Membrane Technology for the Removal of Organic Micropollutants and Emerging Pollutants

A special issue of Membranes (ISSN 2077-0375). This special issue belongs to the section "Membrane Applications".

Deadline for manuscript submissions: closed (31 January 2022) | Viewed by 28452

Special Issue Editors

Institute of Nanotechnology and Water Sustainability, College of Science, Engineering and Technology, Florida Science Campus, University of South Africa, Johannesburg 2092, South Africa
Interests: water treatment; environmental technology; membrane processes; nanotechnology; carbon-based nanomaterials
Special Issues, Collections and Topics in MDPI journals
Department of Chemical Sciences, Faculty of Science, University of Johannesburg, Corner Siemert and Beit Street, Doornfontein, Johannesburg 2094, South Africa
Interests: polymeric membranes and resins for wastewater remediation and water treatment; development of novel filler materials based on metal organic frameworks (MOFs) and graphene oxide (GO) composites
Special Issues, Collections and Topics in MDPI journals
Institute for Nanotechnology and Water Sustainability (iNanoWS), College of Science, Engineering and Technology, University of South Africa, Johannesburg 1709, South Africa
Interests: nanoenabled membranes; polymer blending; membrane structure–property relations; nanofiltration; ultrafiltration; water treatment
Special Issues, Collections and Topics in MDPI journals
Institute for Nanotechnology and Water Sustainability (iNanoWS), College of Science, Engineering and Technology, University of South Africa, Science Campus, Corner Christian de Wet and Pioneer Avenue, Florida 1709, Johannesburg, South Africa
Interests: desalination; forward osmosis; water and wastewater treatment; membrane fabrication; membrane distillation; membrane fouling and cleaning; microporous filters

Special Issue Information

Dear Colleagues,

Emerging pollutants present a new water quality and supply challenge to the water treatment industry. They are often defined as any synthetic or naturally occurring chemicals that are not commonly monitored and regulated in the environment, with known or suggested ecological and human health effects. These chemicals can include a wide variety of classes of organic pollutants including but not limited to pharmaceuticals and personal care products (PPCPs), pesticides, insecticides, illicit drugs, endocrine-disrupting compounds, antibiotics and flame retardants. The source of emerging pollutants in surface water is mostly through inadequately treated wastewater effluents, run-off from informal settlements, agricultural land run-offs, industrial effluents and hospital effluents. Furthermore, the presence of emerging pollutants in water is escalated by the effects of climate change, such as increased temperatures, high evaporation rates and declining water volumes. Known consequences of the presence of emerging pollutants in water include the feminization of fish, increased presence of antibiotic-resistant bacteria and the production of more hazardous disinfection by-products (DBPs) at water treatment plants. The nature (surface properties, size etc.) of micropollutants makes them resistant to treatment by conventional technologies/systems.

The removal of emerging organic pollutants has been primarily performed using various technologies, such as adsorption, membrane filtration and advanced oxidation processes. Membrane processes such as nanofiltration and reverse osmosis have emerged as the most ideal candidates for removing micropollutants in water. Their retention/removal by membranes is a function of several factors, which are dominated by pollutant physicochemical properties and membrane surface properties.

This Special Issue aims to cover recent developments and advances in the application of membrane processes and combined processes in the removal of organic micropollutants and some new emerging pollutants in water, including advances in all aspects of membrane preparation, characterization, transport and separation mechanisms, as well as membrane fouling behaviour during the treatment of wastewater.  

Both original research and review papers are highly welcome.

Prof. Dr. Bhekie Mamba
Dr. Machawe M Motsa
Dr. Nozipho N Gumbi
Prof. Dr. Richard M. Moutloali
Guest Editors

Manuscript Submission Information

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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. Membranes 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 2700 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

  • fouling
  • membrane technology
  • micropollutants
  • separation mechanisms
  • wastewater treatment

Published Papers (8 papers)

