Increase In Water Flux Research Articles

In-situ assembling inorganic nanoparticles on the surface of aramid nanofibers for the enhanced mechanical and insulation performances of the prepared nanopapers

In this work, we used metal ions (Ca2+, Mg2+, and Al3+) to in situ assist the splitting of aramid fibers to prepare their nanofibers, which successfully grafted the CaCO3, Mg(OH)2, and Al(OH)3 nanoparticles (NPs) on the surface of aramid nanofibers (ANFs) since the alkaline environment. The nanopapers assembled from the inorganic NP modified ANFs show higher mechanical and insulation properties than the neat ANF film, as well as the thermal stability and water flux. The Mg2+ yielded sample shows increase of 66.2%, 151.3%, 332.6%, and 28.3% on stress, strain at break, toughness, and dielectric breakdown strength, respectively. The enhanced mechanical and insulation property is attributed to the structural densification and improved interfacial interactions, while the increased water flux is caused by the hydrophilicity of the inorganic NPs. After annealing at 400 °C for 2 h, the dielectric breakdown strength is further improved due to the dense microstructures, but the stress and elongation are decreased. This work provides a general strategy to construct zero-dimensional NPs on the surface of ANFs, which can effectively enrich their structures, properties, and applications without lowering other properties.

Preparation of high flux organic solvent nanofiltration membrane based on polyimide/Noria composite ultrafiltration membrane

Organic solvent nanofiltration (OSN) membrane, a type of thin film composite (TFC) membrane, is widely used in separating organic solvents, but the low permeability of organic solvents is currently challenging to solve. This experiment used cross-linked polyimide (PI) as raw material and Noria as a nanoparticle additive to prepare a composite ultrafiltration membrane through non-solvent-induced phase separation (NIPS). Noria migrated to the composite ultrafiltration membrane surface during NIPS and acted as an interlayer, which can regulate the following interfacial polymerization. Then, the nanofiltration membrane was prepared by interfacial polymerization method using the modified PI membrane as the support layer. The experimental results showed that the hydrophilicity of the PI/Noria composite ultrafiltration membrane was significantly enhanced, in addition to a significant increase in pure water flux to 239 L m-2h-1bar−1. The methanol flux of the prepared composite nanofiltration membrane could be up to 5.472 L m-2h-1bar−1, which was twice as high as that of the unmodified composite membrane, and the G250 dye retention rate remained at over 99.6%. The nanofiltration performance is excellent and has good prospects for application in OSN.

Temporary hydraulic barriers using organic gel for enhanced aquifer remediation during groundwater flushing: Bench-scale experiments

This study presents the use of organic gel-forming material for the construction of hydraulic barriers in aquifer, which can be easily removed after use. Experiments on the performance of the temporary hydraulic barrier during NAPL removal (aquifer flushing) were also conducted. An aqueous solution of sodium alginate was injected into the horizontally oriented, 2-dimensional flow chamber packed with sand, followed by gelation using a calcium solution. The alginate gel formed in the porous media produced a circular shape barrier (24 cm diameter, 1.3 cm thickness) that was successfully removed using sodium bicarbonate solution (1.0 M) in 72 h, whereas the gel was stable for 7 days during simulated groundwater flushing at the same flow rate as the sodium bicarbonate solution. When circular hydraulic barriers (12 cm diameter each, 14 cm apart) were set on either side of the NAPL (n-hexane and PCE mixture)-contaminated zone, the increased water flux during water flushing resulted in significantly increased PCE removal by almost 108%. When a surfactant solution (sodium dodecyl sulfate, 0.037%) was applied, the influenced groundwater flow controlled by hydraulic barriers on the NAPL removal was amplified by 196% removal.

