorption and Removal of Cr⁶⁺, Cu²⁺, Pb²⁺, and Zn²⁺ from Aqueous Solution by Magnetic Nano-Chitosan

by Yuran He, Panqing Zhang and Lijun Wang

Molecules 2023, 28(6), 2607; https://doi.org/10.3390/molecules28062607 - 13 Mar 2023

Cited by 3 | Viewed by 1957

Abstract

Magnetic nano-chitosan (MNC) was prepared and characterized. The kinetics, thermodynamics, and influencing factors of the adsorption of Cr⁶⁺, Cu²⁺, Pb²⁺, and Zn²⁺, as well as their competitive adsorption onto MNC in aqueous solution, were studied. [...] Read more.

Magnetic nano-chitosan (MNC) was prepared and characterized. The kinetics, thermodynamics, and influencing factors of the adsorption of Cr⁶⁺, Cu²⁺, Pb²⁺, and Zn²⁺, as well as their competitive adsorption onto MNC in aqueous solution, were studied. The results showed that the adsorption kinetics and thermodynamics of Cr⁶⁺, Cu²⁺, Pb²⁺, and Zn²⁺ were well described by the pseudo-second-order kinetic model and Langmuir isothermal adsorption model, indicating that the adsorption was mainly chemical adsorption and endothermic. Increasing the dosage of MNC, the equilibrium adsorption capacity (q_e) of Cr⁶⁺, Cu²⁺, Pb²⁺, and Zn²⁺ decreased; their removal rate (η) increased. With the increase in the solution’s pH, the q_e and η of Cr⁶⁺ first increased and then decreased; the q_e and η of Cu²⁺, Pb²⁺, and Zn²⁺ increased. With the increase in the metal ion initial concentration, the q_e increased; the η of Cr⁶⁺, Cu²⁺, and Zn²⁺ decreased, while the η of Pb²⁺ increased first and then decreased. Temperature had a weak influence on the q_e of Cr⁶⁺ and Pb²⁺, while it had a strong influence on Cu²⁺ and Zn²⁺, the q_e and η were greater when the temperature was higher, and the adsorption was spontaneous and endothermic. The q_e and η of Cu²⁺, Pb²⁺, and Zn²⁺ decreased in the presence of co-existing ions. The influences among metal ions existed in a binary and ternary ion system. The current study’s results provide a theoretical support for the simultaneous treatment of harmful metal ions in wastewater by MNC. Full article

(This article belongs to the Special Issue Wastewater Treatment: Functional Materials and Advanced Technology)

► Show Figures

Figure 1

15 pages, 4169 KiB

Open AccessArticle

Amphiphilic Grafted Polymers Based on Citric Acid and Aniline Used to Enhance the Antifouling and Permeability Properties of PES Membranes

by Jiahui Zhao, Peng Zhang, Lin Cao, Haoling Huo, Huaijun Lin, Qiwei Wang, Florian Vogel, Wei Li and Zhidan Lin

Molecules 2023, 28(4), 1936; https://doi.org/10.3390/molecules28041936 - 17 Feb 2023

Cited by 3 | Viewed by 2262

Abstract

Water treatment technology based on ultrafiltration (UF) faces the problem of severe membrane fouling due to its inherent hydrophobicity. The use of amphiphilic polymers that possess both hydrophobic and hydrophilic chain segments can be advantageous for the hydrophilic modification of UF membranes due [...] Read more.

Water treatment technology based on ultrafiltration (UF) faces the problem of severe membrane fouling due to its inherent hydrophobicity. The use of amphiphilic polymers that possess both hydrophobic and hydrophilic chain segments can be advantageous for the hydrophilic modification of UF membranes due to their excellent combination in the membrane matrix. In the present study, we examined a novel amphiphilic CA–g–AN material, constructed by grafting citric acid (CA) to aniline (AN), as a modified material to improve the hydrophilicity of a PES membrane. This material was more compatible with the polymer membrane matrix than a pure hydrophilic modified material. The polyethersulfone (PES) membranes modified by amphiphilic CA–g–AN demonstrated a higher water flux (290.13 L·m⁻²·h⁻¹), which was more than eight times higher than that of the pure PES membrane. Furthermore, the flux recovery ratio (FRR) of the modified membrane could reach 83.24% and the value of the water contact angle (WCA) was 76.43°, demonstrating the enhanced hydrophilicity and antifouling ability of the modified membranes. With this study, we aimed to develop a new amphiphilic polymer to improve the antifouling property and permeability of polymer-based UF membranes to remove organic pollutants from water. Full article