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Research

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24 pages, 5358 KiB  
Article
Low-Cost High Performance Polyamide Thin Film Composite (Cellulose Triacetate/Graphene Oxide) Membranes for Forward Osmosis Desalination from Palm Fronds
Membranes 2022, 12(1), 6; https://doi.org/10.3390/membranes12010006 - 22 Dec 2021
Cited by 3 | Viewed by 2827
Abstract
Novel low-cost cellulose triacetate-based membranes extracted from palm fronds have been fabricated through the phase–inversion procedure. The cellulose tri-acetate (CTA) membrane was modified by incorporation of graphene oxide (GO) prepared from palm fronds according to the modified Hummer method as well as the [...] Read more.
Novel low-cost cellulose triacetate-based membranes extracted from palm fronds have been fabricated through the phase–inversion procedure. The cellulose tri-acetate (CTA) membrane was modified by incorporation of graphene oxide (GO) prepared from palm fronds according to the modified Hummer method as well as the preparation of polyamide thin film composite CTA membranes to improve forward osmosis performance for seawater desalination. The surface characteristics and morphology of the prepared CTA, GO, and the fabricated membranes were investigated. The modified TFC prepared membrane had superior mechanical characteristics as well as permeation of water. The performance of the prepared membranes was tested using synthetic 2 M Sodium chloride (NaCl) feed solution. The water flux (Jw) of the thin-film composite (TFC) (CTA/0.3% GO) was 35 L/m2h, which is much higher than those of pure CTA and CTA/0.3% GO. Meanwhile, the salt reverse flux TFC (CTA/0.3% GO) was 1.1 g/m2h), which is much lower than those of pure CTA and CTA/0.3%. GO (Specific salt flux of TFC (CTA/0.3% GO) substrate membrane was 0.03 g/L indicating good water permeation and low reverse salt flux of the TFC membrane compared to CTA. A real saline water sample collected from Hurgada, Egypt, with totally dissolved solids of 42,643 mg/L with NaCl as the draw solution (DS) at 25 °C and flow rate 1.55 L/min, was used to demonstrate the high performance of the prepared TFC membrane. The chemical analysis of desalted permeated water sample revealed the high performance of the prepared TFC membrane. Consequently, the prepared low-cost forward osmosis (FO) thin-film composite CTA membranes can be introduced in the desalination industry to overcome the high cost of reverse osmosis membrane usage in water desalination. Full article
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19 pages, 5050 KiB  
Article
Synthesis and Evaluation of Asymmetric Mesoporous PTFE/Clay Composite Membranes for Textile Wastewater Treatment
Membranes 2021, 11(11), 850; https://doi.org/10.3390/membranes11110850 - 01 Nov 2021
Cited by 7 | Viewed by 2257
Abstract
Asymmetric mesoporous composite PTFE membranes wit 40, 50, and 85 wt.% of a clay (kaolin) were fabricated and characterized using a scanning electron microscope equipped with EDX for morphology and elemental analysis. The surface chemistry of the membranes was checked using Fourier transform [...] Read more.
Asymmetric mesoporous composite PTFE membranes wit 40, 50, and 85 wt.% of a clay (kaolin) were fabricated and characterized using a scanning electron microscope equipped with EDX for morphology and elemental analysis. The surface chemistry of the membranes was checked using Fourier transform infrared spectroscopy. The effect of incorporating the clay on the hydrophilicity, permeability, morphology, and antifouling properties of the fabricated membranes was investigated. It was observed that incorporating kaolin particles improved the mechanical properties but decreased the contact angle of the membranes, thereby resulting in an improvement in the membrane permeability. The performance of the three composite UF membranes was evaluated through the treatment of a real textile effluent sample containing indigo dye. The results confirmed that these membranes are effective in the removal of COD, color, and turbidity. Indeed, at a transmembrane pressure of 2.5 bar, almost total removal of the turbidity, COD removal > 85%, and color removal > 97% were attained. Furthermore, membrane A85 (with 85% clay) showed the best performance, with a water flux of 659.1 L·h−1·m−2·bar−1. This study highlights the potential of incorporating low-cost clay material for the enhancement of the performance of mixed organic/inorganic matrix membranes, which can be applied to textile wastewater treatment. Full article
