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For nanofiltration (NF) membranes, constructing the interlayer between the substrate and polyamide (PA) layer could balance the trade-off effect between the selectivity and permeability. However, the influencing mechanism of the interlayer to the PA layer is mostly indirect, and how to regulate the physicochemical properties of the PA layer to improve the membrane property remains to be investigated. In this study, porous Zn-TCPP nanosheets with active reaction sites were used to construct interlayer and directly participated in interfacial polymerization (IP) reaction through the edge COOH of nanosheets reacting with piperazine (PIP) to further regulate PA layer physicochemical properties. Controlling the amount of nanosheets involved in the reaction, NF membranes with striated Turing structures, higher negatively charged surface and larger effective filtration area were obtained. The NF membrane permeability with Zn-TCPP interlayer was significantly improved by 123 % while the Cl−/ SO 4 2 − selectivity was greatly enhanced to 72.69, meanwhile it showed excellent performance stability. This study presents a new perspective that the interlayer can modulate the NF membrane physicochemical properties to improve its performance by directly participating in the IP reaction. [Display omitted] • Porous Zn-TCPP interlayer directly participates in the IP reaction via peripheral carboxyl groups. • Zn-TCPP interlayer reduces the pore size of substrate and inhibits the downward growth of polyamide. • Surface morphology of NF membranes is changed, and hydrophilicity and electronegativity are enhanced. • Zn-TCPP interlayer improves the selectivity of NF membrane for mono-/di-anions. [ABSTRACT FROM AUTHOR]

A new configuration of electrodeionisation with a bipolar membrane (EDI-BP) with a segment electrode was proposed for the treatment of simulated dilute Ni 2 + -containing wastewater. The feasibility of EDI-BP was analysed and experimentally validated, and its current density distribution was studied simultaneously. The results showed that the stack allows the removal of nickel and sulphate anions nearly completely from the 30 mg/L Ni 2 + -containing wastewater. Under the experimental conditions, Ni 2 + -free diluate and a 27-times concentrated solution (820 ± 50 mg/L) can be obtained. The current density distribution of the stack is uneven, which is reflected by the following order of the resistances of the resins, Dowex 650C and Dowex 550A, with different ionic forms: Ni 2 + > Na + > H + and SO 4 2 − > Cl − > OH − , respectively. [ABSTRACT FROM AUTHOR]

Abstract: Cogeneration for power and desalination could not only improve the economic benefit of the power plant, but also afford the high quality water to solve the freshwater shortage. Considering the demand of power and water, a detailed mathematical model of the cogeneration system targeting the minimum total annual cost (TAC), which includes the power plant, multistage flash (MSF) and reverse osmosis (RO), is proposed and described as a mixed integer nonlinear programming (MINLP) problem. The modified genetic algorithm (MGA) with mixed coding is put forward to solve the model developed by us. A case study, which is supposed to supply 250MW of power and 12,000m3/h of water for Huangdao District of Qingdao City, is analyzed in order to illustrate the model capabilities. The results show that the operation pattern of the cogeneration system could be varied in terms of the water demand. When the water demand is lower than 8000m3/h, the combination of power plant associated with MSF is adopted and the condensing-extraction steam turbine is selected. When the water demand of water is higher than 8000m3/h, the tri-combination of power plant, MSF and RO is the optimal choice, in which back pressure steam turbine is selected. [Copyright &y& Elsevier]

Organic solvent forward osmosis (OSFO) is a newly developing technology for recovering the organic solvent and concentrating substances. The commercial polyethylene (PE) battery separator is the ideal support for OSFO owing to the low structural parameter, resistance for organic solvents, commercially available and simple preparation process. A novel thin-film nanocomposite (TFN) membrane for OSFO was fabricated on the dopamine (DA)-modified PE support by adding α-cyclodextrin (α-CD) in the polyamide (PA) layer. The inclusion complexes (MPD@α-CD) formed by host-guest chemistry enhanced the stability of the membrane. Because of the Janus path and molecular sieving effect of α-CD, the TFN membrane exhibited superior permeability and selectivity among the recent reports. Moreover, the TFN membrane showed high rejection of Rhodamine B and Oxytetracycline, so it had great potential for solutes concentration. Herein, this work broadens the application of eco-friendly α-CD in membrane field and improves the PE composite membrane for OSFO process. [Display omitted] • PE battery separator can withstand organic solvents and reduce ICP. • α-Cyclodextrin slows down the diffusion of MPD through host guest reactions with MPD. • The ethanol flux of TFN membrane reaches at 3.92 L·m−2·h−1. • TFN membrane show excellent stability and great potential for concentration solutes in organic solution. [ABSTRACT FROM AUTHOR]

Abstract: N,O-carboxymethyl chitosan (NOCC) composite nanofiltration membranes crosslinked by ECH were developed using a method of coating and crosslinking, where an epichlorohydrin/ethanol 96.7% (0.067 M KOH) solution was used as the crosslinking agent. The structure and the morphology of the resulting membrane were characterized by attenuated total reflection infrared spectroscopy (ATR-IR) and environmental scanning electron microscopy (ESEM). The effects of preparation conditions on the rejection performance of the resulting composite membrane were also investigated. At 20°C and 0.40 MPa the rejections of the resulting membrane to Na2SO4 and NaCl solutions (1000 mg L−1) were 90.4% and 27.4%, respectively, and the permeate fluxes were 7.9, and 10.8 kg m−2h−1, respectively. The rejections of this kind of NOCC/PSF composite NF membrane to the inorganic electrolyte solutions decreased in the order of Na2SO4, NaCl, MgSO4, and MgCl2. [Copyright &y& Elsevier]

Abstract: A copolymeric membrane material containing a tertiary amino group was synthesized by radical copolymerization of 2-(N,N-dimethyl amino) ethyl methacrylate and acrylonitrile. The chemical structure of the copolymer was analyzed by viscosity measurement, elemental analysis, FTIR and X-ray diffraction (XRD). The homogeneous copolymeric membrane was prepared. The sorption behavior as well as the permeation performance of the membranes for pure CO2 and CH4 were investigated. The results shown that CO2 sorption behavior of the membrane, which can be classified as a dual-mode sorption model, and CH4 sorption behavior of the membrane accord with the Fickian diffusion model. The membrane appears CO2 selective sorption preferentially, and facilitated transport caused by CO2 reacting reversibly with tertiary amino group for carrier in the membrane. [Copyright &y& Elsevier]

Cellulose triacetate (CTA) hollow fiber membrane for reverse osmosis (RO) desalination of brackish water with high salinity has been modified for pervaporation (PV) membrane of separating organic/organic mixture. The experiments presented that modified performance of CTA hollow fiber membrane treated by the organic solvent was affected by the modifying conditions. PV performance of CTA hollow fiber membrane modified mainly depends on the concentration of the modifying agent and the treatment time of CTA hollow fiber membrane in the aqueous acetone. The results showed that the membrane treated respectively by 5% acetone aqueous solution possesses a good PV separation performance, i.e. the separation factor 1998 and the permeate flux 45.1 (g/m2.h). It was exhibited from scanning electron microscope (SEM) photograph were produced. The structural changes from porous, defect to non-porous, even on the membrane surface and turn from asymmetric membrane of two layers consisting of the active and the support into the homogeneous membrane of single layer in the cross section of the membrane would indicated why the original RO membrane can become that of PV by means of modification treatment. [Copyright &y& Elsevier]

