Humic-substance-enhanced ultrafiltration for removal of heavy metals

The feasibility of a separation technique using ultrafiltration in connection with humic substances-humic-substance-enhanced ultrafiltration (HSEUF)-was investigated for the removal of the toxic heavy metals copper and cadmium. HSEUF is based on the high molecular weight of humic substances, as well as the binding of multivalent metals such as copper and cadmium to these materials. As the humic acid concentration increased, the removal of copper and cadmium was enhanced because of the increase in binding sites. As the pH of the solution increased, the removal of copper and cadmium was further improved because the solubility of the humic substances increased. In the simultaneous removal of copper and cadmium, the binding of cadmium to humic substances was inhibited significantly by the presence of copper at the low concentration of humic acid. However, copper binding was not affected by the presence of cadmium, because the affinity of copper to humic substances was greater than that of cadmium.