Hybrid Inorganic Organic PSF/Hap Dual-Layer Hollow Fibre Membrane for the Treatment of Lead Contaminated Water

Lead (Pb) exposure can be harmful to public health, especially through drinking water. One of the promising treatment methods for lead contaminated water is the adsorption-filtration method. To ensure the cost-effectiveness of the process, naturally derived adsorbent shall be utilised. In this study, hydroxyapatite particles, Ca10(PO4)6(OH)2 (HAP) derived from waste cockle shell, were incorporated into the outer layer of polysulfone/HAP (PSf/HAP) dual-layer hollow fibre (DLHF) membrane to enhance the removal of lead from the water source due to its hydrophilic nature and excellent adsorption capacity. The PSf/HAP DLHF membranes at different HAP loadings in the outer layer (0, 10, 20, 30 and 40 wt%) were fabricated via the co-extrusion phase inversion technique. The performance of the DLHF membranes was evaluated in terms of pure water flux, permeability and adsorption capacity towards lead. The results indicated that the HAP was successfully incorporated into the outer layer of the membrane, as visibly confirmed by microscopic analysis. The trend was towards an increase in pure water flux, permeability and lead adsorption capacity as the HAP loading increased to the optimum loading of 30 wt%. The optimized DLHF membrane displayed a reduced water contact angle by 95%, indicating its improved surface hydrophilicity, which positively affects the pure water flux and permeability of the membrane. Furthermore, the DLHF membrane possessed the highest lead adsorption capacity, 141.2 mg/g. The development of a hybrid inorganic-organic DLHF membrane via the incorporation of the naturally derived HAP in the outer layer is a cost-effective approach to treat lead contaminated water.

Fabrication of Defect‐Engineered MOF‐801 Membrane for Efficient Dye Rejection

AbstractAlthough having shown great promise for efficient water treatment, rational structural design and engineering of polycrystalline MOF membranes remain rarely investigated so far. In this study, we prepared well‐intergrown MOF‐801 membranes with tailorable structural deficiencies in the framework for application in dye rejection. Of particular note, we found that the addition of formic acid as modulator led to the formation of MOF‐801 membrane with higher missing‐linker number, which was beneficial for increasing water flux with little compromise in dye rejection rate. The MOF‐801 membrane prepared in this work exhibited excellent dye rejection performance (CR rejection rate of 99.50 % and water flux of 31.69 L m−2 h−1 bar−1) as well as excellent long‐term stability.

Incorporation of porous materials in forward osmosis membrane for increased water recovery from waste streams

Forward osmosis (FO) is a membrane separation process that involves an osmotic pressure-driven, semi-permeable membrane to selectively separate water from waste streams. Increased water flux and salt removal characterize an ideal FO membrane. In contrast to the first-developed symmetric cellulose triacetate (CTA) membrane, the thin film composite (TFC) membrane had a higher water flow and a lower reverse salt flux. The incorporation of porous and non-porous nano-sized particles in the membrane structure has improved TFC performance even further. The TFC-FO membrane was created in this study by incorporating porous ZIF-8 MOF into the polyethersulphone (PES) support layer. Interfacial polymerization of chitosan (CS) biopolymer and trimesoyl chloride (TMC) produced the thin separation layer. The porous MOFs provided additional water pathways. The water wettability of the separation layer was also improved by CS-TMC polymerization. In comparison to the bare membrane, the water fluxes of the ZIF-8@FO membrane improved by 2.8 times. The newly developed FO membrane was found effective for use in sewage and wastewater treatment.

Regulating the thickness of nanofiltration membranes for efficient water purification.

Fabrication of an organic polymer nanofiltration membrane with both high water permeability and high salt rejection is still a big challenge. Herein, phytic acid (PhA)-modified graphene oxide (GO) was used as the membrane thickness modifier, which was introduced into the thin-film nanoparticle composite (TFN) membrane via in situ interfacial polymerization (IP) on a porous substrate. The water flux of the optimally tuned TFN-GP-0.2 composite membrane is 48.9 L m-2 h-1, which is 1.3 times that of the pristine thin-film composite (TFC) nanofiltration membrane (37.9 L m-2 h-1) (GP represents the PhA modified GO composite). The rejection rate of 2000 ppm MgSO4 for TFN-GP-0.2 membranes was maintained at 97.5%. The increased water flux of the TFN-GP composite membrane compared to that of the TFN nanofiltration membrane was mainly attributed to enhanced hydrophilicity and reduced thickness of the polyamide (PA) layer. Molecular dynamics (MD) simulations confirm that the diffusion rate of amine monomers is reduced by the presence of a GP complex in the IP process, which facilitates the formation of PA layer with thinner thickness. In addition, the TFN-GP-0.2 composite membrane also showed good long-term stability; after 12 h of continuous operation, the water flux only decreased by 0.1%. This study sheds new light on the development of GO-based nanofiltration for potential implementation, as well as a unique concept for manufacturing high-performance nanofiltration membranes.