Novel acyl chloride monomer 5-(1-pyrrolidinyl)-1,3-benzenedicarbonyl dichloride (PIPC) featuring a rigid pyrrolidinyl group was proposed as an organic phase monomer to fabricate reverse osmosis (RO) membranes possessing exceptional water permeability and NaCl rejection via a two-step interfacial polymerization method. First, m -phenylenediamine (MPD) in the aqueous phase solution polymerized with PIPC in the first organic phase solution to form the much looser polyamide. After that the remaining MPD continued to diffuse to polymerize with trimesoyl chloride in the second organic phase solution to form the denser polyamide. The pyrrolidinyl group had steric hindrance effects and formed hydrogen bond with MPD, leading to decreasing the thickness significantly and increasing surface roughness of the separating layer. When the PIPC amount was 0.08 wt%, the PIPC-based RO membrane displayed optimal permselectivity with water flux increasing by 84.20 % compared to the original RO membrane (from 20.38 L·m−2·h−1 to 37.54 L·m−2·h−1) whereas retaining high NaCl rejection with 98.59 %. The PIPC-based RO membrane exhibited steady water flux and NaCl rejection within 120 h of filtration, as well as improved antifouling performance. Thus, preparation of the highly permeable RO membrane could be rationally achieved by the novel acyl chloride monomer with a rigid pyrrolidinyl group. [Display omitted] • The novel monomer PIPC was used to prepare RO membrane by a two-step IP method. • PIPC influenced the diffusion rate of MPD via hydrogen bonds and steric hindrance. • The PIPC-based membrane presented rougher surface and thinner PA layer. • Permeability of PIPC-based membrane was obviously enhanced without losing NaCl rejection. [ABSTRACT FROM AUTHOR]

To effectively separate Mg2+ and Li+ from high Mg2+/Li+ ratio salt lake brine, positively charged thin film composite polyamide (TFC-PA) nanofiltration (NF) membranes were prepared by the interface polymerization involving polyethyleneimine (PEI) with benzenetricarbonyl chloride (TMC). In this work, the structures and performances of PEI based TFC-PA NF membrane prepared on polysulfone (PSF) ultrafiltration substrates from the normal interface polymerization process PSF(NIP), was compared with those on the same substrates from the reverse-phase interface polymerization (RIP) process PSF(RIP), and those on polyethylene substrates from RIP process PE(RIP). Results showed that PSF(RIP) showed improved Mg2+/Li+ separation factor S Li/Mg from PSF(NIP) with an increased surface positive charge, but with greatly reduced water flux values due to reduced surface roughness, increased surface hydrophobicity, and decreased MWCO Stokes pore radius. PE(RIP) NF membrane showed not only higher Mg2+/Li+ separation factor S Li/Mg , but also higher water flux values due to increased surface roughness, decreased PA cross-linking degree, reduced PA separation layer thickness, and increased MWCO Stokes pore radius. PE(RIP) NF membrane also showed high rejection rates to a variety of divalent metal salts with high separation factors S Li/Mg of 40–49, high brine permeability values of 10.5 L·m−2·h−1·bar−1, and excellent chemical and operational stability. PEI based TFC-PA NF membranes with positive surface charges on varied substrates and interface polymerization methods were prepared. Novel PE(RIP) NF membranes made from lower cost PE based substrates, showed high brine flux values of 10.5 L·m−2·h−1·bar−1, >97 % rejection rates to variety of divalent metal salts, high Mg2+/Li+ separation factors S Li/Mg of 40–49. [Display omitted] • PEI based TFC-PA NF membranes with positive charges were prepared; • Impact from substrates and IP methods on Mg2+/Li+ separation of positive NF membranes studied; • PE(RIP) NF membranes showed high flux (10.5 L·m−2·h−1·bar−1), high Mg2+/Li+ separation factors (40–49) and excellent chemical and operational stability. [ABSTRACT FROM AUTHOR]

Most thin film nanocomposite (TFN) membranes with higher permeability are related to hydrophilic nanocomposites. Nevertheless, in nature, water permeates faster in hydrophobic pores (e.g. aquaporin) because of less affinity between water and wall of the pore. Here we show hydrophobic methyltrichlorosilane (MeSiCl 3 , MTS) functionalized polyamide TFN can be used to construct highly efficient desalination membranes. The TFN membranes were synthesized through the interfacial polymerization of aqueous amine and organic MTS/acyl chloride solutions. Both the water flux and water/salt selectivity increased. The water flux increased by more than a factor of 1.96, from 2.4 to 4.7 LMH/bar, as the fraction of MTS increased from 0 to 0.1 mM in the organic solution. Importantly, the water/salt selectivity ratio increased from 11.4 to 18.5 bar−1. Thus, MeSiCl 3 imparted narrow water channels to the polyamide matrix with higher flow rate and better selectivity. The enhanced compatibility and interactions between MTS and the polyamide polymers were attributed to their covalent (Si N) and hydrogen (O...H) bonds. MTS modified TFN membranes also show high water flux and recovery ratio in the bovine serum albumin (BSA) solution. This facile in situ modification provides a new insight into the high performance of hydrophobic TFN membranes. Unlabelled Image • MeSiCl 3 increased water permeability up to 196%. • More hydrophobic TFN membranes with higher water/salt selectivity. • MeSiCl 3 bonded with PA polymers by covalent and hydrogen bonds. • Narrow water channels created by MeSiCl 3. • High water flux and recovery ratio during the antifouling experiments. [ABSTRACT FROM AUTHOR]

Composite membrane consisting of selective layer and support is the mainstream membrane configuration. Support has drawn increasing attention in recent years. In this work, transport through composite membrane with support pore location distributing randomly was studied based on 2D Voronoi tessellations and the corresponding membrane performance calculation method was developed. For the calculation, firstly, irregular Voronoi regions are transformed into regular polygons with fixed number of edges meanwhile maintaining the region area. Then, the membrane performance can be obtained by combining the computation results of regular support surface pore spatial distribution and random support surface pore spatial distribution formulas. Poisson Voronoi diagrams, one of the most representative Voronoi diagrams, were mainly used to describe the support surface pore spatial distribution. The results indicate the importance of the number of support surface pores, which determines the average area of Voronoi regions. Support surface pores should be as many as possible. Another important conclusion is that a certain randomness of support surface pore structure (size and location) may not exert an influence on the composite membrane performance. That is, when calculating the composite membrane performance, the support surface pore spatial distribution and surface pore size distribution can be considered as being regular. • A novel way to calculate the performance of composite membrane with support pore location distributing randomly based on 2D Voronoi tessellations was developed • Poisson Voronoi diagrams were mainly used to describe the support surface pore spatial distribution. • The number of pores is a key parameter since it determines the average area of Voronoi regions. • A certain randomness of support surface pore structure (size and location) may not affect the composite membrane performance. [ABSTRACT FROM AUTHOR]

In this work, a novel coating layer of polyvinyl alcohol (PVA)/polyquaternium-10 (PQ10) was constructed onto the surface of polyamide-based RO membrane via the method of surface coating followed by cross-linking. Permeation tests demonstrated that the incorporation of PQ10 into PVA could efficiently improve the water permeation ability of surface coating layer, showing a significant decrease of hydraulic resistance from 5.9 × 1012 m−1 of the PVA-1.0 coating layer to 2.5 × 1012 m−1 of the PVA-1.0/PQ10-0.2 coating layer. Anti-fouling performance evaluation revealed that the PVA/PQ10-coated membrane not only possessed the good anti-fouling property of the PVA-coated membrane to negatively charged foulants and protein but also exhibited more excellent anti-fouling performance to positively charged foulant due to its relatively lower surface charge density and pseudo-zwitterionic surface character. Long-term filtration tests with dye wastewater illustrated that although the initial water permeability of membrane coated with PVA-1.0/PQ10-0.2 surface layer was lower than that of the virgin RO membrane under the same operation condition, the PVA-1.0/PQ10-0.2-coated membrane exhibited a higher salt rejection, lower flux decline rate and larger cumulative volume of permeated water during a filtration period of 48.0 h. Soaking tests further demonstrated the improvement of membrane chemical durability against acid, alkaline and chlorine by the PVA/PQ10 coating layer. [Display omitted] • A novel surface coating layer of PVA/PQ10 was constructed on PA-based RO membrane. • PQ10 was adopted to satisfy permeability, hydrophilicity and charge of coating layer. • PVA/PQ10 coating layer improves membrane salt rejection and anti-fouling property. • PVA/PQ10-coated membrane exhibits enhanced separation efficiency to dye wastewater. • PVA/PQ10-coated membrane has improved durability against acid, alkaline and chlorine. [ABSTRACT FROM AUTHOR]

