Chlorine Resistance Research Articles

Ethanol activation of polyester membrane for superior dye/salt separation performance

Dye wastewater poses a severe danger to the environment and human health. The purification of dye wastewater is the focus and hotspot of most researchers. In this work, ethylene glycol (EG) was selected as an aqueous phase monomer to fabricate polyester membranes through an interfacial polymerization reaction. Then the polyester membrane was activated by ethanol aqueous solution. By adjusting the activation time and concentration of the ethanol, the network of the polyester membrane can be reshaped to endow the membrane with excellent performance. The activation mechanism was also explored here. Compared to the membrane without activation (PE-0%), the permeability of the optimized membrane (PE-40%) was increased by 8.3 times, and a high rejection was maintained (CR: 99.2%). Importantly, the PE-40% membrane also presented good acid and alkali resistance, chlorine resistance, and excellent antifouling performance. Our work provides an effective and feasible strategy for the development of high-performance polyester membranes.

Dual-functional TFNC polyester membranes utilizing maltitol for dye/salt separation and desalination

To achieve a promising application prospect in nanofiltration (NF) membrane separation, a strategic design tailored to particular functions is crucial. Here, tailor-made thin film nanofibrous composite (TFNC) NF membranes for specific applications were fabricated via interfacial polymerization (IP) between maltitol and trimesoyl chloride (TMC) on PAN nanofibrous substrates. Owing to the moderate reactivity of maltitol, a range of sugar alcohol based polyester membranes with different morphologies and cross-linking degrees were obtained by varying the monomer concentration as well as the reaction time. In this case, the finely tuned loose Mal1-TMC0.2-2 membrane exhibited a prominent permeability (110.34 L m−2 h−1 bar−1) and an extraordinary selectivity for dye/salt mixed solution, with the rejection of Congo Red up to 99.11 % and NaCl retention of only 7.41 %, indicating its suitability for textile wastewater treatment. Further, the dense Mal2-TMC0.4-10 membrane showed an excellent Na2SO4 rejection of 97.40 % with a good permeability of 18.65 L m−2 h−1 bar−1, making it a candidate for seawater and brackish water desalination. In addition, both membranes demonstrated reliable chlorine and pressure resistance along with long-term stability. This study provided new insights and inspiration to the design and preparation of NF membranes for specialized applications.

Effect of household pipe materials on formation and chlorine resistance of the early-stage biofilm: various interspecific interactions exhibited by the same microbial biofilm in different pipe materials.

Microbial community biofilm exists in the household drinking water system and would pose threat to water quality. This paper explored biofilm formation and chlorination resistance of ten dual-species biofilms in three typical household pipes (stainless steel (SS), polypropylene random (PPR), and copper), and investigated the role of interspecific interaction. Biofilm biomass was lowest in copper pipes and highest in PPR pipes. A synergistic or neutralistic relationship between bacteria was evident in most biofilms formed in SS pipes, whereas four groups displayed a competitive relationship in biofilms formed in copper pipe. Chlorine resistance of biofilms was better in SS pipes and worse in copper pipes. It may be helped by interspecific relationships, but was more dependent on bacteria and resistance mechanisms such as more stable extracellular polymeric substance. The corrosion sites may also protect bacteria from chlorination. The findings provide useful insights for microbial control strategies in household drinking water systems.

Advanced sulfonated polyester nanofiltration membranes for superior dye separation, desalination, and chlorine resistance

This study introduces an innovative thin-film composite (TFC) nanofiltration membrane made from sulfonated polyvinyl alcohol (SPVA)-based polyester, specifically engineered for effective wastewater treatment. This novel membrane is developed through interfacial polymerization on a polysulfone substrate, demonstrating exceptional water permeability and filtration efficiency. It is particularly effective in separating dyes and salts due to its superior hydrophilicity, optimized surface charge, and precisely tailored morphology. Critical fabrication parameters were finely tuned, utilizing a 2 wt% SPVA solution and a 0.35 wt% trimesoyl chloride (TMC) in the organic phase, with both immersion and polymerization times set at 2 min. The performance metrics are outstanding, featuring a water permeance of 97 L m−2 h−1·bar−1, high dye rejection rates (99.51 % for Congo Red and 99.55 % for Brilliant Blue), and significant salt permeability (30.35 % for Na2SO4 and 29.93 % for MgSO4). The membrane also exhibits excellent antifouling properties, robust chlorine resistance (up to 48,000 ppm h), and sustained operational stability, underscoring its industrial viability for dye and textile effluent treatment. The TFC-SPVA membrane addresses critical environmental challenges in wastewater management, marking a significant advancement in membrane technology.

