Water Treatment Performance Research Articles

Novel magnetic Carbon@BaBiFe12O19 photocatalyst for efficient pollutants degradation under peroxymonosulfate activation

Mhexaferrite (BaFe12O19) is considered as a potential photocatalyst for PMS activation and water purification. However, as a first report, this study indeed provides a different preparation route in a diverse way to synthesize a novel Carbon@BaBiFe12O19 nanoparticles photocatalyst, which so far has not been reported in literature yet as a main objective of our study. The as-prepared Carbon@BaBiFe12O19 magnetic photocatalyst (NPs) was further used to explore the pollutants removal capacity by triggering peroxymonosulfate (PMS) under visible light irradiation. Methylene Orange (MO) removal capacity of the PMS/NPs/Light system reached 97.2% within 50 min. The enhanced efficacy of MO degradation can be ascribed to the effective generation of exceptionally reactive species, including O2•-, SO4•-, h+ and •OH. The study investigated various experimental parameters, such as the development of novel photocatalysts, PMS, light, pH level of the solution, type of pollutants, generation of active species, presence of inorganic anions, dosage of pollutants, water matrices, stability/recyclability, as well as the reaction mechanism for the NPs/PMS/Light system. Therefore, these findings explain how dopants (Bi-carbon) and faults affect the PMS-based photocatalytic water treatment performance. These intriguing discoveries indeed provide novel insights into the development and application of NPs that exhibit exceptional photocatalytic and chemical stability towards oxidative decontamination process.

Water treatment with free-bubbling corrugated sheet MBR

Having previously introduced a new type corrugated-sheet membrane bioreactor (CS-MBR) with slug bubbling, this work investigates its water treatment performance and hydrodynamic optimization under a free bubbling regime. Experiments in parallel were conducted to compare CS-MBR with flat sheet membrane bioreactor (FS-MBR). The transmembrane pressure (TMP) and permeability results indicate that the corrugated sheet membrane has better anti-fouling performance with a final flux after 15 days of operation that was 45 % higher than that of the flat sheet membrane that had been tested in parallel. The analysis results of effluent quality and sludge extracellular polymeric substances (EPS) indicate that the membrane configuration has little impact on the effluent quality and sludge properties in the system. Scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) revealed the accumulation pattern of foulants on the surface of the corrugated sheet membrane and suggested that the corrugations were the cause of the improved anti-fouling performance. Bis-(3′-5′)-cyclic dimeric guanosine monophosphate (c-di-GMP) was extracted from fouling example at membrane surfaces, which was 50 % lower in the CS-MBR than in the FS-MBR. Computational Fluid Dynamics (CFD) simulations showed that channel gap distance of 2– 4 mm combined with 20 m/s nozzle velocity could produce an intense hydrodynamic effect. Based on the traditional free bubbling air usage, total air consumption of this CS-MBR optimal design is expected to save up to 70 % on energy.

Unveiling the contemporary progress of graphene-based nanomaterials with a particular focus on the removal of contaminants from water: a comprehensive review.

Water scarcity and pollution pose significant challenges to global environmental sustainability and public health. As these concerns intensify, the quest for innovative and efficient water treatment technologies becomes paramount. In recent years, graphene-based nanomaterials have emerged as frontrunners in this pursuit, showcasing exceptional properties that hold immense promise for addressing water contamination issues. Graphene, a single layer of carbon atoms arranged in a hexagonal lattice, exhibits extraordinary mechanical, electrical, and chemical properties. These inherent characteristics have led to a surge of interest in leveraging graphene derivatives, such as graphene oxide (GO), reduced graphene oxide and functionalized graphene, for water treatment applications. The ability of graphene-based nanomaterials to adsorb, catalyze, and photocatalyze contaminants makes them highly versatile in addressing diverse pollutants present in water sources. This review will delve into the synthesis methods employed for graphene-based nanomaterials and explore the structural modifications and functionalization strategies implemented to increase their pollutant removal performance in water treatment. By offering a critical analysis of existing literature and highlighting recent innovations, it will guide future research toward the rational design and optimization of graphene-based nanomaterials for water decontamination. The exploration of interdisciplinary approaches and cutting-edge technologies underscores the evolving landscape of graphene-based water treatment, fostering a path toward sustainable and scalable solutions. Overall, the authors believe that this review will serve as a valuable resource for researchers, engineers, and policymakers working toward sustainable and effective solutions for water purification.

