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24 pages, 2595 KiB

Open AccessArticle

Adsorption of Hexavalent Chromium Using Activated Carbon Produced from Sargassum ssp.: Comparison between Lab Experiments and Molecular Dynamics Simulations

by Yeray Alvarez-Galvan, Babak Minofar, Zdeněk Futera, Marckens Francoeur, Corine Jean-Marius, Nicolas Brehm, Christelle Yacou, Ulises J. Jauregui-Haza and Sarra Gaspard

Molecules 2022, 27(18), 6040; https://doi.org/10.3390/molecules27186040 - 16 Sep 2022

Cited by 10 | Viewed by 2639

Abstract

Adsorption is one of the most successful physicochemical approaches for removing heavy metal contaminants from polluted water. The use of residual biomass for the production of adsorbents has attracted a lot of attention due to its cheap price and environmentally friendly approach. The [...] Read more.

Adsorption is one of the most successful physicochemical approaches for removing heavy metal contaminants from polluted water. The use of residual biomass for the production of adsorbents has attracted a lot of attention due to its cheap price and environmentally friendly approach. The transformation of Sargassum—an invasive brown macroalga—into activated carbon (AC) via phosphoric acid thermochemical activation was explored in an effort to increase the value of Sargassum seaweed biomass. Several techniques (nitrogen adsorption, pH_PZC, Boehm titration, FTIR and XPS) were used to characterize the physicochemical properties of the activated carbons. The SAC600 3/1 was predominantly microporous and mesoporous (39.6% and 60.4%, respectively) and revealed a high specific surface area (1695 m²·g⁻¹). To serve as a comparison element, a commercial reference activated carbon with a large specific surface area (1900 m²·g⁻¹) was also investigated. The influence of several parameters on the adsorption capacity of AC was studied: solution pH, solution temperature, contact time and Cr(VI) concentration. The best adsorption capacities were found at very acid (pH 2) solution pH and at lower temperatures. The adsorption kinetics of SAC600 3/1 fitted well a pseudo-second-order type 1 model and the adsorption isotherm was better described by a Jovanovic-Freundlich isotherm model. Molecular dynamics (MD) simulations confirmed the experimental results and determined that hydroxyl and carboxylate groups are the most influential functional groups in the adsorption process of chromium anions. MD simulations also showed that the addition of MgCl₂ to the activated carbon surface before adsorption experiments, slightly increases the adsorption of HCrO₄⁻ and CrO₄²⁻ anions. Finally, this theoretical study was experimentally validated obtaining an increase of 5.6% in chromium uptake. Full article

(This article belongs to the Special Issue Activated Carbons—Production and Applications)

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22 pages, 3031 KiB

Open AccessArticle

The Use of High Surface Area Mesoporous-Activated Carbon from Longan Seed Biomass for Increasing Capacity and Kinetics of Methylene Blue Adsorption from Aqueous Solution

by Panuwat Lawtae and Chaiyot Tangsathitkulchai

Molecules 2021, 26(21), 6521; https://doi.org/10.3390/molecules26216521 - 28 Oct 2021

Cited by 38 | Viewed by 4196

Abstract

Microporous- and mesoporous-activated carbons were produced from longan seed biomass through physical activation with CO₂ under the same activation conditions of time and temperature. The specially prepared mesoporous carbon showed the maximum porous properties with the specific surface area of 1773 m [...] Read more.

Microporous- and mesoporous-activated carbons were produced from longan seed biomass through physical activation with CO₂ under the same activation conditions of time and temperature. The specially prepared mesoporous carbon showed the maximum porous properties with the specific surface area of 1773 m²/g and mesopore volume of 0.474 cm³/g which accounts for 44.1% of the total pore volume. These activated carbons were utilized as porous adsorbents for the removal of methylene blue (MB) from an aqueous solution and their effectiveness was evaluated for both the adsorption kinetics and capacity. The adsorption kinetic data of MB were analyzed by the pseudo-first-order model, the pseudo-second-order model, and the pore-diffusion model equations. It was found that the adsorption kinetic behavior for all carbons tested was best described by the pseudo-second-order model. The effective pore diffusivity (D_e) derived from the pore-diffusion model had the values of 4.657 × 10⁻⁷–6.014 × 10⁻⁷ cm²/s and 4.668 × 10⁻⁷–19.920 × 10⁻⁷ cm²/s for the microporous- and mesoporous-activated carbons, respectively. Three well-known adsorption models, namely the Langmuir, Freundlich and Redlich–Peterson equations were tested with the experimental MB adsorption isotherms, and the results showed that the Redlich–Peterson model provided the overall best fitting of the isotherm data. In addition, the maximum capacity for MB adsorption of 1000 mg/g was achieved with the mesoporous carbon having the largest surface area and pore volume. The initial pH of MB solution had virtually no effect on the adsorption capacity and removal efficiency of the methylene blue dye. Increasing temperature over the range from 35 to 55 °C increased the adsorption of methylene blue, presumably caused by the increase in the diffusion rate of methylene blue to the adsorption sites that could promote the interaction frequency between the adsorbent surface and the adsorbate molecules. Overall, the high surface area mesoporous carbon was superior to the microporous carbon in view of the adsorption kinetics and capacity, when both carbons were used for the removal of MB from an aqueous solution. Full article