(This article belongs to the Special Issue Wastewater Treatment: Functional Materials and Advanced Technology)

► Show Figures

Graphical abstract

14 pages, 2145 KiB

Open AccessArticle

Removal of Malachite Green Dye from Aqueous Solution by Catalytic Wet Oxidation Technique Using Ni/Kaolin as Catalyst

by Abdelhak Moumen, Youghourta Belhocine, Najoua Sbei, Seyfeddine Rahali, Fatima Adam Mohamed Ali, Fedia Mechati, Fouad Hamdaoui and Mahamadou Seydou

Molecules 2022, 27(21), 7528; https://doi.org/10.3390/molecules27217528 - 3 Nov 2022

Cited by 16 | Viewed by 2952

Abstract

In this study, natural Algerian kaolin was used as a support and impregnated with nickel at different loading amounts (2 wt.%, 5 wt.%, and 7 wt.%) in order to prepare a supported catalyst. The wet impregnation technique was used in this preparation; nickel [...] Read more.

In this study, natural Algerian kaolin was used as a support and impregnated with nickel at different loading amounts (2 wt.%, 5 wt.%, and 7 wt.%) in order to prepare a supported catalyst. The wet impregnation technique was used in this preparation; nickel oxide (NiO) was the active phase precursor of the catalyst, and the catalysts were designated as follows: 2%, 5%, and 7% Ni/kaolin. These catalysts were put to the test in catalytic wet peroxide oxidation (CWPO) for degrading the organic contaminant malachite green dye (MG). Analytical techniques such as FTIR spectroscopy, X-ray diffraction, BET, and X-fluorescence were used to examine the structure, morphology, and chemical composition of the support and the produced catalysts. Several parameters, including temperature, catalytic dose, metal loading, hydrogen peroxide volume, and kinetic model were systematically investigated. The combination of improved parameters resulted in a significant increase in the catalytic activity, achieving a high removal rate of MG dye of 98.87%. Full article

(This article belongs to the Special Issue Wastewater Treatment: Functional Materials and Advanced Technology)

► Show Figures

Figure 1

11 pages, 3414 KiB

Open AccessFeature PaperArticle

Enhanced Crude Oil Sorption by Modified Plant Materials in Oilfield Wastewater Treatment

by Ya Shi, Liwa Ma, Shan Hou, Miao Dou, Yongfei Li, Weichao Du and Gang Chen

Molecules 2022, 27(21), 7459; https://doi.org/10.3390/molecules27217459 - 2 Nov 2022

Cited by 6 | Viewed by 1744

Abstract

The treatment of oilfield wastewater with high crude oil content and complex composition is a problem requiring considerable attention. In order to effectively remove crude oil contained in wastewater, in this work, rice straw, as an oil-absorbing material, was modified and used as [...] Read more.

The treatment of oilfield wastewater with high crude oil content and complex composition is a problem requiring considerable attention. In order to effectively remove crude oil contained in wastewater, in this work, rice straw, as an oil-absorbing material, was modified and used as a sorbent for crude oil. Rice straw was modified with alkali and cetyltrimethylammonium chloride (CTAC) by simple substitution reaction. The adsorption capacity of modified rice straw for oil was evaluated. The results illustrate that the adsorption rate of rice straw for crude oil was increased from 0.83 to 8.49 g/g, with the optimal conditions of 18% NaOH reacted for 90 min at 50 °C and 2% CTAC reacted for 60 min at 20 °C. The proposed modification method could be used for different materials to enhance the adsorption rate. The results of the contact angle test show that the modified straw changed from hydrophilic to hydrophobic, which may be the main reason for the improvement in the oil absorption rate. Finally, the surface structure of rice straw was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and N₂ adsorption–desorption isotherms, which further confirmed the hydrophobicity of the modified rice straw. Full article