Abstract This paper reports a novel class of thin film composite (TFC) membranes for forward osmosis (FO) desalination. The TFC membranes were fabricated via interfacial polymerization (IP) of aqueous mixture of polyethyleneimine (PEI) and graphene quantum dots (GQDs) with organic solution of trimesoyl chloride (TMC) on modified polyacrylonitrile (PAN) ultrafiltration substrates. The chemical structures and morphologies of the synthesized GQDs and the GQDs-incorporated membranes were studied by various characterization techniques. The synthesized GQDs exhibited a narrow size distribution of 1.0–4.0 nm with an average size of 2.19 nm, and the thickness were one to three graphene layers. The results showed that GQDs nanoparticles were covalently bonded to the polyamide chains. The optimized TFC membrane with 0.050 wt% GQDs loading exhibited quite hydrophilic and neutrally charged membrane surface, along with an enhanced water flux of 12.9 L m−2 h−1 and a comparable reverse salt flux of 1.41 g m−2 h−1 when DI water and 0.5 M MgCl 2 were used as the feed solution and the draw solution, respectively. Also, the optimized GQDs-incorporated TFC membrane presented an especially good anti-fouling performance. Thus, incorporating the novel graphene nanomaterial into polymer membranes may present its great potential application in desalination, purification and wastewater treatment. Graphical abstract Unlabelled Image Highlights • TFC FO membranes fabricated via interfacial polymerization with GQDs incorporated. • GQDs nanoparticles are covalently bonded to the polyamide chains to avoid leaching. • Water flux increases 22%, reverse salt flux decreases 32% at optimal GQDs loading. • Optimal GQDs loading mitigates the inner concentration polarization extent by 21%. • The optimal TFC FO membrane exhibits remarkable anti-fouling capacity. [ABSTRACT FROM AUTHOR]

Polyamide/polyethylene thin film composite (PA/PE-TFC) NF membranes were prepared from reverse-phase interface polymerization (RIP) for improved Mg(II)/Li(I) separation. RIP processes between 1,3,5-benzenetricarbonyl chloride (TMC) in bottom organic phase and piperazine (PIP) in upper aqueous phase were developed to form continuous and intact surface PA separation layers on PE porous substrates thinner than traditional polysulfone (PSF) based substrates. After activation with isopropyl alcohol (IPA), PA/PE-TFC-IPA NF membranes were formed, whose NF performance could be tuned by adjusting the preparation conditions. When TMC concentration was kept at 0.15 % w/v, RIP with low PIP concentration (0.025 wt%) yield PA/PE-TFC-IPA NF membranes with negatively charged surfaces, high Na 2 SO 4 rejection rate (95 % ± 3 %) and water permeance (13–19 L·m−2·h−1·bar−1). RIP with high PIP concentration (0.3 wt%) formed PA/PE-TFC-IPA NF membranes with less negative surfaces, high MgCl 2 rejection rate (94.3 ± 0.7 %), low water permeance (4.8 ± 0.3 L·m−2·h−1·bar−1), and high Mg(II)/Li(I) separation coefficient S Li/Mg (18 ± 1) for 1000 ppm LiCl and MgCl 2 mixed solution. PA/PE-TFC-IPA NF membranes also showed good long-term stability and improved anti-fouling performance for positively charged pollutants, bearing high potential for applications in the lithium extraction processes. Polyamide/polyethylene thin film composite NF membranes (PA/PE-TFC-IPA) with superior NF performance for Mg(II)/Li(I) separation had been prepared by using thinner and lower cost PE porous substrates to replace the thicker and more expensive PSF substrates, coupled with reverse phase interface polymerization and isopropanyl alcohol activation strategies. [Display omitted] • PE based PA TFC NF membranes showed superior Mg(II)/Li(I) separation. • Reverse phase IP (RIP) led to NF surfaces with less negative charge. • NF performance could be tuned by RIP reaction conditions. • Anti-fouling property controlled mainly by the surface charges. • Activation by isopropanol could survive long term testing. [ABSTRACT FROM AUTHOR]

Membrane desalination has become an important solution to global water problems. Graphene-based materials have excellent advantages in the desalination process due to their intriguing features, including single atomic layer structure, large specific surface area, hydrophobic property, rich modification approaches, etc. After an introduction of membrane, graphene and graphene oxide (GO), this review systematically summarizes the current progress and gives an insight into the graphene-based separation membranes (GBSMs). The applications of the pressure-driven graphene-based membranes are introduced and their performances are listed and analyzed. By molecular dynamics simulation (MDS), the researchers predict the excellent performances of GBSMs, including high water flux, good salt rejection, etc. which have been verified in subsequent experiments. We believe that the application of graphene-based materials in pressure-driven membrane is worthy of further exploration. Several researchers have prepared electric-driven membranes with graphene-based materials, since their good stabilities and water-retention. However, graphene is not efficient in forward osmosis membrane area for now. In spite of the shortcomings like weak mechanical strength of single layer graphene, difficult to prepare nanopores on graphene film and hard to integrate with polymer, we hold the opinion that graphene-based films still have great research value especially in the membrane separation technology. [ABSTRACT FROM AUTHOR]

Based on the fact that when inlet bulk solution with low or medium concentration was involved, scaling was apt to appear on nanofiltration (NF) membrane surface in retentate side. Therefore, study on its surface charge performance under threshold concentration condition is necessary. Two polyamide composite NF membranes (DL and DK) were characterized with streaming potential ( E s ), zeta ( ξ ) potential and other measurements encountering with a wide ionic strength range (1.5–108 mol·m −3 ). Then, the interactional relations between membrane surface charge and concentration polarization ( CP ) degree, along with the relevant constituting factors were investigated. The results showed that even when the sparingly soluble salt concentration for CaSO 4 exceeded its threshold point, both NF membranes at pressure drop of 180 kPa still exhibited low and medium-intensity surface electrokinetic phenomena (−5.94 ≤  E s  ≤ −3.41 mV; −38.82 ≤  ξ -potential ≤ −36.34 mV). It turned out that solvent flux decreased almost linearly, but measured concentrations of the scalant ions in NF retentate streams increased slightly at first and then rapidly with the enlargement of ξ -potential, respectively. Meanwhile, mass transfer coefficient and boundary layer thickness had a negligible change in the scope of testing ξ -potential. Therefore, CP SO4 2− and CP Ca 2+ decreased apparently with ξ -potential becoming less negative for the adopted NF membranes. [ABSTRACT FROM AUTHOR]