Structures and performance of alcohol activated thin film composite polyamide (TFC-PA) nanofiltration (NF) membranes prepared with and without Co(II) modulation

Structures and NF performance of TFC-Co and TFC membranes activated with 50 % alcohol solutions were studied. Methanol and glycol solution activation increased water flux 2–4 times without trading off salt rejection while glycerin solution activation increased water flux 3–4 times with reduced salt rejection and increased dye/salt retention selectivity. The Stokes radius of TFC-Co membrane changed from 0.77 nm to 0.66, 0.78 and 0.92 nm while the TFC membrane changed from 0.54 nm to 0.55, 0.65 and 0.70 nm after activation with methanol, glycol and glycerin solutions, respectively. Capillary pore filling models were developed from pure alcohol absorption experiments including the stages of initial pore filling, pore expansion, pore relaxation and pore adjustment, while most Stokes radius after 50 % solutions activation were found to be close to the relaxed pore radius values (rrx) or half of the expanded pore radius values (rex) from pure alcohol absorption experiments.

Boosting brackish water treatment via integration of mesoporous γ-Al2O3NPs with thin-film nanofiltration membranes

In this study, a simple method based on non-ionic surfactant polysorbates-80 was used to create mesoporous γ-Al2O3NPs. The properties of the prepared mesoporous alumina nanoparticles (Al2O3NPs) were verified using ATR-FTIR, XRD, SEM, TEM, DLS, and BET surface area analysis. Then, thin-film nanocomposite (TFN) nanofiltration membranes were fabricated by interfacial polymerization of embedded polyamide layers with varied contents (0.01 to 0.15 wt.%) of mesoporous γ-Al2O3NPs. The surface roughness, porosity, pore size, and contact angle parameters of all the prepared membranes were also determined. The performance of the fabricated membranes was investigated under various mesoporous γ-Al2O3NPs loads, time, and pressure conditions. Mesoporous γ-Al2O3NPs revealed an important role in raising both the membrane hydrophilicity and the surface negativity. The addition of 0.03 wt.% mesoporous γ-Al2O3NPs to the TFN membrane increased water flux threefold compared to the TF control (TFC) membrane, with maximum water flux reaching 96.5, 98, 60, and 52 L/(m2.h) for MgSO4, MgCl2, Na2SO4, and NaCl influent solutions, respectively, with the highest salt rejection of 96.5%, 92.2%, 98.4%. The TFN-Al2O3 membrane was also able to soften water and remove polyvalent cations such as Mg2+ with a highly permeable flux. The TFN-Al2O3 membrane successfully removed the hardness of the applied water samples below the WHO limit compared to using merely the TFC membrane. Furthermore, the TFN-Al2O3 nanofiltration membrane unit proved to be a promising candidate for the desalination of real brine like that collected from the Safaga area, Egypt.

Polyamide nanofiltration membranes with rigid–flexible microstructures for high-efficiency Mg2+/Li+ separation

Lithium extraction from salt-lake brine with a high Mg2+/Li+ ratio is crucial for mitigating lithium supply shortage. Positively charged polyamide nanofiltration membranes, which are often prepared by performing interfacial polymerization (IP) using polyethyleneimine and trimesoyl chloride, are considered to be promising candidates for Mg2+/Li+ separation owing to their high energy efficiency and low environmental impact. However, the performance of these membranes is severely hindered by “useless pores” and “defects” present in the flexible polyamide layer. Herein, we provide a facile strategy for modifying flexible semi-aromatic polyamide chains by intercalating a rigid electropositive monomer, histamine, to remold the internal pores and positive charge density at a molecular level. Two routes, namely, “swelling-embedding-reacting-shrinking (SERS)” and “in-situ interposition (SIP)” were used to construct a new polyamide layer with rigid–flexible microstructures. The fabricated SERS-0.50 membrane showed a 5-fold higher water flux and 2-fold increase in the Mg2+/Li+ separation factor compared with the IP membrane. Moreover, the SIP-0.15 membrane with an enhanced positive charge density exhibited a considerably higher Mg2+/Li+ separation factor (15.38, 500 % increase compared with that of the IP membrane) for brine with a Mg2+/Li+ ratio of 20. This study provides a reference for developing nanofiltration membranes used for high-efficiency Mg2+/Li+ separation.

