Concentration and Recovery of Dyes from Textile Wastewater Using a Self-Standing, Support-Free Forward Osmosis Membrane

Treatment of industrial textile wastewater by means of forward osmosis aiming to recover dyes and clean water

The textile industry is one of the largest water consumers, and, as a result of its activity, it generates tons of wastewater. In this research, forward osmosis has been employed to tackle the critical need of treating textile wastewater. The HFFO2 membrane (Aquaporin) was used to process large volumes of real cotton dyeing wastewater, wool dyeing wastewater, and several types of textile end-of-pipe wastewater. In all cases, the permeate flux was between 6 and 8 L·h- 1 m- 2 during the major part of the process. The recovery of clean water from each wastewater surpassed 90 %, whereas the membrane rejected more than 87 % of total dissolved solids. As a result, textile dyes were concentrated on the feed side of the membrane, which enables their recovery and potential reutilization in a subsequent dying process, along with the reclaimed water. The HFFO2 membrane was efficiently cleaned by a backwash process, restoring the initial water flux. These results indicate the suitability of forward osmosis to reuse dyes and water from textile wastewater, reducing the environmental impact of this industry and favoring its sustainability.

Critical review on salt tolerance improvement and salt accumulation inhibition strategies of osmotic membrane bioreactors

The osmotic membrane bioreactor (OMBR) is a novel wastewater treatment and resource recovery technology combining forward osmosis (FO) and membrane bioreactor. It has attracted attention for its low energy consumption and high contaminant removal performance. However, in the long-term operation, OMBR faces the problem of salt accumulation due to high salt rejection and reverse salt flux, which affects microbial activity and contaminants removal efficiency. This review analyzed the feasibility of screening salt-tolerant microorganisms and determining salinity thresholds to improve the salt tolerance of OMBR. Combined with recent research, the inhibition strategies for salt accumulation were reviewed, including the draw solution, FO membrane, operating conditions and coupling with other systems. It is hoped to provide a theoretical basis and practical guidance for the further development of OMBR. Finally, future research directions were prospected. This review provides new insights for achieving stable operation of OMBR and promotes its wide application.

Synergistically enhancing the selective adsorption of cationic dyes through copper impregnation and amino functionality into iron-based metal-organic frameworks

Dyes contaminating the sewages have seriously threatened the living beings and their separation from wastewater in terms of potential resource recovery is of high value. Herein, both of metal node doping and ligand group grafting were taken into account to enhance the adsorption selectivity of Fe-MOFs towards cationic dyes. The positive correlation between copper doping amount and selective coefficient (∂MOMB) for methylene blue (MB) over methyl orange (MO) within a certain range was mainly attributed to the increased surface negative charges via partial replacement of Fe(III) with Cu(II). Moreover, the amount of surface negative charges was further increased after amino functionalization and there was a synergism between Cu(II) and -NH2 in selectivity enhancement. As a result, Fe0.6Cu0.4-BDC-NH2 exhibited a 22.5-times increase in ∂MOMB and other cationic dyes including malachite green (MG) and rhodamine B (Rh. B) could also be selectively separated from binary and quaternary mixed dye systems. Moreover, Fe0.6Cu0.4-BDC-NH2 showed many superiorities like a wide pH range of 4.0-8.0, strong anti-interference ability over various inorganic ions, good recyclability, and stability. The adsorption kinetics and isotherm suggested that the MB adsorption process was a homogeneous single-layer chemisorption. Additionally, the thermodynamics manifested that the overall process was exothermic and spontaneous. According to the FT-IR and XPS spectra analysis, the electrostatic interaction and hydrogen bonding were determined as the main driving forces, and π-π interaction also contributed to the adsorption process.

Surface Bioengineering of Mo2Ga2C MAX Phase to Develop Blended Loose Nanofiltration Membranes for Textile Wastewater Treatment

The potential of blended loose nanofiltration membranes (LNMs) to fractionate dyes and inorganic salts in textile wastewater has become a focus of attention in recent years. In this research work, we fabricated LNMs based on polysulfone (PSf) membranes blended with l-histidine amino acid-functionalized Mo2Ga2C MAX phase (His-MAX). Scanning electron microscopy (SEM), atomic force microscopy (AFM), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), contact angle, ζ-potential, porosity, and pore size analyses were employed to characterize the LNMs. Blending 0.75 wt % of His-MAX additive with the PSf tailored the LNM's features by making it more water-friendly, increasing its porosity, enlarging its pores, and making its surface smoother. The pure water flux of 127.6 L/m2 h was achieved by LNM containing 0.75 wt % His-MAX, which was 2.5 times greater than the bare one. The mentioned LNM displayed a flux recovery ratio (FRR) of 68.27 and 98.57, 98.31, and 99.7% rejections for Direct red 23, Acid brown 75, and Reactive blue 21 solutions (100 mg/L), respectively. The 0.75 wt % His-MAX LNM could reject 99.1% of dye and 11.5% of salt while maintaining an FRR of 91.19% after four cycles of filtering a binary mixture solution containing Reactive blue 21 and Na2SO4. These findings highlight the potential of the fabricated LNM for desalinating dye solutions.