To improve the dimensional stability of electrodialysis membranes, a series of crosslinked sulphonated polysulfone cation exchange membranes with different degrees of sulfonation were prepared by a simple and low energy consumption method, namely UV-crosslinking. The crosslinking reaction was performed by UV irradiation and using 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (TPO) as photoinitiator and trimethylolpropane tri-acrylate (TMPTA) as crosslinker. The scanning electron microscopy (SEM) and atomic force microscopy (AFM) results showed that crosslinking leads to a denser and smoother surface. Compared with the swelling and water uptake results of pristine membranes, the crosslinked membranes exhibited an enhanced dimensional stability, especially at higher temperature (40–70 °C). The thermogravimetric analysis and measurement of mechanical properties indicated that the crosslinked membrane has better mechanical and thermal properties. The electrochemical properties were analyzed, and the membrane after crosslinking showed a better ion permselectivity. When applied in electrodialysis and compared to the commercial membrane with a NaCl removal ratio of 75.6%, the crosslinked membranes showed a more efficient performance (NaCl removal ratio = 89.1% for SPSU-60). These improvements showed that the crosslinked membranes can be promising candidates for high-temperature and industrial application. [ABSTRACT FROM AUTHOR]

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 (r rx) or half of the expanded pore radius values (r ex) from pure alcohol absorption experiments. The porosity and NF performance of TFC and TFC-Co NF membranes could be well tuned in activation processes using 50 % alcohols. The MWCO solute permeating pore size (Stokes) values of activated TFC-PA membranes were related to the pore size values derived from the pore filling, expanding and relaxing processes observed in the pure solvent absorption experiments. [Display omitted] • Capillary pore filling models for solvent activation of NF membranes were developed. • Methanol and glycol activation increased water flux 2–4 times at same salt rejection. • Glycerin activation increased water flux 3–4 times with reduced salt rejection. • MWCO Stokes radius had relationship with capillary filling pore radius. [ABSTRACT FROM AUTHOR]

This work focused on salt rejection restoration and simultaneous anti-fouling and anti‑chlorine functionalization of partially deteriorated polyamide-based reverse osmosis membrane by surface chemical deposition of tannic acid (TA) followed with polyethyleneimine (PEI). TA molecules were chemically deposited onto membrane surface with glutaraldehyde as bridging and cross-linking agent. The deposited TA molecules were then employed for sequential chemical deposition of PEI molecules through Schiff base reaction under hot alkaline condition. Restoration process was optimized and its influences on membrane physico-chemical properties were systematically studied. Under desired restoring conditions, deposition of TA molecules was found to recover NaCl rejection from 93.2 % to 96.5 %, the sequential deposition of PEI molecules further improved NaCl rejection up to 98.6 %. The depositions of TA and PEI were found to greatly improve membrane surface hydrophilicity and make the membrane hardly charged under neutral pH. The fouling resistance of restored membrane was better than the new polyamide based membrane for its excellent hydrophilicity and surface brushes induced by the PEI molecules grafted. Chlorination tests proved that the antioxidant structures of the deposited TA and PEI molecules endowed the restored membrane with better chlorine stability compared to the new polyamide membrane. • Performance of deteriorated RO membrane was restored by reconstructing selective layer. • Selective layer was reconstructed by chemical deposition of TA followed with PEI. • Membrane rejection to NaCl was effectively recovered from 93.2 % to 98.6 %. • Anti-fouling and anti‑chlorine functionalizations were achieved simultaneously. • Chlorine and fouling resistances of restored membrane were better than new membrane. [ABSTRACT FROM AUTHOR]

In this study, an electrodialysis (ED) system which was divided into three-stage operation was designed to treat seawater concentrate. The experiment was carried using a laboratory ED-cell with an effective area of 189 cm 2 . Two types of monovalent selective ion-exchange membranes were investigated: CIMS/ACS and CSO/ASV. The effect of applied current density during ED process was also studied. The experimental results indicate that the separation performance for divalent ions (i.e., Ca 2 + , Mg 2 + ) with CIMS/ACS membranes stack was superior to CSO/ASV membranes stack; furthermore, a lower current density can increase the selectivity in monovalent ions to divalent ions with either the CIMS membrane or the CSO membrane. The current efficiency and energy consumption were optimal at a current density of 4 mA/cm 2 by using CIMS/ACS membranes stack as the first stage of system in this experiment. Furthermore, the desalination rate (70%) was chosen as the experimental operation endpoint of the first-stage ED operation based on the experimental results. Moreover, the latter two-stage operation was used to concentrate brine to produce coarse salt after evaporation process. Finally, the repeated batch experiments confirmed the system feasibility for treating seawater concentrate to produce coarse salt with the purity of ~ 85% under continuous operation. [ABSTRACT FROM AUTHOR]

In this study, on a basis of the single additive optimization experiments of the cellulose triacetate (CTA) forward osmosis (FO) membranes, the CTA FO membranes with binary mixed pore-forming additives were designed and fabricated to retrofit the membrane structure and separation performance for FO desalination. The binary mixed additives such as acetic acid-lactic acid (AA-LA), acetic acid-maleic acid (AA-MA) as well as zinc chloride-lactic acid (ZnCl 2 -LA) were selected via combining a single additive with the capacity to improve the salt rejection with another single additive with the capacity to improve the water flux. The effectiveness of the binary mixed additives on the FO performance was extensively evaluated and confirmed. For example, with the ZnCl 2 -LA as binary additive, the resulting CTA membrane exhibited a much improved water flux of ~ 11.5 L/m 2 h and an excellent salt rejection of ~ 98.3% under the fixed FO operating condition (0.1 M NaCl solution as feed, 2 M glucose solution as draw solution, FO mode, 2 h), which were increased by approximately 51.3% and 8.1% compared to the commercial CTA membrane from HTI, respectively. Compared to the single additives, the binary mixed additives could significantly enhance the water flux for the CTA membranes with an insignificant reduction in salt rejection, which might depend on the interaction between two additives as well as the interaction between additives and solvent during the phase inversion. It indicated that the trade-off effect between the selectivity and permeability of a polymer membrane was partially broken for our membranes with binary mixed additives. This study helps us to pave the way to design highly efficient additives for high-performance FO membranes. [ABSTRACT FROM AUTHOR]

The desalting performance of graphene oxide (GO) membranes was further optimized using one-step carboxylation via nucleophilic substitution reactions between epoxy groups of graphene oxide (GO) and amino groups of glycine. GO and GO-COOH membranes with highly ordered structure were prepared by pressure-assisted self-assembly technique. The performance of GO and GO-COOH membranes was investigated and compared. The results showed that GO-COOH membranes exhibited not only higher permeability but also better salt rejections compared with pristine GO membranes. The surface physicochemical properties of GO-COOH membrane including negativity and hydrophilicity were improved as well. The transport mechanism revealed that the improvement of desalting properties was attributed to enhanced electrostatic repulsion by inducing effective negative charge. The higher permeability of GO-COOH membranes resulted from increased water nanochannels and improved surface hydrophilicity. Overall, GO-COOH membranes show great potential in the separation field due to prominent permeation performance and desirable separation property. [ABSTRACT FROM AUTHOR]

Reverse electro-dialysis (RED) is a potentially available technology to harvest salinity gradient power, which can be extracted from high-salinity wastewater in industrial processes. This study proposes a hybrid RED/ED system to simultaneous osmotic energy recovery and complete desalination in the phenol-containing wastewater treatment process. Experimental investigation on standalone ED system reveals that the high stack resistance, resulting from the salinity difference between both feed streams, accounts for the inefficient desalination performance in early stages, which implies potential implication of RED as a pre-desalination process with natural driving force to reduce the salinity difference. Pre-desalination rate is related to power generation in RED stage and energy saving in ED stage under optimal operation conditions. Compared with artificial seawater, greater power generation is produced by using phenol-containing wastewater as the high-salinity stream. Economic analysis suggests that average power generation and limiting wastewater treatment capacity can provide insightful guidelines for the design and improvement of the hybrid system. Control conditions are listed as a fundamental criterion to search for potentially applicable wastewater systems in the hybrid system. Therefore, hybrid RED/ED system can realize triplex advantages of salinity energy usage, high-valued resource reclamation, and low-energy desalination in high-salinity wastewater treatment processes. [ABSTRACT FROM AUTHOR]