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12 pages, 2936 KiB  
Article
Modification of Ceramic Membranes with Carbon Compounds for Pharmaceutical Substances Removal from Water in a Filtration—Adsorption System
Membranes 2021, 11(7), 481; https://doi.org/10.3390/membranes11070481 - 28 Jun 2021
Cited by 15 | Viewed by 2680
Abstract
The aim of this work is to develop a new type of carbon-ceramic membranes for the removal of pharmaceutical substances from water. The membranes were prepared by the chemical modification method using an organosilicon precursor—octadecyltrichlorosilane (ODTS). Graphene oxide, multi-walled carbon nanotubes with carboxylic [...] Read more.
The aim of this work is to develop a new type of carbon-ceramic membranes for the removal of pharmaceutical substances from water. The membranes were prepared by the chemical modification method using an organosilicon precursor—octadecyltrichlorosilane (ODTS). Graphene oxide, multi-walled carbon nanotubes with carboxylic groups, and single-walled carbon nanotubes were used in the modification process. The filtration properties and adsorption properties of the developed membranes were tested. In order to characterize the membrane, the water permeability, the change of the permeate flux in time, and the adsorbed mass of the substance were determined. Additionally, the surface properties of the membranes were characterized by contact angle measurements and porosimetry. The antibiotic tetracycline was used in the adsorption tests. Based on the results, the improved adsorption properties of the modified membrane in relation to the unmodified membrane were noticed. Novel ceramic membranes modified with MWCNT are characterized by 45.4% removal of tetracycline and permeate flux of 520 L·h·m−2·bar−1. We demonstrated the ability of modified membranes to adsorb pharmaceuticals from water streams that are in contact with the membrane. Novel membranes retain their filtration properties. Therefore, such membranes can be used in an integrated filtration–adsorption process. Full article
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21 pages, 5510 KiB  
Article
Carbon Nanodots Embedded on a Polyethersulfone Membrane for Cadmium(II) Removal from Water
Membranes 2021, 11(2), 114; https://doi.org/10.3390/membranes11020114 - 05 Feb 2021
Cited by 8 | Viewed by 2199
Abstract
Cadmium(II) is a toxic heavy metal in aquatic systems. As a potential solution, green carbon nanodots (CNDs) were synthesized from oats and embedded on polyethersulfone membrane (PES) via phase inversion for the adsorption of Cd2+ from water. Characterization techniques for the CNDs [...] Read more.
Cadmium(II) is a toxic heavy metal in aquatic systems. As a potential solution, green carbon nanodots (CNDs) were synthesized from oats and embedded on polyethersulfone membrane (PES) via phase inversion for the adsorption of Cd2+ from water. Characterization techniques for the CNDs and PES membranes were transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), Raman spectroscopy, atomic force microscopy (AFM), contact angle and a pure water flux assessment system operated at 300 kPa. TEM results showed that the CNDs were well dispersed with a uniform shape and size (6.7 ± 2.8 nm). Raman spectroscopy revealed that the CNDs were embedded on the PES and the ID/IG ratio slightly increased, showing that the membranes maintained good structural integrity.The CNDs/PES proved to be more hydrophilic than PES. The glassy carbon electrode (GCE) in anodic stripping voltammetry (ASV) technique detected 99.78% Cd2+ removal by 0.5% CNDs/PES at optimum conditions: 30 min. contact time, at pH 5 and 0.5 ppm Cd2+ solution. The 0.5% CNDs/PES removed Cd(II) due to the hydroxyl group (-OH) and carboxyl group (-COO-) on the membrane composite. It was established that Cu2+ and Pb2+ have a significant interfering effect during the analysis of Cd2+ using GCE in ASV technique. The 0.5% CNDs/PES is recyclable because it removed above 95% of cd2+ in four cycles. In a spiked tap water sample, 58.38% of Cd2+ was sensed by GCE of which 95% was in agreement with the value obtained from inductively coupled plasma optical emission spectrometry (ICPOES). Full article
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Review