Adsorptive Elimination of a Cationic Dye and a Hg (II)-Containing Antiseptic from Simulated Wastewater Using a Metal Organic Framework

Several types of pollutants have acute adverse effects on living bodies, and the effective removal of these pollutants remains a challenge. Safranin O (a biological dye) and merbromin (a topical mercury-containing antiseptic) are considered organic pollutants, and there are only a few reports on their removal. Synthesized and well-characterized (through PXRD, FTIR, FESEM, and EDS analysis) MOF-5 was used for the first time in the removal of safranin O and merbromin from simulated wastewater and real wastewater. In both cases, MOF-5 effectively removed contaminants. We found that in simulated wastewater, the highest efficiency of removal of safranin O was 53.27% (for 15 mg/L) at pH 10, and for merbromin, it was 41.49% (for 25 mg/L) at pH 6. In the case of real wastewater containing natural ions (Na+, K+, F-, Cl-, SO42-, PO43-, Mg2+, and Ca2+) and other molecules, the removal efficiencies of these two dyes decreased (34.00% and 26.28% for safranin O and merbromin, respectively) because of the presence of other ions and molecules. A plausible mechanism for the removal of these pollutants using MOF-5 was proposed.

Membrane-based technology in water and resources recovery from the perspective of water social circulation: A review

In this review, the application of membrane-based technology in water social circulation was summarized. Water social circulation encompassed the entire process from the acquirement to discharge of water from natural environment for human living and development. The focus of this review was primarily on the membrane-based technology in recovery of water and other valuable resources such as mineral ions, nitrogen and phosphorus. The main text was divided into four main sections according to water flow in the social circulation: drinking water treatment, agricultural utilization, industrial waste recycling, and urban wastewater reuse. In drinking water treatment, the acquirement of water resources was of the most importance. Pressure-driven membranes, such as ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO) were considered suitable in natural surface water treatment. Additionally, electrodialysis (ED) and membrane capacitive deionization (MCDI) were also effective in brackish water desalination. Agriculture required abundant water with relative low quality for irrigation. Therefore, the recovery of water from other stages of the social circulation has become a reasonable solution. Membrane bioreactor (MBR) was a typical technique attributed to low-toxicity effluent. In industrial waste reuse, the osmosis membranes (FO and PRO) were utilized due to the complex physical and chemical properties of industrial wastewater. Especially, membrane distillation (MD) might be promising when the wastewater was preheated. Resources recovery in urban wastewater was mainly divided into recovery of bioenergy (via anaerobic membrane bioreactors, AnMBR), nitrogen (utilizing MD and gas-permeable membrane), and phosphorus (through MBR with chemical precipitation). Furthermore, hybrid/integrated systems with membranes as the core component enhanced their performance and long-term working ability in utilization. Generally, concentrate management and energy consumption control might be the key areas for future advancements of membrane-based technology.

A review on existing and emerging approaches for textile wastewater treatments: challenges and future perspectives

This comprehensive review explores the complex environment of textile wastewater treatment technologies, highlighting both well-established and emerging techniques. Textile wastewater poses a significant environmental challenge, containing diverse contaminants and chemicals. The review presents a detailed examination of conventional treatments such as coagulation, flocculation, and biological processes, highlighting their effectiveness and limitations. In textile industry, various textile operations such as sizing, de-sizing, dyeing, bleaching, and mercerization consume large quantities of water generating effluent high in color, chemical oxygen demand, and solids. The dyes, mordants, and variety of other chemicals used in textile processing lead to effluent variable in characteristics. Furthermore, it explores innovative and emerging techniques, including advanced oxidation processes, membrane filtration, and nanotechnology-based solutions. Future perspectives in textile wastewater treatment are discussed in-depth, emphasizing the importance of interdisciplinary research, technological advancements, and the integration of circular economy principles. Numerous dyes used in the textile industry have been shown to have mutagenic, cytotoxic, and ecotoxic potential in studies. Therefore, it is necessary to assess the methods used to remediate textile waste water. Major topics including the chemical composition of textile waste water, the chemistry of the dye molecules, the selection of a treatment technique, the benefits and drawbacks of the various treatment options, and the cost of operation are also addressed. Overall, this review offers a valuable resource for researchers and industry professionals working in the textile industry, pointing towards a more sustainable and environmentally responsible future.

Integrating reverse osmosis and forward osmosis (RO-FO) for printing and dyeing wastewater treatment: impact of FO on water recovery

Reverse osmosis (RO) alone has low water recovery efficiency because of membrane fouling and limited operating pressure. In this study, a combined reverse osmosis-forward osmosis (RO-FO) process was used for the first time to improve the water recovery efficiency of secondary effluent in printing and dyeing wastewater. The effects of operating pressure and pH on water recovery and removal efficiency of RO-FO were investigated. The results showed that the optimum conditions were an operating pressure of 1.5 MPa and a feed solution pH of 9.0. Under optimal operating conditions, most of the organic and inorganic substances in the wastewater can be removed, and the rejection of total organic carbon (TOC), Sb, Ca, and K were 98.7, 99.3, 97.0, and 92.7%, respectively. Fluorescence excitation-emission matrices coupled with parallel factor (EEM-PARAFAC) analysis indicated that two components (tryptophan and tyrosine) in the influent were effectively rejected by the hybrid process. The maximum water recovery (Rw, max) could reach 95%, which was higher than the current single RO process (75%). This research provided a feasible strategy to effectively recover water from printing and dyeing wastewater.