Robust Biobased Membrane: Self-Entangled Cellulose Nanofibrils-ZnO-Ag Composite with High Photocatalytic Performance for Efficient Dye-Contaminated Water Treatment.

This study presents a simple and effective method for fabricating a porous photocatalyst composite membrane with excellent wet strength, utilizing cellulose nanofibril (CNF) and zinc oxide-silver (ZnO-Ag) nanorod (NRs) for treating dye-contaminated water. The self-standing CNF membrane with a high wet strength was prepared by NaOH treatment. Besides wet strength, NaOH treatment also controlled the pore characteristics of the CNF membrane, which could tightly attach NRs in them. The photocatalyst composite was prepared by simply drop-drying ZnO-Ag NRs onto the CNF membrane, ensuring attachment within the pores. The photocatalytic activity of the composite was evaluated for the degradation of the methylene blue dye under visible light. Despite the straightforward drop-drying method used to cast the ZnO-Ag NRs onto the CNF membrane, the NRs were not washed out when in contact with water, resulting in a composite that exhibited both high photocatalytic activity and high wet strength. This exceptional performance can be attributed to the tight attachment of the photocatalytic ZnO-Ag NRs to the porous structure of the CNF. Furthermore, the composite demonstrated satisfactory reusability, as no significant deterioration in the photocatalytic performance was observed even after being reused for three cycles. Given its simple preparation method, impressive photocatalytic performance, and durability, we expect that our composite will hold significant value for practical applications in wastewater treatment.

An eco-friendly construction of superwetting alginate-based aerogels with self-cleaning performance for multifunctional water treatment

The increasingly complex oily wastewater has become a severe environmental issue worldwide, calling for the eco-friendly methods toward multifunctionality, high efficiency and sustainability. This work presents a superwetting alginate-based aerogels prepared by a feasible mineralization without the assistance of intermediates. In this strategy, in-situ grown β-FeOOH nanoparticles on whole porous alginate aerogels, not only provides the hierarchical topography and more –OH groups, enhancing underwater oleophobicity (152 ± 4.4°) and fouling resistance of porous aerogels, but also endows with the outstanding photo-Fenton self-cleaning ability for pollutant degradation. As a result, the outstanding separation selectivity for oil and water (>99.5 %), and superior reusability is achieved without the significant diminution of permeation ability (897–1136 L·m−2·h−1). Furthermore, with the advantage of excellent photocatalytic performance under sunlight, the oily wastewater containing soluble organic pollutants can be remediated by simultaneous separation and photocatalysis decomposition under a gravity-driven filtration solely, revealing a promising potential for complex oily wastewater treatment with the rationally usage of sunlight.

Investigation of the water treatment performance of cyclodextrin functionalized-graphene oxide incorporated new generation nanoporous polymeric composite membranes

It is of great importance to meet the need for clean and usable water in the world, which is one of the main priority issues of the European Foresight Platform action plan, and to improve and develop existing technologies in this regard. Membrane technology is one of the most used technologies in water treatment, which can be easily and economically modernized. In this study, we aimed to eliminate some disadvantages that affect the performance and cost of membranes, such as physical/chemical stability and contamination of the surface, by incorporating cyclodextrin derivatives (x-CDs, x: α,β,γ) functionalized reduced graphene oxide (rGO). Membrane performance studies such as contamination tests using water permeability, bovine serum albumin (BSA), flux, and arsenic (As) removal in the table-top pilot system were examined and compared for each composite membrane prepared at different rates. The results showed that the salt rejection values were ranked as Na2SO4 > NaCl> MgSO4 > MgCl2 according to the salt type and it increased depending on the amount of substance. Besides, the arsenate removal studies were performed with the prepared membranes and it was observed that a maximum of 87.6% of the As was removed from the groundwater sample obtained from the Emet (Kütahya/Turkey) district.