In this paper, one brackish water quality, which typically represented the water quality in the Huanghuai region of China, was simulated and used as feedwater to run an ultrafiltration (UF)–nanofiltration (NF) integrated membrane system. Laboratory-scale experiments were carried out to evaluate NF softening performance. The influences of transmembrane pressure (0.6–2.2 MPa), inlet tangential flow velocity (0.087–0.384 m·s − 1 ) and feedwater temperature (7–35 °C) on the softening efficiencies of two NF membranes denoted as DK (termed as NF1) and DL (termed as NF2) were investigated. The experimental results revealed that the calculated total hardness and the bivalent ion (SO 4 2 − , CO 3 2 − , Mg 2 + and Ca 2 + ) concentrations in NF2 product water on the same operation were all slightly lower than those in NF1 permeate in two schemes. Additionally, pH value of NF permeate decreased prominently than those in feedwater with increasing of transmembrane pressure, inlet tangential flow velocity or decreasing of feedwater temperature within the testing scope. [ABSTRACT FROM AUTHOR]

Monodispersed spherical MCM-48 nanoparticles with three-dimensional cubic mesostructure were synthesized and used as nanofillers dispersed in the aqueous or organic phase to prepare thin film nanocomposite (TFN) membranes through the interfacial polymerization of m -phenylenediamine and trimesoyl chloride. Scanning and transmission electron microscope images of the isolated polyamide (PA) active layer confirm that MCM-48 nanoparticles were embedded throughout the PA layer with dispersion in the organic phase as they were clipped between the PA layer and the polysulfone support with dispersion in the aqueous phase. Water flux was measured at 16 bar with 2000 ppm NaCl solution. Furthermore, water flux increased gradually from 24 L/m 2 ·h to 40 L/m 2 ·h with the increase in MCM-48 content in the organic phase, without significantly affecting salt rejection (>95%). Water flux increased from 24 L/m 2 ·h to 68 L/m 2 ·h, whereas salt rejection decreased from 97% to 80% with the increase in MCM-48 content in the aqueous phase. Less MCM-48 can be used in the aqueous phase than in the organic phase with similar performances. The two kinds of TFN membranes exhibit enhanced long-term durability, which confirms that MCM-48 can stably reside in the TFN membranes by dispersing whether in the organic or aqueous phase. [ABSTRACT FROM AUTHOR]

Thin-film nanocomposite (TFN) membrane with polyamide (PA) layer containing nanofillers have attracted extensive attention due to their excellent properties. In this study, hollow polymer phenolic resin nanospheres (HPS) and silver nanoparticles immobilized HPS (Ag/HPS) were synthesized with 2,4-dihydroxy benzoic acid and hexamethylene tetramine, and used as nanofillers to prepare TFN-HPS and TFN-Ag/HPS membrane. In this paper, the effects of HPS and Ag/HPS addition (0.002 wt%, 0.004 wt%, 0.006 wt%, 0.008 wt% and 0.010 wt%) on TFN membranes separation performance were investigated. The results showed that the water fluxes of TFN-HPS and TFN-Ag/HPS membranes reaches 64.7 L·m−2·h−1 and 64.0 L·m−2·h−1, respectively, when the addition amount of HPS and Ag/HPS was 0.006 wt%, which is about 80 % higher than that of TFC membranes (36.0 L·m−2·h−1). Furthermore, the TFN-HPS and TFN-Ag/HPS membrane have excellent long-term stability. After seven days of continuous operation, the water flux of TFN-HPS and TFN-Ag/HPS membranes remains at 50.0 L·m−2·h−1 and 45.6 L·m−2·h−1, respectively. In addition, the fouling resistance of TFN-HPS and TFN-Ag/HPS membranes is significantly improved, with flux recovery rates reaching 88.8 % and 91.4 %, respectively. Importantly, the sterilization rate of TFN-Ag/HPS membrane containing antibacterial silver to Escherichia coli is up to 96.7 %. [Display omitted] • Hollow polymer nanospheres (HPS) and Ag immobilized HPS nanofillers were prepared. • Two new-type TFN membranes containing HPS and Ag/HPS nanofillers were prepared. • HPS and Ag/HPS greatly improved the permselectivity and stability of TFN membranes. • TFN-Ag/HPS membrane showed high water flux (64 LMH) with NaCl rejection of 97.9 %. • TFN-Ag/HPS membrane showed a high antibacterial ratio of 96.7 % against E. coli. [ABSTRACT FROM AUTHOR]

This work studied the feasibility of ultrasonic-assisted (US-assisted) chemical cleaning of nanofiltration (NF) membranes that fouled with inorganic scales. We carried out US-assisted acid cleaning experiments by filter arsenic-rich brackish water to investigate the influencing conditions of US-assisted cleaning technology. We first optimized the proper ultrasonic power intensity (1 W/cm 2 ) in avoiding of membrane damage. US-assisted water flushing can recover the membrane water flux by around 75%, which suggested that the removal of inorganic scales was inadequate. However, US-assisted acid cleaning is efficient for removing the inorganic scales on membrane surface, and cleaning time was significantly shortened by 1/3 to 2/3 when compared with acid cleaning. It is worth to note that US-assisted acid cleaning can be carried out at a lower pH value of 3.0, while traditional acid cleaning usually conducted at pH of 2.0.This would reduce disposal amount of chemical contaminants by up to 90%. Additionally, our investigation suggests the optimal temperature for US-assisted acid cleaning was around 30 °C. This study revealed that the US-assisted acid cleaning method is an effective and environmental-friendly method for NF membrane cleaning. [ABSTRACT FROM AUTHOR]

Novel carbon nanotubes (CNTs) incorporated double-skinned thin film nanocomposite (TFN) membranes were fabricated by interfacial polymerization of polydopamine/CNTs and trimesoylchloride (TMC) on polysulfone (PSf) substrate. As controls, thin film composite (TFC) membrane without CNTs and FO membranes with single-skinned structures (top-skinned or bottom-skinned) was also fabricated. The prepared membranes were characterized and evaluated in terms of membrane morphology, structure, surface property, separation performance and antifouling capacity. The effect of membrane orientation, composition and concentration of draw solutions on FO performance was studied as well. It was found that CNTs had significant influence on the properties and the performances of the synthesized FO membranes. The double-skinned membranes owned excellent solute rejection without sacrificing water flux. By incorporation of CNTs, TFN membranes exhibited higher FO water flux than TFC membranes. The double-skinned TFN0.05 membrane, the optimal FO membrane, showed a 54% enhancement in water flux than double-skinned TFC membrane at TOP-FS orientation by using MgCl 2 as draw solution and DI water as feed solution. Moreover, the double-skinned TFN0.05 membrane demonstrated remarkable antifouling capacity because of the prominent foulant resistance induced by CNT addition. This work paved a new way to fabricate high performance FO membrane by the utilization of double-skinned structure and incorporation of CNTs. [ABSTRACT FROM AUTHOR]