Performance evaluation of deep eutectic solvent as a draw solute and vertical up-flow forward osmosis module for desalination of seawater

Forward osmosis (FO) has gained prominence in recent years particularly in desalination due to its ability to operate at low or no hydraulic pressure, with relatively limited membrane fouling and high-water recovery. However, pre-treatment of seawater is required to reduce membrane fouling caused by the presence of suspended solid particles. Also, a significant area of research in forward osmosis is still finding a suitable draw solute (DS) with the ideal characteristics. In this study, a novel deep eutectic solvent (DES) draw solute was used and able to extract water after the 500% dilution of DS. This signifies it as the potential candidate for the ideal DS. A comparative study of plate and frame and vertical up-flow forward osmosis (VUF) FO modules has been evaluated to eliminate the drawbacks associated with FO in terms of membrane fouling and draw solute. In addition, the performance of a novel DES as reline (choline chloride-urea) has been tested in both the modules. In VUF module, significantly less fouling was observed than in the plate and frame module. The initial water flux in plate and frame module was 2.30 LMH with seawater (without pre-treatment) as feed. However, it dropped to 1 LMH after 26 h of run. However, initial water flux in VUF was 1.90 LMH, and it was maintained to 1.50 LMH after 89 h of run. Regeneration of draw solute was carried out using a phase separation method and it was observed that phase separation was only observed for 10% dilution of DES.

Recovering and reuse of textile dyes from dyebath effluent using surfactant driven forward osmosis to achieve zero hazardous chemical discharge

This experimental study explores the feasibility of the reuse of dyes recovered from denim and polyester dyebath effluents using forward osmosis (FO) system to achieve zero hazardous material discharge. In batch experiments, the sodium dodecyl sulfate (SDS) at 0.5 M concentration generated an average flux of 3.5 L/m²/h (LMH) and reverse salt flux (RSF) of only 0.012 g/m²/h (GMH), while maintaining 100% dye rejection. This flux stability comes from the property of surfactants to form micelles and exert a stable osmotic pressure (π) above their critical micelle concentration (CMC). The low RSF is due to the greater micelle size. A colored fouling layer was formed on the membrane active layer (AL), which was easily removed using sodium hydroxide (NaOH) and citric acid. According to Fourier transform infrared spectra and atomic forces microscopy images of the AL, the interaction between foulants and membrane active groups did not significantly affect the physiochemical properties of the membrane. In the semi-continuous experiment, a very stable average flux of 7.3 LMH and RSF of 0.03 GMH was obtained using 0.75 M SDS as draw solution. The stacked 1D proton nuclear magnetic resonance analysis (¹HNMR) spectra of both original and recovered disperse dyes showed 100% similarity, which validates the concept that the recovered dyes maintained their integrity during reconcentration and can be reused in the next batch dyeing process. Importantly, the diluted SDS concentration can be directly reused within the same textile industry in scouring and finishing processes. The processes of dye recovery and reuse developed in this study do not produce any waste or hazardous by-products and are suitable for scale-up and onsite industrial applications.

Hydrothermally-Derived Silver-Decorated Nanocrystalline Anatase Photocatalyst for Reactive Violet 2 Photodegradation

A photocatalyst comprised of Ag nanoparticles dispersed on an anatase matrix has been prepared using a simple hydrothermal method without additional thermal treatment. The prepared material was characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), UV-Vis spectroscopy, and N2 adsorption–desorption isotherms. The prepared catalyst activity was evaluated by photocatalytic degradation of C.I. Reactive Violet 2 (RV2) aqueous solution under UVA and visible light illumination. SEM revealed the non-uniform dispersion of silver particles throughout the matrix composed of fine particles. According to XRD analysis, the matrix was composed of pure anatase with a crystallite size of 8 nm calculated through the Scherrer equation. HRTEM micrograph analysis showed that anatase nanoparticles possess a spherical morphology and a narrow size distribution with an average particle size of 8 nm with more active anatase {100} crystal surface exposed, while silver nanoparticles were between 60 and 90 nm. A bandgap of 3.26 eV has been calculated on the basis of the DRS UV-Vis spectrum, while a specific surface area of 209 m2g−1 has been established from adsorption isotherms. Thus, through a simple synthesis approach without subsequent thermal treatment, the agglomeration of nanoparticles and the reduction of specific surface area have been avoided. Prepared nano Ag/anatase photocatalyst exhibits excellent efficiency for the photodegradation of RV2 under UVA and visible irradiation.

New Materials and Phenomena in Membrane Distillation

In recent decades, membrane-based processes have been extensively applied to a wide range of industrial processes, including gas separation, food industry, drug purification, and wastewater treatment. Membrane distillation is a thermally driven separation process, in which only vapour molecules transfer through a microporous hydrophobic membrane. At the operational level, the performance of membrane distillation is negatively affected by wetting and temperature polarization phenomena. In order to overcome these issues, advanced membranes have been developed in recent years. This review, which focuses specifically on membrane distillation presents the basic concepts associated with the mass and heat transfer through hydrophobic membranes, membrane properties, and advances in membrane materials. Photothermal materials for solar-driven membrane distillation applications are also presented and discussed.