The Mechanical Properties and Chlorine Resistance of Concrete Based on the Effects of Pouring Interval Time

In practical engineering construction, differences in time intervals during concrete pouring arise due to issues in concrete quality control and construction procedures, thereby affecting the mechanical and durability properties of concrete. This study conducted compressive strength tests, splitting tensile strength tests, and natural immersion tests to investigate the influence of time intervals in layered pouring on the mechanical strength and chloride ion concentration distribution of staged pouring concrete. Additionally, the study elucidated the mechanism by which pouring interval time affects the mechanical properties and resistance to chloride ion erosion of staged pouring concrete at the microstructure level. The results indicate that compared to ordinary concrete specimens, the splitting tensile strength of staged pouring concrete demonstrates a continuous decrease with increasing pouring interval time. The most significant splitting tensile strength decrease occurred at a 24 h interval. The compressive strength of staged pouring concrete initially decreases and then increases with increasing pouring interval time. At a pouring interval time of 12 h, the compressive strength of staged pouring concrete decreased the most. Results from the natural immersion tests demonstrate that chloride ion concentrations at the bonding interface and on both sides of staged pouring concrete increase continuously with the extension of pouring interval time. The chloride ion concentration at the bonding interface is consistently higher than that on both sides, and the difference between them decreases with increasing diffusion depth. The chloride ion concentration difference ΔC was proposed to evaluate the influence of bonding interface performance on chloride ion concentration, which decreases to varying degrees with increasing depth. The findings of this study can provide guidance for the research on the mechanical properties and durability of staged pouring concrete in practical engineering construction, as well as for engineering protective measures.

Dual functionalization of polyamide reverse osmosis thin film composite membrane for improving chlorine resistance

Contemporary high-efficiency polyamide (PA) membranes are constructed using aliphatic or aromatic amines combined with acyl chlorides. Nevertheless, the aromatic rings attached to the N–H group within the amide linkages are vulnerable to degradation by chlorine. The surface of a PA reverse osmosis (RO) membrane was altered in this work through the dual functionalization of tannic acid (TA) and silver nanoparticles (Ag NPs) to improve separation performance, chlorine resistance, and anti-bacterial capabilities of membranes. This study provides an insight in the role and synergistic effects of TA and Ag NPs for enhancing the chlorine resistance of the modified TFC membranes. The outcome indicated that the RO-TA/Ag modified membrane exhibited the maximum rejection of 98.31%, slightly surpassing the pristine RO membrane, which had a rejection rate of 96.52%. The RO-TA/Ag modified membrane also shown improved chlorine tolerance against 500 ppm sodium hypochlorite solution (NaClO), as evidenced by X-ray photoelectron spectroscopy (XPS) measurement which revealed reduced chlorine content in contrast to pristine RO and RO-TA membrane. The RO-TA/Ag membrane exhibited the largest inhibitory zone for both Gram-positive, S. aureus and Gram-negative, E. coli bacteria. The synergistic effects of the dual functionalization of TA and Ag NPs which render the modified membrane with high anti-chlorine and anti-bacterial capabilities are discussed.

Synergistic interfacial polymerization between hydramine/diamine and trimesoyl chloride: A novel reaction for NF membrane preparation

Polyester-amide (PEA) thin film composite (TFC) NF membranes have rapidly evolved towards a competitive performance, benefiting from their remarkable antifouling capability and superior chlorine resistance. In this report, a new concept of synergistic interfacial polymerization is explored, which promptly triggers the reaction between hydramines and trimesoyl chloride (TMC) in the presence of a trace amount of diamines. This rapid-start mode enables the formation of defect-free PEA films without the requirement of catalysis. A comprehensive characterization of physicochemical properties using high-resolution mass spectrometer (HRMS) reveals that the recombination and formation of a “hydramine-diamine” coupling unit plays a decisive role in activating the synergistic interfacial polymerization reaction with TMC molecules. Taking the pair of serinol and piperazine (PIP) as an example, the PEA-NF membrane fabricated with 0.1 w/v% serinol mixed with 0.04 w/v% PIP as water-soluble monomer and 0.1 w/v% TMC as oil phase monomer was found to have a pure water permeability (PWP) of 18.5 L·m−2·h−1·bar−1 and a MgSO4 rejection of 95.5 %, which surpasses almost all the reported PEA NF membranes. Findings of the current research provide more possibilities for the low-cost and rapid synthesis of high-performance PEA membranes aiming for water purification.