(This article belongs to the Special Issue Activated Carbons—Production and Applications)

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9 pages, 1525 KiB

Open AccessArticle

Evaluation of Extraction Procedure of PCDD/Fs, PCBs and Chlorobenzenes from Activated Carbon Fibers (ACFs)

by Marina Cerasa, Ettore Guerriero and Silvia Mosca

Molecules 2021, 26(21), 6407; https://doi.org/10.3390/molecules26216407 - 23 Oct 2021

Cited by 5 | Viewed by 2143

Abstract

Active carbon-based sorbents are well known and are used in analytical chemistry. Activated carbon fibers (ACFs) are mainly used as abatement systems in industrial emission pollution control. The objective of this study was to extend the use of ACFs in analytical chemistry for [...] Read more.

Active carbon-based sorbents are well known and are used in analytical chemistry. Activated carbon fibers (ACFs) are mainly used as abatement systems in industrial emission pollution control. The objective of this study was to extend the use of ACFs in analytical chemistry for the analysis of polychlorodibenzo-p-dioxins (PCDDs), polychlorodibenzofurans (PCDFs), dioxin-like polychlorobiphenyls (PCBs), and chlorobenzenes (CBs). For this purpose, the extraction efficiency was evaluated based on the QA/QC criteria defined by EPA/ISO reference methods on ¹³C-standards recovery rates. The procedures tested were ultrasonic assisted extraction (UAE), Soxhlet extraction (SE), accelerated solvent extraction (ASE), and microwave-assisted extraction (MAE). Each experiment was performed in triplicate to ensure the repeatability of the results, and a second extraction assessed the complete extraction. The comparison of the results of each set of experiments with the minimum requirements of the reference methods for each class of compounds led to SE being chosen as the best technique. SE with toluene resulted in a reduction of time and costs and with respect to the other investigated techniques. The present work demonstrated that ACFs can be used in environmental fields means of both prevention and control (exploiting the adsorbent characteristics) and for analytical purposes (exploiting the desorption) for the described chlorinated classes of pollutants. Full article

(This article belongs to the Special Issue Activated Carbons—Production and Applications)

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26 pages, 6771 KiB

Open AccessArticle

The Analysis of Pore Development and Formation of Surface Functional Groups in Bamboo-Based Activated Carbon during CO₂ Activation

by Krittamet Phothong, Chaiyot Tangsathitkulchai and Panuwat Lawtae

Molecules 2021, 26(18), 5641; https://doi.org/10.3390/molecules26185641 - 17 Sep 2021

Cited by 34 | Viewed by 4490

Abstract

Pore development and the formation of oxygen functional groups were studied for activated carbon prepared from bamboo (Bambusa bambos) using a two-step activation with CO₂, as functions of carbonization temperature and activation conditions (time and temperature). Results show that [...] Read more.

Pore development and the formation of oxygen functional groups were studied for activated carbon prepared from bamboo (Bambusa bambos) using a two-step activation with CO₂, as functions of carbonization temperature and activation conditions (time and temperature). Results show that activated carbon produced from bamboo contains mostly micropores in the pore size range of 0.65 to 1.4 nm. All porous properties of activated carbons increased with the increase in the activation temperature over the range from 850 to 950 °C, but decreased in the temperature range of 950 to 1000 °C, due principally to the merging of neighboring pores. The increase in the activation time also increased the porous properties linearly from 60 to 90 min, which then dropped from 90 to 120 min. It was found that the carbonization temperature played an important role in determining the number and distribution of active sites for CO₂ gasification during the activation process. Empirical equations were proposed to conveniently predict all important porous properties of the prepared activated carbons in terms of carbonization temperature and activation conditions. Oxygen functional groups formed during the carbonization and activation steps of activated carbon synthesis and their contents were dependent on the preparation conditions employed. Using Boehm’s titration technique, only phenolic and carboxylic groups were detected for the acid functional groups in both the chars and activated carbons in varying amounts. Empirical correlations were also developed to estimate the total contents of the acid and basic groups in activated carbons in terms of the carbonization temperature, activation time and temperature. Full article