Synergistic effects of microplastics and organic foulants on the performance of forward osmosis membranes

Microplastics (MPs) are emerging contaminants that are abundantly present in the influent and effluent of wastewater treatment plants (WWTPs). Forward osmosis (FO) is an advanced treatment technology with potential applications in WWTPs. The presence of MPs in WWTP effluents can contribute to FO fouling and performance deterioration. This study focuses on FO membrane fouling by MPs of different sizes, and the interactional impacts of MPs and Humic acid (HA) (as the most common organic foulant in WWTPs) on FO membrane performance. The synergistic effect of combined MPs and HA fouling is shown to cause higher flux decline for FO membranes than that of HA or MPs alone. Reverse salt flux increased in the presence of MPs, and decreased when HA was present. Further, full flux recovery was obtained for all fouled membranes after hydraulic cleaning. This indicates the efficiency of FO systems for treating wastewater with high fouling potential. This study highlights the necessity of considering MPs in studying fouling behaviour, and for mitigation strategies of membranes used in WWT. The fundamentals created here can be further extended to other membrane-assisted separation processes.

A novel conductive carbon-based forward osmosis membrane for dye wastewater treatment

Forward osmosis (FO) membrane fouling is one of the main reasons that hinder the further application of FO technology in the treatment of dye wastewater. To alleviate membrane fouling, a conductive coal carbon-based substrate and polydopamine nanoparticles (PDA NPs) interlayer composite FO membrane (CPFO) was prepared by interfacial polymerization (IP). CPFO-10 membrane prepared by depositing 10 mL of PDA NPs solution exhibited an optimum performance with water flux of 7.56 L/(m²h) for FO mode and 10.75 L/(m²h) for pressure retarded osmosis (PRO) mode, respectively. For rhodamine B and chrome black T dye wastewater treatment, the water flux losses were reduced by 21.6%, and 14.5% under the voltages of +1.5 V, and -1.5 V, respectively, compared with no voltage applied after the device was operated for 8 h. The applied voltage had little effect on the fouling mitigation performance of the CPFO membrane for neutral charged cresol red. After the device was operated for 4 cycles, the rejection rates of dyes wastewater treated by the CPFO membranes with applied voltage were close to 100%. The flux decline rate and flux recovery rate of CPFO membrane for rhodamine B and chrome black T wastewater treatment under application of +1.5 V and -1.5 V voltage after 4 cycles were 11.6%, 99.2%, and 16.7%, 98.9%, respectively. Therefore, the voltage-applied CPFO membrane still maintained good rejection and antifouling performance in long-term operation. This study provides a new insight into the preparation of conductive FO membranes for dye wastewater treatment and membrane fouling control.

Dye recovery with photoresponsive citric acid-modified BiOCOOH smart material: Simple synthesis, adsorption-desorption properties, and mechanisms

Dye recovery is of great significance for a circular economy and sustainable development. However, green recovery strategies without secondary pollution remain a significant challenge. To resolve this issue, a light-responsive smart material (citric acid-modified BiOCOOH (m-BOCH)) was synthesized and applied for dye recovery through adsorption in the dark, and desorption under visible light. With the modification of citric acid, the adsorption level of methylene blue (MB) on m-BOCH (43.4%) was more than six times that of pure BiOCOOH (7.1%). The desorption rate was ∼90% in 120 min under 420 nm light irradiation (there was no desorption for pure BOCH). Further, the adsorption rate was improved to 83.9% and the desorption rate remained stable at an optimal pH of 10.09. Characterization results indicated that carboxyl groups were modified onto the surface of BiOCOOH and served as adsorption sites for MB. Under visible light exposure, the connections between the carboxyl groups and BiOCOOH were damaged, which led to the desorption of MB from the surface of the m-BOCH. The recovered MB exhibited a good staining effect on hepatic stellate cells (HSC) as a fresh dye. The regeneration of m-BOCH was achieved through a moderate hydrothermal process, and the adsorption and desorption capacities were restored to 80.8% and 85.7%, respectively. This research provides a novel environmentally compatible strategy for dye recovery without secondary pollution. This is a very promising treatment technique for dye effluents, which highlights the application of smart materials resource recycling for environmental remediation.

Regeneration and reuse of salt-tolerant zwitterionic polymer fluids by simple salt/water system

Highly-efficient separation of adsorbent and pollutant from chemical sludge is urgent for the recycled materials and chemical resources and minimization of sludge production in industry. Herein, an effortless and cost-efficient salt/water system is developed for efficient zwitterionic polymer/dye separation from chemical sludge. To achieve this aim, a novel salt-tolerant zwitterionic polymer (STZP) is synthesized through etherifying 2-chloro-4,6-bis(4-carboxyphenyl amino)-1,3,5-triazine onto corn starch. It is found that "all-surface-area" adsorption of dye can be achieved by in-situ sol-gel transition of STZP. Spent polymer fluid and solid-state dye can be easily regenerated and separated from sewage sludge by a simple salt/water system. At a high NaCl concentration (225 g/L), the separation factor between zwitterionic polymer and dye is up to 50.4, which is 50 times larger than that of salt-free solution. More importantly, the regenerated polymer fluids exhibit an outstanding reusability ability and can maintain over 92.8% decoloration efficiency for dyeing effluent after multiple adsorption-desorption cycles. This study thus provides a technically feasible and economically acceptable strategy for the recycling and reuse of polymer from hazardous textile sludge waste, greatly promising to achieve zero emissions toward conventional adsorption units.

