Current forward osmosis (FO) membranes are unsuitable for arsenic removal from water because of their poor arsenic selectivity. In this study, we designed and synthesized a series of novel imidazolium-based ionic liquids via one-step quaternization reactions and grafted these novel compounds on to conventional thin-film composite FO membranes for treatment of arsenic-containing water. The newly developed ionic membranes contained a functionalized selective polyamide layer grafted with either carboxylic acid/carboxylate or sulfonate groups that drastically enhanced membrane hydrophilicity and thus FO water permeation. Ionic membranes modified with sodium 1-ethanesulfonate-3-(3-aminopropyl) imidazolium bromide (NH2-IM-(CH2)2-SO3Na) outperformed pristine membranes with higher water recovery efficiency. Exceptional performance was achieved with this ionic membrane in FO arsenic removal with a water flux of 11.0 LMH and a rejection higher than 99.5% when 1000 ppm arsenic (HAsO42-) as the feed with a dilute NaCl solution (0.5 M) as the draw solution under the FO mode. Ionic membranes developed in this work facilitated FO for the treatment of arsenic-containing water while demonstrating its superiority over incumbent technologies with more efficient arsenic removal.
Keywords: FO membrane; arsenic removal; forward osmosis; ionic liquid; membrane modification; water treatment.