Modification and acidification of polysulfone as effective strategies to enhance adsorptive ability of chromium (VI) and separation properties of ultrafiltration membrane

Abstract

In order to improve the hydropilicity, polysulfone was first modified by grafting diethanolamine and further made into the ultrafiltration membranes by a phase inversion process. Ultrafiltration membranes were characterized by nuclear magnetic resonance spectrum, contact angle, thermogravimetric analysis, differential scanning calorimetry, scanning electron microscopy, adsorption, and ultrafiltration experiments. The ultrafiltration membrane containing tertiary amine groups had a 99.2% rejection to bovine serum albumin (BSA), 235.2 L m−2 h−1 pure water flux and 78.6% flux recovery rate. Usually, the ultrafiltration membrane containing tertiary amine groups has a low rejection and a poor adsorptive ability to Cr(VI) in the neutral condition. A novel strategy of acidification in advance was adopted to adjust the separation performance of the polysulfone ultrafiltration membrane containing tertiary amine groups. The pre‐acidification strategy could improve the Cr(VI) rejection from below 10% to 100% in the neutral condition, since ultrafiltration membranes acidified in advance did not lose its H+ in storage. Moreover, the acidification could improve the glass transition temperature and only caused a slight decrease of water flux and BSA rejection.