Self-cleaning anti-fouling hybrid ultrafiltration membranes via side chain grafting of poly(aryl ether sulfone) and titanium dioxide

Interfacial hydrophilicity induced CoAl-LDH/Ti3C2Tx@PVDF Fenton-like catalytic filtration membrane for efficient anti-fouling and water decontamination

The catalytic filtration membrane, combining the interfacial hydrophilic effect with PMS based Fenton-like oxidation processes, demonstrates great potential as an advanced solution for alleviating membrane fouling and removing contaminants. Herein, a novel type of hollow fiber CoAl-LDH/Ti3C2Tx@PVDF membranes was successfully fabricated. The well-designed hybrid membrane incorporating 0.5 wt% of CoAl-LDH/Ti3C2Tx (denoted as M-0.5) as PMS activator exhibited excellent anti-fouling behavior and remarkable TC degradation efficiency. The anchored hetero-structural CoAl-LDH/Ti3C2Tx was pivotal in driving the reaction, where the synergistic redox cycles (Ti+/Ti2+, Ti2+/Ti3+ and Co2+/Co3+) facilitated the activation of PMS. Concurrently, the plentiful hydrophilic groups especially -OH of CoAl-LDH/Ti3C2Tx endowed M-0.5 with robust interfacial hydrophilicity, extremely boosting interactions among CoAl-LDH/Ti3C2Tx, PMS and TC at the surface of M-0.5. Mechanism analysis revealed that the formed ∙OH, SO4·-, ·O2- and 1O2 collectively contributed to the non-selective degradation of TC. Moreover, the M-0.5 +PMS system showed exceptional stability in the presence of various environmental interferences and continuous flow device. Ultimately, the degradation pathways and toxicological assessment of TC and its intermediates further substantiated the impressive catalytic oxidation performance of the M-0.5 +PMS system. This insightful work cleverly integrates the macro/micro-scale design of membrane structure, promising to unlock novel opportunities for the development of water treatment.

Clean-In-Place (CIP) wastewater management using nanofiltration (NF)-forward osmosis (FO)-direct contact membrane distillation (DCMD): Effects of draw salt

A substantial amount of water is being used during Clean-in-Place (CIP) operation, and is transformed into wastewater that can cause eutrophication to the nearby ecosystem. The present study proposed the Nanofiltration (NF) - Forward Osmosis (FO) - Direct Contact Membrane Distillation (DCMD) to recover the cleaning agents and reclaim freshwater from the model CIP wastewater. NF steps were suggested as prefiltration steps to remove organic compounds from the CIP wastewater. NF steps reduced the lactose and protein contents by 100 % and 95.6 %, respectively. The permeates from NF steps were further managed by the integrated FO-DCMD system. Several draw salts such as NaCl, KCl, MgCl2, and CaCl2 were compared to investigate the influence on FO and DCMD performance. It was found that monovalent salts (NaCl and KCl) outperformed the divalent salts (MgCl2 and CaCl2) in terms of water flux for both FO and DCMD. This can be attributed to the lower viscosity and higher mass transfer coefficient. In addition, the replenishment costs of each salt were evaluated since salts loss occurred during FO and DCMD operation. The cost evaluation revealed that NaCl is most the cheapest salts per reclaimed water. All of this observation indicates that NaCl is preferred in terms of water flux and replenishment cost. The NF permeate kept concentrated using the integrated FO-DCMD or single FO with 2 M of NaCl. Compared to a single FO that showed a consistent decline in draw solution concentration, FO-DCMD could maintain the concentration of the draw solution. Despite the constant concentration, flux decline of FO was observed due to fouling formation caused by the high-temperature operation. However, the FO-DCMD could accomplish the recovery of pure water. Finally, the cleaning agents recovered by the NF-FO-DCMD showed the cleaning efficacy comparable to the fresh NaOH. These results suggest the potential of the proposed system to manage the CIP wastewater.

Recovery of cleaning agents from Clean-In-Place (CIP) wastewater using nanofiltration (NF) and direct contact membrane distillation (DCMD)

