Enhanced morphology and hydrophilicity of PVDF flat membrane with modified CaCO3@SMA additive via thermally induced phase separation method

Modified CaCO3@SMA nanoparticles obtained by coordination reaction between poly(styrene-co-maleic anhydride) (SMA) and calcium carbonate (CaCO3) nanoparticles were adopted as additive to prepare polyvinylidene fluoride (PVDF) flat membrane via thermally induced phase separation (TIPS) method with dioctyl phthalate (DOP) and dibutyl phthalate (DBP) as mixed diluent. The CaCO3 nanoparticles modified by SMA effectively reduced the adverse agglomeration of nanoparticles and made the additive disperse evenly in PVDF matrix. The presence of modified CaCO3@SMA changed the membrane morphology from dispersed spherulites with large pores to fuzzy dendrite structures with uniform pore sizes. The membrane pore sizes, pore size distribution and tensile strength were significantly improved compared to both virgin membranes and those containing unmodified CaCO3 nanoparticles. After the CaCO3 was pickled, the porosity and the connectivity between membrane pores were greatly enhanced, resulting in a significant increase in pure water flux. At the same time, the amphiphilic SMA fixed in and on the membrane surface improved the hydrophilic and anti-fouling properties demonstrated in a three-cycle test. The present study provided a potential TIPS method for the fabrication of PVDF membrane combined with a simple strategy of modified inorganic particle additive.