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25 pages, 3970 KiB  
Review
Removal of Emerging Contaminants from Wastewater Streams Using Membrane Bioreactors: A Review
Membranes 2022, 12(1), 60; https://doi.org/10.3390/membranes12010060 - 31 Dec 2021
Cited by 25 | Viewed by 4190
Abstract
Water is a very valuable natural resource. As the demand for water increases the presence of emerging contaminants in wastewater has become a growing concern. This is particularly true when one considers direct reuse of wastewater. Obtaining sufficient removal of emerging contaminants will [...] Read more.
Water is a very valuable natural resource. As the demand for water increases the presence of emerging contaminants in wastewater has become a growing concern. This is particularly true when one considers direct reuse of wastewater. Obtaining sufficient removal of emerging contaminants will require determining the level of removal for the various unit operations in the wastewater treatment process. Membrane bioreactors are attractive as they combine an activated sludge process with a membrane separation step. They are frequently used in a wastewater treatment process and can operate at higher solid loadings than conventional activated sludge processes. Determining the level of removal of emerging contaminants in the membrane bioreactor step is, therefore, of great interest. Removal of emerging contaminants could be by adsorption onto the biomass or membrane surface, biotransformation, size exclusion by the membrane, or volatilization. Given the fact that most emerging contaminants are low molecule weight non-volatile compounds, the latter two methods of removal are usually unimportant. However, biotransformation and adsorption onto the biomass are important mechanisms of removal. It will be important to determine if the microorganisms present at given treatment facility are able to remove ECs present in the wastewater. Full article
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27 pages, 2316 KiB  
Review
Recent Advances in Biopolymeric Membranes towards the Removal of Emerging Organic Pollutants from Water
Membranes 2021, 11(11), 798; https://doi.org/10.3390/membranes11110798 - 20 Oct 2021
Cited by 25 | Viewed by 4008
Abstract
Herein, this paper details a comprehensive review on the biopolymeric membrane applications in micropollutants’ removal from wastewater. As such, the implications of utilising non-biodegradable membrane materials are outlined. In comparison, considerations on the concept of utilising nanostructured biodegradable polymeric membranes are also outlined. [...] Read more.
Herein, this paper details a comprehensive review on the biopolymeric membrane applications in micropollutants’ removal from wastewater. As such, the implications of utilising non-biodegradable membrane materials are outlined. In comparison, considerations on the concept of utilising nanostructured biodegradable polymeric membranes are also outlined. Such biodegradable polymers under considerations include biopolymers-derived cellulose and carrageenan. The advantages of these biopolymer materials include renewability, biocompatibility, biodegradability, and cost-effectiveness when compared to non-biodegradable polymers. The modifications of the biopolymeric membranes were also deliberated in detail. This included the utilisation of cellulose as matrix support for nanomaterials. Furthermore, attention towards the recent advances on using nanofillers towards the stabilisation and enhancement of biopolymeric membrane performances towards organic contaminants removal. It was noted that most of the biopolymeric membrane applications focused on organic dyes (methyl blue, Congo red, azo dyes), crude oil, hexane, and pharmaceutical chemicals such as tetracycline. However, more studies should be dedicated towards emerging pollutants such as micropollutants. The biopolymeric membrane performances such as rejection capabilities, fouling resistance, and water permeability properties were also outlined. Full article
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32 pages, 10701 KiB  
Review
Photocatalytic Nanofiber Membranes for the Degradation of Micropollutants and Their Antimicrobial Activity: Recent Advances and Future Prospects
Membranes 2021, 11(9), 678; https://doi.org/10.3390/membranes11090678 - 31 Aug 2021
Cited by 21 | Viewed by 4859
Abstract
This review paper systematically evaluates current progress on the development and performance of photocatalytic nanofiber membranes often used in the removal of micropollutants from water systems. It is demonstrated that nanofiber membranes serve as excellent support materials for photocatalytic nanoparticles, leading to nanofiber [...] Read more.
This review paper systematically evaluates current progress on the development and performance of photocatalytic nanofiber membranes often used in the removal of micropollutants from water systems. It is demonstrated that nanofiber membranes serve as excellent support materials for photocatalytic nanoparticles, leading to nanofiber membranes with enhanced optical properties, as well as improved recovery, recyclability, and reusability. The tremendous performance of photocatalytic membranes is attributed to the photogenerated reactive oxygen species such as hydroxyl radicals, singlet oxygen, and superoxide anion radicals introduced by catalytic nanoparticles such as TiO2 and ZnO upon light irradiation. Hydroxyl radicals are the most reactive species responsible for most of the photodegradation processes of these unwanted pollutants. The review also demonstrates that self-cleaning and antimicrobial nanofiber membranes are useful in the removal of microbial species in water. These unique materials are also applicable in other fields such as wound dressing since the membrane allows for oxygen flow in wounds to heal while antimicrobial agents protect wounds against infections. It is demonstrated that antimicrobial activities against bacteria and photocatalytic degradation of micropollutants significantly reduce membrane fouling. Therefore, the review demonstrates that electrospun photocatalytic nanofiber membranes with antimicrobial activity form efficient cost-effective multifunctional composite materials for the removal of unwanted species in water and for use in various other applications such as filtration, adsorption and electrocatalysis. Full article
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16 pages, 2415 KiB  
Review
Donnan Membrane Process for the Selective Recovery and Removal of Target Metal Ions—A Mini Review
Membranes 2021, 11(5), 358; https://doi.org/10.3390/membranes11050358 - 14 May 2021
Cited by 17 | Viewed by 4096
Abstract
Membrane-based water purification technologies contribute significantly to water settings, where it is imperative to use low-cost energy sources to make the process economically and technically competitive for large-scale applications. Donnan membrane processes (DMPs) are driven by a potential gradient across an ion exchange [...] Read more.
Membrane-based water purification technologies contribute significantly to water settings, where it is imperative to use low-cost energy sources to make the process economically and technically competitive for large-scale applications. Donnan membrane processes (DMPs) are driven by a potential gradient across an ion exchange membrane and have an advantage over fouling in conventional pressure driven membrane technologies, which are gaining attention. DMP is a removal, recovery and recycling technology that is commonly used for separation, purification and the concentrating of metals in different water and waste streams. In this study, the principle and application of DMP for sustainable wastewater treatment and prospects of chemical remediation are reviewed and discussed. In addition, the separation of dissolved metal ions in wastewater settings without the use of pressure driven gradients or external energy supply membrane technologies is highlighted. Furthermore, DMP distinctive configurations and operational factors are explored and the prospects of integrating them into the wastewater treatment plants are recommended. Full article
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