A Study On Pretreatment Of Dimethoate-containing Wastewater And Wastewater In Synthetic Perfume Production By Electro-Fenton Method

The organic wastewater of pesticide wastewater and fine chemical industry wastewater contains high COD (COD>4000 mg·L^-1) or the compound (ammonia nitrogen, polycyclica romatich ydrocarbons, Bap, et.al) that couldn't be degraded by conventional biological wastewater treatment methods. The organic wastewater is harmful because it is high concentration, poisonous and difficult to degrade. It will poison the creature in the water, reduce the corps production and cause serious sickness if it is let out into the rivers without treatment. The way of conventional biological wastewater treatment cannot treat it efectively. So it is significant to find more eficient methods to solve it.The main disadvantage for Conventional Fenton (CF) is the lacking of Fe²⁺ due to the rapid oxidation process (Fe²⁺ to Fe³⁺), to solve this problem, a Circulating Electro-Fenton (CEF-FeRe) was employed to degrade Dimethoate, during which H₂O₂ was added to the electrolytic cell continuously by a peristaltic pump and Fe²⁺ could be regenerated to Fe³⁺ on the cathode. The operating conditions for this CEF-FeRe were optimized by individual factor experiments, such as pH value, electrical current, Fenton's reagent dosage, and the molar ratio of Fe²⁺ to H₂O₂.Research results showed that the suitable condition for Dimethoate (200 mg·L^-1) degradation are: pH=3.0, n(Fe²⁺)/n(H₂O₂)=0.1, electric current=0.5A and Fenton's reagent dosage at its theoretical dosage, under which, COD removal rates reached 81.67% within 120 min, while Dimethoate 99.4% within 25 min. The mechanism of the CEF-FeRe reaction was investigated by monitoring the changes of H₂O₂ and Fe²⁺concentration during the process. Kinetics research results revealed that Dimethoate oxidation follows the pseudo-first-order kinetic model at different pH value. The productions of Dimethoate oxidation were also discussed by mineralization studies.A study on pretreatment of wastewater in synthetic perfume production (COD is132580mg·L^-1) has also been executed. In the groping experiment, adsorption, flocculation and extraction method were applied on treating the wastewater respectively. Research results revealed that the best pretreatment technology method is that, initially treated by electro-dialysis, in which we find the best electric current is 1.5A and the value of R is 6.7322×10-6mol·mL^-1·cm-2 after 120min's electrolysis. Then it is treated by air flotation method to degrease and get 59.8% of COD removal rate. Finally it is treated by electro-Fenton method, for which the suitable conditions are pH=3.5, electric current=0.75A, m(Fe²⁺)=3g·L^-1, n(Fe²⁺)/n(H₂O₂)=0.1, under which, COD removal rate reached 66.62% within 75 min. The total COD removal rate reached 86.60% after the best pretreatment technology method.