Effects of Pulse Frequency on Performance of Electrochemical Cooling Water Treatment for Cooling Tower of Water-Cooled Chiller

Due to the rapid economic development in recent years, water-chiller is being used more and more in hotels, restaurants, resorts, and industrial zones in Vietnam. The cooling tower’s cooling water quality is an important factor in determining the effect on electrical consumption and the coefficient of performance of a water-cooled chiller. Therefore, it is necessary to maintain the quality of cooling water during the operation time of the water-cooled chiller. The aim of this work is to investigate the effects of the pulse frequency and operational parameters such as current density, pulse duty cycle, and energy consumption on the performance of removing hardness ion of electrochemical cooling water treatment for the cooling tower of the water-cooled chiller. The results show that the highest efficiency of the total hardness removal corresponding to a pulse frequency of 1 kHz, a pulse duty cycle of 0.7, and a current density of 80A/m2.

РОЛЬ ЭЛЕКТРОДНЫХ МАТЕРИАЛОВ ПРИ ЭЛЕКТРОХИМИЧЕСКОЙ ОЧИСТКЕ ВОДЫ

Electrochemical processes are a versatile way to remove a wide range of water contaminants, especially those that are difficult to achieve by conventional methods. They do not require the use of chemicals and utilise renewable energy more efficiently. This review describes the fundamental principles of some electrochemical water treatment processes, shows the crucial role of electrode materials in the interfacial processes that control the transport and transformation of pollutants, and reviews the state of knowledge on the development and application of new electrode materials. In addition, the advantages and disadvantages of existing and new electrode materials are analysed, and strategies for their development are discussed. Ways to improve approaches to the development of electrodes for electrochemical treatment of natural and waste water are outlined. Advances in electrocatalysis, electrode fabrication techniques and process optimisation have significantly improved the performance of water treatment. In particular, new catalysts (such as bi-, tri-metals and oxides) and electrode structures (porous structure, fluidised bed, nozzles and electrode stacks) designed for specific processes and new modes of operation are the basis for improving contaminant mass transfer and transformation kinetics through preferred reaction pathways. Such studies provide valuable data for future material selection and design, especially for the implementation of artificial intelligence (AI)-based approaches such as BigData, machine learning, which require large amounts of data.

Composites of Carbons/Indium Sulfide for Hydrogen Peroxide Production and Water Purification

Photocatalysis enables room temperature synthesis of hydrogen peroxide (H2O2) without any byproducts as well as offering advantages such as low cost, and no release of toxic chemicals [1]. Thus, photocatalysis is an appealing approach for the environmentally friendly synthesis of H2O2. Two-dimensional (2D) layered transition metal chalcogenide (TMC) photocatalysts are good at light harvesting due to their high specific surface area and exhibit excellent optoelectronic properties which make them suitable for environmental remediation and energy production [2]. Metal sulfides have a narrower band gap, which improves their light absorption ability in the visible spectrum. However, they often suffer from low quantum yield and high charge recombination rate. Carbonaceous materials have been proven as very effective co-catalysts with semiconductors at increasing their photoactivity and decreasing recombination rate [3]. The present study focusses on indium sulfide (In2S3) and its composites with carbon nano tubes (CNTs) and carbon quantum dots (CQDs) for H2O2 generation via two-electron oxygen reduction reaction. In2S3, In2S3-CNT and In2S3-CQD are synthesized via hydrothermal method. Structural and optical properties characterized using several techniques such as XRD, Raman, UV-Vis-DRS, PL spectra, SEM, TEM etc. show high crystallinity of In2S3 lattice, good dispersion of carbons on In2S3 lattice, improved light absorption and decrease in recombination rate in In2S3 carbon composites. Photoelectric properties are studied using chronoamperometry, EIS, cyclic voltammetry etc. The In2S3 carbon composites show good stability and lower charge transfer resistance and higher active surface area than pure In2S3. The carbon composite materials show a significantly higher performance than the pure In2S3. In2S3-CQD achieves H2O2 production rate of 634 µM h-1, which is ~ 17 times higher than that of pure In2S3. These composites also show good performance for water treatment with In2S3-CQD removing 93% chromium(VI) and 94% rhodamine B (RhB) from contaminated water upon 2h of irradiation. The mechanism of removal of the impurities is also discussed. In2S3-CQD has shown good results owing to their good light absorption, high specific surface area, and CQDs being able to act as electron reservoir. Keywords : Photocatalysis, Hydrogen peroxide photosynthesis, Advanced Oxidation processes, Wastewater Treatment.

