Coupling of zero-valent magnesium or magnesium–palladium-mediated reductive transformation to bacterial oxidation for elimination of endosulfan

Abstract

The feasibility of employing sequential treatment method for detoxification of endosulfan using metal-mediated reductive reactions followed by bacterial oxidation was demonstrated. Gas chromatography revealed that zero-valent magnesium (Mg0) was able to remove 70% of 10 mg L−1 of endosulfan, while the bimetallic system, Mg0/Pd0–carbon, was able to remove 92% of 10 mg L−1 of endosulfan after 30 min of reaction. Monometallic and bimetallic systems resulted in the accumulation of lower chlorinated compounds and hydrocarbon end product(s) in the reaction medium. Lower chlorinated and dechlorinated products were subjected to aerobic biodegradation using the bacterial isolate, Agrobacterium strain PT-3. Residual concentrations of endosulfan isomers and products were reduced to below-detectable levels following 3.5 to 4 h of biological treatment. Recycling of immobilized Pd0 (Pd0–carbon) is required to reduce the expense of treatment process. Results obtained in this study indicated that a sequential Mg0 or Mg0/immobilized palladium-biological treatment approach may be useful for the disposal of post-expiry-dated endosulfan or remediation of pesticide contaminated sites. The integrated technology would be beneficial in terms of reducing the time as well as overall cost for the treatment endosulfan in comparison with individual chemical or biological treatment methods. In addition, this approach will eliminate the risk of accumulation of metabolites that may pose toxicity.