Simultaneous removal of antimony, chromium and aniline by forward osmosis membrane: Preparation, performance and mechanism

Antimony (Sb), chromium (Cr) and aniline are typical contaminants in printing and dyeing wastewater, which are toxic and have potential carcinogenicity to humans. The rejection performance of forward osmosis (FO) membranes for the mixed pollutants of Sb, Cr, and aniline under different cross-linking degree of polyamide (PA) selective layer, concentration and type of draw solution (DS) were analyzed. Results showed that the water flux of PAN-1.5LiCl FO membrane was about two times higher than that of unmodified membrane and the rejection of Sb, Cr, and aniline was 98.2%, 99.9%, and 92.6% with 0.5 M NaCl as DS, respectively. While NaCl concentration increased from 0.5 M to 2.0 M, the rejection of aniline enhanced from 92.6% to 95.2%. When 0.5 M Na2SO4 was used as DS, the rejection of aniline increased to 95.6% due to the relatively low water flux during FO process. The high rejection of Sb, Cr and aniline should be ascribed to the steric hindrance and electrostatic interaction between FO membrane and the contaminants. When secondary clarifier effluent from a wastewater treatment plant (WWTP) in a printing and dyeing factory was used as feed solution (FS), rejection efficiencies of Sb, Cr, aniline all attained over 98%.