Increasing concerns about freshwater sources necessitate the management of wastewater, such as the wastewater generated from Clean-in-Place (CIP) operations. In this investigation, a membrane system composed of nanofiltration (NF) and direct contact membrane distillation (DCMD) was proposed to manage model dairy CIP wastewater that contained NaOH as an alkaline cleaning agent. During the NF step, prefiltration by a 4 kDa membrane or a 4 kDa membrane followed by a 200 Da membrane (4 kDa/200 Da) was used to remove the whey protein and lactose. With these two membranes in series of NF, the protein concentration was reduced by 92.4% and the lactose content was reduced to a non-detectable level when compared to the model CIP wastewater. Before concentrating the permeates from NF steps, three DCMD membranes (FR, Solupor, and ST) with different characteristics were evaluated to manage the NF permeates from 4 kDa or 200 Da NF. An increase in the feed temperature from 40 °C to 60 °C resulted in an increase in the water flux during DCMD operation, except for FR. In addition, it was found that ST generated the highest water flux when compared to the other membranes. Using ST and a feed temperature of 60 °C, the permeates from 4 kDa or 4 kDa/200 Da were continuously concentrated for 7 h with DCMD. During this concentration, there was no significant decline in flux. The cleaning effectiveness of the cleaning agent (NaOH) recovered by NF and DCMD was compared with a fresh cleaning solution using quartz crystal microbalance with dissipation (QCM-D). It was found that the cleaning agents recovered by 4 kDa/200 Da NF presented a statistically identical cleaning rate compared to fresh NaOH. This research highlights the potential of NF and DCMD to regenerate alkaline cleaning agents, while reclaiming water from dairy CIP wastewater.

Novel Engineered Carbon Cloth-Based Self-Cleaning Membrane for High-Efficiency Oil-Water Separation

A novel engineered carbon cloth (CC)-based self-cleaning membrane containing a Cu:TiO2 and Ag coating has been created via hydrothermal and light deposition methods. The engineered membrane with chrysanthemum morphology has superhydrophilic and underwater superoleophilic performance. The cooperativity strategy of Cu doping and Ag coating to the TiO2 is found to be critical for engineering the separation efficiency and self-cleaning skill of the CC-based membrane under visible light due to the modulated bandgap structure and surface plasmon resonance. The CC-based membrane has excellent oil-water separation performance when Cu is fixed at 2.5 wt% and the Ag coating reaches a certain amount of 0.003 mol/L AgNO3. The contact angle of underwater oil and the separation efficiency are 156° and 99.76%, respectively. Furthermore, the membrane has such an outstanding self-cleaning ability that the above performance can be nearly completely restored after 30 min of visible light irradiation, and the separation efficiency can still reach 99.65% after 100 cycles. Notably, the membrane with exceptional wear resistance and durability can work in various oil-water mixtures and harsh environments, indicating its potential as a new platform of the industrial-level available membrane in dealing with oily wastewater.

Membrane Surface Modification via In Situ Grafting of GO/Pt Nanoparticles for Nitrate Removal with Anti-Biofouling Properties

Nanofiltration processes for the removal of emerging contaminants such as nitrate are a focus of attention of research works as an efficient technique for providing drinking water for people. Polysulfone (PSF) nanofiltration membranes containing graphene oxide (GO)/Pt (0, 0.25, 0.5, 0.75, 1 wt%) nanoparticles were generated with the phase inversion pathway. The as-synthesized samples were characterized by FTIR, SEM, AFM, and contact angle tests to study the effect of GO/Pt on hydrophilicity and antibacterial characteristics. The results conveyed that insertion of GO/Pt dramatically improved the biofouling resistance of the membranes. Permeation experiments indicated that PSF membrane embracing 0.75 wt% GO/Pt nanoparticles had the highest nitrate flux and rejection ability. The membrane's configuration was simulated using OPEN-MX simulating software indicating membranes maintaining 0.75 wt% of GO/Pt nanoparticles revealed the highest stability, which is well in accordance with experimental outcomes.

A novel PES-C/(GO-COOH/Ce) blended membrane for treating heavy-metal-ion wastewater

A GO-COOH/Ce complex was introduced into a phenolphthalide polythersulfone (PES-C) matrix to prepare a PES-C/(GO-COOH/Ce) blended membrane by nonsolvent-induced phase transformation (NIPS). FT-IR and EDS analysis confirmed that the GO-COOH/Ce complex was successfully incorporated into the PES-C matrix. SEM showed that the blended membrane possessed an asymmetric structure with finger-like pores. The best comprehensive performance was obtained for a PES-C/(GO-COOH/Ce) blended membrane prepared using 0.1 wt.% of the GO-COOH/Ce complex in the casting liquid. The specific results for the blended membrane were as follows: the fluxes of pure water and 0.1 g/L lead nitrate solution were 272 L/m2·h and 214 L/m2·h, respectively; the rejection of bovine serum albumin (BSA) was 99.4%; the rejection of lead ions was 96.2%; the moisture content was 10.9%; the contact angle was 67.1°; the Young's modulus was 35.7 MPa; and the flux recovery ratio was 1.5 times higher than that of the pure PES-C membrane. The antibacterial-zone diameters of the PES-C/(GO-COOH/Ce) blended membrane used against Escherichia coli and Staphylococcus aureus were 2.50 cm and 2.88 cm, respectively. A catalytic cleaning test showed a flux recovery ratio of 63% after washing the PES-C/(GO-COOH/Ce) blended membrane with a 0.2 g/L acetic acid solution for 0.5 h.

