Water reclamation from emulsified oily wastewater via effective forward osmosis hollow fiber membranes under the PRO mode

Abstract

By using a novel hydrophilic cellulose acetate butyrate (CAB) as the membrane material for the hollow fiber substrate and modifying its outer surface by polydopamine (PDA) coating and inner surface by interfacial polymerization, we have demonstrated that the thin-film composite (TFC) membranes can be effectively used for sustainable water reclamation from emulsified oil/water streams via forward osmosis (FO) under the pressure retarded osmosis (PRO) mode. The newly developed TFC-FO hollow fiber membrane shows characteristics of high water flux, outstanding salt and oil rejection, and low fouling propensity. Under the PRO mode, the newly developed TFC-FO membrane exhibits a water flux of 37.1 L m−2 h−1 with an oil rejection of 99.9% using a 2000 ppm soybean oil/water emulsion as the feed and 1 M NaCl as the draw solution. Remarkable anti-fouling behaviors have also been observed. Under the PRO mode, the water flux decline is only 10% of the initial value even after a 12 h test for oil/water separation. The water flux of the fouled membrane can be effectively restored to 97% of the original value by water rinses on the fiber outer surface without using any chemicals. Furthermore, the flux declines are only 25% and 52% when the water recovery of a 2000 ppm soybean oil/water emulsion and a 2000 ppm petroleum oil/water emulsion containing 0.04 M NaCl reaches 82%, respectively. This study may not only provide insightful guidelines for the fabrication of effective TFC-FO membranes with high performance and low fouling behaviors for oily wastewater under the PRO mode but also add an alternative perspective to the design of new materials for water purification purposes.