•A simple and low energy consumption method was used to crosslink cation membrane.•A series of sulphonated polysulfone membranes with different degrees were prepared and investigated.•The crosslinked membranes exhibited enhanced dimensional stability and application performance.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.Crosslinked structural cation exchange membrane with improved dimensional stability.Download high-res image (249KB)Download full-size image

Bipolar membrane electrodialysis (BMED) has already been described for the preparation of quaternary ammonium hydroxide. However, compared to quaternary ammonium hydroxide, di-quaternary ammonium hydroxide has raised great interest due to its high thermal stability and good oriented performance. In order to synthesize N,N-hexamethylenebis(trimethyl ammonium hydroxide) (HM(OH)2) by EDBM, experiments designed by response surface methodology were carried out on the basis of single-factor experiments. The factors include current density, feed concentration and flow ratio of each compartment (feed compartment: base compartment: acid compartment: buffer compartment). The relationship between current efficiency and the above-mentioned three factors was quantitatively described by a multivariate regression model. According to the results, the feed concentration was the most significant factor and the optimum conditions were as follows: the current efficiency was up to 76.2% (the hydroxide conversion was over 98.6%), with a current density of 13.15 mA·cm− 2, a feed concentration of 0.27 mol·L− 1 and a flow ratio of 20 L·h− 1:26 L·h− 1:20 L·h− 1:20 L·h− 1 for feed compartment, base compartment, acid compartment, and intermediate compartment, respectively. This study demonstrates the optimized parameters of manufacturing HM(OH)2 by direct splitting its halide for industrial application.

•The monovalent anion-selective membranes have been prepared by simply electro-depositing PEI.•The membranes have been prepared from partial quaternization reaction of BPPO (QPPO).•The strong chemical bonds were formed between the substrate QPPO and PEI.•The membrane exhibits a perm-selectivity (Cl- against SO42-) of 4.27 under normal condition.Surface modification by generating a dense anionic layer on the surface of a substrate membrane is the main method for preparing monovalent selective anion exchange membranes. However, this method has a trade-off between the permselectivity and the stability of the surface layer. To overcome this problem, a simple preparative pathway is devised to covalently immobilize the polyethyleneimine (PEI) onto the surface of an anion exchange membrane (partly quaternized poly (phenylene oxide) (QPPO)). Firstly, a brominated poly (2,6-dimethyl-1, 4-phenylene oxide) (BPPO) based anion membrane was prepared by quaternization. Then, this membrane was modified by electro-deposition of a PEI solution. The composition and structure of the membrane were observed by infrared spectroscopy and scanning electron microscopy. The permselectivity was evaluated by electrodialysis in a Cl-/SO42-system. The experimental results prove that the PEI modification method is an effective, simple, feasible and well-controlled strategy to fabricate mono-valent selective anion membranes.Download high-res image (198KB)Download full-size image