Photocatalytic removal of pharmaceutical water pollutants by TiO2 - Carbon dots nanocomposites: A review

Pharmaceuticals are becoming increasingly more relevant water contaminants, with photocatalysts (such as TiO₂) being a promising approach to remove these compounds from water. However, TiO₂ has poor sunlight-harvesting capacity, low photonic efficiency, and poor adsorption towards organic pollutants. One of the emerging strategies to enhance the photocatalytic performance of TiO₂ is by conjugating it with fluorescent carbon dots. Herein, we performed a critical review of the development of TiO₂ - carbon dots nanocomposites for the photocatalytic removal of pharmaceuticals. We found that carbon dots can improve the photocatalytic efficiency of the resulting nanocomposites, mostly due to increasing the adsorption of organic pollutants and enhancing the absorption in the visible range. However, while this approach shows significant promise, we also identified and discussed several aspects that need to be addressed before this strategy could be more widely used. We hope that this review can guide future studies aiming to the development of enhanced photocatalytic TiO₂ - carbon dots nanocomposites.

High-performance photocatalytic membranes for water purification in relation to environmental and operational parameters

Growing technologies, increasing population and environmental pollution lead to severe contamination of water and require advanced water treatment technologies. These aspects lead to the need to purify water with advanced smart materials. This paper reviews the recent advances (during the last 5 years) in photocatalytic composite membranes used for water treatment. For this purpose, the authors have reviewed the main materials used in the development of (photocatalytic membranes) PMs, environmental and operational factors affecting the performance of photocatalytic membranes, and the latest developments and applications of PMs in water purifications. The composite photocatalytic membranes show good performance in the removal and degradation of pollutants from water.

Response Surface Methodology and Artificial Neural Network Modelling of Membrane Rotating Biological Contactors for Wastewater Treatment

Membrane fouling is a major hindrance to widespread wastewater treatment applications. This study optimizes operating parameters in membrane rotating biological contactors (MRBC) for maximized membrane fouling through Response Surface Methodology (RSM) and an Artificial Neural Network (ANN). MRBC is an integrated system, embracing membrane filtration and conventional rotating biological contactor in one individual bioreactor. The filtration performance was optimized by exploiting the three parameters of disk rotational speed, membrane-to-disk gap, and organic loading rate. The results showed that both the RSM and ANN models were in good agreement with the experimental data and the modelled equation. The overall R2 value was 0.9982 for the proposed network using ANN, higher than the RSM value (0.9762). The RSM model demonstrated the optimum operating parameter values of a 44 rpm disk rotational speed, a 1.07 membrane-to-disk gap, and a 10.2 g COD/m2 d organic loading rate. The optimization of process parameters can eliminate unnecessary steps and automate steps in the process to save time, reduce errors and avoid duplicate work. This work demonstrates the effective use of statistical modeling to enhance MRBC system performance to obtain a sustainable and energy-efficient treatment process to prevent human health and the environment.

Fabrication of Polyvinylidene Difluoride Membrane with Enhanced Pore and Filtration Properties by Using Tannic Acid as an Additive

Potential use of tannic acid (TA) as an additive for fabrication of polyvinylidene difluoride (PVDF) membrane was investigated. The TA was introduced by blending into the dope solution with varying concentrations of 0, 1, 1.5, and 2 wt%. The prepared membranes were characterized and evaluated for filtration of humic acid (HA) solution. The stability of the membrane under harsh treatment was also evaluated by one-week exposure to acid and alkaline conditions. The results show that TA loadings enhanced the resulting membrane properties. It increased the bulk porosity, water uptake, and hydrophilicity, which translated into improved clean water flux from 15.4 L/m².h for the pristine PVDF membrane up to 3.3× for the TA-modified membranes with the 2 wt% TA loading. The flux recovery ratio (FRR) of the TA-modified membranes (FRRs = 78–83%) was higher than the pristine one (FRR = 58.54%), with suitable chemical stability too. The improved antifouling property for the TA-modified membranes was attributed to their enhanced hydrophilicity thanks to improved morphology and residual TA in the membrane matric.