More resilient polyester membranes for high-performance reverse osmosis desalination.

Thin-film composite reverse osmosis membranes have remained the gold standard technology for desalination and water purification for nearly half a century. Polyamide films offer excellent water permeability and salt rejection but also suffer from poor chlorine resistance, high fouling propensity, and low boron rejection. We addressed these issues by molecularly designing a polyester thin-film composite reverse osmosis membrane using co-solvent-assisted interfacial polymerization to react 3,5-dihydroxy-4-methylbenzoic acid with trimesoyl chloride. This polyester membrane exhibits substantial water permeability, high rejection for sodium chloride and boron, and complete resistance toward chlorine. The ultrasmooth, low-energy surface of the membrane also prevents fouling and mineral scaling compared with polyamide membranes. These membranes could increasingly challenge polyamide membranes by further optimizing water-salt selectivity, offering a path to considerably reducing pretreatment steps in desalination.

Construction of ZIF-derived CoCrOx/HZSM5 catalysts for deep catalytic oxidation of dichloromethane: Synergistic of B acid, L acid, and redox sites

The acidic and oxidizing properties of the catalyst are critical for the removal of chlorinated volatile organic compounds (CVOCs). An excellent catalyst often requires outstanding chlorine resistance and byproduct inhibition. In this study, CoOx, which is widely used for the removal of volatile organic compounds (VOCs) because of its outstanding activity was chosen to provide oxidizing properties. To address the potential for chlorination byproducts and the lack of activity, we loaded CoOx on the acidic carrier HZSM-5 by ZIF-derived method, then doped CrOx using impregnation method to enhance both oxidation and acidity. It was found that ZIF-derived method disperse CoOx nicely thus providing more oxidation sites. Besides, CrOx effectively increases the superficial lattice oxygen of the catalyst to compensate for the loss of sites due to the occupation of oxygen vacancies by DCM during the oxidation process. This contributes to the superior oxidizability of the modified catalysts, which explains the high CO2 selectivity. Invigoratingly, CrOx can increase the ratio of Lewis acid to Brønsted acid to completely break the C–Cl bond, hence eliminating the possibility of chlorine-containing byproducts and accomplishing a deeper degradation of CVOCs. The bimetallic catalysts we prepared have high activity and can achieve very low or even zero byproduct generation. In addition, the catalyst shows outstanding stability and water resistance, which is quite meaningful in the field of catalytic oxidation of CVOCs.

Unraveling the Tandem Effect of Nitrogen Configuration Promoting Oxygen Reduction Reaction in Alkaline Seawater

AbstractDeveloping seawater‐based high‐performance oxygen reduction reaction (ORR) electrocatalysts is meaningful to renewable energy storage and conversion, and the Fe‐based derivatives encapsulated by nitrogen (N) doped carbon are the typical representative. Nevertheless, unrevealing the mechanism of N configuration to ORR activity and chlorine resistance is still a great challenge. In this work, a feasible strategy is developed to prepare controllable pyridinic/pyrrolic‐N doped carbon‐coated Fe‐based electrocatalysts (FexN‐NC). Drawing support from the H3PO4 blocking based in situ Fourier transform infrared spectroscopy (FTIR) test and density‐functional theory (DFT) calculation, the tandem effect of pyridinic‐N and pyrrolic‐N on ORR is proved. Additionally, the low hydrogen peroxide (H2O2) yield and 4e− pathway of FexN‐NC demonstrate that N doping effectively reduces the adsorption of Cl−, which is consistent with the low Cl− adsorption energy of DFT. The half‐wave potential (E1/2) of FexN‐NC for ORR reaches 0.874 V in alkaline seawater, and ZABs assembled with FexN‐NC as the air cathode deliver a remarkable power density (162 mW cm−2), along with excellent long‐term durability (>400 h).

