Hydroxyl-terminated poly(ethyleneimine) polymer enhanced ultrafiltration for boron removal

Abstract

© 2019 Elsevier B.V. Boron removal is an important separation process which requires an excessive operational cost owing to the complex nature of boron in aqueous solutions. Polymer-enhanced ultrafiltration (PEUF) has been widely adopted for boron separation due to the low operational cost and high separation productivity. In this study, novel hydroxyl-terminated poly(ethyleneimine) (HPEI) polymers; namely, HPEI-Diol and HPEI-Gluconamide, were designed and synthesized as the boron chelating polymers. A polyphenylenesulfone (PPSU) UF membrane was fabricated to have a pure water permeance of around 82.8 L.m −2 .h −1 .bar −1 with a molecular weight cut off (MWCO) of around 128 kDa. The boron rejection coefficient of the pristine PPSU UF membrane was as low as 6.38% which was attributed to the negatively charged surface of the PPSU membrane. Introducing either HPEI or HPEI-Diol polymer into the boron feed solution increased the boron rejection of the UF process to around 45%. Meanwhile, the HPEI-Gluconamide polymer was found to possess the highest boron retention efficiency with a boron rejection of around 94% at pH 4, which may be ascribed to the higher number of grafted hydroxyl groups.