A Facile Co-Deposition Approach to Construct Functionalized Graphene Quantum Dots Self-Cleaning Nanofiltration Membranes

In this study, a novel photocatalytic self-cleaning nanofiltration (NF) membrane was fabricated by constructing aspartic acid-functionalized graphene quantum dots (AGQDs) into the polydopamine/polyethyleneimine (PDA/PEI) selective layer via the co-deposition method. The chemical composition, microstructure, and hydrophilicity of the prepared membranes were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), attenuated total reflection (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), and water contact angle (WCA). Meanwhile, the effects of PEI molecular weight and AGQDs concentration on NF membrane structures and separation performance were systematically investigated. The photocatalytic self-cleaning performance of the PDA/PEI/AGQDs membrane was evaluated in terms of flux recovery rate. For constructing high-performance NF membranes, it is found that the optimal molecular weight of PEI is 10,000 Da, and the optimal concentration of AGQDs is 2000 ppm. The introduction of hydrophilic AGQDs formed a more hydrophilic and dense selective layer during the co-deposition process. Compared with the PDA/PEI membrane, the engineered PDA/PEI/AGQDs NF membrane has enhanced water flux (55.5 LMH·bar^-1) and higher rejection (99.7 ± 0.3% for MB). In addition, the PDA/PEI/AGQDs membrane exhibits better photocatalytic self-cleaning performance over the PDA/PEI membrane (83% vs. 69%). Therefore, this study provides a facile approach to construct a self-cleaning NF membrane.

Amorphous TiO2 Bridges Stabilized WS2 Membranes with Excellent Filtration Stability and Photocatalysis-Driving Self-Cleaning Ability

Two-dimensional (2D) membranes as a new type of water filtration membrane have shown great potential in water separation and purification. However, their long-term stability under cross-flow conditions and their antifouling property are two main concerns for practical separation and purification processes. In this work, a strategy of nanoparticle bridges based on amorphous TiO₂ is developed to link adjacent WS₂ nanosheets on a WS₂ membrane surface, leading to a strong membrane surface with excellent stability during 204 h of continuous cross-flow filtration. Moreover, the amorphous TiO₂ bridges also form a TiO₂/WS₂ heterojunction on the WS₂ membrane surface, exhibiting an impressive photocatalysis-driving self-cleaning property by pollutant photodegradation. And the flux recovery ratio (FRR) exceeds 95% after three cycles of separation experiments. The excellent long-term stability and photocatalysis-driving self-cleaning property of the WS₂/TiO₂ membrane provide a new approach to construct robust 2D membranes.

Recent advances of monoelemental 2D materials for photocatalytic applications

As a sustainable environmental governance strategy and energy conversion method, photocatalysis has considered to have great potential in this field due to its excellent optical properties and has become one of the most attractive technologies today. Among 2D materials, the emerging two-dimensional (2D) monoelemental materials mainly distributed in the -IIIA, -IVA, -VA and -VIA groups and show excellent performance in solar energy conversion due to their graphene-like 2D atomic structure and unique properties, thereby drawing increasing attention. This review briefly summarizes the preparation processes and fundamental properties of 2D single-element nanomaterials, as well as various modification strategies and adjustment mechanisms to enhance their photocatalytic properties. In particular, this article comprehensively discusses the related practical applications of 2D single-element materials in the field of photocatalysis, including photocatalytic degradation for contaminants removal, photocatalytic pathogen inactivation, photocatalytic fouling control and photocatalytic energy conversion. This review will provide some new opportunities for the rational design of other excellent photocatalysts based on 2D monoelemental materials, as well as present tremendous novel ideas for 2D monoelemental materials in other environmental conservation and energy-related applications, such as supercapacitors, electrocatalysis, solar cells, and so on.

Two-Step Dopamine-to-Polydopamine Modification of Polyethersulfone Ultrafiltration Membrane for Enhancing Anti-Fouling and Ultraviolet Resistant Properties

Polydopamine has been widely used as an additive to enhance membrane fouling resistance. This study reports the effects of two-step dopamine-to-polydopamine modification on the permeation, antifouling, and potential anti-UV properties of polyethersulfone (PES)-based ultrafiltration membranes. The modification was performed through a two-step mechanism: adding the dopamine additive followed by immersion into Tris-HCl solution to allow polymerization of dopamine into polydopamine (PDA). The results reveal that the step of treatment, the concentration of dopamine in the first step, and the duration of dipping in the Tris solution in the second step affect the properties of the resulting membranes. Higher dopamine loadings improve the pure water flux (PWF) by more than threefold (15 vs. 50 L/m²·h). The extended dipping period in the Tris alkaline buffer leads to an overgrowth of the PDA layer that partly covers the surface pores which lowers the PWF. The presence of dopamine or polydopamine enhances the hydrophilicity due to the enrichment of hydrophilic catechol moieties which leads to better anti-fouling. Moreover, the polydopamine film also improves the membrane resistance to UV irradiation by minimizing photodegradation's occurrence.

