Effect of chitosan gelation time on the structure and antifouling performance of PVDF membrane

Abstract

Polyvinylidene fluoride (PVDF) porous membrane was prepared were prepared by a two-step method of surface gelation-immersion precipitation phase inversion. The surface of the scraping PVDF solution film was sprayed with acetic acid solution of chitosan （CS） and glutaraldehyde aqueous solution successively, and the film surface gelled with chitosan crosslinking. And then the liquid film was immersed in coagulation bath water for phase transformation to obtain the modified PVDF porous membranes. The influence of crosslinking degree of chitosan and glutaraldehyde on the structure and properties of PVDF porous membrane was discussed by controlling the gelation time. The results showed that with the extension of gel time, the surface structure of PVDF membranes changed from dense cortex to porous structure, the porosity gradually decreased, the average pore size first increased and then decreased, the contact angle gradually decreased, and the pure water flux first increased and then decreased. The dynamic circulating filtration experiment of bovine serum albumin (BSA) solution showed that the rejection rate of the modified membrane increased from 68.3% to 90.0%, and the flux recovery rate increased from 73.0% to 84.4%, the irreversible fouling ratio decreased from 27.7% to 15.6%. Therefore, the hydrophilicity and antifouling of PVDF membrane were improved after surface chitosan crosslinking.

Tuning pore size and density of rigid polylactic acid foams through thermally induced phase separation and optimization using response surface methodology

“…In addition, excessive aging time and high levels of cross-linking level caused PLA to agglomerate and block the foam pores. The occurrence resulted in a decrease in both the mean pore diameter and total porosity, consequently causing an increase in foam density, as observed in the PVDF membrane system by Sun et al 45 .…”