In situ electrochemical remediation of real marine sediments polluted by PAHs and TPHs

Abstract

In this work, real marine sediments from Bagnoli-Coroglio Bay (Naples, Italy), used as a model of real and complex matrix polluted by persistent organic pollutants, were treated by electrochemical process under a wide range of electric fields (E) (0.05-1.00 V cm-1). Experiments were conducted using compact graphite electrodes directly inserted into the sediment for 96 h. The attention was focused on both TPHs and PAHs removal. Overall, this study demonstrates that electrochemical remediation (ER) applied to real marine sediments simultaneously promotes both the in situ i) desorption and transport of TPHs and PAHs and, also, ii) their chemical transformation, even under mild operating conditions. In detail, for all the applied E, a spatial redistribution of both TPHs and PAHs within the sediments bed was observed coupled with a partial removal of these compounds. This indicates that ER not only mobilizes contaminants but also promotes their oxidative transformation. Evidence of in situ transformation was supported by the formation of water-soluble organics. Furthermore, targeted analyses allowed to identify chloroacetic acids and low-molecular-weight carboxylic acids as major transformation products, whose formation and transport were E-dependent. Overall, results demonstrate that ER, even under mild E, enables both in situ desorption/transport and electrochemically driven transformation of hydrophobic contaminants in real sediments.