This study explored the application of iron turning waste for the degradation of heptachlor and endosulfan. In batch experiments, 2.5 g of iron turning waste efficiently removed 96% of heptachlor and 85% of endosulfan in 200 mL of water (20 mu g/L for each pesticide) in ten minutes. By increasing the iron turning dose from 1 g to 2.5 g, pseudo second order removal rates of heptachlor and endosulfan increased 1.5-fold and 137-fold, respectively. Among the minerals in groundwater, calcium and potassium lowered heptachlor removal (8-10%), whereas their effect on endosulfan removal was minimal. Endosulfan removal increased 16%, when water pH was raised from 4 to 10. The effect of water pH on heptachlor removal was minimal. The removal of heptachlor and endosulfan dropped to 55% and 46%, respectively, when the initial concentration was 1 mu g/L. in a continuous flow system, iron turning worked better in combination with sand media. Water flow rate (5-15 mL/min) had a limited effect on the removal of both pesticides (initial concentration of 2 mu g/L) which increased with increasing iron turning dose (100-150g) for endosulfan. Heptachlor removal remained stable (100%) regardless of the iron turning amount (100-150 g) used in a filtration column. Iron turning based filter completely removed heptachlor throughout the filtration period (600 h), whereas endosulfan removal dropped from 100% to 88-90% after 300 h. Endosulfan and heptachlor were degraded into nonanal and heptanal, respectively. Iron turning waste was characterized using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) before and after its reactions with both pesticides. XRD and XPS analyses revealed that virgin iron turning waste consisted of zerovalent iron (Fe-0) and iron oxides, and Fe-0 was transformed to magnetite (Fe3O4) after reacting with both pesticides. Based on detected degradation by-products, the removal mechanism and degradation pathways for both pesticides were elucidated. (C) 2019 Elsevier B.V. All rights reserved.
Iron turning waste;Endosulfan;Heptachlor;Degradation by-products;Water filtration;