Permeability is the Critical Factor Governing the Life Cycle Environmental Performance of Drinking Water Treatment Using Living Filtration Membranes

Living Filtration Membranes (LFMs) are a water filtration technology that was recently developed in the lab (Technology Readiness Level 4). LFMs have shown filtration performance comparable with that of ultrafiltration, far better fouling resistance than conventional polymer membranes, and good healing capabilities. These properties give LFMs promise to address two significant issues in conventional membrane filtration: fouling and membrane damage. To integrate environmental considerations into future technology development (i.e., Ecodesign), this study assesses the life cycle environmental performance of drinking water treatment using LFMs under likely design and operation conditions. It also quantitatively ranks the engineering design and operation factors governing the further optimization of LFM environmental performance using a global sensitivity analysis. The results suggest that LFMs' superior fouling resistance will reduce the life cycle environmental impacts of ultrafiltration by 25% compared to those of a conventional polymer membrane in most impact categories (e.g., acidification, global warming potential, and carcinogenics). The only exception is the eutrophication impact, where the need for growth medium and membrane regeneration offsets the benefits of LFMs' fouling resistance. Permeability is the most important factor that should be prioritized in future R&D to further improve the life cycle environmental performance of LFMs. A 1% improvement in the permeability will lead to a ∼0.7% improvement in LFMs' environmental performance in all the impact categories, whereas the same change in the other parameters investigated (e.g., LFM lifespan and regeneration frequency) typically only leads to a <0.2% improvement.

In Situ Electrochemical Generation of Reactive Chlorine Species for Efficient Ultrafiltration Membrane Self-Cleaning

Reactive membranes based on hydroxyl radical generation are hindered by the need for chemical dosing and complicated module and material design. Herein, we utilize an electrochemical approach featuring in situ generation of reactive (radical) chlorine species (RCS) through anodization of chloride ions for membrane self-cleaning. A hybridized carbon nanotube (CNT)-functionalized ceramic membrane (h-CNT/CM), possessing high hydrophilicity, permeability, and conductivity, was fabricated. Using carbamazepine (CBZ) as a probe, we confirmed the presence of RCS in the electrified h-CNT/CM. The rapid and complete degradation of CBZ in a single-pass ultrafiltration indicates a high localized RCS concentration within the three-dimensional porous CNT interwoven layer. We further demonstrate that the electrogeneration of RCS is a critical prestep for free chlorine (HClO and ClO^-) formation. The self-cleaning efficiency of the membrane after fouling with a model organic foulant (alginate) was assessed using an electrified cross-flow membrane filtration system. The fouled h-CNT/CM exhibits a near complete water flux recovery following a short (1 min) self-cleaning with an applied voltage of 3 or 4 V and feed solutions of 100 or 10 mM sodium chloride, respectively. Considering the superior performance of the RCS-mediated self-cleaning compared to conventional membrane chemical cleaning using sodium hypochlorite, our results exemplify an effective strategy for in situ electrogeneration of RCS to achieve a highly efficient membrane self-cleaning.

Critical Issues and Guidelines to Improve the Performance of Photocatalytic Polymeric Membranes

Photocatalytic membrane reactors (PMR), with immobilized photocatalysts, play an important role in process intensification strategies; this approach offers a simple solution to the typical catalyst recovery problem of photocatalytic processes and, by simultaneous filtration and photocatalysis of the aqueous streams, facilitates clean water production in a single unit. The synthesis of polymer photocatalytic membranes has been widely explored, while studies focused on ceramic photocatalytic membranes represent a minority. However, previous reports have identified that the successful synthesis of polymeric photocatalytic membranes still faces certain challenges that demand further research, e.g., (i) reduced photocatalytic activity, (ii) photocatalyst stability, and (iii) membrane aging, to achieve technological competitiveness with respect to suspended photocatalytic systems. The novelty of this review is to go a step further to preceding literature by first, critically analyzing the factors behind these major limitations and second, establishing useful guidelines. This information will help researchers in the field in the selection of the membrane materials and synthesis methodology for a better performance of polymeric photocatalytic membranes with targeted functionality; special attention is focused on factors affecting membrane aging and photocatalyst stability.