Review on effect of different type of dyes on advanced oxidation processes (AOPs) for textile color removal

The textile industry is one of the most valuable industries, especially in developing countries, because it employs a large portion of the workforce. However, the development of the textile industry has led to increasing concern about environmental issues. Wastewater from the textile industry has a high COD and an undesirable color. Color is one of the problems with the wastewater due to its toxicity and low biodegradability. Color in textile wastewater mainly originates from the dyestuff used during the dyeing or printing process. Amongst all of available technology for color removal, advanced oxidation processes (AOPs) are considered one of the best and the most potential technology. However, the understanding of AOPs reaction mechanism to degrade dyestuff is still limited. In general, dyes degradation mechanism will vary and mainly depend on the chemical structure of the dyes itself. Some reaction pathway that seems less favorable thermodynamically can still happen during the process. Understanding the mechanism will be beneficial for future dyes improvement, especially on developing the moiety of the aromatic compound in order to produce easily degraded dyes while maintaining the fastness quality.

Exploring flowery MnO2/Ag nanocomposite as an efficient solar-light-driven photocatalyst

An efficient approach was developed to boost the solar light driven photocatalytic efficacy of pristine flowery MnO2 NCs through the immobilization of Ag NPs, which in turn produces MnO2/Ag NCs.

Water recovery from yarn fabric dyeing wastewater using electrochemical oxidation and membrane processes

This study intended to evaluate and compare the efficiency of electrochemical oxidation (EO), nanofiltration (NF), and reverse osmosis (RO) membranes processes in the treatment of yarn fabric dyeing wastewater (YFDW) in terms of chemical oxygen demand (COD) removal, color removal, salinity reduction, and conductivity removal. EO tests of the textile effluent were conducted under various current densities and solution pH conditions employing a graphite electrode. Membrane filtration experiments were conducted using two different NF membranes: NP010 and NP030 and two distinct RO membranes: BW30 and SW30 flat-sheet membranes. The experimental results showed that NF membrane process is not suitable for yarn fabric wastewater treatment showing low removal efficiencies for COD, color, and conductivity. However, both EO and RO membranes could reduce COD and color to high removal performances. EO results showed more than 99% of color removal and 80% of COD elimination at pH = 6 and current density of 50 mA/cm² after 180 min of reaction. Using RO membrane for yarn fabric wastewater treatment demonstrated relatively complete removal of color concentration and 98% of COD elimination. However, EO process showed less performance in conductivity removal efficiency compared to the RO membranes. EO treatment of YFDW decreased conductivity by 31.2%, whereas RO membrane process reduced conductivity to a greater extent and recorded 97.1% of removal elimination percentage. Therefore, the treated water by RO membrane could be recycled back to the process such as washing and dyeing, in that way offering economic profits by decreasing water consumption and wastewater treatment cost. PRACTITIONER POINTS: Electrochemical oxidation and membrane filtration processes were combined for the treatment of yarn fabric dyeing wastewater (YFDW). A 100% color removal of color and 98.5% COD elimination efficiencies were obtained for the electrochemical oxidation (EO) + RO combined process. EO treatment of YFDW decreased conductivity by 32.7%, whereas the RO membrane process reduced conductivity to a greater extent and recorded 97.7% of removal elimination percentage.

Optimization of nutrient rich solution for direct fertigation using novel side stream anaerobic forward osmosis process to treat textile wastewater

The current study focused on the performance of a lab scale side stream anaerobic fertilizer drawn forward osmosis (An-FDFO) setup and optimization of nutrient rich solution to achieve sustainable water reuse from high strength synthetic textile wastewater. Three fertilizer draw solutes including Mono Ammonium Phosphate (MAP), Ammonium Sulphate (SOA) and Mono Potassium Phosphate (MKP) were blended in six different ratios with total molar concentration not exceeding 1 M. Among six blended draw solutions (DS), combination with high concentration of SOA have shown highest flux and combination with high concentration of MKP have shown highest reverse solute flux, while those with high concentration of MAP remain moderate both in flux and RSF. During long term runs, SOA: MKP (0.75: 0.25 M) showed longest filtration duration of 217 h in Run 1, with highest initial flux of 8.29 LMH and minimum dilution factor to achieve final nutrients concentration fit for direct fertigation, followed by Run 3 MAP: SOA: MKP (0.2: 0.6: 0.2 M) and then Run 2 MAP: MKP (0.75: 0.25). Moreover, deterioration of mixed liquor characteristics occurs in membrane tank due to high RSF. Similarly, the same inhibitory effect of reverse salt on biogas production was also assessed through Bio-Methane Potential experiments. However, Anaerobic Continuous Stirring Tank Reactor exhibited high performance efficacy, highlighting the importance of side stream submerged configuration in forward osmosis (FO) process.