(This article belongs to the Special Issue Wastewater Treatment: Functional Materials and Advanced Technology)

► Show Figures

Figure 1

15 pages, 3018 KiB

Open AccessArticle

Recovery of Acid and Alkaline from Industrial Saline Wastewater by Bipolar Membrane Electrodialysis under High-Chemical Oxygen Demand Concentration

by Xiangfei Lü, Shuai Shao, Jinlong Wu, Yongguo Zhao, Bishuai Lu, Jieying Li, Linlin Liang and Lei Tian

Molecules 2022, 27(21), 7308; https://doi.org/10.3390/molecules27217308 - 27 Oct 2022

Cited by 3 | Viewed by 1840

Abstract

Actual high saline wastewater containing concentrated organics and sodium chloride is a bioenergy and renewable resource. This study compared two different bipolar membrane electrodialysis membranes from two companies’ stacks to recover HCl and NaOH from sodium chloride solution and actual chemical wastewater. The [...] Read more.

Actual high saline wastewater containing concentrated organics and sodium chloride is a bioenergy and renewable resource. This study compared two different bipolar membrane electrodialysis membranes from two companies’ stacks to recover HCl and NaOH from sodium chloride solution and actual chemical wastewater. The results demonstrated that the electrolysis rates were around 1.5 kg/m²h, the HCl and NaOH production rates were about 0.9 kg/m²h, energy consumption was in the range of 1.05–1.27 kWh/kg, and the economic benefits were above 1 yuan/h in BMED systems. From analyzing the performance of seven different BMED membrane stacks, the B2 stack was chosen for electrolyzing actual high salt wastewater to observe the effect of chemical oxygen demand on BMED systems, where electrolytic salt performance, HCl-NaOH alkali production rates, and energy consumption show linear dependence on time for 5000 mg/L chemical oxygen demand wastewater. It illustrated chemical oxygen demand can enhance energy consumption and reduce electrolytic salt performance and the acid and alkali production rates, due to improving the membrane area resistance. In this study, the effect of high COD saline wastewater on the performance of a BMED membrane stack was clarified and the mechanism was analyzed for its practical application in treating chemical high salt wastewater. Full article

(This article belongs to the Special Issue Wastewater Treatment: Functional Materials and Advanced Technology)

► Show Figures

Figure 1

22 pages, 9311 KiB

Open AccessArticle

Characterization and Optimization of Polymeric Bispicolamine Chelating Resin: Performance Evaluation via RSM Using Copper in Acid Liquors as a Model Substrate through Ion Exchange Method

by Kowit Suwannahong, Chadrudee Sirilamduan, Anat Deepatana, Torpong Kreetachat and Surachai Wongcharee

Molecules 2022, 27(21), 7210; https://doi.org/10.3390/molecules27217210 - 25 Oct 2022

Cited by 19 | Viewed by 2095

Abstract

Advanced technologies of electronics industries have led to environmental contamination concerns, especially waste print circuit boards containing a very high concentration of copper (II) ions, which can be discharged in wastewater containing many contaminated metals. A low pH is a necessity for treating [...] Read more.