Comparison of the performance of prepared pristine and TiO2 coated UF/NF membranes for two types of oil-in-water emulsion separation

Polysulfone ultrafiltration (UF) and polypiperazine-amide nanofiltration (NF) membranes were first fabricated by phase inversion and interfacial polymerization, and then modified by the commonly used TiO₂ on the membrane surface, respectively. Compared with the pristine UF and NF membranes, pure water flux decreased by 40.66% for modified UF membrane and 12.92% for modified NF membrane, while the contact angle of the modified membranes decreased from 66.5° to 35.3° for UF membrane and from 48.2° to37.7° for NF membrane. However, the membrane modified by TiO₂ nanoparticles for both UF and NF membranes exhibited much better anti-fouling and separation performance for two types of oil-in-water emulsions with different droplet size (i.e., prepared oil-in-water emulsion with low salinity and oil produced water in Shengli oilfield, China). It was obvious that water flux of modified UF only slightly decreased and the stable water flux was 2.2 times and 15.6% higher than that of pristine membranes for the prepared oil-in-water emulsion and produced water, respectively. According to the five fouling models for UF, the TiO₂ modified UF membrane could alleviate the fouling on membrane surface and greatly increase water flux by reducing the adsorption, deposition, blockage of membrane pores and formation of cake layer for two types of oil-in-water emulsion. For NF, water flux of the modified membrane increased by 66.1% and 22.8% for prepared oil-in-water emulsion and produced water, respectively. TiO₂ coating effectively alleviated the oil adhesion and cake layer formation on the membrane surface.

Design and Construction of Ag@MOFs Immobilized PVDF Ultrafiltration Membranes with Anti-bacterial and Antifouling Properties

In this work, Ag nanoparticle loading Mg(C10H16O4)2(H2O)2(Ag@MOF) composite material was successfully prepared by a facile strategy, and subsequently Ag-MOFs were used to modify the PVDF ultrafiltration membranes to obtain fouling resistance and higher water flux. The as-prepared PVDF membranes were systematically characterized by a series of analytical techniques such as Water Contact Angle (CA), Scanning Electron Microscopy (SEM), and SEM-mapping. Furthermore, the performance of membranes on antibacterial properties, the pure water flux, and fouling resistance was investigated in detail. Those results showed that the membrane modified by Ag@MOFs containing 30% Ag had the higher anti-bacterial performance, and the clear zone could be increased to 10 mm in comparison with that of blank membrane. Meanwhile, the pure water flux of Ag@MOF membranes increased from 85 L/m2 h to 157 L/m2 h, and the maximum membrane flux recovery rate (FRR) of 95.7% was obtained using SA as pollutant, which is attributed to the introduction of Ag@MOF composite material. Based on the above experimental results, it can be found that the Ag-MOF membranes displayed the excellent antibacterial activity, high water flux, and fine fouling resistance. This work provides a facile strategy to fabricate the Ag@MOFs modified membranes, and it shows an excellent anti-bacterial and water flux performance.

Treatment of vinasse liquid from sugarcane industry using electro-coagulation/flocculation followed by ultra filtration

In this present work, vinasse, a by-product of sugarcane industry, was examined using combined treatment methods to purify it. Electrocoagulation/flocculation, ultrafiltration were applied as pre-treatment and post-treatment, respectively. The effectiveness of combined process was evaluated based on colour, turbidity and chemical oxygen demand (COD) removal. The efficiency of electrochemical reactor was investigated according to process variables such as retention time, electrode distance and electrolyte dose. From the results, the price to treat unit vinasse is found to be 2.5 US$/m3 under optimum conditions. FT-IR analysis of sludge obtained shows the results of electro-coagulation process. Ultrafiltration as post treatment experiments showed the enhanced removal efficiency of colour (91%), turbidity (88%) and COD (85%). The results showed that electrocoagulation followed by ultrafiltration is a suitable combined technique to reduce the colour, turbidity and COD from vinasse liquid.

Preparation and characterization of nano-filtration and its photocatalytic abilities via pre-coated and self-forming dynamic membranes developed by ZnO, PAC and chitosan

In the current work, novel dynamic membranes (DM) were tested and introduced for cheese whey wastewater treatment based on resistant and inexpensive materials, polyesters, and chitosan. For the investigation of dynamic membrane (pre-coated and self-forming) characterizations, polyester as a low-cost and natural material with chitosan were chosen to provide the support of the target membrane. The inherent antifouling character of chitosan accompanied by its high hydrophilicity have made this polymer known as an attractive agent for membrane-based wastewater treatment operations. Zinc oxide (ZnO) and powdered activated carbon (PAC) were employed as the dynamic layer. Neat polyester had a chemical oxygen demand (COD) rejection ratio of about 57.61%, but the flux declined sharply. The higher removal efficiency was for the self-forming type: total phosphate (94%) and citrate (95.5%). Fouled dynamic membranes were backwashed by sodium dodecyl-sulphate (SDS), warm water, and distilled water. Results demonstrated that the pre-coated was reduced and fouling increased the flux recovery rate (FRR) (9.1%) while use of the self-forming DM exhibited an aggravation of fouling by decreasing of support FRR (11.1%). It was found that by substitution of deionized water and hot water with SDS, FRR was enhanced. In the following, the photocatalytic ability of the product was investigated. The UV light source increased the removal ratio and FRR. For example, self-forming COD rejection was enhanced (6.63%).

