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Feature Paper Collection in Section 'Materials in Separation Science'
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Feature Paper Collection in Section 'Materials in Separation Science'

A topical collection in Separations (ISSN 2297-8739). This collection belongs to the section "Materials in Separation Science".

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Editors

Dr. Dimosthenis Giokas

E-Mail Website
Collection Editor
Department of Chemistry, University of Ioannina, 45110 Ioannina, Greece
Interests: sample preparation; extraction and microextraction; HPLC; nanomaterials for separation processes; environmental analysis; environmental remediation; sorbent-based remediation; separation/extraction of nanomaterials
Special Issues, Collections and Topics in MDPI journals
Dr. Manolis Manos

E-Mail Website
Collection Editor
1. Department of Chemistry, University of Ioannina, 45110 Ioannina, Greece
2. Institute of Materials Science and Computing, University Research Center of Ioannina, 45110 Ioannina, Greece
Interests: crystal structure; metal organic framework; materials; single crystal X-ray diffraction; material characterization; structure determination; Inorganic materials; hydrothermal synthesis; solid state synthesis; coordination chemistry

Topical Collection Information

Dear Colleagues,

It is our pleasure to invite you to submit an article to the Topical Collection “Materials for Environmental Separations” launched by Separations.

This Topical Collection aims to gather high-quality original research and critical review articles on new materials or novel uses of micro-/nanomaterials for separations for environmental applications. Such applications include, but are not limited to, water purification, soil/sediment remediation, wastewater treatment, recovery of precious metals and nanomaterials, removal of viruses/bacteria, sorption of toxic gases, oil removal, etc. The articles should demonstrate the practical utilization of the materials at least in proof-of-concept demonstrations or lab-scale investigations and ideally in pilot testing, case studies, or large-scale applications. Contributions related to highly selective sorbents, broad-spectrum sorbents with multifunctional sorption properties, nanosorbents supported onto bulk supports, stand-alone separation techniques, and sorbent-based techniques suitable for the uptake of nanoparticles and micro-/nanoplastics, are particularly encouraged. 

The Topical Collection also welcomes review papers on timely topics that provide a critical evaluation of the state of the art in this specific field, discuss current challenges, and focus on future perspectives for further development. Short communications reporting preliminary but promising results are also within the scope of the Topical Collection. All manuscripts considered for publication will undergo a peer-review process by experts in the field to ensure the high quality of published papers.

Dr. Dimosthenis Giokas
Dr. Manolis Manos
Collection Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the collection website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Separations is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • micro-/nanomaterials
  • environmental restoration
  • chemical and biological pollution
  • water and wastewater treatment
  • removal of emerging pollutants
  • selective sorbents
  • broad-spectrum sorbents
  • supported sorbents

Published Papers (8 papers)

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2024

Jump to: 2023, 2022

12 pages, 3019 KiB  
Article
A Cyanoalkyl Silicone GC Stationary-Phase Polymer as an Extractant for Dispersive Liquid–Liquid Microextraction
by Mohamed A. Abdelaziz and Neil D. Danielson
Separations 2024, 11(1), 18; https://doi.org/10.3390/separations11010018 - 5 Jan 2024
Viewed by 1819
Abstract
In this work, three cyanoalkyl silicone GC stationary-phase polymers, namely OV-105, OV-225, and OV-275, were investigated as potential extractants for dispersive liquid–liquid microextraction (DLLME). The OV-225 polymer (cyanopropylmethyl-phenylmethylsilicone) exhibited the cleanest chromatographic background and was extensively studied. The proposed polymer was tested through [...] Read more.
In this work, three cyanoalkyl silicone GC stationary-phase polymers, namely OV-105, OV-225, and OV-275, were investigated as potential extractants for dispersive liquid–liquid microextraction (DLLME). The OV-225 polymer (cyanopropylmethyl-phenylmethylsilicone) exhibited the cleanest chromatographic background and was extensively studied. The proposed polymer was tested through the DLLME of four non-steroidal anti-inflammatory drugs from aqueous samples, followed by HPLC separation with UV detection at 230 nm. To achieve the maximum enrichment, the experimental conditions that influence the DLLME process were optimized using one-factor-at-a-time and design-of-experiment (DoE) approaches. The extraction variables (polymer mass, dispersive solvent volume, buffer pH, and mixing time) were screened by implementing a two-level full factorial design (FFD). Significant variables were fine-tuned using response surface methodology based on a face-centered central composite design (CCD). The optimum conditions were 10 mg of polymer (extraction medium); 50 µL of tetrahydrofuran (dispersive solvent); 100 µL of phosphate buffer pH 2.75 ([PO43−] = 100 mM); and 3 min of vortex mixing. The addition of salt had a minimal effect on the enrichment factors. In the optimum conditions, enrichment factors up to 46 were achieved using 1.5 mL samples. Calibration curves exhibited correlation coefficients > 0.999 using 4-pentylbenzoic acid as an internal standard. The limits of quantitation were 5 ng/mL for naproxen, 10 ng/mL for diflunisal, 25 ng/mL for indomethacin, and 75 ng/mL for ibuprofen. The analysis of spiked tap water samples showed adequate relative recoveries and precision. In conclusion, the proposed polymer (OV-225) is a potential greener alternative to traditional organic extractants used in DLLME. Full article
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2023