•The anion exchange membranes with improved dimensional stability for electrodialysis has been prepared via internal cross-linking networks.•4,4′-bipyridine not only provides a functional group but also comprises a cross-linking agent without requirements of post-functionalization.•The cross-linked membrane with IEC of 1.98 mmol/g has much more outstanding dimensional stability (swelling ratio: 3.8%) than non-cross-linked BPPO-Tri membrane (swelling ratio: 7.71%) and commercial Neosepta AMX membrane (swelling ratio: 5.08%), at the high temperature (50 °C).•When being applied in ED application, the cross-linked BPPO-20 membrane exhibits much higher desalination efficiency and lower energy consumption than commercial Neosepta AMX membrane, suggesting its promising application in ED.Anion exchange membranes (AEMs) with a high ion exchange capacity, striking water uptake and excellent dimensional stability were prepared via an internal crosslinking networks strategy. Internal crosslinking networks were formed by reacting 4,4′-bipyridine with brominated poly (2,6-dimethyl-1,4-phenylene oxide) (BPPO). 4,4′-bipyridine not only provides a functional group but also comprises a cross-linking agent without requirements of post-functionalization. The variation of the 4,4′-bipyridine amount into the casting polymer solution was explored to regulate the performance of the anion exchange membranes, and the membrane properties were evaluated by AFM, ion exchange capacity (IEC), water uptake, the linear expansion ratio, tensile strength, thermal stability, membrane area resistance and electrodialysis experiments, etc. The results showed that the cross-linked membrane with the IEC of 1.98 mmol/g has much more outstanding dimensional stability (water uptake: 11.68%; swelling ratio: 3.8%) than non-cross-linked BPPO-Tri membrane (water uptake: 53.26%; swelling ratio: 7.71%) and commercial Neosepta AMX membrane (water uptake: 60.29%; swelling ratio: 5.08%), at the high temperature (50 °C). When being applied in ED application, the cross-linked BPPO-20 membrane (NaCl remove: 59.7%; energy consumption: 5.97 kWh/kg NaCl) exhibits slightly higher desalination efficiency and lower energy consumption than commercial Neosepta AMX membrane (NaCl remove: 58.3%; energy consumption: 6.51 kWh/kg NaCl), suggesting its promising application in ED.

•CFGO was fabricated through ring-opening and esterification reactions respectively. CFGO was fabricated through ring-opening and esterification reactions respectively.•Novel CFGOPA membranes are prepared via interfacial polymerization of PIP and TMC. Novel CFGO/PA membranes are prepared via interfacial polymerization of PIP and TMC.•The CFGO/PA membrane shows better performance in permeability and dye desalination than GO/PA membrane.•The CFGO/PA membrane shows great potential in the dye desalination and concentration process.Novel carboxyl-functionalized graphene oxide (CFGO)/polyamide (PA) nanofiltration (NF) membranes were prepared via interfacial polymerization (IP) of piperazine (PIP) and trimesoyl chloride (TMC). CFGO was fabricated by a chemical modification (ring opening followed by esterification) to the epoxide ring of GO. CFGO was then introduced in the PIP aqueous phase as an additive in the IP reaction. Compared with a pristine PA reference membrane, both the GO/PA and CFGO/PA membrane have an enhanced permeability (the optimum concentration of GO and CFGO in the membrane was 0.05% and 0.07%, and the corresponding water flux is 96.5 and 112.1 L/m2/h, respectively),with a slight decrease of the salt rejection. In dye desalination experiment, the permeation flux of 0.05%GO/PA membrane is only 75.5 L/m2/h, with 98.1% rejection of New Coccine (a dye with negative charge) and 28.7% retention for NaCl. For 0.07%CFGO/PA membrane, it can cut off 25.0% NaCl and 95.1% New Coccine, and its permeation flux can reach 110.4 L/m2/h, which shows that the CFGO/PA membrane could be potentially applied to the dye desalination and concentration process. The CFGO/PA membrane shows better performances in permeability and dye desalination than GO/PA membrane, due to the significantly increased hydrophilicity and enhanced surface charge density.

•It is feasible and effective to modify PEMs on AEMs to enhance monovalent selectivity and durability simultaneously.•The modified process significantly improved the monovalent anion selectivity.•A simple UV cross-linking strategy is devised to improve the durability of monovalent anion selective membranes.Layer-by-layer deposition of polycations and polyanions multilayers on the surface of anion exchange membranes (AEMs) is a simple and versatile method to obtain monovalent anion selectivity. However, the stability of the polyelectrolyte multilayers (PEMs) can be compromised by the weak interactions formed between the deposited barrier and the pristine membrane surface. In this sense, cross-linking appears as an efficient method to improve the chemical stability of PEMs by covalent bonding. In this investigation, polyelectrolyte multilayers was coated on commercial AEMs by alternating electro-deposition with polystyrene sulfonate (PSS) and 2-hydro-xypropyltrimethyl ammonium chloride chitosan (HACC). Subsequently, photosensitive molecules (4,4-diazostilbene-2,2-disulfonic acid disodium salt (DAS)) were mixed into the loose multilayers by soaking in the DAS solution and chemical bonds were formed in the membrane by UV irradiation. The chemical composition and structure of the membrane were confirmed and observed by infrared spectroscopy, atomic force microscopy and scanning electron microscopy. The monovalent selectivity and durability were evaluated by electrodialysis (ED) in a Cl-/SO42- system. The optimized membrane was found to have a stable selectivity during the entire duration of testing (76 h), and while a conventional multilayer modified AEMs completely loses its selectivity after 30 h. Furthermore, the modification process improved the monovalent anion selectivity from 0.39 to 4.36. The experimental results demonstrate the effectivity and feasibility of the modified strategy.