Effect of membrane mean pore diameter on water and solute flux in forward osmosis processes

Several forward osmosis (FO) experiments were carried out using aqueous solutions of sodium chloride (NaCl) in different concentrations, as draw solution (DS), and freshwater, as feed water (FW). The experiments were conducted at a constant temperature of ~20°C and using a symmetric cellulosic membrane in two grades different in their values of the molecular weight cut-off (MWCO), which is related to the mean pore diameter. This study investigates the effect of the membrane mean pore diameter on water flux and DS solute diffusional flux across the membrane. The value of water flux indicates the performance of the FO process, while solute flux is an important factor that determines its practicality. A proportionality factor is used to specify the relationship between water flux and solute flux for each membrane type and operational conditions. The results of this study show that water flux and solute flux increase as the solute concentration difference across the membrane increases. It is also found that, in the range of the tested membranes, membranes with larger mean pore diameters have lower water flux and higher solute flux.

A coupled molybdenum disulfide - copper modification of NF membrane for enhanced anti-bacterial performance

Biofouling is a bottleneck in restricting nanofiltration (NF) application for drinking water treatment. In current study, we reported a novel molybdenum disulfide (MoS2) ‑ copper (Cu2+) modification of polyamide NF membrane for enhanced anti-bacterial performance. The incorporation of Cu2+ into the separation layer through interfacial polymerization was to enhance the anti-microbial ability, while the introduction of lamellar MoS2 into the polyamide active layer was to stably immobilize copper, as well as to provide an interlayer nanochannels for water transport and also to enhance membrane hydrophilicity. The resultant membrane showed an excellent anti-bacterial ability, with 99.1% and 96.7% inactivation efficiencies of Escherichia coli and Bacillus subtilis, respectively, at MoS2 - Cu molar ratio of 1:0.3. Compared to the control membrane, the obtained membrane exhibited a 44% increase of pure water flux. Membrane stability assessment indicated that > 93% of initial loaded Cu2+ and Mo4+ remained in the membrane matrix after a 5-d shaking test. Membrane characterization suggested that the MoS2 - Cu complexes were uniformly dispersed into the membrane active layer, which led to an increased membrane roughness that was favorable for antibiofouling. Overall, the facile MoS2 – Cu addition with intensified anti-biofouling ability created in this study provides a promising membrane modification approach for practical application.

Selective separation of volatile fatty acids, nitrogen and phosphorus from anaerobic acidogenic fermentation via forward osmosis membrane process

Selective separation and recovery of volatile fatty acids (VFA) and other valuable resources promotes a sustainable wastewater treatment system, but its cost-effective separation approaches are poorly understood. This study investigated the feasibility of applying a forward osmosis (FO) dewatering process for the selective separation of VFA, ammonium and phosphate from anaerobic acidogenic fermentation. Limited VFA rejection of fermentation broth, i.e., less than 20 %, was observed under acidic conditions, while the rejection rate was significantly increased to ∼90 % at neutral pH. The transfer of ammonium across the membranes was remarkably impacted by the feed solution pH. Lower pH (∼4) values resulted in higher rejection rates of ammonium (∼96 %), and the rate gradually declined as pH increased. The rejection of phosphate, which remained higher than 98 %, was less sensitive to pH variations. The increase in water flux promoted the rejection of VFA, ammonium and phosphate, and the membrane orientation significantly impacted the transfer of nutrients in the FO process. The active layer facing the feed solution (AL-FS) mode exhibited higher rejection rates of VFA, ammonium and phosphate than the active layer facing the draw solution (AL-DS) mode, which was ascribed to the internal concentration polarization effect. Furthermore, approximately 80 % of water could be effectively reduced from a real acidogenic fermentation liquor during the FO process; ammonium and phosphate were 3.72-fold and 4.10-fold concentrated in feed solution, respectively, and VFA was selectively separated in draw solution. The work confirmed the feasibility of utilizing FO processes in separating and enriching VFA, ammonium and phosphate from anaerobic fermentation liquors, providing meaningful information on promoting FO-based processes in treating wastewater.