Advanced technologies of electronics industries have led to environmental contamination concerns, especially waste print circuit boards containing a very high concentration of copper (II) ions, which can be discharged in wastewater containing many contaminated metals. A low pH is a necessity for treating industrial wastewater containing heavy metals to meet engineering process design. A novel polymeric bispicolamine chelating resin, Dowex-M4195, was applied as an alternative for investigating the behavior of copper (II) in acidic solution via an ion exchange method in a batch experiment system. Characterization of physical and chemical properties before and after ion exchange were also explored through BET, SEM-EDX, FTIR and XRD. Response surface methodology was also applied for optimization of copper (II) removal capacity using design of experiment for selective chelating resin at a low pH. The results indicate that H⁺ Dowex-M4195 chelating resin had a high-carbon content and specific surface area of >64% and 26.5060 m²/g, respectively. It was predominantly macropore porous in nature due to the N₂ gas adsorption isotherm and exhibited type IV with insignificant desorption hysteresis loop of H1-type. It was spherical and cylindrical. After the ion exchange process of copper (II)-loaded H⁺ Dowex-M4195, the specific surface area and total pore volume decreased by about 17.82% and 5.39%, respectively, as compared to H⁺ Dowex-M4195. Hysteresis loop, isotherm and pore size distribution were also similar. Regarding the functional group, the surface morphology and crystalline structures of H⁺ Dowex-M4195 showed copper (II) compound based on the structure of chelating resin that confirmed effective ion exchange behavior. The design of optimization indicated that copper (II) removal capacity of about 31.33 mg/g was achieved, which could be obtained at 6.96 h, pH of 2 (a desirable low pH), dose of 124.13 mg and concentration of 525.15 mg/L. The study indicated that the H⁺ Dowex-M4195 (which is commercially available on the market) can successfully be applied as an alternative precursor through the ion exchange method for further reuse and regeneration of the copper (II) in the electronic waste industries and other wastewater applications needed to respond the policy of biocircular green economy in Thailand. Full article

(This article belongs to the Special Issue Wastewater Treatment: Functional Materials and Advanced Technology)

► Show Figures

Figure 1

16 pages, 5616 KiB

Open AccessArticle

Preparation of a Chitosan/Coal Gasification Slag Composite Membrane and Its Adsorption and Removal of Cr (VI) and RhB in Water

by Deqiang Peng, Shuyun Zhang, Kai Wang, Tingting Dong, Min Zhang and Guohui Dong

Molecules 2022, 27(21), 7173; https://doi.org/10.3390/molecules27217173 - 23 Oct 2022

Cited by 5 | Viewed by 1867

Abstract

At present, there are many kinds of pollutants, including dyes and heavy metal ions, in wastewater. It is very important to develop adsorbents that can simultaneously remove heavy metal ions and dyes. In this study, a renewable composite membrane material was synthesized using [...] Read more.

At present, there are many kinds of pollutants, including dyes and heavy metal ions, in wastewater. It is very important to develop adsorbents that can simultaneously remove heavy metal ions and dyes. In this study, a renewable composite membrane material was synthesized using chitosan and treated coal gasification slag. The Cr (VI) maximum adsorption capacity of the composite membrane was 50.0 mg/L, which was 4.3~8.8% higher than that of the chitosan membrane. For the adsorption of RhB, the removal rate of the chitosan membrane was only approximately 5.0%, but this value could be improved to 95.3% by introducing coal gasification slag. The specific surface area of the chitosan membrane could also be increased 16.2 times by the introduction of coal gasification slag. This is because coal gasification slag could open the nanopores of the chitosan membrane (from 80 μm to 110 μm). Based on the adsorption kinetics and adsorption mechanism analysis, it was found that the adsorption of Cr (VI) occurred mainly through the formation of coordination bonds with the amino groups on the molecular chains of chitosan. Meanwhile, RhB adsorption occurred through the formation of hydrogen bonds with the surface of coal gasification slag. Additionally, coal gasification slag can improve the mechanical properties of the chitosan membrane by 2.2 times, which may facilitate the practical application of the composite membrane. This study provides new insight into the adsorbent design and the resource utilization of coal gasification slag. Full article

(This article belongs to the Special Issue Wastewater Treatment: Functional Materials and Advanced Technology)

► Show Figures

Figure 1

9 pages, 1761 KiB

Open AccessCommunication

Facile Preparation of Porous Carbon Derived from Pomelo Peel for Efficient Adsorption of Methylene Blue

by Wenlin Zhang, Mingwan Liu, Yuhong Zhao and Qinhong Liao

Molecules 2022, 27(10), 3096; https://doi.org/10.3390/molecules27103096 - 11 May 2022

Cited by 13 | Viewed by 2171

Abstract

Pomelo peel waste-derived porous carbon (PPPC) was prepared by a facile one-step ZnCl₂ activation method. The preparation parameters of PPPC were the mass ratio of ZnCl₂ to pomelo peel of 2:1, carbonization temperature of 500 °C, and carbonization time of 1 [...] Read more.

