Evaluation of Electrokinetic Technique for Industrial Waste Decontamination

Several industrial activities produce large amounts of metal-polluted sludge, disposal of which could pose serious environmental and ecological problems because of the usual high content of mobile metals. In this work, an electrokinetic technique was used to reduce the high metal content of two industrial wastes: sludges from mining (SM) and from the iron-steel (SIS) industry. Initially, a physical-chemical characterization of the sludge was carried out and different extraction assays were tested. Due to the particular characteristics of each of the sludges, in terms of acid buffering capacity or electrical conductivity, different operational conditions were necessary to enhance the electrokinetic treatment. The results established that for metal remediation of wastes with low acid buffering capacity, such as SM sludge, pH control in the cathode chamber could be an alternative to enhance the electrokinetic technique. The best metal removal results (around 66% Mn) were obtained when sulphuric acid was used to control the pH. Then, to remediate sludges with high acid buffering capacity, such as SIS sludge, pH control in electrode chambers was an inefficient technique and the addition of complexing agents was the best alternative for the electrokinetic process. The extraction assays established that EDTA and citric acid were adequate enhancement agents. However, in the electrokinetic experiments, the use of EDTA as enhancement agent gave the best remediation values with Pb removal of 75%. The results obtained in the present work demonstrate that the electrokinetic technique could be enhanced by the selection of an adequate strategy that depends on the physical-chemical characteristics of the sludges to treat.