(This article belongs to the Special Issue Activated Carbons—Production and Applications)

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15 pages, 3728 KiB

Open AccessArticle

Experimental and Theoretical Insights on Methylene Blue Removal from Wastewater Using an Adsorbent Obtained from the Residues of the Orange Industry

by Stephanie Giraldo, Irma Robles, Luis A. Godínez, Nancy Acelas and Elizabeth Flórez

Molecules 2021, 26(15), 4555; https://doi.org/10.3390/molecules26154555 - 28 Jul 2021

Cited by 49 | Viewed by 3031

Abstract

Chemical and thermochemical transformations were performed on orange peel to obtain materials that were characterized and further tested to explore their potential as adsorbents for the removal of methylene blue (MB) from aqueous solutions. The results show the high potential of some of [...] Read more.

Chemical and thermochemical transformations were performed on orange peel to obtain materials that were characterized and further tested to explore their potential as adsorbents for the removal of methylene blue (MB) from aqueous solutions. The results show the high potential of some of these materials for MB adsorption not only due to the surface area of the resulting substrate but also to the chemistry of the corresponding surface functional groups. Fitting of the kinetic as well as the equilibrium experimental data to different models suggests that a variety of interactions are involved in MB adsorption. The overall capacities for these substrates (larger than 192.31 mg g⁻¹) were found to compare well with those reported for activated carbon and other adsorbents of agro-industrial origin. According to these results and complementary with theoretical study using Density Functional Theory (DFT) approximations, it was found that the most important adsorption mechanisms of MB correspond to: (i) electrostatic interactions, (ii) H-bonding, and (iii) π (MB)–π (biochar) interactions. In view of these findings, it can be concluded that adsorbent materials obtained from orange peel, constitute a good alternative for the removal of MB dye from aqueous solutions. Full article

(This article belongs to the Special Issue Activated Carbons—Production and Applications)

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14 pages, 9647 KiB

Open AccessArticle

Enhancing the Decolorization of Methylene Blue Using a Low-Cost Super-Absorbent Aided by Response Surface Methodology

by Nor Hakimin Abdullah, Mazlan Mohamed, Norshahidatul Akmar Mohd Shohaimi, Azwan Mat Lazim, Ahmad Zamani Abdul Halim, Nurasmat Mohd Shukri and Mohammad Khairul Azhar Abdul Razab

Molecules 2021, 26(15), 4430; https://doi.org/10.3390/molecules26154430 - 22 Jul 2021

Cited by 9 | Viewed by 2880

Abstract

The presence of organic dyes from industrial wastewater can cause pollution and exacerbate environmental problems; therefore, in the present work, activated carbon was synthesized from locally available oil palm trunk (OPT) biomass as a low-cost adsorbent to remove synthetic dye from aqueous media. [...] Read more.

The presence of organic dyes from industrial wastewater can cause pollution and exacerbate environmental problems; therefore, in the present work, activated carbon was synthesized from locally available oil palm trunk (OPT) biomass as a low-cost adsorbent to remove synthetic dye from aqueous media. The physical properties of the synthesized oil palm trunk activated carbon (OPTAC) were analyzed by SEM, FTIR-ATR, and XRD. The concurrent effects of the process variables (adsorbent dosage (g), methylene blue (MB) concentration (mg/L), and contact time (h)) on the MB removal percentage from aqueous solution were studied using a three-factor three-level Box–Behnken design (BBD) of response surface methodology (RSM), followed by the optimization of MB adsorption using OPTAC as the adsorbent. Based on the results of the analysis of variance (ANOVA) for the three parameters considered, adsorbent dosage (X₁) is the most crucial parameter, with an F-value of 1857.43, followed by MB concentration (X₂) and contact time (X₃) with the F-values of 95.60 and 29.48, respectively. Furthermore, the highest MB removal efficiency of 97.9% was achieved at the optimum X₁, X₂, and X₃ of 1.5 g, 200 mg/L, and 2 h, respectively. Full article

(This article belongs to the Special Issue Activated Carbons—Production and Applications)