Preparation of chitosan microcapsules containing modified graphene oxide and investigation of water treatment performance

Preparation of chitosan microcapsules containing modified graphene oxide and investigation of water treatment performance

Biochar-integrated reactive filtration of wastewater for P removal and recovery, micropollutant catalytic oxidation, and negative CO2 e: Life cycle assessment and techno-economic analysis.

Life cycle assessment (LCA) and techno-economic analysis (TEA) models are developed for a tertiary wastewater treatment system that employs a biochar-integrated reactive filtration (RF) approach. This innovative system incorporates the utilization of biochar (BC) either in conjunction with or independently of iron-ozone catalytic oxidation (CatOx)-resulting in two configurations: Fe-CatOx-BC-RF and BC-RF. The technology demonstrates 90%-99% total phosphorus removals, adsorption of phosphorus to biochar for recovery, and >90% destructive removal of observed micropollutants. In this work, we conduct an ISO-compliant LCA of a 49.2 m3 /day (9 gpm) field pilot-scale Fe-CatOx-BC-RF system and a 1130 m3 /day (0.3 MGD) water resource recovery facility (WRRF)-installed RF system, modeled with BC addition at the same rate of 0.45 g/L to quantify their environmental impacts. LCA results indicated that the Fe-CatOx-BC-RF pilot system is a BC dose-dependent carbon-negative technology at -1.21 kg CO2 e/m3 , where biochar addition constitutes a -1.53 kg/m3 CO2 e beneficial impact to the process. For the WRRF-installed RF system, modeled with the same rate of BC addition, the overall process changed from 0.02 kg CO2 e/m3 to a carbon negative -1.41 kg CO2 e/m3 , demonstrating potential as a biochar dose-dependent negative emissions technology. Using the C100 100-year carbon accounting approach rather than Cnet reduces these CO2 e metrics for the process by about 25%. A stochastic TEA for the cost of water treatment using this combinatorial P removal/recovery, micropollutant destructive removal, and disinfection advanced technology shows that at scale, the mean cost for treating 1130 m3 /day (0.3 MGD) WRRF secondary influent water with Fe-CatOx-BC-RF using the C100 metric is US$0.18 ± US$0.01/m3 to achieve overall process carbon neutrality. Using the same BC dose in an estimation of a 3780 m3 /day (1 MGD) Fe-CatOx-BC-RF facility, the carbon neutral cost of treatment is reduced further to US$0.08 ± $0.01 with added BC accounting for US$0.03/m3 . Overall, the results demonstrate the potential of carbon negativity to become a water treatment performance standard as important and attainable as pollutant and pathogen removal. PRACTITIONER POINTS: Life cycle assessment (LCA) of a pilot scale tertiary biochar water treatment process with or without catalytic ozonation at a WRRF shows a carbon negative global warming potential of -1.21-kg CO2e/m3 while removing 90%-99% TP and >90% of detected micropollutants. Biochar-integrated reactive filtration use can aid in long-term carbon sequestration by reducing the carbon footprint of advanced water treatment in a dose-dependent manner, allowing an overall carbon-neutral or carbon-negative process. A companion paper to this work (Yu et al., 2023) presents the details related to the process operation and mechanism and evaluates the pollutant removal performance of this Fe-CatOx-BC-RF process in engineering laboratory pilot research and field WRRF pilot-scale water resource recovery trials. Techno-economic analysis (TEA) of this biochar catalytic oxidation reactive filtration process using Monte Carlo stochastic modeling shows a forecasted carbon-neutral process cost with low P and micropollutant removal as US$0.11/m3 ± 0.01 for a 3780-m3/day (1 MGD) scale installation with BC cost at US$0.03/m3 of that total. The results demonstrate the potential of carbon negativity to become a water treatmentperformance standard as important and attainable as pollutant and pathogen removal.