This study reports the fabrication of mixed matrix membranes (MMMs) using immersion precipitation phase inversion for promising application in desalination of dye solutions. Aromatic poly(m-phenylene isophthalamide) is used as the polymer material, and the metal–organic framework MIL-53(Al) is added to develop integrally skinned asymmetric membranes. Successful dispersion of MIL-53(Al) particles into the membrane-separating layer is confirmed by scanning electron microscopy. The optimum performance of the membranes is obtained at 0.5 wt % MIL-53(Al) concentration. In particular, the M-0.5 membrane is planned for use in separating dye/salt aqueous mixtures. It is observed that the M-0.5 membrane has a rejection for NaCl and Na2SO4 below 11% and 37%, respectively, in mixed salt/dye solutions. Additionally, the M-0.5 membrane is found to have a rejection rate of 83.9%, 98.3%, and 99.8% for nitroso-R salt, xylenol orange, and ponceau S, respectively, in mixed Na2SO4/dye solutions. The rejection rate for Na2SO4 is lower than that of some commercial nanofiltration membranes (NF90, NF270, and DK). The membrane is promising for dye desalination in industrial-scale applications.

Selectivity for monovalent cations is an important property of cation exchange membranes (CEMs). The cation exchange membranes of the CSO modified with polyethyleneimine type have a higher selectivity for monovalent cations than the multivalent cations. Unfortunately, the loss of selectivity for these kinds of CSO seems to be unavoidable due to fouling and degradation of polyethyleneimine groups. In this situation, a “re-modification” technique was developed for recovery of fouled CSO, activating the fouled CSO by methanol and a sulfuric acid solution with ultrasonic vibration, followed by a layered surfacial electro-deposition method to prolong the lifetime of cation exchange membranes. A series of electrodialysis experiments for Na+/Ca2+ separation was performed for evaluating and comparing the monovalent cation selectivity of the samples. The restoration of the surface and cross section morphology after “re-modification” was demonstrated by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). As a result of the re-modification method the membranes with chemically degraded polyethyleneimine were again made functional. The ion exchange groups of the CSO modified with polyethyleneimine were successfully recovered, giving the membrane a high permselectivity again.

Reverse osmosis (RO) membranes might experience significant changes in surface structure and performance after disinfection has been applied, or after membrane cleaning, because of hydrolysis and oxidation processes. This study reports potential applications of aromatic polyamide RO membrane exposed to a sodium hypochlorite solution for desalination of dye solutions. Changes in the chemical composition, morphology and performance of such membrane were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), contact angle measurements, scanning electron microscope (SEM), atomic force microscopy (AFM) and streaming potential measurements. After chlorination, the water flux of RO membrane doubled, and the NaCl and Na2SO4 rejection of the RO membrane decreased to 46.2% and 86.2%, respectively. However, the rejection of congo red, methyl blue and direct red 80 were 99.4%, 98.0% and 100%, respectively. This indicates that abandoned RO membranes can be recovered as “nanofiltration functional membranes” after sodium hypochlorite exposure, and be suitable for fractionation purposes.