Nanofiltration (NF) is an effective technology for fluoride rejection in drinking water which has characteristics of high water flux, high water recovery rate and low operation pressure, etc. However, high fluoride concentration severely influences the quality of its product water. Herein, nature diatomite was chosen to adsorb fluoride prior to NF process. The characterization of diatomite was investigated by SEM and XRD, and the feasibility was studied by XPS and FT–IR. The influences of diatomite dosage, pH, ionic strength and anions concentration were researched by batches of adsorption experiments. The presence of HA enhanced the adsorption of fluoride at pH < 5 while reduced fluoride adsorption at pH > 5. The adsorption process fitted the Langmuir isotherm and the adsorption kinetics fitted the pseudo-second-order rate equation. In addition, the combination of adsorption process and NF treatment was studied, which confirmed that the nature diatomite can ensure the permeate water of the NF system to meet the standard. Results of this study demonstrated that the nature diatomite was viable and effective to be used as the pretreatment adsorbent for NF system to defluorinate high fluoride water. [ABSTRACT FROM AUTHOR]

A pilot-scale ultrafiltration (UF)–nanofiltration (NF) integrated membrane system (IMS) which included a self-cleaning crossflow UF filtration process and a dual-stage NF process with a capacity of 100 m 3 ·d − 1 NF permeation water was established for seawater softening investigation. The separation performance of the dual-stage NF process under different conditions, such as operating pressure, recovery rate, and inlet flowrate, was extensively investigated; long-term performance and energy consumption of the dual-stage NF process were analyzed as well. The results showed that during the long-term operation, UF could provide qualified filtrate for NF. The dual-stage NF process achieved high separation performance with good permeate quality, especially high rejection of Ca 2 + and Mg 2 + (> 90%). In addition, the dual-stage NF process showed good anti-fouling characteristics, with the normalized NF permeate flux maintaining at an essential constant value of about 14 L·m − 2 ·h − 1 at 3.5 MPa, and DOC rejection around 90% during the long-term experiment. Energy consumption of the dual-stage NF process increased with the increase of the operating pressure and the decrease of the raw seawater temperature, which was about 1.8 kWh·m − 3 at 3.5 MPa and 25 °C. [ABSTRACT FROM AUTHOR]

The integrated membrane technology, consisting of MF, UF, and RO membrane, was used for the concentration of biogas slurry to realize the recovery of fertilizer and water. The pilot test proved the feasibility of the integrated membrane technology in this application. The RO membrane can concentrate the biogas slurry with the concentration factor of 5. RO membrane shows over 97% removal for COD and NH 3 -N, allowing less than 50 ppm of COD and NH 3 -N transport to the permeate side. The RO membrane suffered both organic and inorganic fouling. The optimal strategy for eliminating the fouling in this study is the receipt of NaOH + SDS + STPP → HCl. The salt rejection maintained at around 97.0% by this strategy, and the flux recovery had a sharp increase (~ 50.0%) after the addition of this multiple agent. [ABSTRACT FROM AUTHOR]

Improving fouling resistance and chlorine stability of aromatic polyamide (PA) thin-film composite (TFC) reverse osmosis membrane is still of considerable need in desalination membrane technology. Here, we reported the chemical linkage of neutral hydrophilic polymer polyvinyl alcohol (PVA) on the surface of a commercial PA TFC membrane through a single step of grafting with potassium persulfate as thermal dissociation initiator and its role on the improvement of membrane resistance to both chlorine and fouling. Membrane characterization was conducted through ATR-FTIR spectroscopy, SEM, AFM, measurements of streaming potential and contact angle and cross-flow permeation tests. It was found that membrane surface became smoother, more hydrophilic and less charged after modification and the modified membrane exhibited an increased slat rejection, a slightly declined water flux and improved fouling resistances to the model foulants of bovine serum albumin (BSA), sodium dodecyl sulfate (SDS) and dodecyltrimethyl ammonium bromide (DTAB). The chlorine exposure tests under accelerated conditions also indicated that the membrane chlorine stability has been enhanced effectively. The PVA molecules on the membrane surface could effectively enhance membrane anti-adsorption capability and prevent the underlying polyamide backbones from chlorine attack, and thereby improving membrane resistance to both fouling and chlorine. [ABSTRACT FROM AUTHOR]

This study explored the effect of increasing nanofiltration (NF) permeate recovery ( R NF ) by recirculation and dosage of chemicals on NF separation performance, concentration polarization ( CP ) and accumulation of scaling-prone ion concentration on NF membrane surface. The related coupling effect on seawater reverse osmosis (SWRO) desalination was also evaluated. The results show that when R NF for a single NF membrane element increased from 40% to 65%, pH of NF retentate and recycling ratio ( R r) increased from 5.02 and 0.75 to 5.10 and 3.58, respectively, with the dosage of both acid and antiscalant. In the same R NF range, the rejection of Ca 2 + , CO 3 2 − , SO 4 2 − , TDS and total hardness decreased from 35.1%, 78%, 96.3%, 18.2% and 56.1% to 28%, 76.9%, 96.1%, 10.9% and 33.9%, respectively, for NF in without chemical dosage. The CO 3 2 − and SO 4 2 − ion concentrations both in SWRO brine and on SWRO membrane surface were only around 0.12, 98, 0.12 and 99 mg·L − 1 , respectively, which were much lower than those in typical SWRO brine. Higher rejection for SO 4 2 − ion and higher selectivity of divalent ions over monovalent ions by the NF element were demonstrated in this study, which indicates that ESNA3 membrane yields a relatively higher efficiency of seawater pretreatment. [ABSTRACT FROM AUTHOR]

Membrane fouling is the main problem during the nanofiltration (NF) process of brackish water desalination due to the existence of natural organic matter, especially humic acid (HA). Moreover, the conventional membrane cleaning method would do great harm to the environment because large amount of chemicals were employed. In order to control organic fouling, a novel cleaning method via direct osmosis backwash (DOBW) by injecting high salinity (HS) solution was developed. Different operating conditions for HS-DOBW technology in the actual process were systematically investigated. The results demonstrated that there was a strong driving force to lift and sweep the foulants from the membrane surface which would be carried over to the brine. The optimal conditions in terms of HS (150 kg/m 3 NaCl solution) flow rate of 0.121 L/min were selected for the subsequent experiments. The results showed that the fouling could be almost fully reversible (more than 99.78% permeate water flux recovery), and the membrane needed to be cleaned for about 10 min because of the appearance of HA on membrane surface at the fouling time of 24 h. Most importantly, the HS-DOBW technology is very effective in keeping the membrane continuously clean and ensuring stable permeate production. [ABSTRACT FROM AUTHOR]

In this study, a novel approach, namely surface mineralization, was adopted to modify the commercial thin-film composite (TFC) polyamide (PA) reverse osmosis (RO) membrane for improved membrane properties. BaSO 4 -based mineral coating was deposited on the surface of the PA-RO membrane by alternate soaking process (ASP) using aqueous solutions containing barium chloride (BaCl 2 ) and sodium sulfate (Na 2 SO 4 ), respectively. Membranes with different mineralization degrees were prepared by varying the number of ASP cycles. The mineralized TFC PA-RO membranes were characterized through FESEM microscopy, AFM analysis, EDX analysis, zeta-potential analysis, contact angle measurement and cross-flow permeation test. It was found that the mineral coating composed of BaSO 4 particles distributed evenly on membrane surface. The surface of the membrane became more hydrophilic and negatively charged after mineralization and the membranes modified under certain conditions exhibited both increased water flux and salt rejection. Fouling experiments with bovine serum albumin (BSA) aqueous solution also demonstrated that the BaSO 4 -based surface coating layer could effectively alleviate the adsorption and deposition of foulant molecules on the membrane surface through enhancing electrostatic repulsion and lowing hydrophobic interaction between BSA molecules and membrane surface, and that the mineralized membrane possessed improved fouling resistance to BSA aqueous solution. [ABSTRACT FROM AUTHOR]

