Zinc and chromium removal from liquid wastes by using micellar enhanced ultra filtration

Water or groundwater contamination by heavy metals is a major problem since once metal ions are introduced into the environment, they are not biodegraded and are transported to the ecosystem via various pathways. Moreover, if directly discharged in sewers, metal ions may seriously damage the subsequent biological treatments in depuration plants and render treatment sludge not reusable such as inagriculture. Liquid wastes effluents from several industrial activities often contain metals ions; for example the residual solutions from hydrometallurgical processes of waste electrical and electronic equipment can contain metals as iron, cadmium, chromium, zinc and other dangerous elements. Ultrafiltration process with the addiction of a surfactant (micellar-enhanced ultra filtration, MEUF) is a reliable technique for almost complete heavy metal removal. This research group has already applied with success this method for arsenic and lead removal. In this paper, the MEUF technique is applied to the removal of Zn and Cr ions from synthetic liquid wastes aimed at water reuse, by using; a UF membrane (monotubular ceramic membrane of molecular weight cut-off: 210 kDa) with adding an anionic surfactant (SDS) below and above the CMC. The synthetic liquid waste contains metal ions in a concentration of 10 mg L-1. The preliminary results show that very good removal percentages of these metal ions are achieved. An ANOVA test on zinc and chromium ultrafiltration results allowed to determine the best operating conditions for metal ions’ removal.