Methionine is an important amino acid to block the autophagy in cells. In industry, the production of methionine through the hydantoin pathway generates a huge amount of inorganic salts (i.e., Na2SO4), reducing the product purity. In this work, an efficient bipolar membrane electrodialysis (BMED) technology was proposed to extract high-purity methionine from the mother liquor of reaction. Lab-scale experiments were conducted with an optimized BMED stack at a current density of 150 A/m2. The energy consumption and current efficiency were acceptable, reaching 2.156 kWh/kg NaOH and 75.10%, respectively. Specifically, the base, i.e., NaOH, with a high concentration generated in BMED stack can be used for effective adsorption of H2CO3, in view of reducing the emission of CO2. Furthermore, a simulation of cation migration during the BMED operation was performed on the basis of the relationship between pH and the concentration of different ion species. From the simulation, it is critical to control the pH at ∼4.4 to maximize the purity and reduce the extraneous loss for methionine. Finally, a pilot-scale experiment was designed to evaluate the economic feasibility of BMED for the production of methionine. It can be confirmed that total cost of BMED operation for the production of methionine with high purity (99.4%) was estimated to be 321 $/t Met, which is economically viable in industry.

A series of semi-interpenetrating polymer network (sIPN) composite anion exchange membranes were fabricated depending on immobilized linear PVDF and cross-linked polyepichlorohydrin (PECH), 1,4-diazabicyclo[2.2.2]octane, (DABCO) network through in situ synthetic pathway. A cyclic diamine (DABCO) was used as cross-linking agent and simultaneously improved the ion-exchange capacity by amination. Scanning electron microscopy (SEM) indicated that the composite membranes exhibited a dense and homogeneous structure. Successful formation of PECH-DABCO copolymer within the sIPN membranes was also confirmed by Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS). The PVDF percentage and inherent properties of membranes such as ion exchange capacity (IEC), water uptake (WR), thermal stability, mechanical property, and area resistance were investigated to evaluate their applicability in electrodialysis (ED). The experimental results showed that the composite membrane maintained a good perspective for ED application.

•Mono-valent cation selective membranes for electrodialysis were developed.•Poly-quaternium-7 was used for modification of cation exchange membranes.•The membrane has an excellent performance, particularly with respect to selectivity.Ion exchange membranes are essential for electrodialysis. However, the presence of multivalent ions, such as Ca2+, Mg2+, or CO32−, SO42−, may result in a detrimental risk of membrane scaling. Mono-valent cation selective membranes may solve this problem. In this study, the surfactant N,N-dimethyl-N-2-propenyl-2-propene-1-ammonium chloride-2-propenamide (poly-quaternium-7, PQ7) is used to modificate the cation exchange membranes. Different concentrations of degraded polyquaternium-7 and sodium hydroxide are investigated to determine the optimal point. The composition and characteristics of the membranes were determined with Fourier transform infrared spectroscopy (FTIR), X-ray photo-electron spectroscopy (XPS), Scanning electron microscopy (SEM) and Atomic Force Microscopy (AFM). Hydrophilic and functional groups of the membrane were determined by the water uptake, contact angle and ion exchange capacity. Current–voltage curves were measured to characterize the transport properties of membranes. The obtained results showed that the limiting current was reduced while the Ohmic and electro-convection resistances were increased. Diffusion dialysis experiments have demonstrated that leakage of modified membrane is lower. Furthermore, a series of electrodialysis experiments was conducted to evaluate the monovalent selectivity of the unmodified and modified CEMs. The leakage of Zn2+ was decreased from 22.0% to 14.2% and the leakage of Ca2+ and Mg2+ were both decreased while the membranes are used in seawater concentration. The obtained results indicate that the membrane has an excellent performance, particularly with respect to selectivity.