Morphology effect of cerium dioxide on the catalytic performance of Ru/CeO2 catalyst for the oxidation of different CVOCs

CeO2 with different morphology of rod-shape (R-CeO2), cube-shape (C-CeO2) and octahedra-shape (O-CeO2) were synthesized as supports and impregnated with Ru to obtain Ru/CeO2 catalysts, and the performance of which in catalytic oxidation of different chlorine-containing volatile organic compounds (CVOCs) (1,2-dichloroethylene (DCE) and vinyl chloride (VC)) were investigated. Due to the stronger interaction between Ru and R-CeO2, Ru was highly dispersed on R-CeO2 and more Ru entered support lattice to form Ru-O-Ce structure, thus Ru/R-CeO2 catalyst exhibited better redox property. Ru addition enhanced the acidity of Ru/R-CeO2 and Ru/C-CeO2, while that of Ru/O-CeO2 decreased instead. The acidity mainly affected DCE catalytic activity when catalyst had sufficient redox property and chlorine resistance. Run+ content was the main factor affecting VC catalytic activity. Ru/R-CeO2 catalyst exhibited the best catalytic activity in both DCE and VC catalytic oxidation with T50 of 285 °C and 207 °C, respectively, due to its excellent redox property, acidity, and sufficient Run+. In situ DRIFTS suggested that DCE was first dissociated to VC and then oxidized to carboxylates, and the addition of Ru led to the oxidation of carboxylates to carbonyl and ultimately to complete oxidation to CO2 and H2O. Run+ was important for the oxidation of carboxylate intermediates.

Exploiting sulfonated covalent organic frameworks to fabricate long-lasting stability and chlorine-resistant thin-film nanocomposite nanofiltration membrane

Incorporating hydrophilic and charged porous nanofillers to prepare high-performance thin film nanocomposite (TFN) nanofiltration (NF) membranes is an effective method to achieve efficient water treatment. In this study, we synthesize the sulfonated covalent organic framework nanosheets (S-CONs) with higher hydrophilicity and electronegativity by immobilizing sulfonic acid groups (–SO3H) on TpPa-1 nanosheets. The S-CONs are incorporated in the PA layer by interfacial polymerization (IP) reaction. The results indicated that the S-CONs could modulate the hydrophilicity, thickness, and electronegativity of TFN-NF membranes. At the optimal addition of S-CONs (0.006 g), the pure water permeance increases to 8.84 L⋅m−2⋅h−1⋅bar−1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\rm{L}}\\cdot{\\rm{m}}^{-2}\\cdot{\\rm{h}}^{-1}\\cdot{\\rm{bar}}^{-1}$$\\end{document}, which is about 1.75 times than the TFC membrane, with a high Na2SO4 rejection reaching 98.97%. The improvement of the separation performance mainly results from the reduction of PA layer thickness (from ~178.00–198.00 to ~100.00–128.00 nm) and the increase of surface electronegativity (from −20.37 to −44.41 mV at pH = 7.00). More interestingly, the amide bond formed between the S-CONs and TMC improved the chlorine resistance of the membranes. This study reveals the potential of using functionalized 2D CONs as nanofillers to modify TFC membranes for efficient nanofiltration.

MXene-enhanced sulfonated TFN nanofiltration membranes for improved desalination performance

MXene, a recently identified 2D nanosheet, has drawn interest due to its potential application in the modification of thin film nanocomposite (TFN) membranes for the production of clean water. This study presents the development of MXene-based sulfonated TFN (STFN) nanofiltration membrane for the desalination application and chlorine resistance. A novel amine monomer approach of combination such as 1-(2-aminoethyl)piperazine (APIP) and 2,5-diaminobenzenesulfonic acid (DABSA) was proposed for the interfacial polymerization. The as-prepared MXene displayed a thin-layer nanoflakes-like structure. The surface morphology of the membrane indicated that the MXene bound well on the sulfonated TFN membrane. The hydrophilicity of the membrane was enhanced significantly in the STFN membrane, and the lower contact angle value was decreased up to 24°. The filtration performance showed that the water flux and salt rejection were improved in both sulfonated thin film composite (STFC) and STFN membranes. STFN membranes achieved a higher rejection of >93 % for Na2SO4 and MgSO4. The antifouling and chlorine resistance were also improved in STFC and STFN membranes. This study would be an insight for the development of novel STFN membranes for desalination applications.

