The influence of pH and BSA on the retention of selected heavy metals in the nanofiltration process using ceramic membrane

One of the alternative wastewater treatment methods aimed at the elimination of heavy metals is membrane separation supported by the use of metal-complexing polymers. Many sectors of industry generate wastewater containing both heavy metals and protein substances which show complex-forming properties. In this study, a 450 Da molecular weight cut-off nanofiltration ceramic membrane (TAMI Industries, France) was tested to evaluate the retention of Zn, Cd, Pb, Cu and Fe complexed with bovine serum albumin (BSA). Retention levels were tested in water solutions solely for the metals and for the metals with the addition of BSA, depending on the pH of the solutions (from 2.0 to 9.0). It was noted that the retention tended to increase as the pH increased. For solutions composed with only metals, retentions exceeding 80% were noted for pH > 6.9. The addition of a complexing agent resulted in high retentions of Cu, Cd and Zn already at pH = 2.0. Maximum retentions for Zn, Cd, Pb, Cu and Fe were noted for solutions containing the mixture of metals and BSA at pH = 6.0 (97, 96, 90, 95 and 71%, respectively) and at pH = 9.0 (93, 99, 93,99 and 85%, respectively). The studies confirmed the high metal-complexing capacity of BSA and indicated that heavy metals might be effectively removed from wastewater containing protein in the process of membrane separation using a ceramic membrane. (C) 2015 Elsevier B.V. All rights reserved.