The Adsorption of Methylene Blue by an Amphiphilic Block Co-Poly(Arylene Ether Nitrile) Microsphere-Based Adsorbent: Kinetic, Isotherm, Thermodynamic and Mechanistic Studies

Dye pollution is a serious problem in modern society. We desired to develop an efficient adsorbent for the decontamination of discharged dyes. In this work, the polymeric microspheres derived from a kind of amphiphilic block of co-poly(arylene ether nitrile) (B-b-S-P) were prepared on the basis of “oil-in-water” (O/W) microemulsion method. The B-b-S-P microspheres were found competent to remove the cationic dye, methylene blue (MB); and various influential factors, such as contact time, initial concentration, solution pH and temperature were investigated. Results indicated that the maximum adsorption capacity of B-b-S-P microspheres for MB was 119.84 mg/g at 25 °C in neutral conditions. Adsorption kinetics and isotherm dates were well fitted to a pseudo-second-order kinetic model and the Langmuir isotherm model, and thermodynamic parameters implied that the adsorption process was endothermic. The B-b-S-P microspheres also exhibited a highly selective adsorption for cationic dye MB, even in the presence of anionic dye methyl orange (MO). In addition, the possible adsorption mechanism was studied, suggesting that the electrostatic interaction and π–π interaction could be the main force in the adsorption process.

High-Performance TiO₂ Nanotubes/Poly(aryl ether sulfone) Hybrid Self-Cleaning Anti-Fouling Ultrafiltration Membranes

A series of novel self-cleaning hybrid photocatalytic ultrafiltration (UF) membranes were fabricated to separate polyacrylamide, which is widely used as a commercial flocculant. To maximize the self-cleaning and anti-fouling properties of hybrid membranes, high surface area TiO₂ nanotubes (TNTs) with excellent photocatalytic activity were homogeneously introduced into a poly(aryl ether sulfone) matrix by chemical bonds. The chemical structure, micromorphology, hydrophilicity, separation efficiency, fouling behavior, and self-cleaning property of the prepared hybrid membranes were well characterized and evaluated. For the optimal sample, the flux recovery ratio increased from ~40% to ~80% after simulated sunlight irradiation for 20 min, which was attributable to the homogeneous dispersion and efficient photocatalytic degradation ability of TNTs. Furthermore, the intelligent fabrication strategy enhanced the anti-aging ability of the hybrid membranes via the use of a fluorine-containing poly matrix. This work provided new insight into the fabrication of high-performance self-cleaning inorganic/organic hybrid membranes.

Polysulfide microspheres with chemical modification for generation of interfaces with macroscopic colour variation and biomimetic superhydrophobicity

Both superwettability and structural colours have attracted considerable attention in recent years. In addition, the combination of structural colours and superwettability could endow materials with broader application prospects. The combination provides a new strategy to design novel functional materials, and there are many studies pertaining to these materials that have been reported in recent years. Herein, a polysulfide (PSF) superhydrophobic coating was synthesized successfully. The PSF superhydrophobic coating possesses excellent superhydrophobicity, oleophobicity for diesel and macroscopic structural colour variation when wetted. The colour is changed when the coating is wetted and it returns to its original colour after drying. In addition, the surface presents better reusability and thermostability which satisfies various daily needs. The PSF superhydrophobic coating can be considered as an excellent candidate for designing wetting responsive materials, and it has enormous application potential in the fields of detection, sensing, anti-counterfeiting and security. For the first time, we present a novel and low-cost strategy to fabricate materials with both superhydrophobicity and structural colour, offering significant insights into the practical application of these functional materials.

