Comparison of the influence of EDTA, nitrilotriacetic acid, diethylenetriamine pentaacetic acid, chitosan, fulvic acid and pine needle extract on the removal of multiple heavy metal by electrokinetic remediation

Abstract

Eliminating multiple heavy metal pollution from contaminated soil is challenging and expensive during remediation. In this study, pine needle extract (PNE) coupled with electrokinetic remediation (EKR) was first time implemented to enhance the Cd, Cu and Ni removal from contaminated soil. The PNE enhanced EKR and improved the processing compared to chemical enhancing agents, such as ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA) and diethylenetriamine pentaacetic acid (DTPA) as well as organic enhancing agents, such as chitosan (CTS) and fulvic acid (FA). The Cd, Cu and Ni removal efficiencies (average of five sections) reached 62±1.3%, 37±0.6% and 55±0.9%, respectively. The observations indicated that the exchangeable and reducible fractions of Cd, Cu and Ni decreased close to the anode. Meanwhile, the oxidizable fraction decreased for part of the enhancing agents after the EKR treatments. Possible molecular mechanisms of metal extraction from soils in the PNE treatment are discussed according to the Fourier transform infrared (FTIR) analysis outcome. The metal accumulation did not occur during PNE treatment. Compared to the other five enhancing agents, the removal efficiency of PNE was determined to be identical. However, PNE will be advantageous with respect to its economic cost and natural fertilizing benefits.