Research On Fenton Processes Used For High-salinity Wastewater In Organic Pollutant Removal Treatment

With the development of industrial level,industrial wastewater has become an important source of water pollution.High-salinity organic wastewater contains not only high concentration of refractory organic pollutants,but also a lot of salinity,directly discharging into natural water will cause serious damage to the environment and waste of resource.Most ofthecurrenttreatmentsinhigh-salinityorganicwastewatersuchas ion-exchange membrane electrolysis requires very low TOC concerntration.In this paper,high salinity epoxy resin manufacturing wastewater was used as the object,on the basis of Fenton oxidation,a variety of organic pollutants removal treatment processes in high-salinity organic wastewater were put forward.In the first part,the removal treatments of organic pollutants from wastewater by coagulation and Fenton processes were investigated and compared.The effects of initial pH value,Fenton’s reagent or coagulant dosage and reaction time on organics removal were investigated during the oxidation and coagulation processes.Results showed that:The optimum conditions for Fenton oxidation were obtained at pH=3 and the mole ratio of Fenton’s reagents was n(Fe²⁺)/n（H₂O₂）=1:20,Fe²⁺dosage of 25 mmol/L,H₂O₂ dosage of 500mmol/L.The maximum removal efficiency for TOC by Fenton oxidation was 62.50%after120 min reaction.The removal efficiency of TOC by coagulation process was 23.78% with 300 mg/L dosage of FeSO₄.The removal efficiency of TOC in coagulation-two staged Fenton oxidation process is the highest which is 89.27%.In the second part,ultraviolet light was used to enhance the efficiency of Fenton oxidation.The effect of UV/Fe+H₂O₂ process for wastewater treatment was studied and UV/Cu+H₂O₂ process for high-salinity organic wastewater treatment was put forward for the first time.Reaction mechanism was researched and response surface method was used to looking for optimal conditions.Results showed that:The optimum conditions were obtained at controlling pH in 3,V_H2O2:V_wastewater was 5%,the mole ratio of reagents was n(Fe²⁺/Cu²⁺)/n（H₂O₂）=1:30,H₂O₂ with the method of continuous dosing,the TOC removal efficiency was 94.9%for UV/Fe+H₂O₂ process and 94.9%for UV/Cu+H₂O₂ process.In high-salinity wastewater,in the UV/Fe+H₂O₂ system hydroxyl radicals played more important role than superoxide radical in the oxidation of organic matter,while in the UV/Cu+H₂O₂ system that was on the opposite;In the UV/Fe+H₂O₂ system,the influence of various factors on the TOC removal order as:hydrogen peroxide dosing quantity>UV lamp intensity>ferrous sulfate dosing quantity;while in the UV/Cu+H₂O₂ system,the influence of various factors on the TOC removal order as:hydrogen peroxide dosing quantity>copper nitrate dosing quantity>UV light intensity;The optimal conditions for the UV/Fe+H₂O₂ process were:H₂O₂ dosage of 17.6 ml/L,ferrous sulfate dosage of 2668.8 mg/L,UV lamp power of 500 W and TOC removal efficiency was 96.7%;the optimal conditions for the UV/Cu+H₂O₂ process were:H₂O₂ dosage of 17.6 ml/L,copper nitrate dosage of 713.8mg/L,UV lamp power of 480.88 W and TOC removal efficiency was 95.73%.The costs of different plan were compared in order to choose the preferential selection in practical engineering application.