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19 pages, 4112 KiB

Open AccessArticle

Process Optimization and Modeling of Phenol Adsorption onto Sludge-Based Activated Carbon Intercalated MgAlFe Ternary Layered Double Hydroxide Composite

by Nuhu Dalhat Mu’azu, Mukarram Zubair and Ihsanullah Ihsanullah

Molecules 2021, 26(14), 4266; https://doi.org/10.3390/molecules26144266 - 14 Jul 2021

Cited by 9 | Viewed by 2470

Abstract

A sewage sludge-based activated carbon (SBAC) intercalated MgAlFe ternary layered double hydroxide (SBAC-MgAlFe-LDH) composite was synthesized via the coprecipitation method. The adsorptive performance of the composite for phenol uptake from the aqueous phase was evaluated via the response surface methodology (RSM) modeling technique. [...] Read more.

A sewage sludge-based activated carbon (SBAC) intercalated MgAlFe ternary layered double hydroxide (SBAC-MgAlFe-LDH) composite was synthesized via the coprecipitation method. The adsorptive performance of the composite for phenol uptake from the aqueous phase was evaluated via the response surface methodology (RSM) modeling technique. The SBAC-MgAlFe-LDH phenol uptake capacity data were well-fitted to reduced RSM cubic model (R² = 0.995, R²-adjusted = 0.993, R²-predicted = 0.959 and p-values < 0.05). The optimum phenol adsorption onto the SBAC-MgAlFe-LDH was achieved at 35 °C, 125 mg/L phenol, and pH 6. Under the optimal phenol uptake conditions, pseudo-first-order and Avrami fractional-order models provided a better representation of the phenol uptake kinetic data, while the equilibrium data models’ fitting follows the order; Liu > Langmuir > Redlich–Peterson > Freundlich > Temkin. The phenol uptake mechanism was endothermic in nature and predominantly via a physisorption process (ΔG° = −5.33 to −5.77 kJ/mol) with the involvement of π–π interactions between the phenol molecules and the functionalities on the SBAC-LDH surface. The maximum uptake capacity (216.76 mg/g) of SBAC-MgAlFe-LDH was much higher than many other SBAC-based adsorbents. The improved uptake capacity of SBAC-LDH was attributed to the effective synergetic influence of SBAC-MgAlFe-LDH, which yielded abundant functionalized surface groups that favored higher aqueous phase uptake of phenol molecules. This study showcases the potential of SBAC-MgAlFe-LDH as an effective adsorbent material for remediation of phenolic wastewater Full article

(This article belongs to the Special Issue Activated Carbons—Production and Applications)

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14 pages, 4815 KiB

Open AccessArticle

Enhanced Electrochemical Performance of Supercapacitors via Atomic Layer Deposition of ZnO on the Activated Carbon Electrode Material

by Chongrui Wu, Fuming Zhang, Xiangshang Xiao, Junyan Chen, Junqi Sun, Dayakar Gandla, Yair Ein-Eli and Daniel Q. Tan

Molecules 2021, 26(14), 4188; https://doi.org/10.3390/molecules26144188 - 9 Jul 2021

Cited by 12 | Viewed by 3140

Abstract

Fabricating electrical double-layer capacitors (EDLCs) with high energy density for various applications has been of great interest in recent years. However, activated carbon (AC) electrodes are restricted to a lower operating voltage because they suffer from instability above a threshold potential window. Thus, [...] Read more.

Fabricating electrical double-layer capacitors (EDLCs) with high energy density for various applications has been of great interest in recent years. However, activated carbon (AC) electrodes are restricted to a lower operating voltage because they suffer from instability above a threshold potential window. Thus, they are limited in their energy storage. The deposition of inorganic compounds’ atomic layer deposition (ALD) aiming to enhance cycling performance of supercapacitors and battery electrodes can be applied to the AC electrode materials. Here, we report on the investigation of zinc oxide (ZnO) coating strategy in terms of different pulse times of precursors, ALD cycles, and deposition temperatures to ensure high electrical conductivity and capacitance retention without blocking the micropores of the AC electrode. Crystalline ZnO phase with its optimal forming condition is obtained preferably using a longer precursor pulse time. Supercapacitors comprising AC electrodes coated with 20 cycles of ALD ZnO at 70 °C and operated in TEABF₄/acetonitrile organic electrolyte show a specific capacitance of 23.13 F g⁻¹ at 5 mA cm⁻² and enhanced capacitance retention at 3.2 V, which well exceeds the normal working voltage of a commercial EDLC product (2.7 V). This work delivers an additional feasible approach of using ZnO ALD modification of AC materials, enhancing and promoting stable EDLC cells under high working voltages. Full article