Lattice distortion SnS2 piezoelectric self-Fenton system for efficient degradation and detoxification of pollutants

Both piezoelectricity and self-Fenton catalysis are effective ways to degrade water pollution, but little research has combined them to construct a more efficient water pollution treatment method. Here, a Fe-doped SnS2 (Sn1-xFexS2) piezoelectric self-Fenton system was constructed, which shows superior water treatment performance. The best piezoelectric properties of the Sn0.97Fe0.03S2 system were verified by degrading rhodamine B (RhB). The toxicity analysis of degradation intermediates and solutions confirmed that the toxicity of RhB decreased after degradation. In addition, Kelvin probe force microscopy and photoelectrochemical analysis confirmed the better piezoelectric properties of Sn0.97Fe0.03S2. It has demonstrated the enhancement of systematic piezoelectricity by Fe lattice defects and the formation of self-Fenton by Fe as an active center in the degradation of RhB. In this work, an efficient piezoelectric and self-Fenton technology is constructed to remove organic pollutants from water, which is significant for developing water treatment technology.

A Diamond/Graphene/Diamond Electrode for Waste Water Treatment

Boron-doped diamond (BDD) thin film electrodes have great application potential in water treatment. However, the high electrode energy consumption due to high resistance directly limits the application range of existing BDD electrodes. In this paper, the BDD/graphene/BDD (DGD) sandwich structure electrode was prepared, which effectively improved the conductivity of the electrode. Meanwhile, the sandwich electrode can effectively avoid the degradation of electrode performance caused by the large amount of non-diamond carbon introduced by heavy doping, such as the reduction of the electrochemical window and the decrease of physical and chemical stability. The microstructure and composition of the film were characterized by scanning electron microscope (SEM), atomic force microscopy (AFM), Raman spectroscopy, and transmission electron microscopy (TEM). Then, the degradation performance of citric acid (CA), catechol, and tetracycline hydrochloride (TCH) by DGD electrodes was systematically studied by total organic carbon (TOC) and Energy consumption per unit TOC removal (ECTOC). Compared with the single BDD electrode, the new DGD electrode improves the mobility of the electrode and reduces the mass transfer resistance by 1/3, showing better water treatment performance. In the process of dealing with Citric acid, the step current of the DGD electrode was 1.35 times that of the BDD electrode, and the energy utilization ratio of the DGD electrode was 2.4 times that of the BDD electrode. The energy consumption per unit TOC removal (ECTOC) of the DGD electrode was lower than that of BDD, especially Catechol, which was reduced to 66.9% of BDD. The DGD sandwich electrode, as a new electrode material, has good electrochemical degradation performance and can be used for high-efficiency electrocatalytic degradation of organic pollutants.

A novel Magnéli-phase Ti9O17-containing anode by controlled reductive decomposition of calcium copper titanate perovskite under hydrogen atmosphere for paracetamol degradation

CaCu3Ti4O12 (CCTO) materials show high efficacy in water treatment due to their perovskite structure and exceptional chemical stability. Their combination with electro-oxidation and sulfate-based advanced processes represents a promising approach for water treatment applications. CCTO can be modified through various processes to enhance its activity in water treatment. In this study, CCTO was synthesized using ball milling, and the effects of different sintering treatments were evaluated. The treatment with different atmospheres led to CCTO decomposition. Upon sintering under nitrogen, CCTO broke down into the CaTiO3, Cu2O, and rutile TiO2 phases. Conversely, sintering under hydrogen (CCTOH2) led to the reduction of Cu and TiO2 and the creation of Cu and Magnéli phase Ti9O17. CCTOH2 exhibited the highest electrochemical properties due to the presence of Magnéli phases that enhanced electron transfer and conductivity. The decomposition treatment effect on the water treatment performance was evaluated using an electro-oxidation/peroxymonosulfate system. The results showed that when CCTOH2 membranes were used as anodes, paracetamol was completely removed within 10 min. Toxicity was evaluated using Vibrio fischeri. After 1 h, bacterial luminescence inhibition rate dropped to 0 % (from ∼96 % at 2 min), demonstrating paracetamol degradation into non-toxic compounds. Furthermore, CCTOH2 efficacy was tested in the presence of dissolved and colloidal matter from a laboratory-scale secondary effluent. The results demonstrated consistent efficiency in paracetamol degradation in real water and the additional removal of fluorophores. After demonstrating the efficacy of our CCTOH2 membrane, it is now important to test it in large scale experiments.

