Simultaneous removal of metals and organic compounds from a heavily polluted soil

The paper describes the results of treatment of soil samples, deriving from a dismissed industrial site, contaminated with several metals: Hg, Ni, Co, Zn, Pb, Cu, Cr, As and organic substances. The soil was subjected to remediation based on a process in which an oxidising leaching agent was produced electrochemically in-line in an undivided electrochemical cell reactor equipped with a Ti/Pt-Ir anode and a stainless steel cathode. Leaching of the soil samples was performed under dynamic conditions using a leaching column. A subsequent regeneration of the leaching solution, which consisted in electrodeposition of metals and electro-oxidation of organic substances, was carried out in a packed-bed reactor equipped with a centrally positioned graphite rod, serving as an anode, and stainless steel three-dimensional filling as a cathode. The study was focused on how and to which extent the metals present in the soil, as organic complexes, can be solubilised and how the process rates are impacted by the solution pH and other process variables. Data obtained under non-oxidising conditions, typically adopted for leaching of metals, are compared with the performance of chlorine-enriched leaching solutions. The results obtained under various conditions are also discussed in terms of the total organic carbon (TOC) removal from the water phase.