Study On The Treatment Of Pesticides Wastewater By Fenton Reagent

Pyrethroid pesticide has varieties and complex chemical structures, multi-step synthesis and complicated intermediates, so pyrethroid-contained wastewater has characteristic of high concentrations of high CODCr, high toxicity, complicated components, deep chromaticity, and hard biodegradation. Four methods for pyrethroid pesticide wastewater treatment were studied, and the prospect for the technical development was also discussed in this paper.First, the wastewater was treated by Fenton reagent separately with single factor and orthogonal. The experimental results showed the optimum degradation condition:Fe2+/ H2O2(30%) was 62.5 mg FeSO4-7H2O/mL H2O2(30%)5 H2O2(30%) dosage was 2.0mL. pH 3.5, the reaction time 40 min, temperature 35℃, the CODCr removal rate was 54.10%. At room temperature processing, the CODcr removal rate was 37.8%.Secondly, under co-processing of Fenton and fly ash treating the wastewater was studied. According to the single factor and orthogonal experimental results, the CODcr removal rate can be reached up to 72.00%, when the optimum conditions were as follows: Fenton reagent dosage was 2.5 mL, fly ash dosage was 6.0 g, pH 3.5, temperature 35 ℃ and the reaction time 40 min.The third, with fly ash-based coagulant pretreatment and subsequent treatment of Fenton reagent was studied. (1) the orthogonal and single factor experimental results showed the optimum conditions of pre-trial:fly ash/acid ratio was 1:4 (w/v), fly ash/base ratio was 1:3 (w/v), the curing temperature 40 ℃; coagulation condition:coagulation time 3 h, the coagulation temperature 30 ℃, pH 4 and the dosage 8 mL/100mL.(2) the optimum conditions of post-processing:pH 3.5, H2O2 (30%)dosage was 1.50 mL, FeSO4 · 7 H2O2 dosage was 0.1 g, reaction time 40 min, the temperature 35 ℃. CODCr removal rate can be reached up to 94.18% in this condition.Finally, poly-silicon ferrous sulfate (PFSSⅡ) coupled with H2O2(30%) were studied to treatmenting the wastewater.(1) when flocculantion was added alone, CODCr removal rate was 13.21%,with the optimum conditions:pH value of 3, dosage was 2g/L, reaction time was 60 min, temperature 20 ℃.(2) PFSS Ⅱ coupling treatment with H2O2(30%), when the optimum conditions:Fe-Si molar ratio of PFSS Ⅱ was 1:3, pH 3-3.5, H2O2/PFSS Ⅱ (the Fe-Si molar ratio is 1:3)were all 50 mg/L, pH 3, reaction time 60 min, room temperature (20 ℃), the CODCr removal rate can be reached up to 89.44%.Comparing the four treatments, the treatment efficiency of fly ash-based coagulant pretreatment and subsequent treatment of Fenton reagent was the optimal treatments.