Simultaneous decontamination of multi-pollutants: A promising approach for water remediation

Water remediation techniques have been extensively investigated due to the increasing threats of soluble pollutants posed on the human health, ecology and sustainability. Confronted with the complex composition matrix of wastewater, the simultaneous elimination of coexisting multi-pollutants remains a great challenge due to their different physicochemical properties. By integrating multi-contaminants elimination processes into one unit operation, simultaneous decontamination attracted more and more attention under the consideration of versatile applications and economical benefits. In this review, the state-of-art simultaneous decontamination methods were systematically summarized as chemical precipitation, adsorption, photocatalysis, oxidation-reduction, biological removal and membrane filtration. Their applications, mechanisms, mutual interactions, sustainability and recyclability were outlined and discussed in detail. Finally, the prospects and opportunities for future research were proposed for further development of simultaneous decontamination. This work could provide guidelines for the design and fabrication of well-organized simultaneous decontaminating system.

β-cyclodextrin-containing polymer based on renewable cellulose resources for effective removal of ionic and non-ionic toxic organic pollutants from water

A novel, bio-derived cyclodextrin-based trifunctional adsorbent has been successfully synthesized for efficient, rapid and simultaneous removal of a broad-spectrum of toxic ionic (anionic and cationic dyes) and non-ionic organic pollutants from water. The composition, morphology and the presence of functional groups in the obtained sorption material were characterized by elemental analysis, XRD, SEM, and FTIR spectroscopy. The adsorption results were represented by cationic dye (crystal violet, CV) and endocrine disrupting compound (bisphenol A, BPA) as an adsorbate. The sorption processes of the model pollutants were studied with both kinetic and equilibrium models. The results showed that the sorption was rapid (less than 1 min) and the time evolution could be fitted using a pseudo-second order model. According to Langmuir isotherm model, the maximum adsorption capacities were found at 113.64 and 43.10 mg g^-1 for BPA and CV, respectively. The adsorption ability of β-CDPs was kept nearly on the same level after five regeneration cycles. Furthermore, almost complete removal of the pollutants was observed during the treatment of real effluents samples thus the bio-derived, cheap and reusable BAN-EPI-CDP has a promising potential for practical applications.

Methylene Blue Dye Adsorption from Wastewater Using Hydroxyapatite/Gold Nanocomposite: Kinetic and Thermodynamics Studies

The present work demonstrates the development of hydroxyapatite (HA)/gold (Au) nanocomposites to increase the adsorption of methylene blue (MB) dye from the wastewater. HA nanopowder was prepared via a wet chemical precipitation method by means of Ca(OH)₂ and H₃PO₄ as starting materials. The biosynthesis of gold nanoparticles (AuNPs) has been reported for the first time by using the plant extract of Acrocarpus fraxinifolius. Finally, the as-prepared HA nanopowder was mixed with an optimized AuNPs solution to produce HA/Au nanocomposite. The prepared HA/Au nanocomposite was studied by using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and Scanning Electron Microscopy (SEM) with Energy Dispersive X-Ray Analysis (EDX) analysis. Adsorption studies were executed by batch experiments on the synthesized composite. The effect of the amount of adsorbent, pH, dye concentration and temperature was studied. Pseudo-first-order and pseudo-second-order models were used to fit the kinetic data and the kinetic modeling results reflected that the experimental data is perfectly matched with the pseudo-first-order kinetic model. The dye adsorbed waste materials have also been investigated against Pseudomonas aeruginosa, Micrococcus luteus, and Staphylococcus aureus bacteria by the agar well diffusion method. The inhibition zones of dye adsorbed samples are more or less the same as compared to as-prepared samples. The results so obtained indicates the suitability of the synthesized sample to be exploited as an adsorbent for effective treatment of MB dye from wastewater and dye adsorbed waste as an effective antibacterial agent from an economic point of view.

Membrane Surface Functionalization with Imidazole Derivatives to Benefit Dye Removal and Fouling Resistance in Forward Osmosis

Water contaminated with low concentrations of pollutants is more difficult to clean up than that with high pollutant content levels. Membrane separation provides a solution for removing low pollutant content from water. However, membranes are prone to fouling, losing separation performances over time. Here we synthesized neutral (IM-NH₂) and positively charged (IL-NH₂) imidazole derivatives to chemically functionalize membranes. With distinct properties, these imidazole grafts could tailor membrane physicochemical properties and structures to benefit forward osmosis (FO) processes for the removal of 20-100 ppm of Safranin O dye-a common dye employed in the textile industry. The water fluxes produced by IM-NH₂- and IL-NH₂-modified membranes increased by 67% and 122%, respectively, with DI water as the feed compared to that with the nascent membrane. A 39% flux increment with complete dye retention (∼100%) was achieved for the IL-NH₂-modified membrane against 100 ppm of Safranin O dye. Regardless of the dye concentration, the IL-NH₂-modified membrane exhibited steadily higher permeation performance than the original membrane in long-term experiments. Reproducible experimental results were obtained with the IL-NH₂-modified membrane after cleaning with DI water, demonstrating the good antifouling properties and renewability of the newly developed membrane.

