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The bipolar membrane electrodialysis (BMED) process requires three types of membranes: cation exchange, anion exchange and bipolar membranes. As commercial membranes are limited in performance, and have a relatively high cost, anion and cation exchange hybrid membranes were prepared in this study from poly(2,6-dimethyl-1,4-phenylene oxide) (PPO), polyvinyl alcohol (PVA) and two kinds of alkoxysilanes. The anion and cation exchange layers, containing-N + (CH 3) 3 OHand-SO 3 H groups, respectively, can be combined to prepare a bipolar membrane. These membranes were used in BMED process to regenerate CH 3 COOH and NaOH from the CH 3 COONa waste residue. The newly developed anion and cation exchange hybrid membranes are compact and homogeneous, having the water uptakes between 58.0% and 65.0%, an ion exchange capacity of 1.04-1.58 mmol g-1 and an area resistance of 0.73-1.55 Ω cm 2. The anion and cation exchange layers were combined as a bipolar membrane. This increases the membrane stability and area resistance (6.47 Ω cm 2). The bipolar membrane is intact without layer separation after immersion in 65°C water or NaOH solution (1-2 mol L-1). The PPO/PVA hybrid membranes can produce 0.25-0.43 mol L-1 CH 3 COOH/ NaOH during the BMED process. The energy consumption is 18.2-26.5 kWh kg-1 , and the current efficiency is 70%-72% after running 3 h at 20 mA cm-2 .

a b s t r a c tThe effect of silica nanoparticles (SNPs) deposition on the properties of a commercial forward osmosis (FO) membrane was investigated in this work. Deposition of SNPs on the FO membrane was performed by a conventional sol-gel hydrolysis of tetraethyl orthosilicate and a simple dip-coating procedure. Scanning electron microscopy, X-ray photoelectron spectroscopy and attenuated total reflectance-Fourier transform infrared spectroscopy confirmed the successful deposition of SNPs on the membrane surface. The coated membranes were used in a bench scale FO system and their performance was evaluated through measuring the permeate water flux and fouling resistance. Successful deposition of SNPs smoothed out the membrane surface and increased surface hydrophilicity. The effects of SNP enabled a higher water flux and fouling resistance than for the pristine FO membrane, possibly due to increased hydrophilicity and decreased membrane roughness.

a b s t r a c tAcidic HCl/glyphosate (Gly) liquor is produced largely during the production of Gly herbicide. The HCl component can be recovered by continuous diffusion dialysis (DD), while the Gly is precipitated maximumly at the pH ~1.5. Previous DD process showed that the Gly productivity is only 28.0% due to the serious water osmosis (2.0-2.9 × 10 -4 m/h), which reduced the Gly concentration. Hence in this work, the water osmosis is restricted by membrane cross-linking. Polyvinyl alcohol (PVA) is cross-linked with glutaraldehyde (GA) together with tetra-methoxysilane (TMOS) or 3-aminopropyl-triethoxysilane (APTEOS) to prepare non-charged membranes. Continuous DD process shows that the water osmosis is reduced to 0.71-1.44 × 10 -4 m/h. The optimized flow rate of acidic liquor is 0.34 L/(m 2 h) and the flow ratio between water and acidic liquor is 2:1. The membrane cross-linked with GA can have the recovered HCl concentration (C d-H ) of 0.93 mol/L, HCl recovery ratio (R H ) of 63.9% and Gly rejection (η Gly ) of 99.5%. The membrane cross-linked with GA and TMOS can have the C d-H of 1.00 mol/L, R H of 78.6% and η Gly of 96.8%. Besides, 83.3% Gly productivity can be obtained from the residual solution after concentration. Hence, the water osmosis is reduced and the Gly productivity is elevated by using the cross-linked membranes.

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