Degradation kinetics and transformation pathway of methyl parathion by δ-MnO 2 /oxalic acid reaction system.

Methyl parathion (MP) is a typical organophosphorus pesticide that is widely used worldwide, and hydrolysis, oxidation and reduction are the main abiotic degradation processes. Manganese dioxide (MnO ₂ ) and organic acid can participate in various geochemical processes of pollutants, a reaction system was constructed to degrade MP using δ-MnO ₂ and oxalic acid. The δ-MnO ₂ /oxalic acid reaction system could efficiently degrade MP, and the removal rate of MP (20 μM) reached 67.83% within 30 h under the optimized conditions (pH 5, [δ-MnO ₂ ] = 2 mM, [oxalic acid] = 100 mM). MP was hydrolyzed by substitution reactions of S _N @P and S _N @C, and reduced by conversion of the nitro groups (-NO ₂ ) in MP and its hydrolysates to amino groups (-NH ₂ ). The primary active substance produced in the reaction system was the complexes dominated by Mn(III)-oxalic acid. This study provides a scientific basis for the degradation of organophosphorus pesticides using MnO ₂ and an organic acid. The results have important theoretical significance and application value for pollution control and remediation of organophosphorus pesticides.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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