Fabrication of high-performance and high-fouling resistance reverse osmosis membrane by a natural deep eutectic solvent (NDES) as a new generation of co-solvents

Here, we modify the RO membrane employing thymol:acetic acid (Th:AA) natural deep eutectic solvent (NDES) as a new generation of the co-solvent. The Th:AA NDES was synthesized with the heating method. The co-creation of the NDES synthesis was confirmed by FTIR and NMR spectroscopy. For the impact assessment of Th:AA in the CAIP process, the dosage of the NDES as a co-solvent in the organic phase was initially optimized. Then, in the second step, the effect of the AA molar ratio on the membrane performance was investigated. Alteration changes in the morphology of PA/NDES membranes were investigated by SEM, AFM, ATR-FTIR, zeta potential, and water contact angle analyses. PA/NDES membranes have thinner selective layers, smoother surfaces, and a more hydrophilic nature without changes in the chemical structure. The performance of different types of PA/NDES RO membranes was assessed by the pure water flux and NaCl rejection experiments. The results indicated that at the optimum amount and molar ratio of the Th:AA NDES, the permeability reached 5.35 LMH/bar while the rejection didn't reduce and was constant at 98%. Also, the antifouling performance was explored by the NaCl/HA solution with the 2000/10 mg/L concentration. The outcomes of this experiment showed the PA/NDES13 membrane with a 1.5% flux decline had the best antifouling features. Moreover, the long-term test indicated the PA/NDES13 membrane has long-time stability. Also, the chlorine resistance of this membrane was much better than unmodified PA and commercial membranes. In the end, it was found that using Th:AA NDES as a co-solvent in the CAIP process produced a RO membrane with high permeability and high fouling resistance features along with better features than a commercial BWRO membrane, making it an excellent candidate for industrial application due to the ease of NDES synthesis and membrane fabrication.

Influence of Amino Acid Substitutions in Capsid Proteins of Coxsackievirus B5 on Free Chlorine and Thermal Inactivation.

The sensitivity of enteroviruses to disinfectants varies among genetically similar variants and coincides with amino acid changes in capsid proteins, although the effect of individual substitutions remains unknown. Here, we employed reverse genetics to investigate how amino acid substitutions in coxsackievirus B5 (CVB5) capsid proteins affect the virus' sensitivity to free chlorine and heat treatment. Of ten amino acid changes observed in CVB5 variants with free chlorine resistance, none significantly reduced the chlorine sensitivity, indicating a minor role of the capsid composition in chlorine sensitivity of CVB5. Conversely, a subset of these amino acid changes located at the C-terminal region of viral protein 1 led to reduced heat sensitivity. Cryo-electron microscopy revealed that these changes affect the assembly of intermediate viral states (altered and empty particles), suggesting that the mechanism for reduced heat sensitivity could be related to improved molecular packing of CVB5, resulting in greater stability or altered dynamics of virus uncoating during infection.

Bacterial community assessment of drinking water and downstream distribution systems in highland localities of Ecuador.

Bacterial communities in drinking water provide a gauge to measure quality and confer insights into public health. In contrast to urban systems, water treatment in rural areas is not adequately monitored and could become a health risk. We performed 16S rRNA amplicon sequencing to analyze the microbiome present in the water treatment plants at two rural communities, one city, and the downstream water for human consumption in schools and reservoirs in the Andean highlands of Ecuador. We tested the effect of water treatment on the diversity and composition of bacterial communities. A set of physicochemical variables in the sampled water was evaluated and correlated with the structure of the observed bacterial communities. Predominant bacteria in the analyzed communities belonged to Proteobacteria and Actinobacteria. The Sphingobium genus, a chlorine resistance group, was particularly abundant. Of health concern in drinking water reservoirs were Fusobacteriaceae, Lachnospiraceae, and Ruminococcaceae; these families are associated with human and poultry fecal contamination. We propose the latter families as relevant biomarkers for establishing local standards for the monitoring of potable water systems in highlands of Ecuador. Our assessment of bacterial community composition in water systems in the Ecuadorian highlands provides a technical background to inform management decisions.

Biofilm Formation in Water Distribution Systems

A biofilm is a biologically active matrix attached to the surface of cells and their extracellular products. As they are a mixture of many microorganisms, the microbiological activity of biofilms varies according to their position in the aggregate. With particular emphasis on drinking water distribution systems, this review focuses on the process of biofilm formation, associated bacteria, chlorine resistance of bacteria, and the predominant surface materials. We have compiled studies on the bacteria in drinking water distribution systems and their interactions with biofilm formation on different materials, and we also analysed the chlorine-resistant bacteria and their problems in the water networks. The materials used in the drinking water network are significantly affected by the disinfection method used to produce the biofilm that adheres to them. Some studies propose that the material is inconsequential, with the disinfection process being the most significant factor. Studies suggest that materials based on plastics (such as PVC and HDPE) tend to be more effective in controlling biofilm formation or removal than those based on metals (such as stainless steel), which have been found to be less effective in some instances. Chlorine-resistant strains are becoming more and more common in drinking water networks, resulting in the occurrence of diseases such as typhus and cholera.