Pomelo peel waste-derived porous carbon (PPPC) was prepared by a facile one-step ZnCl₂ activation method. The preparation parameters of PPPC were the mass ratio of ZnCl₂ to pomelo peel of 2:1, carbonization temperature of 500 °C, and carbonization time of 1 h. This obtained PPPC possessed abundant macro-,meso-, and micro-porous structures, and a large specific surface area of 939.4 m² g⁻¹. Surprisingly, it had excellent adsorption ability for methylene blue, including a high adsorption capacity of 602.4 mg g⁻¹ and good reusability. The adsorption isotherm and kinetic fitted with Langmuir and pseudo-second order kinetic models. This work provides a novel strategy for pomelo peel waste utilization and a potential adsorbent for treating dye wastewater. Full article

(This article belongs to the Special Issue Wastewater Treatment: Functional Materials and Advanced Technology)

► Show Figures

Figure 1

Review

Jump to: Editorial, Research

22 pages, 5229 KiB

Open AccessReview

Nanomaterials for Removal of Phenolic Derivatives from Water Systems: Progress and Future Outlooks

by Maricely Ramírez-Hernández, Jordan Cox, Belvin Thomas and Tewodros Asefa

Molecules 2023, 28(18), 6568; https://doi.org/10.3390/molecules28186568 - 11 Sep 2023

Cited by 1 | Viewed by 1779

Abstract

Environmental pollution remains one of the most challenging problems facing society worldwide. Much of the problem has been caused by human activities and increased usage of various useful chemical agents that inadvertently find their way into the environment. Triclosan (TCS) and related phenolic [...] Read more.

Environmental pollution remains one of the most challenging problems facing society worldwide. Much of the problem has been caused by human activities and increased usage of various useful chemical agents that inadvertently find their way into the environment. Triclosan (TCS) and related phenolic compounds and derivatives belong to one class of such chemical agents. In this work, we provide a mini review of these emerging pollutants and an outlook on the state-of-the-art in nanostructured adsorbents and photocatalysts, especially nanostructured materials, that are being developed to address the problems associated with these environmental pollutants worldwide. Of note, the unique properties, structures, and compositions of mesoporous nanomaterials for the removal and decontamination of phenolic compounds and derivatives are discussed. These materials have a great ability to scavenge, adsorb, and even photocatalyze the decomposition of these compounds to mitigate/prevent their possible harmful effects on the environment. By designing and synthesizing them using silica and titania, which are easier to produce, effective adsorbents and photocatalysts that can mitigate the problems caused by TCS and its related phenolic derivatives in the environment could be fabricated. These topics, along with the authors’ remarks, are also discussed in this review. Full article

(This article belongs to the Special Issue Wastewater Treatment: Functional Materials and Advanced Technology)

► Show Figures

Graphical abstract

24 pages, 4286 KiB

Open AccessReview

Radioactive Wastewater Treatment Technologies: A Review

by Hailing Ma, Minghai Shen, Yao Tong and Xiao Wang

Molecules 2023, 28(4), 1935; https://doi.org/10.3390/molecules28041935 - 17 Feb 2023

Cited by 42 | Viewed by 10168

Abstract

With the wide application of nuclear energy, the problem of radioactive pollution has attracted worldwide attention, and the research on the treatment of radioactive wastewater is imminent. How to treat radioactive wastewater deeply and efficiently has become the most critical issue in the [...] Read more.

With the wide application of nuclear energy, the problem of radioactive pollution has attracted worldwide attention, and the research on the treatment of radioactive wastewater is imminent. How to treat radioactive wastewater deeply and efficiently has become the most critical issue in the development of nuclear energy technology. The radioactive wastewater produced after using nuclear technology has the characteristics of many kinds, high concentration, and large quantity. Therefore, it is of great significance to study the treatment technology of radioactive wastewater in reprocessing plants. The process flow and waste liquid types of the post-treatment plant are reviewed. The commonly used evaporation concentration, adsorption, precipitation, ion exchange, biotechnology, membrane separation, and photocatalysis are summarized. The basic principles and technological characteristics of them are introduced. The advantages and disadvantages of different single and combined processes are compared, and the development trend of future processing technology is prospected. Full article

