Comparison of ion-exchange resins and biosorbents for the removal of heavy metals from plating factory wastewater

The NCP (Neurospora crassa gene expressed in the periplasmic space) is a recombinant Escherichia coli expressing the Neurospora crassa metallothionein gene within the periplasmic space. The, NCP has been shown to remove heavy metals from solutions containing low concentration of heavy metals. In this study, the ability of NCP to remove heavy metals from wastewater was compared to the commercial sorbents Duolite GT-73, IRC-718, and BIG-FIX. Three process wastewater streams, acid/alkali, chromate, and cyanide, were tested at their original pH and near neutral pH. In addition to other contaminants, the wastewaters contained metals including Cd, Cu, Ni, and Ag. NCP was most efficient in removing the heavy metals from wastewaters at near neutral pH. Chromium removal per gram of IRC-718 at pH 2.05 was an order of magnitude higher than any other sorbent in either pH-unadjusted or pH-adjusted samples. Duolite GT-73, IRC-718, and BIG-FIX had similar efficiency in removing heavy metals from the pH-adjusted wastewater. When the sorbents were tested for removal of part per billion levels of Cd-109, NCP demonstrated the highest percent removal. These results suggest potential treatment strategies for metal-contaminated wastewaters involving pH adjustment and primary treatment with a commercial sorbent followed by polishing with NCP.