(This article belongs to the Special Issue Activated Carbons—Production and Applications)

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14 pages, 21475 KiB

Open AccessArticle

Green Synthesized Silver Nanoparticles Immobilized on Activated Carbon Nanoparticles: Antibacterial Activity Enhancement Study and Its Application on Textiles Fabrics

by Pratama Jujur Wibawa, Muhammad Nur, Mukhammad Asy’ari, Wijanarka Wijanarka, Heru Susanto, Heri Sutanto and Hadi Nur

Molecules 2021, 26(13), 3790; https://doi.org/10.3390/molecules26133790 - 22 Jun 2021

Cited by 15 | Viewed by 3864

Abstract

This research aimed to enhance the antibacterial activity of silver nanoparticles (AgNPs) synthesized from silver nitrate (AgNO₃) using aloe vera extract. It was performed by means of incorporating AgNPs on an activated carbon nanoparticle (ACNPs) under ultrasonic agitation (40 kHz, 2 [...] Read more.

This research aimed to enhance the antibacterial activity of silver nanoparticles (AgNPs) synthesized from silver nitrate (AgNO₃) using aloe vera extract. It was performed by means of incorporating AgNPs on an activated carbon nanoparticle (ACNPs) under ultrasonic agitation (40 kHz, 2 × 50 watt) for 30 min in an aqueous colloidal medium. The successful AgNPs synthesis was clarified with both Ultraviolet-Visible (UV-Vis) and Fourier Transform Infrared (FTIR) spectrophotometers. The successful AgNPs–ACNPs incorporation and its particle size analysis was performed using Transmission Electron Microscope (TEM). The brown color suspension generation and UV-Vis’s spectra maximum wavelength at around 480 nm confirmed the existence of AgNPs. The particle sizes of the produced AgNPs were about 5 to 10 nm in the majority number, which collectively surrounded the aloe vera extract secondary metabolites formed core-shell like nanostructure of 8.20 ± 2.05 nm in average size, while ACNPs themselves were about 20.10 ± 1.52 nm in average size formed particles cluster, and 48.00 ± 8.37 nm in average size as stacking of other particles. The antibacterial activity of the synthesized AgNPs and AgNPs-immobilized ACNPs was 57.58% and 63.64%, respectively (for E. coli); 61.25%, and 93.49%, respectively (for S. aureus). In addition, when the AgNPs-immobilized ACNPs material was coated on the cotton and polyester fabrics, the antibacterial activity of the materials changed, becoming 19.23% (cotton; E. coli), 31.73% (polyester; E. coli), 13.36% (cotton; S. aureus), 21.15% (polyester; S. aureus). Full article

(This article belongs to the Special Issue Activated Carbons—Production and Applications)

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16 pages, 2362 KiB

Open AccessArticle

Evaluating the Removal of the Antibiotic Cephalexin from Aqueous Solutions Using an Adsorbent Obtained from Palm Oil Fiber

by Nancy Acelas, Sandra M. Lopera, Jazmín Porras and Ricardo A. Torres-Palma

Molecules 2021, 26(11), 3340; https://doi.org/10.3390/molecules26113340 - 2 Jun 2021

Cited by 33 | Viewed by 3694

Abstract

This study aimed to understand the adsorption process of cephalexin (CPX) from aqueous solution by a biochar produced from the fiber residue of palm oil. Scanning electron microscopy, Fourier transform infrared spectroscopy, Boehm titration, and the point of zero charge were used to [...] Read more.

This study aimed to understand the adsorption process of cephalexin (CPX) from aqueous solution by a biochar produced from the fiber residue of palm oil. Scanning electron microscopy, Fourier transform infrared spectroscopy, Boehm titration, and the point of zero charge were used to characterize the morphology and surface functional groups of the adsorbent. Batch tests were carried out to evaluate the effects of the solution pH, temperature, and antibiotic structure. The adsorption behavior followed the Langmuir model and pseudo-second-order model with a maximum CPX adsorption capacity of 57.47 mg g⁻¹. Tests on the thermodynamic behavior suggested that chemisorption occurs with an activation energy of 91.6 kJ mol⁻¹ through a spontaneous endothermic process. Electrostatic interactions and hydrogen bonding represent the most likely adsorption mechanisms, although π–π interactions also appear to contribute. Finally, the CPX removal efficiency of the adsorbent was evaluated for synthetic matrices of municipal wastewater and urine. Promising results were obtained, indicating that this adsorbent can potentially be applied to purifying wastewater that contains trace antibiotics. Full article

