Treatment of synthetic wastewater containing heavy metal ions (cadmium, cobalt and lead) by nanofiltration

Drinking water quality is very important for human health. Small amounts of hazardous contaminants are strictly forbidden. Due to the discharge of large amounts of metal-contaminated wastewater, industries bearing heavy metals, such as Cd, Cr, Co, Cu, Ni, As, Pb, and Zn, are the most hazardous among the chemical-intensive industries. The removal of heavy metals from wastewater has significant importance due to their high toxicity and tendency to accumulate in body tissues. In the present work, performance of a nanofiltration (NF) polyamide membrane has been studied to separate cadmium, cobalt and lead ions from synthetic wastewater solutions at different operating conditions. Rejection experiments were conducted with Cd(NO3)2, Co(NO3)2 and Pb(NO3)2 in single-salt solutions. The effect of feed pH, trans-membrane pressure and metal concentration on the ion separation and permeate flux was explored. The maximum observed solute rejection of Cd2+, Co2+ and Pb2+ ions were 98.12%, 98.60% and 96.24%, respectively. It is observed that the ion rejection decreases with increase in feed pH and slightly increases with rise in feed concentration. Also, it is found that the metal rejection and the permeate flux, slightly reduces and significantly increases respectively, when the trans-membrane pressure increases. The low level of the ions concentration in permeate implies that water with good quality could be reclaimed for further reuse.