Micellar-Enhanced Ultrafiltration of Heavy Metals Using Lecithin

Abstract

Conventional treatment methods for removal of heavy metals from metal finishing operations are usually energy-intensive and costly. Micellar-enhanced ultrafiltration (MEUF) with synthetic surfactants is a recently developed technique which can remove heavy metals and other small molecular weight ions from wastestreams at relatively lower costs and without a phase change. Lecithin, a natural, inexpensive, nontoxic, and biodegradable surfactant exhibits emulsifying characteristics which can be used in a MEUF. The binding of various lecithins to cadmium, copper, lead, nickel, and zinc—in a mixture and individually—was studied using a continuous diafiltration method. This technique uses small volumes of toxic waters and produces an entire isotherm with just one experiment. In the presence of all five heavy metals, the lecithin in this study showed the following affinity: Cu > Cd ～ Zn > Ni. In experiments when only one metal was present, lecithin exhibited the following affinity: Ni > Cu ～ Zn > Cd. Lead was not bound significantly in either scenario.