(This article belongs to the Special Issue Activated Carbons—Production and Applications)

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15 pages, 3995 KiB

Open AccessArticle

Efficient Adsorption of Methylene Blue by Porous Biochar Derived from Soybean Dreg Using a One-Pot Synthesis Method

by Zhiwei Ying, Xinwei Chen, He Li, Xinqi Liu, Chi Zhang, Jian Zhang and Guofu Yi

Molecules 2021, 26(3), 661; https://doi.org/10.3390/molecules26030661 - 27 Jan 2021

Cited by 41 | Viewed by 3676

Abstract

Soybean dreg is a by-product of soybean products production, with a large consumption in China. Low utilization value leads to random discarding, which is one of the important sources of urban pollution. In this work, porous biochar was synthesized using a one-pot method [...] Read more.

Soybean dreg is a by-product of soybean products production, with a large consumption in China. Low utilization value leads to random discarding, which is one of the important sources of urban pollution. In this work, porous biochar was synthesized using a one-pot method and potassium bicarbonate (KHCO₃) with low-cost soybean dreg (SD) powder as the carbon precursor to investigating the adsorption of methylene blue (MB). The prepared samples were characterized with scanning electron microscopy (SEM), transmission electron microscopy (TEM), elemental analyzer (EA), Brunauer-Emmett-Teller (BET), X-ray diffractometer (XRD), Raman spectroscopy (Raman), Fourier transform infrared spectrometer (FTIR), and X-ray photoelectron spectroscopy (XPS). The obtained SDB-K-3 showed a high specific surface area of 1620 m² g⁻¹, a large pore volume of 0.7509 cm³ g⁻¹, and an average pore diameter of 1.859 nm. The results indicated that the maximum adsorption capacity of SDB-K-3 to MB could reach 1273.51 mg g⁻¹ at 318 K. The kinetic data were most consistent with the pseudo-second-order model and the adsorption behavior was more suitable for the Langmuir isotherm equation. This study demonstrated that the porous biochar adsorbent can be prepared from soybean dreg by high value utilization, and it could hold significant potential for dye wastewater treatment in the future. Full article

(This article belongs to the Special Issue Activated Carbons—Production and Applications)

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15 pages, 4243 KiB

Open AccessArticle

Adsorption Characteristics of Activated Carbon for the Reclamation of Eosin Y and Indigo Carmine Colored Effluents and New Isotherm Model

by Ratna Surya Alwi, Ramakrishnan Gopinathan, Avijit Bhowal and Chandrasekhar Garlapati

Molecules 2020, 25(24), 6014; https://doi.org/10.3390/molecules25246014 - 18 Dec 2020

Cited by 11 | Viewed by 2497

Abstract

The adsorption response of eosin Y and indigo carmine acid dyes on activated carbon as a function of system temperature for a fixed concentration was investigated at various temperatures via adsorption isotherms and their thermodynamic quantities such as enthalpy, entropy, and Gibbs free [...] Read more.

The adsorption response of eosin Y and indigo carmine acid dyes on activated carbon as a function of system temperature for a fixed concentration was investigated at various temperatures via adsorption isotherms and their thermodynamic quantities such as enthalpy, entropy, and Gibbs free energy changes. The adsorption data were exploited to develop a new adsorption isotherm. The new isotherm was developed with the spirit of solid–liquid phase equilibrium and regular solution theory. The proposed model has four adjustable constants and correlates adsorption isotherm in terms of the system temperature and melting temperature of the dye. The effect of pH on the removal of acid dyes was reported. The pH variation was observed to affect the adsorption efficiency. The removal of eosin Y and indigo carmine decreased from 99.4% to 82.6% and 92.38% to 79.48%, respectively, when the pH of the solution varied from 2 to 12. The thermodynamic analysis of the process reveals that the process of the removal of acid dyes is exothermic and spontaneous. Moreover, the kinetics parameters of the batch process are reported. Full article

(This article belongs to the Special Issue Activated Carbons—Production and Applications)

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15 pages, 14057 KiB

Open AccessArticle

Preparation and Characterization of MgO-Modified Rice Straw Biochars

by Xianxian Qin, Jixin Luo, Zhigao Liu and Yunlin Fu

Molecules 2020, 25(23), 5730; https://doi.org/10.3390/molecules25235730 - 4 Dec 2020

Cited by 23 | Viewed by 2913

Abstract

Rice straw is a common agricultural waste. In order to increase the added value of rice straw and improve the performance of rice straw biochar. MgO-modified biochar (MRBC) was prepared from rice straw at different temperatures, pyrolysis time and MgCl₂ concentrations. The [...] Read more.