Jump to: 2024, 2022

15 pages, 4074 KiB  
Article
Upcycling Textile White Mud to Fabricate MIL-125-Derived Amorphous TiO2@C: Effective Electrocatalyst for Cathodic Reduction of Antibiotics
by Jinmei Zhu, Xiaofei Wen, Yuanhui Feng, Shuaibing Ren, Zimo Lou and Jiansheng Li
Separations 2023, 10(12), 580; https://doi.org/10.3390/separations10120580 - 23 Nov 2023
Viewed by 1686
Abstract
Cathodic reduction is a green and promising remediation strategy for reducing the antibacterial activity of antibiotic contaminants and increasing their biodegradability. However, the lack of cost-effective electrocatalysts has restricted its application. In this study, we upcycled textile white mud by separating 1,4-dicarboxybenzene (BDC) [...] Read more.
Cathodic reduction is a green and promising remediation strategy for reducing the antibacterial activity of antibiotic contaminants and increasing their biodegradability. However, the lack of cost-effective electrocatalysts has restricted its application. In this study, we upcycled textile white mud by separating 1,4-dicarboxybenzene (BDC) and fabricating MIL-125(Ti)-derived amorphous TiO2@C (TiO2@C-W) as a functional electrocatalyst. The separated BDC from white mud shows lower crystallinity than BDC chemicals, but the resulting TiO2@C-W features a much higher degree of oxygen vacancies and a 25-fold higher specific surface area than that of TiO2@C derived from BDC chemicals. With florfenicol (FLO) as a probe, TiO2@C-W exhibits similar cathodic reductive activity (0.017 min−1) as commercial Pd(3 wt.%)/C (0.018 min−1) does, which was 1.4 and 3.7 times higher than that of oxygen vacancy-engineered TiO2 and TiO2@C, respectively. The as-fabricated TiO2@C-W could not easily remove FLO via the oxygen reduction reaction-based pathway with the applied bias for cathodic reduction. Though the activity of TiO2@C-W undergoes a slight decline with continuous running, more than 80% of 20 mg L−1 FLO can still be reduced in the eighth run. Water chemistry studies suggest that a lower initial solution pH boosts the cathodic reduction process, while common co-existing anions such as Cl−, NO3−, HCO3−, and SO32− show a limited negative impact. Finally, TiO2@C-W shows reductive activity against several representative antibiotics, including nitrofurazone, metronidazole, and levofloxacin, clarifying its potential scope of application for antibiotics (e.g., molecules with structures like furan rings, nitro groups, and halogens). This study couples the upcycling of textile white mud with the remediation of antibiotics by developing functional electrocatalysts, and offers new insights for converting wastes from the printing and dyeing industry into value-added products. Full article
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17 pages, 6478 KiB  
Article
Fenton Oxidation Combined with Iron–Carbon Micro-Electrolysis for Treating Leachate Generated from Thermally Treated Sludge
by Xiaoqing Dong, Hui Liu, Ji Li, Ruiqi Gan, Quanze Liu and Xiaolei Zhang
Separations 2023, 10(11), 568; https://doi.org/10.3390/separations10110568 - 14 Nov 2023
Cited by 1 | Viewed by 1704
Abstract
In this study, Iron–Carbon Micro-Electrolysis (ICME), Fenton oxidation, and their combination were investigated to treat the leachate obtained from a wastewater treatment plant located in southern China. The results show that the Fenton-ICME process was the most efficient one. After the leachate was [...] Read more.
In this study, Iron–Carbon Micro-Electrolysis (ICME), Fenton oxidation, and their combination were investigated to treat the leachate obtained from a wastewater treatment plant located in southern China. The results show that the Fenton-ICME process was the most efficient one. After the leachate was treated with the Fenton-ICME process, the COD concentration was reduced from the initial 35,772 mg/L to 13,522 mg/L, and the removal efficiency was up to 62.2%. In addition, the biological oxygen demand (BOD) to COD ratio increased by 40% at optimal conditions. This suggests that the biodegradability of the leachate has been increased, facilitating the biodegradation of the leachate after it is mixed with the raw wastewater. By studying the characteristic variation of the leachate treated with the Fenton-ICME process, it was found that the combined process mainly removes organic compounds such as aromatic compounds, ketones, and aldehydes. The separated sludge does not have a crystalline structure, and the iron in it mainly exists in the form of trivalent iron. It reveals that the Fenton-ICME process has great potential to be used as a pretreatment of leachate. Full article
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26 pages, 2281 KiB  
Review
Advancements in Adsorption Techniques for Sustainable Water Purification: A Focus on Lead Removal
by Amal M. Badran, Uthumporn Utra, Nor Shariffa Yussof and Mohammed J. K. Bashir
Separations 2023, 10(11), 565; https://doi.org/10.3390/separations10110565 - 10 Nov 2023
Cited by 18 | Viewed by 7835
Abstract