High-flux and chlorine-resistant nanofiltration membrane fabricated via phase inversion using polysulfone-b-polyglycerol hyperbranched block copolymer

The nanofiltration (NF) membranes having excellent chlorine resistance and sufficient perm-selectivity are highly desired in drinking water treatment and other applications. Herein, a novel block copolymer NF membrane with superior chlorine resistance, especially high water permeance was prepared via phase inversion, using a tailor-made polysulfone-block-hyperbranched polyglycerol (PSf-b-hPG) material. The fabricated PSf-b-hPG NF membrane shows an extremely thin separation layer with a thickness of around 80 nm and a high overall porosity of 65 %, thanks to the structural advantage of hyperbranched hydrophilic hPG segments and the unique feature of the PSf-b-hPG casting solution of possessing a very low viscosity at a high solid content. The membrane exhibits an effective pore diameter of 1.6 nm, and the molecular weight cut-off (MWCO) was around 4 kDa. The membrane displayed extremely high pure water permeance of 34 LMH/bar as well as a satisfactory Na2SO4 rejection of 74 %. Moreover, the membrane exhibits superior chlorine resistance with no change in separation performance when challenged with 36,000 ppm∙h chlorination intensity and also maintains a stable Na2SO4 rejection and water permeance during the 14 h NF test. Our results suggest the NF membrane prepared by PSf-b-hPG has superior chlorine resistance and high water permeance, and is capable of efficiently removing sulfate from drinking water or others.

Integrating binary organic phosphonic acid into nanofiltration membrane for high precision separation of mono-/divalent anions

Nanofiltration membrane (NF) have become increasingly crucial in ion separation. However, traditional polyamide (PA) NF suffers from poor selectivity for mono-/divalent anions due to weak charges and structure defects. Thus, a novel binary organic phosphonic acid, alendronic acid (AA), was firstly used as an aqueous co-monomer via interfacial polymerization (IP) to create negatively charged nanofiltration membranes with both higher charge density and pore size homogeneity for the separation of mono-/divalent anions. Both structure characterization and performance tests demonstrated the successful introduction of AA in the separation layer. Compared with pristine membrane, the NaCl/Na2SO4 selectivity of membrane incorporated with AA was four times improved, while the permeability exhibited no decline. Simultaneously, the separation efficiency of Cl-/SO42- was tested in NaCl/Na2SO4 binary mixed solutions with varying total concentrations and different mass ratios, and the separation factor consistently exceeded 500 across a concentration range of 1 g/L to 20 g/L. Moreover, the AA-integrated membrane exhibited excellent chlorine resistance after 20000 ppm·h of chlorine treatment, which is promising for high efficiency separation of mono-/divalent anions in industrial applications.

Hydrophilicity and surface charge modulation of Ti3C2T x MXene based membranes for water desalination.

Lamellar membranes obtained by stacking 2D layers possess ample transport pathways due to their intricate network of interlayer gaps. This makes them suitable for molecular separation applications. However, controlling the surface chemistry of the nanochannels within the membrane to tune the desired transport properties of water and ions is challenging. Ti3C2T x has been considered for water desalination because of its hydrophilic surface and negative surface charge. Most of the studies of Ti3C2T x membranes have presented promising salt rejection values in forward osmosis mode, which is less practical for water purification. Here, we investigate two types of reverse osmosis MXene-based lamellar membranes consisting of Ti3C2T x nanosheets hybridized with (i) WS2 nanosheets and (ii) polyvinyl phosphonic acid (PVPA). When hydrophilic and flexible Ti3C2T x nanosheets are interleaved with softer and more hydrophobic WS2 nanosheets in 2 : 1 mass ratio, nano capillaries with Janus chemistry are created with comparable rejection to bare Ti3C2T x membrane and threefold higher permeance values. Further, we find that decorating Ti3C2T x nanosheets with anionic polymers improves salt rejection. Our Ti3C2T x /PVPA composite membranes reject ∼97% of divalent ions and ∼80% of monovalent ions with ∼0.2 Lm-2 h-1 bar-1 of water permeance when tested with brackish water, and exhibit significantly improved chlorine resistance and cost benefits over the commercial Toray membranes.