One step surfactant entrapment onto PVDF hollow fiber membrane surface by the TIPS process using a triple-layer orifice spinneret

Abstract

One step entrapment of the several kinds of surfactants on the outer surface of the PVDF hollow fiber membrane during the air gap distance was studied by extruding the surfactant solution as the outermost layer of the triple layer nozzle via thermally induced phase separation (TIPS) process. Effect of the membrane preparation conditions, including the air gap distance, surfactant concentration and types of surfactant with different hydrophilic-lipophilic balance (HLB) number and molecular weight on the membrane surface hydrophilicity and protein fouling resistance were evaluated. Using a long air gap distance with optimal surfactant concentration was resulted in a membrane with a considerable improvement in hydrophobicity. Surfactants with the lowest HLB number and molecular weight improved membrane hydrophilicity and resistance against pure water permeability decrease after drying membrane in air. Based on water contact angle results, entrapment of the surfactant with a more hydrophobic segment to hydrophilic segment ratio (smaller HLB) plays a crucial role to increase the membrane surface hydrophilicity regardless the intrinsic hydrophilicity of the surfactant molecule. The stability of the surfactant entrapped by this method was higher than that of the simple coating method. Static adsorption of the lysozyme on the surface of the surfactant entrapped membrane was in line with water contact angle results. Thus, entrapping surfactants with low HLB number and molecular weight was recommended to obtain a membrane with the considerable anti-fouling property.