R-HGO/MXene composite membrane with enhanced permeability and rejection performance for water treatment

Pure graphene oxide (GO) membranes have a tendency to swell in water and have a relatively low flux, making them impractical for water treatment applications. Herein, a novel two-dimensional (2D) composite membrane based on reduced-holey GO (r-HGO) and MXene materials was developed. As a consequence of synergistic effects arising from its unique heterogeneous structure, the r-HGO/MXene composite membrane exhibited an exemplary performance for water treatment, in terms of its permeability and pollutant rejection, and high physical stability. The preparation conditions, especially the reduction degree of GO and the proportions of r-HGO and MXene, determine the properties and performance of the composite membrane. The water flux of the r-HGO/MXene composite membrane with a r-HGO/MXene mass ratio of 1/1 achieved 121.0 L m−2 h−1·bar−1, which was 23 times higher than that of pure GO membrane (∼5.2 L m−2 h−1·bar−1). The removal rates of Coomassie brilliant blue, Methyl blue, Crystal violet, Rhodamine B, Methylene blue, were all above 90 %. Furthermore, the r-HGO/MXene composite membrane was found to be physically stable for more than a week in an aqueous environment. The results of this work show that the r-HGO/MXene composite membrane has great potential as a separation method in water treatment by overcoming some of the important limitations of other current 2D materials.

Synchronously improved permeability, selectivity and fouling resistance of Fe-N-C functionalized ceramic catalytic membrane for effective water treatment: The critical role of Fe

Constructing catalytic membrane simultaneously displaying high permeability, selectivity and antifouling performance in water treatment remains challenging. Herein, the surface and pore channels of the ceramic membrane were co-functionalized with nitrogen doped carbon supported Fe catalyst (CN-F), and the Fe content was varied to investigate its effect on performance of CN-F coupled with peroxymonosulfate (PMS) activation (CN-F/PMS) for water treatment. Results confirmed the introduced Fe (in Fe-N coordination form) greatly enhanced the permeability, selectivity and fouling resistance of CN-F. Optimal CN-F3/PMS achieved 96.5% removal and 52.1% mineralization of sulfamethoxazole in short retention duration (2.7 min), whose performance was 5.4 and 6.7 times higher than that of nitrogen doped carbon functionalized ceramic catalytic membrane (CN/PMS) and CN-F3 filtration alone, respectively. CN-F3/PMS also efficiently inhibited fouling on both surface and pores with 2.8 and 2.4 times lower flux loss than that of CN/PMS and CN-F3 filtration alone, respectively. Moreover, CN-F3/PMS displayed superior performance in long-term treatment of real coking wastewater. The outstanding performance of CN-F was mainly attributed to the dual role of supported Fe, which served as hydrophilic site for enhanced water permeation and major active site for PMS adsorption and reduction into reactive species (mainly high-valent Fe(IV)=O species) towards pollutant elimination.

Co-enhancement of permeability and selectivity on mixed matrix catalytic membrane with high loading of porous Co-N-C filler for efficient water purification

The water treatment performance of membrane filtration is usually restricted via the paradox between permeability and selectivity. Herein, the nitrogen doped porous carbon supported Co catalysts (CoNPC), serving as both porous filler and peroxymonosulfate (PMS) activator, were firstly filled into polyvinylidene fluoride (PVDF) matrix to construct a novel mixed matrix catalytic membrane (CoNPC@PVDF) for enhanced water purification. Owing to the robust binding between CoNPC and PVDF, a high loading (50 wt%) and even dispersion of CoNPC were realized in CoNPC@PVDF, and its permeability and selectivity were both improved with the increase of CoNPC content. The optimum CoNPC@PVDF with PMS activation assistance (FCP) exhibited effective phenol removal at short retention time (1.5 s) and high permeability (256.6 L m−2h−1 bar−1). The performance of CoNPC@PVDF FCP was 2.9 and 2.5 times higher than that of filtration alone and PMS activation alone, respectively, and even dramatically outweighed the reported catalytic membranes and heterogeneous catalysts. The outstanding performance of CoNPC@PVDF catalytic membrane was mainly attributed to its thin membrane structure and high filling degree of CoNPC, resulting in ultrahigh mass transfer rate (1.8 × 10−4 m s−1) and more exposed active sites for enhanced PMS activation into radicals (mainly •OH and SO4•−) towards pollutant removal.

