| Modification of microporous membranes to improve the flux and antifouling performances in practical applications has been a hot topic. Among modification methods, adding additives shows broad application prospects because of its simple operation, high selectivity. In this paper, two kinds of membranes i. e. poly(phenylene sulfone) and poly(vinylidene fluoride) were prepared with phase inversion method. Casting solution viscosity, water static contact angle, water flux, rejection of bovine serum albumin and scanning electron microscopy characterization methods were used to investigate membrane filtration performances and cross-sectional structure of membranes.Polyphenylene sulfone is a novel polysulfone membrane material. Firstly, three solvents, i. e. N-methylpyrrolidone, N, N-dimethylformamide amides and N, N-dimethylacetamide were compared. Membranes prepared with N, N-dimethylacetamide showed a more suitable water flux and membrane strength, and water flux reached878L/m2h. Secondly, polymer dosage was investigated. When adding polyethylene glycol400and polyethylene glycol1000, the water flux was higher with polymer dosage of12%than that of16%. Finally, the effect of additives was studied. Additives were divided into three categories, i. e. inorganic salts, polyethylene glycols and small molecule alcohols. Adding zinc chloride and magnesium chloride led to better membrane properties, and the pure water flux reached991L/m2h and808L/m2h, rejection was88.79%and87.46%, respectively. The influence of polyethylene glycol molecular weight on membrane performances was investigated. The results showed that water flux increased with the increase in molecular weight from400to2000. When dosage of polyethylene glycol2000was10%, the pure water flux reached1135L/m2h and rejection reached90.1%. Cross-sectional morphologies showed that support layer of the membranes changed from finger-like to network structure, which improved the water flux. When small molecule alcohols, ethanol, n-propanol, isopropanol and n-butanol were used as additives, adding n-propanol led to the best performances of membranes. When adding10%n-propanol, pure water flux and rejection rates were1125L/m2h and89%, respectively.Poly(vinylidene fluoride) is a widely used membrane material as a semi-crystalline polymer, and the modification of poly(vinylidene fluoride) membranes has been a hot issue. Three additives were investigated, i. e. amphiphilic block copolymers of polyethylene oxide-polypropylene oxide polyethylene oxide (PEO-PPO-PEO), oxalic acid and titanium oxide. When PEO-PPO-PEO was added in PVDF, water static contact angle was declined from76°to66°. With increasing the PEO-PPO-PEO dosage, water flux increased and rejection decreased. When the PEO-PPO-PEO dosage was3%, pure water flux reached1136L/m2h and rejection was64%, indicating the pore-formation function and the role of hydrophilic modification of PEO-PPO-PEO. When oxalic acid and PEO-PPO-PEO were added, a significant improvement on water flux was observed. When dosage of oxalic acid and PEO-PPO-PEO was3%and2%respectively, a maximum water flux of2271L/m2h was achieved. When titanium oxide and PEO-PPO-PEO were added, the water flux showed same tendency as the single addition of PEO-PPO-PEO, but rejection significantly increased with the addition of titanium oxide. When PEO-PPO-PEO dosage was3%and titanium oxide dosage was1%, pure water flux reached1136L/m2h, and rejection was90%. |
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