Study On Degradation Of Several Kinds Of Pfcs By Uv Photocatalytic-oxidation System

With the rapid development of the fluorine industry, perfluorinated compounds（PFCs） because of its strong heat resistance, strong anti-oxidation, strong corrosion resistance, stable chemical properties and surface activity characteristics, is widely used in electroplating, dyes, chemical industry, textile, food and other fields. This leads to an increase in the emissions of organic fluoride industrial wastewater. Because the hydrogen atom in the whole fluorine organic compound is completely replaced by fluorine, the C-F bond is formed. The C-F bond is the covalent bond which has the largest bond energy, so that the stability of the PFCs is very strong. Therefore, it is difficult to degrade the PFCs in the wastewater, which can be persistent in the environment. Because of the accumulation of organisms and the persistent existence of the environment, the PFCs have potential toxicity to humans and the environment. And the degradation of them has attracted people’s attention.This study takes PFTBA, PFBSK and PFOA as the target. These three targets are currently widely used in the fields of electronics, optics, building materials and medical treatment.The experiment used a UV lamp with a wavelength of 185 nm, and the removal of fluoride from the organic compounds in the aqueous solution was carried out in the aqueous phase. The different influencing factors are controlled by the orthogonal experiment, and the optimal degradation conditions of PFOA, PFBSK and PFTBA were determined and verified by the UV-fenton, UV-fenton-like and UV-TiO₂ systems. Then compared and analyzed the processing results of different treatment methods. In order to achieve the objective of determining the optimal degradation conditions for them, and compared the treatment results of different treatment methods. The main results obtained are as follows:1. UV-Fenton method was used to deal with the best experimental conditions for the degradation of PFCs:1) For the treatment of PFTBA the optimum processing conditions of UV-Fenton degradation: the temperature of 40 DEG C and p H is 3, light intensity of illumination for 0 cm and the ionic strength is 0.3 mol/L, the concentration of catalyst for 10 mmol/L, Fe2+/H2O₂ ratio of 1:150, the optimal reaction time for 18 hours. Under the optimum experimental conditions of perfluorinated three butylamine fluoride removal rate was 59.31%.2) By UV-Fenton oxidation degradation processing PFBSK for the optimum processing conditions: temperature of 20 DEG C and pH = 4, the light according to the strength of 2 cm and ionic strength 0.1 mol/L, the concentration of the catalyst Fe2+ was 5 mmol/L, Fe2+/H2O₂ ratio of 1:100, the optimal reaction time 20 hours. Under the best experimental conditions, the rate of fluoride removal of potassium fluoride was 19.26%.3) UV-Fenton degradation of PFOA optimal processing conditions: temperature of 50 DEG C, pH = 5 and light according to the strength of 5cm, ionic strength of 0.01 mol/L, the concentration of the catalyst Fe2+ was 3 m mol/L, Fe2+/H2O₂ ratio of 1:150, the optimal reaction time was 20 hours. Under the best experimental conditions, the total fluoride removal rate was 48.32%.2. UV- Fenton like method was used to study the best experimental conditions for the degradation of three kinds of organic compounds with different types of PFCs:1) UV-Fenton-like process for the degradation of PFTBA the optimum processing conditions for: temperature 60 DEG C, pH = 4, light illumination intensity was 0 cm, ionic strength of 0.3 mol/L, catalyst concentration of Fe3+ was 5 m mol/L, the concentration of H2O₂ was 600 mmol/L, the optimum reaction time was 16 hours. Under the optimum experimental conditions of perfluorinated three butylamine fluoride removal rate was 73.09%.2) the optimum processing conditions of UV-Fenton like process for the degradation treatment PFBSK as: temperature 30 DEG C, pH was 3, and light illumination intensity was 5 cm and ionic strength was 0.1 mol/L, catalyst concentration of Fe3+ was 5 mmol/L, and the concentration of H2O₂ was 500 mmol / L, the optimum reaction time was 18 hours. Under the best experimental conditions, the rate of fluoride removal of potassium fluoride was 26.57%.3) UV-Fenton like process for the degradation treatment PFOA for the optimum processing conditions: temperature of 20 DEG C and pH was 4, light illumination intensity was 5 cm and ionic strength was 0.1 mol/L, catalyst concentration of Fe3+ was 5 mmol/L, and the concentration of H2O₂ was 500 mmol/L, the optimum reaction time was 20 hours. Under the best experimental conditions, the total fluoride removal rate was 62.36%.3. UV-TiO₂ degradation method was used to study the effect of PFCs degradation. By orthogonal experiment, the results of the optimal treatment condition of the ultraviolet lamp at the wavelength of 185 nm are obtained:1) the UV-TiO₂ optimal treatment conditions for degradation of PFTBA method were as follows: temperature 40 DEG C, pH was 2, light intensity 0 cm, ionic strength 0.01 g/L, and the amount of catalyst used 0.8mol/L, the best reaction time was 20 hours. Under the optimum conditions, processing three perfluorinated butylamine defluorination rate was 65.29% by UV-TiO₂ method.2) the UV-TiO₂ optimal treatment conditions for degradation of PFBSK method are as follows: temperature 40 DEG C, p H was 2, light intensity was 0 cm, ionic strength was 0.5mol/L, catalyst usage was 0.8g/L, the best reaction time wass 20 hours. Under the optimum experimental conditions, the removal rate of fluoride was 15.37%.3) the optimal processing conditions of UV-TiO₂ degrading treatment for PFOA: temperature of 60 DEG C, pH was 4, light intensity 0 cm and ionic strength 0.1 mol/L, catalyst usage 0.8 g/L, optimal reaction time was 18 h, under the optimum experimental conditions of PFOA defluorination rate was 64.21%.4. Through of PFCs were used under the best conditions for three different photocatalytic oxidation system to determine the treatment effect were compared and analyzed. Through comparison of the results found that UV-Fenton like system degradation of PFTBA and PFBSK treatment effect is better than the two other system, not only the reaction process with shorter defluorination effect is the best, and in actual operation can simplify the process, save cost. UV-TiO₂ system has the best effect on the removal of fluoride in the degradation process of PFOA, and the shortest treatment time. The experimental results show that the three kinds of reaction systems have obvious effects on the degradation of the organic fluorine compounds.