In this work, textile wastewater is explored for resource recovery in a hybrid loose nanofiltration (NF)-bipolar membrane electrodialysis (BMED) process for fractionation of dyes and salt, in view of dye purification and water and salt reuse. A loose nanofiltration membrane, i.e., Sepro NF 6 (Ultura), found to have a low salt rejection (0.27% in 120 g·L–1 NaCl solution) and high rejection for direct dyes and reactive dyes (≥99.93%), was used for fractionation of dye/salt mixtures through diafiltration. In diafiltration, the addition of pure water with a volume factor of 5.0 can effectively remove the NaCl salt by using Sepro NF 6 with an invariable dye concentration, in view of the recovery of high purity dyes. The overall salt rejections in diafiltration for the dye/salt mixtures with 40, 50 and 60 g·L–1 NaCl are 2.2%, 1.8% and 1.1%, respectively, enabling a further treatment by BMED. Subsequently, application of BMED for reuse of salt-containing NF permeate demonstrates that desalinated water with ∼100 ppm of NaCl can be obtained, and base/acid can be produced from the salts without any membrane fouling by dyes. Therefore, the hybrid loose NF-BMED process allows for resource (i.e., dye, salt and pure water) extraction from textile wastewater, which closes the salt and water cycle, in view of process intensification.Keywords: Dye/salt mixture; Hybrid loose NF-BMED process system; Resource recovery; Zero liquid discharge;

The application of electrodialysis (ED) for desalination requires the use of natural seawater or river water, in which the presence of multivalent ions is inevitable. This currently limits the process performance. Membranes with selectivity for monovalent ions may overcome this limitation. This study used the method of electro-deposition with chitosan/aniline polymer as a modification material to coat a commercial anion exchange membrane in view of obtaining selectivity for monovalent ions. Chitosan was grafted with polyaniline through copolymerization using ammonium persulfate as an initiator. FTIR spectra of the composites revealed that there was a strong interaction between substituted polyanilines and chitosan. The method was used to prepare a series of membranes by varying the aniline ratio and polymerization time. The chemical composition and surface properties of the membranes were characterized by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM), respectively. Current–voltage curves and resistance were measured to characterize the transport properties of the membranes and the membrane conductivity. The results show that the membrane conductivity increases with the aniline ratio; the selectivity initially increases with the aniline ratio, and then decreases again. The optimum modification condition was an electrodeposition time of 4 h with an aniline ratio of 0.4. Using the modified membrane in concentrated sea water, it was demonstrated that the modified membrane has an excellent selectivity towards monovalent cations.

Aromatic poly(m-phenyleneisophthalamide) (PMIA) and the metal-organic framework (MOF) MIL-53(Al) were employed as the polymer matrix and additive, respectively, to develop mixed matrix membranes (MMMs) via non-solvent induced phase separation for potential application in organic solvent nanofiltration. The prepared membranes were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and water contact angle measurements. The membrane water permeance enhanced when MIL-53(Al) was incorporated into the membrane structure while the rejection had no significant change. The optimum MMM (with 0.5 wt% MOF concentration) passes mono and bivalent inorganic salts but rejects larger charged organic molecules and has a mean effective pore size of 0.7 nm. The influence of organic solvents on MMM performance was also investigated and the result shows that the performance shifts towards a lower pure water permeance and a higher rejection after exposure to organic solvents (ethyl acetate or methanol). The membrane performance in organic solvent nanofiltration was evaluated on the basis of the permeance and rejection of brilliant blue G in ethanol, and the result showed that the permeance of MMMs significantly increased (by 289%) while the rejection slightly reduced by 4% in contrast to the pure membrane.