Zwitterionic Hydrogel-Impregnated Membranes with Polyamide Skin Achieving Superior Water/Salt Separation Properties

Support-free nonporous membranes have emerged as a new material platform for osmotic pressure-driven processes due to its insusceptibility to internal concentration polarization (ICP). Herein, we demonstrate high-performance membranes of zwitterionic hydrogels impregnated in porous membranes with a skin layer of highly cross-linked polyamides on both sides prepared by gel-liquid interfacial polymerization (GLIP). Such a configuration eliminates the pores and thus ICP, while the thin polyamide layer provides high salt rejection but negligible resistance to the water transport compared with the hydrogels. The polyamide skin layers are characterized using scanning electron microscopy and atomic force microscopy. The effect of the hydrogel compositions and polyamide formation conditions on the water/salt separation properties is thoroughly investigated. Example membranes show water permeance and salt rejection comparable to state-of-the-art commercial forward osmosis membranes and essentially no ICP.

Performance Evaluation of 1-Cyclohexylpiperidine as a Draw Solute for Forward Osmosis Water Separation and CO2 Recovery

Membrane-based technologies, such as forward osmosis (FO), offer the advantage of treating water through a spontaneous process that requires minimal energy input while achieving favorable water permeability and selectivity. However, the FO process still has some challenges that need to be solved or improved to become entirely feasible. The main impediment for this technology is the recovery of the draw solute used to generate the osmotic potential in the process. In this paper, we discuss the use of a switchable polarity solvent, 1-cyclohexylpiperidine (CHP), as a draw solute that responds to external stimuli. Specifically, the miscibility of CHP can be switched by the presence of carbon dioxide (CO₂) and is reversible by applying heat. Thus, in this study, the hydrophobic CHP is first converted to the hydrophilic ammonium salt (CHPH⁺), and its capability as a draw solution (DS) is thoroughly evaluated against the typical osmotic agent, sodium chloride (NaCl). Our results show that the water permeability across the thin film composite membrane increases by 69% when CHPH⁺ is used as the DS. Also, the water permeability when using different feed solutions: aqueous solutions of (a) urea and (b) NaCl were evaluated. In both cases, the CHPH⁺ generates water fluxes in the range of 65 ± 4 LMH and 69 ± 2 LMH, respectively. We then separate the diluted DS by applying 75 °C to the solution to recover the pure CHP and water. The results of this work provide a proof-of-concept of a CHP wastewater and desalination method via an FO process.

Membrane processes

This literature review provides a review for publications in 2018 and 2019 and includes information membrane processes findings for municipal and industrial applications. This review is a subsection of the annual Water Environment Federation literature review for Treatment Systems section. The following topics are covered in this literature review: industrial wastewater and membrane. Bioreactor (MBR) configuration, membrane fouling, design, reuse, nutrient removal, operation, anaerobic membrane systems, microconstituents removal, membrane technology advances, and modeling. Other sub-sections of the Treatment Systems section that might relate to this literature review include the following: Biological Fixed-Film Systems, Activated Sludge, and Other Aerobic Suspended Culture Processes, Anaerobic Processes, and Water Reclamation and Reuse. This publication might also have related information on membrane processes: Industrial Wastes, Hazardous Wastes, and Fate and Effects of Pollutants.

Insight into Adsorption Performance and Mechanism on Efficient Removal of Methylene Blue by Accordion-like V2CTx MXene

Dye-bearing wastewaters leading to the water pollution and ecological upset is a crucial issue in the textile industry. Herein, we report a facile method using two-dimensional transition metal carbides (MXenes) for the removal of the methylene blue (MB) in the water. The accordion-like V₂CT_x MXene is originally demonstrated to have high and spontaneous adsorption capacity of MB at 111.11 mg·g^-1, thrice over that of Ti₃C₂T_x as previously reported. The wide lamellar space of V₂CT_x is certain to have large accommodation for MB. The electrostatic interaction effect and hydrogen bond between V₂CT_x and MB not only promote the efficient adsorption process but also provide the selectivity between anionic and cationic dyes. Combined with good reusability, we anticipate that the V₂CT_x MXene is a promising candidate for the removal of cationic dyes from textile-dye-bearing wastewaters.

Polyamide nanofilms synthesized via controlled interfacial polymerization on a "jelly" surface

A thermal-sensitive "jelly" was used to control the diffusion of a diamine monomer for synthesizing polyamide free-standing nanofilms with an adjustable thickness of 5-35 nm. The reduced reaction rate of the interfacial polymerization at the hexane-"jelly" interface made the synthesized nanofilms show high water permeation flux and suitable salt rejection, and they also have highly negative surface charges and fairly smooth surfaces.

Feasibility of concentrating textile wastewater using a hybrid forward osmosis-membrane distillation (FO-MD) process: Performance and economic evaluation

The forward osmosis-membrane distillation (FO-MD) hybrid process has shown great promise in achieving zero liquid discharge in the textile industry, recovering valuable dye molecules while producing large amounts of clean water. However, the progress of this technology seems to have stagnated with the direct coupling of commercial asymmetric FO and MD membranes, because water management in the system is found to be rather complicated owing to the processing of the different membranes. Herein, we propose, for the first time, an FO-MD hybrid process using a custom-made self-standing and symmetric membrane and a hydrophobic polytetrafluoroethylene membrane in the FO and MD units, respectively. Three types of operation modes were investigated to systematically study the process performance in the concentration treatment of model textile wastewater; two commercial FO membranes were also tested for comparison. Owing to its low fouling propensity and lack of an internal concentration polarization effect, the water transfer rate of our symmetric FO membrane quickly reaches equilibrium with that in the MD unit, resulting in continuous and stable operation. Consequently, the hybrid process using the symmetric FO membrane was found to consume the least energy, as indicated by its lowest total cost in both lab- and large-scale systems. Overall, our study provides a new strategy for using a symmetric FO membrane in the FO-MD hybrid process and highlights its great potential for use in the treatment of textile wastewater.

