Radiation-induced grafting of polyethyleneimine onto cellulose triacetate membrane for separation of cesium ions from aqueous solution

Abstract

Radiation grafting of polyethyleneimine (PEI) onto the surface of cellulose triacetate (CTA) membrane was successfully performed. Pre-radiation and co-radiation were applied by gamma rays at the dose of 12 kGy. FT-IR, SEM, XPS, contact angle, zeta-potential, grafting ratio, etc. Were used to characterize the PEI-CTA membranes before and after grafting. The FT-IR spectrum showed that a notable discernible shoulder peak of N–H appeared for amide at co-radiation and pre-radiation, and XPS analysis indicated that co-radiation achieved the highest N percent of 9.75%, suggesting that PEI was introduced into the membrane surface. In a forward osmosis (FO) process, the PEI-CTA membrane obtained higher cesium, Cs(I), retention (95–97%) than the CTA membrane with Cs(I) retention of 92%. Cs(I) fluxes significantly decreased from 0.09 to 0.02–0.03 mmol m−2h−1 after PEI modification. Effective Cs(I) retention was attributed to increase of the positive charges on CTA membrane when PEI was added, which exerted a repulsive effect on Cs(I), preventing them from moving towards the membrane direction. In the FO process, the PEI-CTA membrane featured the water flux of 23 L m−2 h−1 a little lower than that of CTA membrane (24 L m−2 h−1). Although modified PEI increased the hydrophilicity, the increase of water flux did not occur with the co-irradiated membrane, which was related to the high graft, higher thickness and resistance of the membrane.