The long-term sustainability of the global water supply, with a paramount emphasis on cleanliness and safety, stands as a formidable challenge in our modern era. In response to this pressing issue, adsorption techniques have emerged as pivotal and widely recognized solutions for the [...] Read more.
The long-term sustainability of the global water supply, with a paramount emphasis on cleanliness and safety, stands as a formidable challenge in our modern era. In response to this pressing issue, adsorption techniques have emerged as pivotal and widely recognized solutions for the removal of hazardous pollutants, with a particular emphasis on lead adsorption from wastewater. This comprehensive review explores the relentless advancements made in the adsorption domain, highlighting innovations using separation and purification techniques that surpass traditional metal oxide-based adsorbents. Of particular note is the growing exploration of alternative materials, such as starch, chitosan, nanoscale structures like zeolites and metal-organic frameworks, magnetic materials, and carbon-based substances for the development of inorganic adsorbents. These materials, with their remarkable capacity for nanoscale structural adjustment, possess extraordinary capabilities for effective contaminant removal, facilitating swift water purification. The literature survey for this review was conducted using the Google Scholar engine, with “adsorbents for lead remediation” as the starting keywords, resulting in approximately 6000 papers. The search was refined to focus on the last three years and specifically targeted review papers which are most relevant to lead remediation. More than 100 papers were analysed to investigate various techniques, surface modifications, and adsorbent materials for managing inorganic pollutants in water. This review also illuminates research limitations, with a specific focus on starch-based adsorbents in lead remediation. As we progress towards practical commercial applications, this review identifies challenges associated with the development of inorganic adsorbents and provides invaluable insights into future prospects. Surface modification emerges as a promising path, with the potential to substantially enhance adsorption capacity, potentially doubling or even quadrupling it. Moreover, the adsorbents demonstrate impressive regenerative capabilities, maintaining up to 90% regeneration efficiency after multiple cycles. In conclusion, starch-based adsorbents show considerable potential as effective agents for lead purification from aquatic environments. Nevertheless, the need for further research persists, emphasizing the optimization of the adsorption process and exploring the long-term stability of starch-based adsorbents in real-world scenarios. Full article
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15 pages, 2178 KiB  
Article
Preconcentration of Volatile Organic Compounds on Carbon Magnetic Sorbents in the Analysis of Air by Using the Configuration Change of the Sorbent Bed during the Transition from Sorption to Thermodesorption GC-FID
by Oleg Rodinkov, Victor Postnov, Valery Spivakovskyi, Ekaterina Znamenskaya, Anastasia Zheludovskaya and Pavel Nesterenko
Separations 2023, 10(7), 416; https://doi.org/10.3390/separations10070416 - 23 Jul 2023
Cited by 3 | Viewed by 1285
Abstract
The new scheme of the rapid preconcentration of volatile organic substances followed by the thermodesorption and gas chromatographic determination by using a flame ionization detector is proposed for the analysis of air. The scheme implies a change in the geometry of the adsorbent [...] Read more.
The new scheme of the rapid preconcentration of volatile organic substances followed by the thermodesorption and gas chromatographic determination by using a flame ionization detector is proposed for the analysis of air. The scheme implies a change in the geometry of the adsorbent layer in a column during the transition from adsorption to thermal desorption steps. The extraction of analytes is carried out in a wide tube, allowing quantitative adsorption at higher flow rates of the analyzed air passed through the magnetic sorbent held in a thin layer retained by a permanent magnet without any supporting frits. Novel magnetic adsorbents composed of magnetite or a zirconia/magnetite core and pyrocarbon shell are developed for this application. At the end of the adsorption step, the magnet moved out of the system, and the adsorbent transferred under the gravity force into a narrow tube, which provides the more efficient heating of the adsorbent and minimal blurring of the analyte zones during the subsequent thermal desorption. The proposed scheme allows a significant reduction (approximately 10 times) of the time required for the preconcentration of analytes, which is illustrated by the GC determination of alcohols (butanol-1, pentanol-1), phenol, and o-cresol in the air. Full article
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18 pages, 2257 KiB  