•NaOH with 1.45 mol L−1 was produced with a 80.8% current efficiency at a low current density.•A satisfactory purity of 96.5% for NaOH and a glyphosate recovery of 98.2% were achieved.•Overall CO2 balance is positive when employing electricity from renewable sources in BMED.Post-combustion CO2 capture by reaction with a strong alkali such as NaOH appears a promising strategy to mitigate CO2 emission. This study proposes bipolar membrane electrodialysis (BMED) as a technology for the reclamation of NaOH from glyphosate neutralization liquor and its subsequent use as an absorbent for CO2 capture. The proposed method produces a NaOH solution for further reaction with CO2 while recovering the glyphosate from the wastewater.A NaOH solution with a concentration of ∼1.45 mol L−1 and purity of ∼96.5% was obtained. Accordingly, a current efficiency of 80.8%, 76.2%, 68.7% and 69.0% at current densities of 30, 40, 50 and 60 mA cm−2 was observed, respectively. In addition, the lowest energy utilization recorded as 2.15 kW h kg−1 was obtained by the BMED process at a low current density of 30 mA cm−2, resulting in a better performance in view of energy saving. A glyphosate recovery of ca. 98.2% was also achieved.The environmental impact of the BMED process was evaluated in terms of the amount of CO2 emissions produced and the total amount of CO2 captured taking into account of the CO2 production through BMED process. The results demonstrate that a promising CO2 capture (up to 530.65 g CO2 kg−1 NaOH) can be only achieved if the electricity resources originate from renewable sources such as wind, hydroelectric, as well as solar photovoltaics or nuclear energy. However, the utilization of non-renewable energy resources for NaOH production by BMED process imposes a risk on producing a significant emission of CO2, which makes the application of BMED unviable for a CO2 capture scenario.

•Small AgCl nanoparticles generated in microemulsion using the ionic liquid as a surfactant.•AgCl nanoparticles distributed well in hybrid membrane after polymerization.•The size and the number of AgCl nanoparticles changed with preparation conditions.•Hybrid membrane including small AgCl particles have high solubility of benzene.AgCl nanoparticles were synthesized in a water-in-oil microemulsion using the ionic liquid 1-dodecyl-3-methyl imidazoium chloride (C12mimCl) as the surfactant and methyl methacrylate–acrylamide (MMA–AM) mixture as the oil phase. An aqueous AgNO3 solution was added to the microemulsion as the source of Ag+ ions. Subsequently, AgCl/poly(MMA-co-AM) hybrid membranes were prepared by in situ microemulsion polymerization, and applied for pervaporation of mixtures of benzene and cyclohexane. The effects of C12mimCl (CC12mimCl) and AgNO3 (CAgNO3) concentrations on the formation and morphology of AgCl nanoparticles were studied. The structure of AgCl/poly(MMA-co-AM) hybrid membranes was examined and analyzed with SEM and XRD. The swelling–sorption behavior of AgCl/poly(MMA-co-AM) hybrid membranes in the benzene and cyclohexane solutions, and their separation ability were measured. The AgCl nanoparticles that were formed in the ionic liquid-based microemulsion were found to be spherical with a mean diameter of 20 nm within a narrow size range. The number of AgCl nanoparticles increased with increasing CC12mimCl, and the mean diameter of the AgCl nanoparticles increased with increasing CAgNO3. The AgCl/poly(MMA-co-AM) hybrid membranes were found to have a core–shell structure with AgCl as the core and poly(MMA-co-AM) as the shell. The AgCl nanoparticles were uniformly dispersed in the poly(MMA-co-AM) matrix. The AgCl/poly(MMA-co-AM) hybrid membranes displayed the characteristics of preferentially selective sorption–swelling benzene and demonstrated better pervaporation performance than that of the membrane without nanoparticles in separating the benzene/cyclohexane mixture.Graphical abstract

•Monodisperse Stöber silica (MSS) was first used aiming at enhancing membrane performance.•MSS with ultralow concentration regularly altered the membrane morphology.•Optimal content of MSS significantly enhanced membrane permselectivity and antifouling property.SiO2 nanoparticles offer promising prospects as additives for the synthesis of organic–inorganic hybrid composite membranes due to their facile synthesis procedure with low cost and toxicity to aqueous systems. This requires silica nanoparticles with good monodispersity to form a regular hydrophilic surface. In this study, monodisperse silica synthesized by the Stöber method was explored as an additive in ultralow concentration for the synthesis of organic–inorganic composite membranes based on polyethersulfone, aiming at potential application in water treatment. The results indicate the polyethersulfone membrane doped with monodisperse silica has an enhanced performance. The hydrophilicity of the modified membranes was also enhanced due to the high water affinity of nano-SiO2, resulting in a higher permeability. However, in the high concentration interval of nano-SiO2, the permeability of modified membranes decreases due to pore plugging and the alteration of macrovoids in the sublayer of membranes. Simultaneously, the selectivity of the modified membranes was improved, which is an indicator for a more narrow pore size. The optimum permselectivity was obtained with the addition of 0.30% nano-silica. Additionally, the fouling resistance increased by ca. 70%. Thus, doping of nano-silica in the membranes is an alternative method to enhance permselectivity and fouling property for water treatment.Download high-res image (243KB)Download full-size image

