A kinetic study of heavy metals removal from contaminated marine sediment with chelating agents

Batch sediment washing experiments were conducted to remove six metals (Cu, Zn, Ni, Cd, Cr, and Pb) from contaminated sediments. The effect of different operating parameters such as: type of washing solutions, reaction time, solution concentration, pH, and liquid/solid ratio were investigated. Besides, the kinetic of the extraction process was also studied. In the proposed work, cheating agent, i.e., di-sodium salt of ethylenediamine tetraacetate (Na(2)EDTA), was applied for extraction of heavy metals from contaminated sediment and showed significantly high efficiency compared with other agents. The extraction efficiency was 33%, 73%, 29%, 88%, 13%, and 83% for Cu, Zn, Ni, Cd, Cr, and Pb, respectively, at a 0.1 M Na(2)EDTA washing solution, liquid/solid ratio of 10, pH 4.0, and 2 h washing time. The chelant extraction process was a first-order reaction. The k(1) (apparent rate constant for metal desorption) values were 0.0822-0.5598 h(-1), and the order was Pb > Zn > Cd > Ni > Cu > Cr. Moreover, the results indicated that the extraction efficiency of metals is directly proportional to the liquid/solid ratio and concentration of washing solution while inversely proportional to the pH in the range of 3-10. The results will be useful as preliminary evaluation of the removal of heavy metals from the contaminated sediments using chelating agents in washing operation.