Structural Regulation And Properties Of Polyphenylene Sulfide Microporous Membranes

Membrane separation technology is simple,energy-saving,and high-effective,and it has been widely used in many fields.However,membranes commonly used do not have excellent properties against strong acid,strong alkaline and mixed organic solvent.Polyphenylene sulfide（PPS）is a material which has superior thermal stability and solvent resistance performance.Therefore,PPS is expected to be a promising membrane separation material to deal with strong acid and alkaline solution or organic solvent.Herein,studies are focus on preparing PPS membranes via thermally induced phase separation（TIPS）and analyzing the mechanism of membranes formation based on the kinetics and thermodynamic of phase equilibrium.The effects of different parameters on structure and performance of membrane were investigated and anti－fouling properties of membrane improved by introducing hydrophilic nanoparticles.Firstly,six different solvents containing caprolactam（CPL）,diphenyl ketone（DPK）,1-Naphthyl chloride,benzoin,diphenyl ether and diphenyl sulfone were selected to prepared PPS membrane by TIPS method.The morphology and performance of membranes were characterized and analyzed.Liquid-liquid separation behavior was identified for a group of solvents including BZ,DPE,and DPS,whereas the systems with the solvents CPL,DPK or I-Naphthyl chloride underwent solid-liquid separation during the cooling process.In addition,the effect of polymer concentration,coagulation bath temperature,pore-forming agent on membrane structure and properties were investigated when CPL was used as solvent.Secondly,PPS flat sheet membranes were prepared from the ternary system of PPS/DBS/DPK by TIPS method.The effect of mixed solvents composition,polymer concentration,cooling rate and types of coagulation bath on membrane structure and performance were studied.As the weight ratio of DBS to DPK increases from 10/66 to 17/59,the cloud point temperature of PPS/DBS/DPK increases from 250℃ to 263.5℃,crystalization temperature decreases from 225.4℃ to 219.2℃ and the interaction parameter between PPS and diluents changes from 1.57 to 1.91,which prolonged the time of L-L phase separation and provided more opportunity for casting solution to form the desired PPS membrane structure.When DBS concentration reached 16wt%,an interesting sandwich-like PPS membrane possessed higher porosity,supreme water permeation,better mechanical properties and anti-fouling properties was prepared,in which the mass fraction of PPS is fixed at 24wt%.In addition,the lower cooling rate,decreased polymer concentration and less diluents outflowed were beneficial to the increase of water flux and membrane porosity.Most importantly,the evaluation system of membrane separation performance shows that PPS membrane has incomparableperformance against strong acid,strong alkaline and polar solvents than other common membrane used frequently and its thermally stability is perfect.Finally,PPS-based hybrid matrix membrane was prepared from partially reduced graphene oxide（GO）or TiO₂ nanoparticle.Compared with the bare membrane,the membranes with the addition of appropriate nanoparticles is beneficial to the improvement of membrane permeability,mechanical properties and anti fouling performance.The fouling resistance of membranes studied by bovine serum albumin（BSA）solution filtration showed that 0.7wt%GO/TiO₂ membrane had the best antifouling performance.Compared with PPS/TiO₂ and PPS/GO membranes,PPS/TiO₂/GO membranes presented the best water permeation rate and antifouling ability.