Separation and Recycling of Concentrated Heavy Metal Wastewater by Tube Membrane Distillation Integrated with Crystallization

Tube membrane distillation (MD) integrated with a crystallization method is used in this study for the concurrent productions of pure water and salt crystals from concentrated single and mixed system solutions. The effects of concentrated Zn2+ and Ni2+ on performance in terms of membrane flux, permeate conductivity, crystal recovery rates, and crystal grades are investigated. Preferred crystallization and co-crystallization determinations were performed for mixed solutions. The results revealed that membrane fluxes remained at 2.61 kg·m-2·h-1 and showed a sharp decline until the saturation increased to 1.38. Water yield conductivity was below 10 μs·cm-1. High concentrated zinc and nickel did not have a particular effect on the rejection of the membrane process. For the mixed solutions, membrane flux showed a sharp decrease due to the high saturation, while the conductivity of permeate remained below 10 μs·cm-1 during the whole process. Co-crystallization has been proven to be a better method due to the existence of the SO42- common-ion effect. Membrane fouling studies have suggested that the membrane has excellent resistance to fouling from highly concentrated solutions. The MD integrated with crystallization proves to be a promising technology for treating highly concentrated heavy metal solutions.

Green synthesis of a magnetic β-cyclodextrin polymer for rapid removal of organic micro-pollutants and heavy metals from dyeing wastewater

Adsorption is one of the most preferred techniques in the advanced treatment of dyeing wastewater. Magnetic porous materials with good adsorption performance, excellent reusability, and a green synthesis route are highly desirable adsorbents in commerce. In this study, we synthesized a magnetic β-cyclodextrin polymer (MNP-CM-CDP) containing many macro- and ultramicropores in aqueous phase. CO₂ adsorption-desorption isotherms and a dye adsorption method provided Langmuir specific surface areas for the MNP-CM-CDP of 114.4 m² g^-1 and 153 m² g^-1, respectively. Model pollutants (BPA, MB, BO₂, RhB, Cr(III), Pb(II), Zn(II), and Cu(II)) were rapidly and efficiently removed from the aqueous solution by the MNP-CM-CDP. In addition, the polymer could be easily separated from the solution under an external magnetic field. The adsorption of the contaminants was dependent on pH, while the effects of ionic strength and humic acid were slight in the concentration range studied. The polymer could be easily regenerated at room temperature and retained good adsorption performance. Moreover, the MNP-CM-CDP showed good feasibility for the removal of pollutants from actual dyeing wastewater samples.

Forward osmosis: dyeing draw solutions for water reclamation from feed water resources

Reactive Black 5 and Basic Blue 41 GRL dyeing solutions (dye-to-salt mixture in a 1:10 dye-to-salt mass ratio) were investigated as draw solutions (DS) in a forward osmosis (FO) system with a biomimetic membrane. Synthetic seawater (SSW) and textile wastewater (TWW1 and TWW2) were evaluated as feed solutions (FS) for water reclamation. Reactive Black 5 and Basic Blue 41 GRL were diluted from 0.02 M to concentrations of 0.002 and 0.004 M, respectively. With Reactive Black 5 as DS and SSW as FS, an initial flux of 20.24 L/m² h and water recovery of 75% was achieved. Using TWW1 and TWW2, initial water fluxes of 19.51 and 13.43 L/m² h were achieved, respectively, with a 30% water recovery. Using Basic Blue 41 GRL, initial water fluxes of 18.72, 15.13 and 13.42 L/m² h were achieved with SSW, TWW1, and TWW2 as FS with water recoveries of 50%, 20% and 20%, respectively. The average reverse solute fluxes for Reactive Black 5 and Basic Blue 41 GRL were 0.06 to 0.34 g/m² h, respectively. Diluted dyeing solutions were produced, with simultaneous water reclamation from SSW and TWW resulting in similar or higher water fluxes and lower reverse solute fluxes compared with other commercially available membranes.

Modelling Forward Osmosis Treatment of Automobile Wastewaters

Forward osmosis (FO) has rarely been investigated as a treatment technology for industrial wastewaters. Within this study, common FO model equations were applied to simulate forward osmosis treatment of industrial wastewaters from the automobile industry. Three different models from literature were used and compared. Permeate and reverse solute flux modelling was implemented using MS Excel with a Generalized Reduced Gradient (GRG) Nonlinear Solver. For the industrial effluents, the unknown diffusion coefficients were calibrated and the influences of the membrane parameters were investigated. Experimental data was used to evaluate the models. It could be proven that common model equations can describe FO treatment of industrial effluents from the automobile industry. Even with few known solution properties, it was possible to determine permeate fluxes and draw conclusions about mass transport. However, the membrane parameters, which are apparently not solution independent and seem to differ for each industrial effluent, are critical values. Fouling was not included in the model equations although it is a crucial point in FO treatment of industrial wastewaters. But precisely for this reason, modelling is a good complement to laboratory experiments since the difference between the results allows conclusions to be drawn about fouling.