Article
Multivariate Simultaneous Determination of Some PAHs in Persian Gulf Oil-Contaminated Algae and Water Samples Using Miniaturized Triton X-100-Mediated Fe3O4 Nanoadsorbent and UV-Vis Detection
by Maryam Abbasi Tarighat, Ameneh Behroozi, Gholamreza Abdi and Charalampos Proestos
Separations 2023, 10(6), 334; https://doi.org/10.3390/separations10060334 - 29 May 2023
Cited by 2 | Viewed by 1174
Abstract
This research shows the development of a miniaturized solid-phase extraction method with UV-Vis detection for simultaneous determination of dibenzofuran, fluoranthene and phenanthrene using chemometrics approaches. After synthesis of Fe3O4 nanoparticles (Fe3O4 NPs), the surface of the nanoparticles [...] Read more.
This research shows the development of a miniaturized solid-phase extraction method with UV-Vis detection for simultaneous determination of dibenzofuran, fluoranthene and phenanthrene using chemometrics approaches. After synthesis of Fe3O4 nanoparticles (Fe3O4 NPs), the surface of the nanoparticles was modified by Triton X100 coating. The influence of extraction solvent and volume, concentration of Triton X100, extraction time, and sample pH were studied and optimized. Due to high spectral overlapping, resolving ternary mixtures for simultaneous determination of targets with classical analytical methods is impossible. Therefore, the recorded UV-Vis spectra were transformed using continuous wavelet transform and then subjected to artificial neural networks (ANNs). The Db4 mother wavelet was used as the better mother wavelet. For simultaneous detection of analytes, a comparison of feed-forward back-propagation and radial basis function networks was accomplished. The calibration graphs showed linearity in the ranges of 2.4–250 ng mL−1, 50–3750 ng mL−1, and 48–5000 ng mL−1 with a limit of detection of 0.58, 9.5 ng mL−1, and 12.5 ng mL−1 under optimal conditions for phenanthrene, fluoranthene, and dibenzofuran, respectively. The limit of quantitation was achieved at 3.52 ng mL−1, 16.35 ng mL−1, and 31.3 ng mL−1 for phenanthrene, fluoranthene and dibenzofuran, respectively. The method involving TX-100-coated Fe3O4 NPs in a liquid sample phase for analyte extraction, followed by ethanol desorption and UV-Vis detection, was successfully applied for the determination of polycyclic aromatic hydrocarbons in oil-field water and algae samples. Full article
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11 pages, 2070 KiB  
Article
Development of a New Method to Estimate the Water Purification Efficiency of Bulk-Supported Nanosorbents under Realistic Conditions
by Elias Moisiadis, Anastasia D. Pournara, Manolis J. Manos and Dimosthenis L. Giokas
Separations 2023, 10(2), 140; https://doi.org/10.3390/separations10020140 - 18 Feb 2023
Cited by 1 | Viewed by 1660
Abstract
The direct use of nanosorbents for water purification is limited due to their aggregation and the lack of techniques for their recovery from natural waters. To overcome these problems, the affixation of nanomaterials onto bulk, non-mobile supports has been proposed. However, a method [...] Read more.
The direct use of nanosorbents for water purification is limited due to their aggregation and the lack of techniques for their recovery from natural waters. To overcome these problems, the affixation of nanomaterials onto bulk, non-mobile supports has been proposed. However, a method to simulate the efficiency of these sorbents under realistic conditions is still not available. To address this need, this work describes a method for evaluating the sorption efficiency of nanosorbent materials incorporated on bulk supports under non-equilibrium conditions. The method combines the principles of passive sampling, an environmental monitoring technique that is based on passive diffusion of dissolved contaminants from water to a sorbent, with batch sorption experiments that measure sorption under equilibrium conditions, to determine the parameters associated with water purification. These parameters are the maximum sorption capacity of the sorbent and the sampling rate, which is the volume of contaminated water treated per unit of time. From these variables, the deployment time of the sorbent until reaching saturation is proposed as an alternative indicator of sorbent efficiency. As proof-of-principle, the removal of oxyanions from a Zr-metal-organic framework (MOR−1) immobilized on cotton textiles was investigated. The results show that the sorption capacity under passive diffusion uptake conditions, is approximately 20 mg/g for As(VI) and 36 mg/g Se(IV), which is 10 to 30 times lower compared to that determined in batch sorption studies, indicating that conventional equilibrium sorption overestimates the efficiency of the sorbents under realistic conditions. The application of the method to a worst-case scenario, involving the severe contamination of freshwaters with arsenate species, is also demonstrated. Full article
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2022