(This article belongs to the Special Issue Wastewater Treatment: Functional Materials and Advanced Technology)

► Show Figures

Figure 1

40 pages, 5379 KiB

Open AccessReview

A Review on Polyacrylonitrile as an Effective and Economic Constituent of Adsorbents for Wastewater Treatment

by Archana Gupta, Vishal Sharma, Pawan Kumar Mishra and Adam Ekielski

Molecules 2022, 27(24), 8689; https://doi.org/10.3390/molecules27248689 - 8 Dec 2022

Cited by 16 | Viewed by 3855

Abstract

Water gets polluted due to the dumping of untreated industrial waste into bodies of water, particularly those containing heavy metals and dyes. Industrial water contains both inorganic and organic wastes. Numerous adsorbents that are inexpensive and easily available can be used to address [...] Read more.

Water gets polluted due to the dumping of untreated industrial waste into bodies of water, particularly those containing heavy metals and dyes. Industrial water contains both inorganic and organic wastes. Numerous adsorbents that are inexpensive and easily available can be used to address the issue of water deterioration. This review report is focused on polyacrylonitrile as an efficient constituent of adsorbents to extract toxic ions and dyes. It discusses the various formulations of polyacrylonitrile, such as ion exchange resins, chelating resins, fibers, membranes, and hydrogels, synthesized through different polymerization methods, such as suspension polymerization, electrospinning, grafting, redox, and emulsion polymerization. Moreover, regeneration of adsorbent and heavy metal ions makes the adsorption process more cost-effective and efficient. The literature reporting successful regeneration of the adsorbent is included. The factors affecting the performance and outcomes of the adsorption process are also discussed. Full article

(This article belongs to the Special Issue Wastewater Treatment: Functional Materials and Advanced Technology)

► Show Figures

Figure 1

29 pages, 2213 KiB

Open AccessReview

Interaction of Antibiotics and Humic Substances: Environmental Consequences and Remediation Prospects

by Natalia A. Kulikova, Alexandra A. Solovyova and Irina V. Perminova

Molecules 2022, 27(22), 7754; https://doi.org/10.3390/molecules27227754 - 10 Nov 2022

Cited by 13 | Viewed by 2703

Abstract

The occurrence and distribution of antibiotics in the environment has received increasing attention due to their potential adverse effects on human health and ecosystems. Humic substances (HS) influence the mobility, reactivity, and bioavailability of antibiotics in the environment significantly due to their interaction. [...] Read more.

The occurrence and distribution of antibiotics in the environment has received increasing attention due to their potential adverse effects on human health and ecosystems. Humic substances (HS) influence the mobility, reactivity, and bioavailability of antibiotics in the environment significantly due to their interaction. As a result, HS can affect the dissemination of antibiotic-resistance genes, which is one of the main problems arising from contamination with antibiotics. The review provides quantitative data on the binding of HS with fluoroquinolones, macrolides, sulfonamides, and tetracyclines and reports the proposed mechanisms of their interaction. The main issues of the quantification of antibiotic–HS interaction are discussed, which are a development of standard approaches and the accumulation of a dataset using a standard methodology. This would allow the implementation of a meta-analysis of data to reveal the patterns of the binding of antibiotics to HS. Examples of successful development of humic-based sorbents for fluoroquinolone and tetracycline removal from environmental water systems or polluted wastewaters were given. Data on the various effects of HS on the dissemination of antibiotic-resistance genes (ARGs) were summarized. The detailed characterization of HS properties as a key point of assessing the environmental consequences of the formation of antibiotic–HS complexes, such as the dissemination of antibiotic resistance, was proposed. Full article

(This article belongs to the Special Issue Wastewater Treatment: Functional Materials and Advanced Technology)

► Show Figures

Figure 1

Journal Menu

Journal Browser

Wastewater Treatment: Functional Materials and Advanced Technology

Share This Special Issue

Special Issue Editors

Special Issue Information

Keywords

Benefits of Publishing in a Special Issue

Related Special Issue

Published Papers (35 papers)

Editorial

Research

Review

Further Information

Guidelines

MDPI Initiatives

Follow MDPI