Studies Of Biological Nondegradale Organic Wastewater By Sub-Fenton Process

Many research shows that homogeneous Fenton can arrive at a solution of problems that heterogeneous Fenton oxidation reaction must under the condition of low pH (2-3) and usually need to adjust the pH, and the iron ion in the heterogeneous Fenton system would stain the water and product lots of iron mud which difficult to handle and reclaim. Homogeneous Fenton illustrates a good prospect of economic and environmental advanced oxidation technology.Fenton oxidation experiments of wastewater from methyltin mercaptide production were conducted by the application of heterogeneous Fenton and homogeneous Fenton including castrion chips-Fenton, hematite-Fenton and goethite-Fenton.In the first place, the effect of reaction conditions such as the dosage of H₂O₂, the catalyst, initial pH, initial chemical oxygen demand (COD) ntration, reaction temperature were compered in terms COD between different Fenton system. The optimum condtion of the heterogeneous Fenton oxidizes the wastewater from methyltin mercaptide production was that the dosage of H₂O₂ =1200 mg/L, initial pH=3, the molar ratio of H₂O₂/Fe²⁺=5.5:1, the removal rate of COD was 44.4% after 90min. For castrion chips-Fenton system, the optimum condtion was the dosage of H₂O₂=1200 mg/L, initial pH=4, the molar ratio of H₂O₂/Fe²⁺=5.5:1, the removal rate of COD was 44.7% after 90min. For hematite-Fenton system, the optimum condtion was the dosage of H₂O₂ =600 mg/L, initial pH=3, the molar ratio of H₂O₂/Fe²⁺=4.1:1, the removal rate of COD was 44.7% after 90min. And for goethite-Fenton system, the optimum condtion was the dosage of H₂O₂ =400 mg/L, initial pH=3, the molar ratio of H₂O₂/Fe²⁺=4.7:1, the removal rate of COD was 45.5% after 90min.In the second place, the studies of the coagulation experiments of different Fenton effluent and the biodegradability of the effluent of different dosage of H₂O₂ series experiment were discussed. The coagulation experiments included the pH and different dosage of FeCl₃ series. We can concluded that the higher the initial pH the lower the removal rate of COD. It because that the wastewater from methyltin mercaptide production changed in itself under the acid environment. With the increasing of the dosage of FeCl₃, the removal rate of COD was rise. When the dosage of iron was more than 80 mg/L, the removal rate of COD was rise slower.Considering the economic factors and analysising the the biodegradability of the effluent of different dosage of H₂O₂ series experiment, the optimum condtion of the heterogeneous Fenton oxidition was that the dosage of H₂O₂=800 mg/L, the B/C was 0.36 after 90min. For castrion chips-Fenton system, the optimum condtion was the dosage of H₂O₂=800 mg/L, the B/C was 0.38 after 90min. For hematite-Fenton system, the optimum condtion was the dosage of H₂O₂ =100 mg/L, the B/C was 0.51 after 90min. And for goethite-Fenton system, the optimum condtion was the dosage of H₂O₂=100 mg/L, the B/C was 0.45 after 90min.Kinetic models were studied for heterogeneous Fenton and homogeneous Fenton including castrion chips-Fenton, hematite-Fenton and goethite-Fenton systems respectively. The order kinetic of the whole process of heterogeneous Fenton reaction was complex, but the previous period (0～25min) and the later period (240～480min) of the reaction can be well simulated by the first- order kinetic(y=-0.0116x+0.0554, y=-0.0009x+0.0237). The order kinetic of the whole process of the castrion chips-Fenton and the ematite-Fenton reaction can be well simulated by the first- order kinetic (y=-0.0013x-0.3872, y=-0.0014x-0.4675. ). The order kinetic of the whole process of goethite-Fenton reaction was complex, but the previous period (0～30min) of the reaction can be well simulated by the first- order kinetic(y=-0.0083x-0.5672).