Rice straw is a common agricultural waste. In order to increase the added value of rice straw and improve the performance of rice straw biochar. MgO-modified biochar (MRBC) was prepared from rice straw at different temperatures, pyrolysis time and MgCl₂ concentrations. The microstructure, chemical and crystal structure were studied using X-ray diffraction (XRD), a Scanning Electron Microscope (SEM), Fourier transform infrared spectroscopy (FTIR), nitrogen adsorption desorption isotherms and Elementary Analysis (EA). The results showed that the pyrolysis temperature had significant influence on the structure and physicochemical property of MRBCs. MRBC-2 h has the richest microporous structure while MRBC-2 m has the richest mesoporous structure. The specific surface area (from 9.663 to 250.66 m²/g) and pore volume (from 0.042 to 0.158 cm³/g) of MRBCs increased as temperature rose from 300 to 600 °C. However, it was observed MgCl₂ concentrations and pyrolysis time had no significant influence on pore structure of MRBCs. As pyrolysis temperature increased, pH increased and more oxygen-containing functional groups and mineral salts were formed, while MgO-modified yield, volatile matter, total content of hydrogen, oxygen, nitrogen, porosity and average pore diameter decreased. In addition, MRBCs formed at high temperature showed high C content with a low O/C and H/C ratios. Full article

(This article belongs to the Special Issue Activated Carbons—Production and Applications)

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35 pages, 24223 KiB

Open AccessArticle

Activated Carbon from Agricultural Wastes for Adsorption of Organic Pollutants

by Magdalena Blachnio, Anna Derylo-Marczewska, Barbara Charmas, Malgorzata Zienkiewicz-Strzalka, Viktor Bogatyrov and Mariia Galaburda

Molecules 2020, 25(21), 5105; https://doi.org/10.3390/molecules25215105 - 3 Nov 2020

Cited by 51 | Viewed by 5909

Abstract

Agricultural waste materials (strawberry seeds and pistachio shells) were used for preparation of activated carbons by two various methods. Chemical activation using acetic acid and physical activation with gaseous agents (carbon dioxide and water vapor) were chosen as mild and environmentally friendly methods. [...] Read more.

Agricultural waste materials (strawberry seeds and pistachio shells) were used for preparation of activated carbons by two various methods. Chemical activation using acetic acid and physical activation with gaseous agents (carbon dioxide and water vapor) were chosen as mild and environmentally friendly methods. The effect of type of raw material, temperature, and activation agent on the porous structure characteristics of the materials was discussed applying various methods of analysis. The best obtained activated carbons were characterized by high values of specific surface area (555–685 m²/g). The Guinier analysis of small-angle X-ray scattering (SAXS) curves showed that a time of activation affects pore size. The samples activated using carbon dioxide were characterized mostly by the spherical morphology of pores. Adsorbents were utilized for removal of the model organic pollutants from the single- and multicomponent systems. The adsorption capacities for the 4-chloro-2-methyphenoxyacetic acid (MCPA) removal were equal to 1.43–1.56 mmol/g; however, for adsorbent from strawberry seeds it was much lower. Slight effect of crystal violet presence on the MCPA adsorption and inversely was noticed as a result of adsorption in different types of pores. For similar herbicides strong competition in capacity and adsorption rate was observed. For analysis of kinetic data various equations were used. Full article

(This article belongs to the Special Issue Activated Carbons—Production and Applications)

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18 pages, 3504 KiB

Open AccessArticle

Preparation and Characterisation of Activated Carbon from Palm Mixed Waste Treated with Trona Ore

by Kalu Samuel Ukanwa, Kumar Patchigolla, Ruben Sakrabani and Edward Anthony

Molecules 2020, 25(21), 5028; https://doi.org/10.3390/molecules25215028 - 29 Oct 2020

Cited by 17 | Viewed by 3159

Abstract

This study explores the use of a novel activating agent and demonstrates the production and characterisation of activated carbon (AC) from a combine palm waste (CPW) in 3:2:1 proportion by weight of empty fruit bunch, mesocarp fibre and palm kernel shell. The resulting [...] Read more.

