Degradation of HCHs by thermally activated persulfate in soil system: Effect of temperature and oxidant concentration

Soils contaminated with hexachlorocyclohexanes (HCHs) are a legacy of the heavy use lindane during 20th century. This pesticide production generated large amounts residues other HCH isomers, which were habitually mismanaged. The sediments treated in this work (coming from an old landfill) example environmental problem global dimensions. efficient remediation these sediments, mainly β-HCH (99 mg kg−1) and α-HCH (254 is still challenge. thermal activation persulfate (PS) required excessive reaction times, could be reduced by optimizing variables process. study aims to explore effect using higher temperatures (35, 45, 55 ºC) initial oxidant concentrations (10, 20, 40, 60, 80 g L−1). Batch experiments (liquid/soil = 2/1, 100 rpm) performed evaluate influence two HCHs abatement, dechlorination degree, generation intermediate compounds, consumption. An increase temperature accelerates pollutant oxidation rate decreases concentration chlorinated byproducts. PS also plays crucial role degradation. At selected operating conditions (55 ºC, L−1), conversion around 83% was achieved, without byproducts (chlorine balance ≈ 100%) at only 9 days treatment. A plausible pathway for degradation HCHs-polluted soils thermally activated has been proposed identified species, involving scheme series-parallel reactions.