Introduction of poly(acrylic acid) sodium into traditional draw solution to enhance its driving capacity in forward osmosis process.

In this study, poly(acrylic acid) sodium (PAA-Na) salt was selected as representative polymer additive and the effect on forward osmosis (FO) performance of traditional draw solute NaCl was investigated. Results showed that PAA-Na increased water flux in both FO and PRO mode at 25 °C (up to 50%). Water flux and specific RSF firstly increased and then kept stable with the increasing concentration of PAA-Na additive. However, PAA-Na cannot enhance water permeation effectively at 35 and 45 °C. PAA-Na influenced FO performance by (1) increasing membrane hydrophilicity, which can increase water permeation, and was dominant at low temperature, and (2) causing pore-clogging, leading water flux decline, which was significant at high temperature. Furthermore, the influence of PAA-Na was compared with another polymer PAM and divalent salts MgCl2. The addition of PAM increased water flux slightly (lower than 25%), but increased RSF at the same time, due to the negative charge. Although MgCl2 decreased RSF and kept water flux fixed, its role was not obvious. In all, PAA-Na had advantages to improve FO performance.

Graphene oxide nanofiltration membranes with confined Na+ in two-dimensional nanochannels

The interactions between metal cations and graphene derivatives may bring about significant changes to the properties and structures of graphene-based devices, which further affect their performance. Under practical pressure-driven separation conditions, the presence of metal cations in the feeding solutions is universal. They not only play the role of target solutes but also act as the modifier to tune the structure and transmembrane resistance of graphene oxide (GO) membranes. Herein, the influences of hydrated Na+/Mg2+ on the two-dimensional nanochannels of GO membranes under pressure driven conditions are revealed. Hydrated Na+ tend to be confined in between GO sheets, leading to the expansion of the nanochannels which facilitates the passage of water molecules. The accumulation of hydrated Mg2+ at the edges of GO sheets reduces both the cross-sectional area and the number of the transport pathways, increasing the transmembrane resistance of water molecules. On this basis, high flux Na+-GO nanofiltration membranes were designed, which exhibited ∼ 6 times increase in pure water flux compared with GO membranes. The water flux in dye solutions was increased by 4– 5 times without scarifying the rejection for methyl orange and direct yellow. The Na+-GO membranes showed good structural stability both in water and salt/dye solutions, confirming that the treatment with dynamic Na+ flow is a reliable strategy to improve the nanofiltration efficiency of GO membranes. It was demonstrated that hot water filtration was a simple but efficient way to recover the initial structure and performance of GO membranes.

Improved Forward Osmosis Performance of Thin Film Composite Membranes with Graphene Quantum Dots Derived from Eucalyptus Tree Leaves.

The major challenges in forward osmosis (FO) are low water flux, high specific reverse solute flux (SRSF), and membrane fouling. The present work addresses these problems by the incorporation of graphene quantum dots (GQDs) in the polyamide (PA) layer of thin-film composite (TFC) membranes, as well as by using an innovative polyethersulfone nanofiber support for the TFC membrane. The GQDs were prepared from eucalyptus leaves using a facile hydrothermal method that requires only deionized water, without the need for any organic solvents or reducing agents. The nanofiber support of the TFC membranes was prepared using solution blow spinning (SBS). The polyamide layer with GQDs was deposited on top of the nanofiber support through interfacial polymerization. This is the first study that reports the fouling resistance of the SBS-nanofiber-supported TFC membranes. The effect of various GQD loadings on the TFC FO membrane performance, its long-term FO testing, cleaning efficiency, and organic fouling resistance were analyzed. It was noted that the FO separation performance of the TFC membranes was improved with the incorporation of 0.05 wt.% GQDs. This study confirmed that the newly developed thin-film nanocomposite membranes demonstrated increased water flux and salt rejection, reduced SRSF, and good antifouling performance in the FO process.