This study explores the use of a novel activating agent and demonstrates the production and characterisation of activated carbon (AC) from a combine palm waste (CPW) in 3:2:1 proportion by weight of empty fruit bunch, mesocarp fibre and palm kernel shell. The resulting biomass was processed by a microwave-assisted method using trona and compared with material produced by conventional routes. These results demonstrate the potential of trona ore as an activating agent and the effectiveness of using a combined palm waste for a single stream activation process. It also assesses the effectiveness of trona ore in the elimination of alcohol, acids and aldehydes; with a focus on increasing the hydrophilicity of the resultant AC. The optimum results for the conventional production technique at 800 °C yielded a material with S_BET 920 m²/g, V_total 0.840 cm³/g, a mean pore diameter of 2.2 nm and an AC yield 40%. The optimum outcome of the microwave assisted technique for CPW was achieved at 600 W, S_BET is 980 m²/g; V_total 0.865 cm³/g; a mean pore diameter 2.2 nm and an AC yield of 42%. Fourier transform infrared spectrometry analyses showed that palm waste can be combined to produce AC and that trona ore has the capacity to significantly enhance biomass activation. Full article

(This article belongs to the Special Issue Activated Carbons—Production and Applications)

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18 pages, 4541 KiB

Open AccessArticle

Sulfamethoxazole Removal from Drinking Water by Activated Carbon: Kinetics and Diffusion Process

by Mohamed BIZI

Molecules 2020, 25(20), 4656; https://doi.org/10.3390/molecules25204656 - 13 Oct 2020

Cited by 24 | Viewed by 4825

Abstract

Sulfamethoxazole (SMX), a pharmaceutical residue, which is persistent and mobile in soils, shows low biodegradability, and is frequently found in the different aquatic compartments, can be found at very low concentrations in water intended for human consumption. In conditions compatible with industrial practices, [...] Read more.

Sulfamethoxazole (SMX), a pharmaceutical residue, which is persistent and mobile in soils, shows low biodegradability, and is frequently found in the different aquatic compartments, can be found at very low concentrations in water intended for human consumption. In conditions compatible with industrial practices, the kinetic reactivity and performance of tap water purification using activated carbon powder (ACP) are examined here using two extreme mass ratios of SMX to ACP: 2 µg/L and 2 mg/L of SMX for only 10 mg/L of ACP. In response to surface chemistry, ACP texture and the intrinsic properties of SMX in water at a pH of 8.1, four kinetic models, and two monosolute equilibrium models showed a total purification of the 2 µg/L of SMX, the presence of energetic heterogeneity of surface adsorption of ACP, rapid kinetics compatible with the residence times of industrial water treatment processes, and kinetics affected by intraparticle diffusion. The adsorption mechanisms proposed are physical mechanisms based mainly on π–π dispersion interactions and electrostatic interactions by SMX⁻/Divalent cation/ArO⁻ and SMX⁻/Divalent cation/ArCOO⁻ bridging. Adsorption in tap water, also an innovative element of this study, shows that ACP is very efficient for the purification of very slightly polluted water. Full article

(This article belongs to the Special Issue Activated Carbons—Production and Applications)

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Chemical Activation of Lignocellulosic Precursors and Residues: What Else to Consider?

by Juan Alcañiz-Monge, María del Carmen Román-Martínez and María Ángeles Lillo-Ródenas

Molecules 2022, 27(5), 1630; https://doi.org/10.3390/molecules27051630 - 1 Mar 2022

Cited by 27 | Viewed by 3629

Abstract

This paper provides the basis for understanding the preparation and properties of an old, but advanced material: activated carbon. The activated carbons discussed herein are obtained from “green” precursors: biomass residues. Accordingly, the present study starts analyzing the components of biomass residues, such [...] Read more.

This paper provides the basis for understanding the preparation and properties of an old, but advanced material: activated carbon. The activated carbons discussed herein are obtained from “green” precursors: biomass residues. Accordingly, the present study starts analyzing the components of biomass residues, such as cellulose, hemicellulose, and lignin, and the features that make them suitable raw materials for preparing activated carbons. The physicochemical transformations of these components during their heat treatment that lead to the development of a carbonized material, a biochar, are also considered. The influence of the chemical activation experimental conditions on the yield and porosity development of the final activated carbons are revised as well, and compared with those for physical activation, highlighting the physicochemical interactions between the activating agents and the lignocellulosic components. This review incorporates a comprehensive discussion about the surface chemistry that can be developed as a result of chemical activation and compiles some results related to the mechanical properties and conformation of activated carbons, scarcely analyzed in most published papers. Finally, economic, and environmental issues involved in the large-scale preparation of activated carbons by chemical activation of lignocellulosic precursors are commented on as well. Full article

(This article belongs to the Special Issue Activated Carbons—Production and Applications)

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