In situ surface crosslinked tight ultrafiltration membrane prepared by one-step chemical reaction-involved phase inversion process between activated PAEK-COOH and PEI

Abstract

Carboxylated cardo poly(arylene ether ketone)s (PAEK-COOH) is a thermally stable and hydrophilic membrane fabrication material. Herein, PAEK-COOH was employed as membrane material, being dissolved in N-methyl-2-pyrrolidone (NMP) and 1,4-dioxane (DO) mixed solvent and activated by adding 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) to prepare polymer casting solution. Then the activated polymer film was immersed into polyethylenimine (PEI) aqueous solution that served as coagulation bath for taking the one-step chemical reaction-involved phase inversion process. As illustrated by the SEM images, the fabricated crosslinked tight ultrafiltration membrane had a dense and integrally skinned separation skin layer. Chemical composition and hydrophilicity of membrane surface were studied by ATR-FTIR and water contact angle, respectively. Those results revealed that, via the in situ crosslinking of activated carboxylic acid group and PEI along with the phase inversion process, the PEI molecules had been covalently bonded onto membrane surface and resulted in the increase of membrane hydrophilicity. The optimized membrane had a molecular weight cut off (MWCO) of 12.7kDa and an isoelectric point of 7.4, indicating which is slightly positively charged. The one-step chemical reaction involved phase inversion between reactive macromolecules, i.e., activated PAEK-COOH original polymer film and PEI crosslinker in coagulant, was an efficient and convenient approach for fabrication of highly permeable and selective tight ultrafiltration membranes. Membrane had a dye solution permeability of 80–84Lm−2h−1bar−1 and Congo red (CR) rejection of 99.9% in 100h long-term filtration testing, being capable for dye removal from textile wastewater.