The role of CuO/TS-1, ZnO/TS-1, and Fe2O3/TS-1 on the desalination performance and antifouling properties of thin-film nanocomposite reverse osmosis membranes

The thin-film nanocomposite reverse osmosis (TFN-RO) membranes were prepared by the introduction of hydrophilic nanoparticles into the polyamide (PA) layer to improve desalination performance. First, the hydrothermal method was used to synthesize titanium silicate-1 (TS-1) as a base additive for the fabrication of the TFN-RO membrane. Since the particle size has a significant effect on its dispersion in the membrane matrix, changing the nucleation rate of TS-1 precursor solution with a simple method conducted to reduce the size of TS-1. Then metal oxide composites were prepared via the wet impregnation method. FESEM and AFM analyses were performed to investigate the surface alteration of the membranes due to the introduction of nanoparticles. The results showed that the surface of the TFN membranes was smoother than the unmodified one. To assess the changes in membrane properties after incorporating additives, the water contact angle, and zeta potential were measured. Compared to TFC, the 0.02TS1-Fe-TFN membrane had a ∼ 30% increase in pure water flux. Meanwhile, the rejection of NaCl increased from ∼ 95% to ∼ 99%. The probing of antifouling performance using bovine albumin serum (BSA) and humic acid (HA) contaminants also showed that due to reduced roughness, the modified membranes had higher fouling resistance than TFC. Also, the TFN membranes exhibited good long-term and pH stability.

Thin-Film Nanocomposite Reverse Osmosis Membrane with High Flux and Antifouling Performance via Incorporating Maleic Anhydride-Grafted Graphene Oxide

Water flux is one of the most important performance parameters of the reverse osmosis (RO) membrane. The higher water flux means lower energy cost when treating the same volume of feed solution with membrane separation technology. However, the increase of membrane water flux always corresponds to the decrease of solvent rejection, known as the “trade-off” effect. In addition, the surface fouling of membranes is often a serious problem, as frequent cleaning not only increases the operating cost but also shortens the life of the membranes. Recently, various hydrophilic nanomaterials have been used to improve the performance of membranes. To fabricate thin film nanocomposite (TFN) RO membrane with high flux and antifouling performance, maleic anhydride-grafted graphene oxide (MG) was successfully synthesized and incorporated into the polyamide (PA) layer via the interfacial polymerization (IP) method. We performed the IP reaction with m-phenylenediamine (MPD) and trimesoyl chloride (TMC) as reactive monomers on a polysulfone (PSF) substrate, and acid absorbent (TEA) and surfactant (SDS) were added to improve the separation performance of the membrane. The effects of MG incorporation on the membrane morphology and separation performance were investigated. SEM and AFM results show that the surface of the MG membrane is rougher than that of the membrane without MG. In addition, excessive loading of MG will lead to aggregation of MG nanosheets. FT-IR spectra indicate that the interaction between MG and PA layers results in an increase of hydrophilic groups on the surface of the TFN membrane, which is further confirmed by the results of the contact angle. The optimal MG doping concentration in the aqueous solution is 0.004 wt%, the water flux of the resultant TFN membrane is significantly increased to 51 L·m-2·h-1, 150% higher than the blank control membrane, which also performs a higher NaCI rejection (97.5% vs. 96.6%). Furthermore, the MG-incorporated RO membrane exhibits superior antifouling performance compared with the blank control membrane.

