Treatment of water networks (waters and deposits) contaminated with chlorfenvinphos by oxidation with Fenton's reagent

Abstract

The treatment of waters/deposits from drinking water networks contaminated with chlorfenvinphos (CFVP) was performed through the Fenton's process. Concerning the CFVP degradation in water matrices, the mineralization and CFVP concentration in a batch reactor were analysed along time for several operating conditions. A detailed parametric study was done to analyse the effect of the initial concentrations of oxidant (H2O2) and catalyst (Fe2+), temperature and initial pH, allowing concluding that temperature significantly affects the degradation process. In fact, in the range from 10 to 70 C, the time for complete degradation of CFVP decreased from 3 h to only 5 min. In the same temperature range, the mineralization after 3 h increased from 5% to 35%. The effect of other parameters is not so significant; depending on their values they can affect positively or negatively the responses. The degradation of the pesticide was assessed for the first time using deposits from water networks as catalysts. These deposits result from the natural deposition of small particles in suspension, being in some cases highly rich in iron, and therefore it is envisaged the valorisation of these materials for off-line applications and the possibility of avoiding the use of some reagents -catalyst - if an in situ treatment is required. The decontamination of deposits was assessed in a slurry batch system, showing to be possible to use iron-rich deposits as catalysts in the oxidation process, as well as to decontaminate them using as catalyst the iron present in their composition. Results showed that oxidation is fast and effective in the liquid phase (conversion >95% in 1 h); the pesticide was also removed from the solid, although apparently not always in a complete manner, in the conditions tested.