The performance of forward osmosis in treating high-salinity wastewater containing heavy metal Ni2+

In this study, the performance of forward osmosis (FO) in treating the high-salinity feed waters containing heavy metal Ni2+ with different salinities was investigated using two different FO membranes (cellulose triacetate (CTA) and polyamide-based thin-film composite (TFC) membrane). Moreover, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) were selected to analyze the used membrane. The result showed that, heavy metals Ni2+ stimulated the formation of CP, and then decreased the water flux. However, this effect decreased with the increase of FS salinity and membrane hydrophilicity. Due to the amphiprotic characteristics, SDBS promoted the water permeation by increasing the hydrophilicity of the membrane surface. The effect of SDBS on CTA-FO membrane was greater than TFC-FO membrane for that CTA-FO membrane was weakly hydrophilic. However, the role decreased with the salinity increasing. Ni2+ removal efficiencies were more than 93%. Specifically, TFC-FO membrane was higher than CTA-FO membrane in high-salinity wastewater, and the FO mode maintained an advantage over the PRO mode. SDBS enhanced Ni2+ removal efficiency greatly at low salinity, and decreased it instead at high salinity. The SEM-EDS analysis supplied the technique support and reflected the role of Ni2+ and SDBS in the membrane directly.