Estudo da degradação do pesticida organofosforado clorpirifós por processos Fenton e Foto-fenton

Abstract

The presence of organophosphorus pesticide chlorpyrifos in drinking and superficial waters indicates the inefficiency in the conventional water treatment processes. The compound is known for acting in the inhibition of acetylcholinesterase and being ex-tremely toxic for aquatic organisms. Therefore, the adoption of treatments that are able to remove this kind of micropollutants has become necessary. The Advanced Oxidation Processes, specially the Fenton process, stands out for its low cost and easy operation, when compared to other advanced processes. The aim of this work was to assess the potential of Fenton and photo-Fenton processes in the remediation of aqueous solutions containing analytical standard chlorpyrifos, in bench scale. The 2 mg L-1 chlorpyrifos solution was prepared in 80:20 solution of water:acetonitrile, due to the compound’s low solubility in water. The initial and final amounts of the re-agents and the formation of phenolic compounds were determined by spectrophoto-metric methods. The concentration of chlorpyrifos was monitored by HPLC-DAD. The optimization of the best degradation condition was conducted by complete 22 factorial design, with central point tested in triplicate. The optimized conditions found were of 15 mg L-1 of Fe2+ and 50 mg L-1 of H2O2. In degradation tests conducted for 60 minutes, the Fenton process presented a maximum degradation in the order of 35%, with production of phenolic compounds that were only partially treated. The photo-Fenton process demonstrated to be efficient in the degradation of the analytical standard chlorpyrifos with area reduction greater than 99%, however it showed an increase in the order of 80% of phenolic compounds.