Jump to: 2024, 2023

16 pages, 3411 KiB  
Article
Elaboration of Highly Modified Stainless Steel/Lead Dioxide Anodes for Enhanced Electrochemical Degradation of Ampicillin in Water
by Yasmine Ben Osman, Samar Hajjar-Garreau, Dominique Berling and Hanene Akrout
Separations 2023, 10(1), 5; https://doi.org/10.3390/separations10010005 - 22 Dec 2022
Viewed by 2801
Abstract
Lead dioxide-based electrodes have shown a great performance in the electrochemical treatment of organic wastewater. In the present study, modified PbO2 anodes supported on stainless steel (SS) with a titanium oxide interlayer such as SS/TiO2/PbO2 and SS/TiO2/PbO [...] Read more.
Lead dioxide-based electrodes have shown a great performance in the electrochemical treatment of organic wastewater. In the present study, modified PbO2 anodes supported on stainless steel (SS) with a titanium oxide interlayer such as SS/TiO2/PbO2 and SS/TiO2/PbO2-10% Boron (B) were prepared by the sol–gel spin-coating technique. The morphological and structural properties of the prepared electrodes were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). It was found that the SS/TiO2/PbO2-10% B anode led to a rougher active surface, larger specific surface area, and therefore stronger ability to generate powerful oxidizing agents. The electrochemical impedance spectroscopy (EIS) measurements showed that the modified PbO2 anodes displayed a lower charge transfer resistance Rct. The influence of the introduction of a TiO2 intermediate layer and the boron doping of a PbO2 active surface layer on the electrochemical degradation of ampicillin (AMP) antibiotic have been investigated by chemical oxygen demand measurements and HPLC analysis. Although HPLC analysis showed that the degradation process of AMP with SS/PbO2 was slightly faster than the modified PbO2 anodes, the results revealed that SS/TiO2/PbO2-10%B was the most efficient and economical anode toward the pollutant degradation due to its physico-chemical properties. At the end of the electrolysis, the chemical oxygen demand (COD), the average current efficiency (ACE) and the energy consumption (EC) reached, respectively, 69.23%, 60.30% and 0.056 kWh (g COD)−1, making SS/TiO2/PbO2-10%B a promising anode for the degradation of ampicillin antibiotic in aqueous solutions. Full article
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