Tunable nano-wrinked channels of reduced graphene oxide membranes for molecular sieving gas separation

Graphene oxide (GO) lamellar membranes have exhibited excellent performance in watertreatment, however there has been far less progress in the application of gas purification. Actually, exposure of the underlying graphitic framework of GO basically determines the gas permeableness of the GO lamellar membranes, which is usually neglected in the fabrication of GO lamellar membranes. Herein, we report nano-wrinkled lamellar reduced GO (rGO) sheets as gas separation membranes with oxygen-rich domains as face-to-face spacer for CO2 blockage and oxygen-poor domains for fast H2 permeation. Thanks to the excellent size-sieving mechanism of the nano-wrinkled channels, the rGO membranes exhibit high H2 permeance of 6.12 × 10−7 mol·m−2·s−1·pa−1 with exceptional selectivity of 529.9 for H2/CO2 gas mixture, surpassing the state-of-the-art ones. The membranes also show excellent stability in separation performance for H2/CO2 gas mixture under a long-term operation. Therefore, such lamellar membranes with well-tuned reduced GO nanosheets hold great potential in gas separation applications.

PH-Responsive graphene oxide/poly (methacrylic acid) hybrid nanofiltration membrane performance for water treatment

Graphene oxide (GO) membranes have been proposed for water treatment. GO can be used to prepare membranes that remove organic molecules, such as model dyes from contaminated wastewater. In practical applications, wastewater is often acidic or alkaline. The physico-chemical properties of GO are only weakly affected by pH, and this can lead to poor membrane performance for the removal of positively charged model compounds. In this work, we used pH-responsive poly (methacrylic acid) (PMAA) to prepare GO-PMAA materials through chemical crosslinking. GO-PMAA materials with different compositions were used to prepare membranes via physical intercalation. The membranes were tested for removal of five different dyes of different sizes and valency (including those that are positively charged, negatively charged, and neutral at neutral pH). We identify a membrane composition that works well for the removal of negatively charged methyl orange and Evans blue under acidic conditions (with 73.1% and 99.7% rejection, respectively) with improved water permeance compared to membranes prepared with GO alone. In addition, we evaluated the long-term stability of the nanofiltration membrane. After continuous operation for 20 h, the rejection rate of MnB by 5p-nGOM was about 85.37%, and the water permeance relatively stable, while the rejection rate of MnB by nGOM was about 26.59%, and the water permeance changed greatly. These findings indicate that GO membranes modified with pH-responsive polymers can achieve superior performance with respect to separation, water permeance, long-term operation, and pressure resistance, compared to GO membranes.

Tree-based ensemble machine learning model for nitrate reduction by zero-valent iron

The use of zero-valent iron (ZVI) for nitrate reduction has long been a topic of interest owing to its excellent reactivity compared to other inorganic electron donors. However, there is currently a lack of comprehensive and sophisticated models that can effectively integrate and analyze the dynamic data generated by this type of experiment. Such modeling is necessary to facilitate information mining and improve our understanding of the underlying mechanisms. Taking advantage of available published experimental data, a gradient-boosting decision tree and extreme gradient boosting were applied to 288 data points collected from peer-reviewed publications and compared with conventional non-tree-based models, i.e., artificial neural networks (ANN) and support vector regression (SVR). First, a predictive analysis was performed for the rate constant and the percentages of ammonium and nitrogen conversion using seven predictors related to ZVI properties, reactant concentration, and experimental parameters. Both tree-based models accurately predicted the target variables with comparable performance (R2 = 0.88–0.97) and outperformed ANN and SVR (R2 = 0.60–0.89). In addition, SHapley Additive exPlanations analysis revealed that ZVI properties (44 % average contribution) and experimental condition (68.5 % average contribution) were the key variables affecting the nitrate reduction rate constant and conversion product, respectively. Aerobic conditions were favorable for the conversion of nitrate to ammonium, with anoxic conditions being beneficial for the selectivity of nitrogen gas conversion. This study demonstrates a promising approach using machine learning with complex cross-system data for predicting the performance of water treatment and for mining valuable insights into the process by model interpretation. This method presents a new approach to revolutionize data analysis and modeling in water remediation, which can simplify the experimental operational burden.