Ex situ remediation technology for heavy metals in contaminated sediment

Abstract

The importance of metal mobile fractions rather than total contents in environmental matrices is increasing in the risk assessment evaluation of contaminated sites. Ethylenediaminetetraacetic acid (EDTA), aimed at the measurements of metals mobile fractions, was used to extract the metals from the contaminated dredged sediments based on chemical extraction technology. This work examined the influences of contact time and EDTA concentration on the extraction efficiency for metals from polluted dredged sediment. In addition, the sequential extraction method was carried out to show the change in distribution pattern of metals in sediment before and after EDTA extraction. The dredged sediment from Helwan area (H) was mainly polluted by Pb (685 mg/kg), and the dredged sediment from Talkha area (T) was significantly polluted by Cd (236 mg/kg), Cu (229 mg/kg), and Zn (2,888 mg/kg). For sediment (H), the maximum lead removal of 72.54% was achieved using EDTA under the optimum conditions. While For sediment (T), the maximum cadmium removal of 53.58% was achieved under the same conditions. Finally, EDTA can be used as washing solution for contaminated sediment as well as single-step extraction to identify non-residual metal content (the anthropogenic fraction) and to evaluate the potential bioavailability of metal.