Effectiveness of soil washing, nanofiltration and electrochemical treatment for the recovery of metal ions coming from a contaminated soil

This research was conducted to integrate soil washing, nanofiltration (NF) membranes and electrochemical treatment as feasible methods for the remediation of contaminated soils. For this investigation, two acidic leachates (pH = 2) were prepared using HCl and H2SO4-NaCl as soil-washing agents. The results of the soil washing indicated that HCl and the combined H2SO4-NaCl were effective for the extraction of ions resulting from a contaminated soil. It was observed that both leachates presented similar chemical compositions. Following this procedure, the leachate solutions were pre-filtered by microfiltration, followed by NF using the Desal-5 (DK) membrane. The experiment results showed that NF membranes presented a high ion-retention rate for the two leachates. In general, better retentions were observed with the leachate prepared with HCl than H2SO4-NaCl. In order to treat the concentrate resulting from the NF treatment, it underwent an electrochemical procedure (electrochemical deposition) as an alternative method for safe disposal. The results showed a high reduction of toxic ions, such as Pb and Cu, from the solution. These three processes applied in conjunction not only indicated that the treatment of solutions heavily contaminated with inorganic pollutants resulting from contaminated soils were feasible but also suggested the possibility of treating different types of heavy industrial effluents. (C) 2007 Elsevier Ltd. All rights reserved.