Removal of organochlorine pesticides from lindane production wastes by electrochemical oxidation
2018
Dominguez, Carmen M. | Oturan, Nihal | Romero, Arturo | Santos, Aurora | Oturan, Mehmet A.
This study is focused on the effective removal of recalcitrant pollutants hexaclorocyclohexanes (HCHs, isomers α, β, γ, and δ) and chlorobenzenes (CBs) present in a real groundwater coming from a landfill of an old lindane factory. Groundwater is characterized by a total organic carbon (TOC) content of 9 mg L⁻¹, pH₀ = 7, conductivity = 3.7 mS cm⁻¹, high salt concentration (SO₄²⁻, HCO₃⁻, Cl⁻), and ferrous iron in solution. The experiments were performed using a BDD anode and a carbon felt (CF) cathode at the natural groundwater pH and without addition of supporting electrolyte. The complete depletion of the four HCH isomers and a mineralization degree of 90% were reached at 4-h electrolysis with a current intensity of 400 mA, the residual TOC (0.8 mg L⁻¹) corresponding mainly to formic acid. A parallel series reaction pathway was proposed: HCHs and CBs are transformed into chlorinated and hydroxylated intermediates that are rapidly oxidized to non-toxic carboxylic acids and/or mineralized, leading to a rapid decrease in solution pH.
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