Functionalized MoS2 nanosheets enabled nanofiltration membrane with enhanced permeance and fouling resistance

In this study, a novel thin film nanocomposite (TFN) membrane incorporated with -OH functionalized molybdenum disulfide (OH-MoS 2 ) nanosheets was fabricated through interfacial polymerization between piperazine (PIP) and trimesoyl chloride (TMC) by addition of nanosheets in the aqueous phase. The physicochemical characterizations of the resultant TFN membrane confirmed the embedding of OH-MoS 2 nanosheets and showed excellent compatibility with polypiperazine amide (PPA) matrix, as well as the nanosheets incorporation significantly increased the hydrophilicity, negative charge, surface roughness. In addition, the hydroxyl groups attached to the MoS 2 nanosheets can be covalently bonded into the skin layer through its reaction with TMC, promoting excellent compatibility with the polymer matrix. At an optimum concentration of 0.010 wt% OH-MoS 2 , the TFN membrane exhibited 45.17% increase in pure water flux (84.14 L m −2 h −1 ) when compared to control membrane (57.96 L m −2 h −1 ) and maintained stable salt rejection for Na 2 SO 4 (96.67%). This optimized TFN membrane exhibited high normalized flux of 96.92% when compared to 91.22% for control membrane and high flux recovery ratio of 98.88% was maintained as well as enhanced organic removal at 89.14% in terms of dissolved organic carbon (DOC) and 99.2% as ultraviolet absorbance at 254 nm (UV 254 ) was recorded during 6 h filtration studies with humic acid containing feed water. 0.010 wt% OH-MoS 2 incorporated membranes exhibited enhanced permeance, salt rejection and stability along with excellent fouling resistance and organic removal demonstrating the potential of OH-MoS 2 nanosheets for engineering high performance and fouling resistant TFN NF membranes for water treatment. • TFN NF membrane by embedding OH-MoS 2 nanosheet into PPA layer via IP reaction. • OH-MoS 2 with abundant oxygen, sulphur groups improved hydrophilicity of membrane. • 0.01 wt% OH-MoS 2 membrane showed 45.17% higher flux and 96.67% Na 2 SO 4 rejection. • TFN membrane shows 96.92% normalized flux compared to 91.22% for control membrane. • Excellent organic removal and stability was exhibited by TFN membrane.

Response of terrestrial water storage and its change to climate change in the endorheic Tibetan Plateau

Terrestrial water storage (TWS) and its change (TWSC) are extremely sensitive to climate change, and are good indicators of the response of the hydrological system to climate change in the Tibetan Plateau (TP). However, long-term variation in TWS and its components, as well as contributions of these component changes to TWSC, are still not well documented. In this study, we extended monthly TWS anomaly (TWSA) and TWSC from 1989 to 2019 using the random forest (RF) method, analyzed the long-term contribution rates of each component change to TWSC using a mass balance approach, and compared them with the rates estimated by the RF method. Our major findings are: (1) the warming and wetting trend in the entire analysis period (PA) and in the pre-mutation period (P1) was slowed down or even reversed in the post-mutation period (P2), which was caused mainly by the decrease in temperature and precipitation in the north-eastern Inner Basin (IB) and southern Qaidam Basin (QB); (2) the RF method is capable of estimating monthly TWSA and TWSC (0.872 ≤ R2 ≤ 0.957 in training data, 0.528 ≤ R2 ≤ 0.860 in test data). Variable selection has an important impact on the method, and TWSC can be used as an alternative when TWSA estimate is poor; (3) Significant annual TWSA increase (2.20 mm/a, P < 0.05) in the IB during PA comes from a higher increase during P2 (3.62 mm/a, P < 0.05) and a small variation during P1 (−0.65 m/a, P > 0.1). Spatially, the increase is attributed to the higher increase trends (> 4.50 mm/a, P < 0.05) in north-eastern IB during PA and P2, and slight decrease in western and southern IB during PA. The spatial and temporal heterogeneity was mainly caused by the differences in precipitation amount, glacier proportions, and permafrost types. (4) During PA, TWSC in the IB was mainly determined by lake water storage change (LWSC) with a contribution rate of 62 %, while in the QB it was mainly determined by soil water change (−43 %), and LWSC had a contribution rate of −27 %. LWSC impact on TWSC was more significant in the IB, especially in the southeastern sub-regions with regional water storage surplus (TWSC > 0). The overall increase in water storages and fluxes, and exchanges imply an intensified hydrologic cycle in the region.