Poly(vinyl pyrrolidone) modified poly(vinylidene fluoride) ultrafiltration membrane via a two-step surface grafting for radioactive wastewater treatment

Poly(vinylidene fluoride) (PVDF) ultrafiltration (UF) membranes were modified with poly(vinyl pyrrolidone) (PVP) through a two-step surface grafting method in order to enhance the antifouling properties. PVP of small molecular was used to modify the membrane pores and cross-linked PVP modified the membrane surface. The pore modification enhanced the membrane flux from 130.0 Lm(-2) h(-1) to 170.7 L m(-2) h(-1), and the surface modification increased the membrane hydrophilicity (i.e., the contact angle decreases from 93 degrees to 83 degrees). During the fouling tests with bovine serum albumin (BSA) solution and laboratory simulation low-level radioactive wastewater (LLRW), the modified membrane had a much slower flux reduction compared with the raw membrane. After water wash, the flux recovery rates of the BSA fouled membranes were 98% for the modified membrane and 46% for the raw membrane, respectively. Additionally, the modified membrane had the same rejection on nuclide and surfactant as the raw membrane. Based on these results, the two-step modified membrane is suitable to be used in LLRW treatment with advantages of less frequent membrane cleaning and longer membrane lifetime.