Abstract: In desalination process, the effect of concentration factor (CF) and concentration polarization degree (CP degree) on water recovery in nanofiltration (NF) system displays a significant difference from that in reverse osmosis (RO) system due to their different salt rejections. In this work, the relationship between CF, salt rejection and water recovery was firstly discussed in a single NF element. In order to keep a stable performance, a spiral NF2 membrane was taken as an example, and water recovery for the single NF2 element should be about 25% instead of 15%, which is generally considered suitable for the single RO element. Then, the CP degree was calculated according to the theoretical model and experimental test, and the ultimate value was pointed out to be below 1.2. Thus, when calculating the scaling tendency of the sparingly soluble salts, the salt concentration near the membrane surface was recommended to be 1.15 times as high as that in bulk solution. Finally, a calculation method for maximum recovery was proposed for NF system. Because of the varied rejection with different NF membranes for the same feed water, which is significantly different from that in RO system, the pre-test is very necessary for NF system design. [Copyright &y& Elsevier]

Abstract: Pilot-scale tests were carried out on a nanofiltration (NF)–seawater reverse osmosis (SWRO) integrated membrane system (IMS) using a kind of ultra-low pressure and high selectivity NF membrane (ESNA3, Hydranautics). Three different schemes were investigated for the NF seawater softening processes. The effect of increasing NF permeate recovery rate (R NF) on the potential of scaling in the NF and RO modules was investigated in term of concentration polarization modulus (CP) of scalant ions, Stiff and Davis Stability Index (S&DSI), and Supersaturation Index (SI) of CaCO3 and CaSO4. The results show that within the test range, high R NF, large permeate flux and low specific energy consumption (Es) could be achieved simultaneously for the loosen NF membrane. The Es for ESNA3 membrane could be lower than 0.95kWh·m−3. CP SO4 2− was larger than CP CO3 2− in the NF module under the NF retentate recycling operating conditions. The SI data indicated that at R NF of higher than 65% and with antiscalant addition and pH adjustment, CaSO4 would preferentially precipitate on NF membrane surface. However, with pH adjustment, the S&DSI values on the NF and SWRO membrane surface remained negative, which indicated that CaCO3 scaling could not form in the pilot test operating range. [Copyright &y& Elsevier]

Abstract: Positively charged thin-film composite hollow fiber nanofiltration membranes were developed by the dip-coating method using polypropylene hollow fiber microfiltration membrane as support, polyvinyl alcohol (PVA) and polyquaternium-10 (the reaction product of hydroxyethyl cellulose with a trimethylammonium substituted epoxide, PQ-10) as coating materials, and glutaraldehyde as cross-linking agent. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), measurements of streaming potential and contact angle were employed to characterize the obtained membranes. The permeation properties were estimated through pressurized cross-flow permeation tests and the dye removal performance were evaluated through submerged filtration tests using cationic dye aqueous solutions. It was found that the salt rejection order of the membrane was CaCl2 >MgCl2 >NaCl>MgSO4 >Na2SO4 at neutral pH. The desired membrane with a molecular weight cut-off of about 650Da had a pure water flux of 25.7l/m2 h and a rejection of 92.8% to 500mg/l CaCl2 aqueous solution at 3.0bar. The membrane could effectively remove cationic dyes from aqueous solution with good long-term performance stability through submerged filtration. The observed rejections to Brilliant green, Victoria blue B and Crystal violet were 99.8, 99.8 and 99.2%, respectively, under the trans-membrane pressure of 0.7bar. [Copyright &y& Elsevier]

The electrical neutrality of ionic liquids (ILs) was exploited to enhance the antifouling property of polyamide (PA) reverse osmosis (RO) membranes in this work. We solely tethered the aminated imidazolium cation of ILs [AVIM] Br onto the top-surface of PA RO membranes via mild amidation. The molecular simulation results confirmed that the tethered imidazolium cation and the dissociated bromine anion were stably existed in the form of ion pairs on PA RO membrane surface. In virtue of the electrical neutrality of these ion pairs, the ionic-solvation induced hydration layer formed in ILs above the modified membrane surface was thick and evenly distributed, similar to that formed in conventionally electroneutral zwitterion antifouling materials. Thereby, the cation-tethered membrane surface intuitively achieved balanced charge and strong hydrophilicity, and stably exhibited low protein adsorption and excellent antifouling behaviors to diverse foulants, even when the imidazolium cation was paired with anions of different molecular size. Meanwhile, the typical ridge-and-valley surface morphology for PA RO membrane was well preserved due to the mild modification condition, and thereby harvested satisfactory separation performance. The integration of high performance, abundant ILs and mild conditions was expected to expand the application of superb antifouling materials in a variety of biofouling areas. [Display omitted] • The electroneutrality of ionic liquids was exploited for antifouling application. • The PA RO membrane surface was solely tethered with the aminated cation of ILs. • The tethered cation and dissociated anion were still stably existed as ion-pairs. • The ionic-solvation of ion pairs induced a strong hydration layer above membrane. • The cation-tethered PA RO membrane exhibited enhanced antifouling properties. [ABSTRACT FROM AUTHOR]

Chitosan (CTS) and 1,3,5-triglycidyl isocyanurate (TGIC) were gradiently cross-linked on the polyethersulfone ultrafiltration membrane (PES) to prepare a new type of positively charged composite nanofiltration membrane. The influence of preparing conditions on the membrane performance, such as permeability, mechanical strength, membrane morphology, and nanostructures was systematically discussed. The rejection performance to MgCl 2 , Na 2 SO 4 , MgSO 4 , and NaCl revealed that the prepared membrane was positively charged. The membrane prepared under the optimal conditions showed a molecular weight cut-off of 1500 Da. Finally, rejections to heavy metal ions were determined, and excellent removal rate was found. Among the nanofiltration membranes prepared from chitosan, CTS/TGIC-NF membranes prepared in the current work exhibited superior permeability and mechanical strength to the membranes shown in literature, indicating that our membranes can be used to reduce water hardness and produce portable water. [Display omitted] • 1.High permeability due to gradient cross-linking. • High selectivity to divalent cations and heavy metal ions. • The excellent mechanical properties. [ABSTRACT FROM AUTHOR]

Abstract: Thin-film composite (TFC) nanofiltration (NF) membranes with improved acid stability were fabricated through the interfacial polymerization of trimesoyl chloride (TMC) naphthalene-1,3,6-trisulfonylchloride (NTSC), and piperazine (PIP) on a porous polysulfone support membrane by varying the NTSC content in TMC-organic solution. The physico-chemical characteristics of the membranes were analyzed by ATR-FTIR, streaming potential measurement and surface contact angle measurement, the permeation properties were evaluated through cross-flow permeation tests, and the acid stability was investigated through both static acid soaking tests and long-term permeation tests under acidic condition. It was found that, as the NTSC content in TMC-organic solution increased, the membrane surface became more hydrophilic and negatively charged, the pure water permeability and molecular weight cut-off of the formed NF membrane increased from 5.5 to 10.6l/m2 hbar and about 360 to 660Da, respectively, while the rejection rate to Na2SO4 firstly increased from 98.2 to 98.7% and then declined to a lower value of 97.8%. After soaking in 8w/v% H2SO4 for 30days or filtration with 4.9w/v% H2SO4 for 60days, the TFC membranes prepared from TMC and NTSC showed little performance change, while serious performance deterioration occurred with the TFC membrane prepared from TMC. [Copyright &y& Elsevier]

