Feasibility of micellar-enhanced ultrafiltration (MEUF) for the heavy metal removal in soil washing effluent

Heavy metals are the major pollutants in the soil and groundwater. They are not only toxic but also non-biodegradable. In field application of heavy metal remediation, soil washing is the most prevalent technology due to its low cost and wide applicability for various pollutants. However, a drawback of soil washing is the treatment of effluent which contains heavy metals and chelating agent used to enhance the extraction capacity. To treat soil washing effluent with conventional technologies such as precipitation are not appropriate. Because chelating agents disturb to extract or precipitate heavy metals from the wastewater. Therefore in this study micellar-enhanced ultrafiltration (MEUF) was suggested as an alternative technology to treat heavy metals from washing effluent. Through centrifugal MEUF and conventional dead-end MEUF tests, the conditions were optimized. When complexing agent and metal ratio was around 1, metal complexation reached the maximum at pH 8. In addition the value of surfactant over metals was 10, the removal efficiency showed 97% for all metals. The feasibility of MEUF for washing effluent was determined with removal efficiency, flux and COD reduction during the treatment of lab-scale soil washing effluent. In the effluent from soil washing, total metal concentration and complexing agent was 10.14 and 9.03 mM respectively and the pH was 6.34. When the optimized conditions were employed to treat washing effluent, the removal efficiency and COD reduction reached over 92% and 80%, respectively. However the flux decline was severe, but this can be improved by introducing cross-flow filtration.