Proof of Concept for Light Conducting Membrane Substrate for UV-Activated Photocatalysis as an Alternative to Chemical Cleaning

Adopting an effective strategy to control fouling is a necessary requirement for all membrane processes used in the water/wastewater treatment industry to operate sustainably. The use of ultraviolet (UV) activated photocatalysis has been shown to be effective in mitigating ceramic membrane fouling by natural organic matter. The widely used configuration in which light is directed through the polluted water to the membrane’s active layer suffers from inefficiencies brought about by light absorption by the pollutants and light shielding by the cake layer. To address these limitations, directing light through the substrate, instead of through polluted water, was studied. A UV conducting membrane was prepared by dip coating TiO₂ onto a sintered glass substrate. The substrate could successfully conduct UV from a lamp source, unlike a typical alumina substrate. The prepared membrane was applied in the filtration of a humic acid solution as a model compound to study natural organic matter membrane fouling. Directing UV through the substrate showed only a 1 percentage point decline in the effectiveness of the cleaning method over two cleaning events from 72% to 71%, while directing UV over the photocatalytic layer had a 9 percentage point decline from 84% to 75%. Adapting the UV-through-substrate configuration could be more useful in maintaining membrane functionality during humic acid filtration than the current method being used.

Biomimetic self-slippery and transferable transparent lubricant-infused functional surfaces

Self-slippery liquid-infused porous surfaces (SLIPSs) have been presented owing to their enormous number of potential applications and have widely attracted the attention of researchers in recent years. In comparison with superhydrophobic surfaces, SLIPSs not only exhibit interfacial performance that corresponds to superhydrophobicity but also do not require the construction of a complicated and delicate morphology. Here, a facile strategy has been proposed for constructing silica SLIPSs. Three common lubricants (perfluoropolyethers, liquid paraffin and ethyl oleate) were employed in this study. Using a facile brush process, the surface can be coated on a substrate, and, after infusion of the lubricant, the transformation from superhydrophobicity to self-slippage properties can be achieved. In addition, changing the kind of lubricant and adjusting the amount of nanoscale hybrid silica particles in the coating solution can modulate the surface transparency and interfacial characteristics, which makes the surface meet the various requirements of different service conditions. This transferable performance endows the surface with the possibility of meeting the various requirements of different conditions and demonstrates the enormous value of the application of the coatings in many fields.

Preparation and characterization of PSF/PEI/CaCO3 nanocomposite membranes for oil/water separation

Ultrafiltration (UF) is one of the significant advanced processes for oily wastewater treatment due to its clear advantages, for instance, ease in operation and efficient separation. The main drawback of these processes is the fouling problem and many researchers' effort on fabrication of high-performance membranes with higher hydrophilicity and antifouling properties. In this study, flat-sheet polysulfone (PSF)/polyethylenimine (PEI)/CaCO₃ nanocomposite membranes were prepared by phase inversion method for oil/water emulsion separation. Structural properties of membranes were characterized by SEM, FT-IR, contact angle, tensile strength, and atomic force microscopy analysis. Increasing the CaCO₃ nanoparticle loading exhibited the increased the water flux and BSA rejection. PSF/PEI/10 wt% CaCO₃ nanocomposite membranes have 145 L/m² h water flux at 2 bar with a contact angle of 84° and with 92% BSA rejection. All prepared CaCO₃ nanocomposite membranes reached similar oil rejections at above 90%. Besides the higher water flux and oil removal efficiencies, 10 wt% of CaCO₃ nanoparticle-blended PSF membranes has notable antifouling capacity with the highest flux recovery ratio (FRR) and lowest flux decay ratio (DR) values. The results showed that there is a great potential to use PSF/PEI/CaCO₃ nanocomposite membranes for the treatment of oil water emulsions with higher permeability and antifouling capacity.

Facile surface modification of textiles with photocatalytic carbon nitride nanosheets and the excellent performance for self-cleaning and degradation of gaseous formaldehyde

Great advances in photocatalysis have been made by developing various efficient photocatalysts, but investigation on practical applications of photocatalysis is relatively backward. Herein we report a facile surface modification approach to functionalize textiles with excellent ability for photocatalytic self-cleaning and degradation of indoor volatile organic pollutants. Graphitic carbon nitride nanosheets (CNNS) in colloidal suspension were directly sprayed onto the surface of cellulose fibers in textiles, and the powerful hydrogen bonding action between surface hydroxyl groups of cellulose and plentiful hydroxyl and amino groups of exfoliated CNNS from alkali-treating realizes high stability of CNNS modified textiles. Due to ultrathin 2D thickness and high visible light transparency, the modification of CNNS would not affect the hand feeling of textiles and shield their original colors. The obtained textiles show superior photocatalytic self-cleaning performance to remove stains from various colored pollutants under solar light irradiation, including industrial organic dyes and juices. Meanwhile, gaseous formaldehyde also can be efficiently decomposed using Xe lamp or commercial LED lamp as light sources. This work realizes photocatalytic performance of textiles using a simple spraying method, and it has great potential application in textile self-cleaning, not only for surface stains but also for volatile organic compounds from textile release.