Abstract: Color removal and chemical oxygen demand (COD) reduction of biologically treated textile effluent through submerged filtration using nanofiltration membrane were investigated in this study. Submerged filtration tests of biologically treated textile effluent were conducted under different trans-membrane pressures (TMP) and various volume concentrating factors (VCF) employing lab-made hollow fiber membrane modules. It was found that the color and COD presented in the biologically treated textile wastewater could be effectively removed through submerged filtration using hollow fiber nanofiltration membranes with molecular weight cut-off of about 620Da, while the electrolytes presented in the effluent were retained by the membrane to a very small extent, especially under VCF higher than 2.0, so that the nanofiltration membrane module could be operated under a low suction pressure. The increase of TMP and/or VCF resulted in a decline in water permeability and an increase in both color removal and COD reduction. Under the TMP of 0.8bar and VCF of 4.0, the submerged nanofiltration system exhibited a steady permeate flux of 5.15l/m2 h, a color removal rate of 99.3% and a COD reduction rate of 91.5%. Furthermore, the submerged nanofiltration system possessed high water cleaning efficiency of more than 93.0%. [Copyright &y& Elsevier]

Abstract: Monodispersed spherical mesoporous nanosilicas were synthesized by the hydrothermal method using tetraethoxysilane as silica source, cetyltrimethylammonium bromide as template, ethanol as co-solvent, and sodium hydroxide as alkali source. The synthesized silica has an average particle diameter of 164nm with a relative standard deviation of 4.87%, specific surface area of 1141m2·g−1, pore size of 2.47nm, pore volume of 0.77cm3·g−1, and a pore structure radiating from the heart to the outer surface of the sphere. The spherical mesoporous nanosilica–polyamide thin film composite reverse osmosis (TFC RO) membranes were obtained by interfacial polymerization. The silica nanoparticles are visible in the TFC RO membranes based on the surface and cross-sectional SEM images. Correspondingly, energy dispersive X-ray spectroscopy analysis confirms that the silica has been successfully doped into the TFC RO membranes. The hydrophilicity of the TFC RO membranes is improved and water flux is increased from 19L·h−1·m−2 (without nanosilica) to 53L·h−1·m−2 (with 0.1% (w/v) mesoporous nanosilica loading), whereas all solute rejection rates are greater than 96%. [Copyright &y& Elsevier]

Abstract: Flat sheet asymmetric polysufone (PSf) membrane and PSf/clay nanocomposite membranes with different clay contents were prepared by the nonsolvent induced phase inversion method. N,N‐dimethyl acetamide, deionized water and LiCl were used as a solvent, a coagulant and a pore forming agent, respectively. The morphology and structure of membranes were analyzed by scanning electron microscope, transmission electron microscope and X‐ray diffractometer. The performance of the membranes was evaluated in terms of pure water flux (PWF), protein rejection, porosity, contact angle, tensile strength and elongation at break. Results showed that clay had a good dispersion in the PSf matrix. The addition of clay additive could improve the hydrophilicity of the membranes and increase the ratio of large pore in the skin layer. PWF and porosity of membranes increased with the increase in clay content. With increase in clay content from 0wt.% to 6wt.%, the PWF increased from 199L·m−2·h−1 to 263L·m−2·h−1. The tensile strength attained its maximum when the clay content was 3wt.% and the value was 5.34MPa. Clay had high stability in the nanocomposite membranes. [Copyright &y& Elsevier]

Abstract: Modification of polypropylene (PP) hollow fiber microfiltration membranes for nanofiltration through dip-coating sodium carboxymethyl cellulose (CMCNa) skin layer followed by cross-linking with AlCl3 was investigated in this study. Modification parameters were studied to optimize the membrane performance and the obtained modified membranes were characterized in terms of surface and permeation properties. It was found that the surface property and solute separation capability of the PP hollow fiber membrane were significantly improved by coating CMCNa surface layer, and the optimized modified membrane took on a composite structure with a hydrophilic selective skin layer having an isoelectric point of pH 3.7. The composite layer was negatively charged at neutral pH and was relatively looser in acidic pH compared with that in basic or neutral. Permeation tests revealed that the desired modified membrane possessed a molecular weight cut-off (MWCO) of 760Da and a high pure water permeability of 10.8l/m2 hbar, and exhibited rejections to salts following the order of MgCl2

Abstract: An integrated membrane system (IMS) of ultrafiltration–nanofiltration (UF–NF) technology has been investigated extensively as a means of seawater softening for offshore oilfield water and polymer flooding. The results showed that the softened water generated by the selected NF membrane could meet the water flooding standard for offshore oilfield. At appropriate mixing ratio of softened water and formation water, scales may be avoided completely. Furthermore, the reservoir formation sensitivity evaluation proved the compatibility of NF permeation water with the formation core, which indicates that the permeation water of the selected NF membrane module could be safely used for offshore oilfield water flooding. The prepared aqueous polymer solution using NF softened seawater showed relatively high viscosity and stability at formation temperature for long time, which could meet the demand for offshore polymer flooding. Therefore, the UF–NF integrated membrane technology could efficiently resolve the softened water shortage problem in offshore oilfield water flooding and polymer flooding and ensure continuous and stable oil production. [Copyright &y& Elsevier]

Abstract: An ultrafiltration–nanofiltration (UF–NF) integrated membrane system (IMS) was operated for 500h to examine the performance of the NF membrane in seawater desalination pretreatment. The rejection of divalent ions, TDS, TOC and UV254 by the NF membrane as well as the permeation flux decreased gradually with operating time before each chemical cleaning procedure, while the calculated Stiff and Davis Stability Index (S&DSI) increased gradually from negative up to positive. The result indicates that there exists inorganic fouling during the long run. However, the IMS produced excellent effluent with 93.6% removal of total organic carbon (TOC) for long-term operation. The TOC concentration of the NF permeation samples was in the range of 0.06–0.35mg/L. The chemical cleaning results indicated that inorganic fouling should be preferentially paid attention to, and a combination of citric acid cleaning and NaOH cleaning may achieve an optimal cleaning efficiency. The long-term operation reveals that the membrane is more prone to fouling gradually after chemical cleaning. [Copyright &y& Elsevier]

Abstract: This study focus on the preparation and nanofiltration properties of a novel thin-film composite polyamide membrane formed by the interfacial polymerization of polyvinylamine (PVAm) and trimesoyl chloride (TMC) on a porous polysulfone supporting membrane. The fabrication of the PVAm–TMC composite membrane was conducted by studying preparation parameters including reaction time, pH of the aqueous phase solution, reactant concentration, as well as curing temperature and time. The properties of the resultant membrane were characterized in terms of morphological structure, surface zeta potential, pure water flux, molecular weight cut-off (MWCO) and rejections to different solutes including electrolytes and organic dyes. The results showed that the optimized composite membrane had a smooth and amphoteric surface with an isoelectric point at pH about 6.5, a MWCO of around 650Da, a pure water permeability of about 8.5l/m2 hbar and good long-term stability. The rejection order of the membrane to inorganic salts changed from MgCl2

Abstract: Flat sheet asymmetric PSf/clay nanocomposite membranes with different clay dosage were prepared by phase inversion method. Dimethyl acetamide was used as a solvent and water was used as a coagulant. PEG 400 was used as a pore forming additive in the casting solution. The morphology and structure of membranes were analyzed by scanning electron microscope, transmission electron microscope and X-ray diffractometer. The performance of membranes was evaluated in terms of pure water flux (PWF), protein rejection, porosity, contact angle, tensile strength and elongation at break respectively. Results showed that clay had a good dispersion in the PSf matrix. The addition of clay additive increased the ratio of large pore in the skin layer and weakened the tensile strength. PWF and porosity of membranes increased with the increase of clay dosage. With increase in clay dosage from 0wt.% to 6wt.%, the PWF increased from 342Lm−2 h−1 to 382Lm−2 h−1. [Copyright &y& Elsevier]