In-situ synthesis of silica nanoparticle modified PVDF hydrophobic microporous membrane

Nano-silica (nSiO 2 ) was synthesized in-situ by sol–gel method, then a (polyvinylidene fluoride) PVDF-nSiO 2 hydrophobic microporous composite membrane was prepared by mixing nSiO 2 sol into casting solution using non-solvent phase inversion. The effect of nSiO 2 sol addition on the surface and cross-sectional structure of the membrane, porosity, average pore size, pure water flux, membrane flux, and hydrophobic properties was investigated. Compared with the microporous membrane without nSiO 2 sol, the cross-sectional structure of the PVDF-nSiO 2 composite membrane is fully developed, the porosity is higher, the average pore diameter is larger, and the hydrophobicity is stronger. The direct contact membrane distillation (DCMD) experiment was carried out using the prepared composite membrane to simulate seawater desalination with a 30 g/L sodium chloride solution as feed solution. Compared with the microporous membrane without nSiO 2 sol added, the membrane flux was greatly improved to 31.02 kg m –2 h –1 , and the porosity of the membrane was 75%. On the previous basis, the double coagulation bath method was employed to further improve the film-forming process. The properties and structure of the composite membrane were optimized. The membrane flux was 42.7 kg m –2 h –1 , the porosity was 78.7%, and the contact angle was 127.3°. The performance of composite membrane was greatly improved.