•BMED was adopted for clean post-processing of AMP sulphate.•A high AMP recovery and low energy consumption was obtained.•An industrial application proved that the BMED process is feasible.2-Amino-1-propanol (AMP) is a key intermediate compound in the production of antibiotics, with increasing demand in industry. In this study, we propose a newly designed bipolar membrane electrodialysis (BMED) system with a novel three-compartment configuration for the processing of AMP from the AMP sulphate solution. The operational parameters were investigated for optimizing the performance of this novel BMED stack, compared to the traditional two-compartment BMED stack in the pilot scale experiment. The experimental results indicate that this novel type of BMED stack offers a better performance for AMP processing than the conventional two-compartment BMED stack. The optimum performance was observed at the current density ranging from 40 to 60 mA cm−2 and a spacer thickness of 0.70 mm. The corresponding current efficiency and energy consumption reached up to 53.4% and 3.135 kWh kg−1, respectively. The two-compartment BMED stack was found to have a low current efficiency (39.8%) and a high energy consumption (3.864 kWh kg−1). Pilot-scale experiments for an industrial application of this novel BMED stack have been applied, demonstrating that the BMED process is feasible and economically alternative for AMP purification in the industry.Download full-size image

•A zero discharge process was proposed to recover acid, base and glyphosate.•A cost assessment of the recovery of glyphosate is presented.•Membrane technology is environmentally friendly to treat the glyphosate liquor.Glyphosate is a contaminant in organisms including humans, but also in food, fodder and ecosystems. The direct discharge of mother liquor as a waste stream can cause the loss of the target product as well as a severe water pollution, which should be controlled. This study presents two alternative technologies, i.e., pressure driven membrane and electrodriven membrane, to recover glyphosate from waste liquor for resource recovery and pollution control. A cost assessment is presented. Integrated systems using nanofiltration/reverse osmosis (RO) combinations could be effectively applied in glyphosate recovery from mother liquor produced by the iminodiacetic acid process. NF and electrodialysis with bipolar membranes (BMED) are feasible and environmentally friendly technologies, and cost effective choices to treat the glyphosate liquor of the glycine dimethylphosphite (DMP) process compared to conventional technology. However, both NF and BMED are not industrially applied for glyphosate liquor treatment. For NF, the presence of phosphate in the mother liquor is a huge challenge to the membrane filtration because phosphite could lead to severe membrane scaling, which substantially reduce the membrane efficiency and membrane lifetime. The membrane price, especially for bipolar membranes, was found to be the bottleneck for BMED to be applied in large-scale applications.Download full-size image

•The feasibility of the treatment of biogas slurry by integrated membrane technology was evaluated at the pilot scale.•The mechanism of membrane fouling was deeply investigated and analyzed.•The multiple agents can effectively improve the cleaning efficiency due to the synergic effect.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 NH3-N, allowing less than 50 ppm of COD and NH3-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.Download full-size image

•A designed electrodialysis system was used to treat seawater concentrate.•Divalent ions removal was significantly achieved by using CIMS/ACS membranes stack as the first stage of system.•The repeated experiments confirmed the system feasibility to enhance the purity of coarse salt.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 cm2. 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., Ca2 +, Mg2 +) 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/cm2 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.Download high-res image (143KB)Download full-size image