Optimization And Application Research Of Fluidized Bed Deep Defluorination Process Conditions For Refrigerant Fluorine-Containing Wastewater

With the rapid development of fluorine chemical industry,semiconductor and other industries,the discharge of fluorine-containing wastewater is increasing day by day,especially for refrigerant manufacturing enterprises.As a fast-growing fluorine chemical enterprise,its production activities often produce a lot of high-concentration fluorinecontaining wastewater.Fluoride-containing wastewater discharged into water without treatment will pose a threat to the ecological environment and human health.In this context,as an important measure to reduce the discharge of fluorine pollutants,the deep defluorination of industrial wastewater has increasingly become a hot research topic.Fluidized bed defluorination,as a new defluoridation water treatment technology,can effectively reduce the discharge of fluoride in industrial fluorine-containing wastewater,and provides a new idea for deep defluorination of wastewater.This paper takes refrigerant fluorine-containing wastewater as the research object,by analyzing the influence of thermodynamic conditions and kinetic conditions on the effect of fluoride removal,the process operation parameters are optimized,and verified by productive test research,and the main research conclusions are as follows:(1)The results of the isothermal adsorption test show that the adsorption between aluminum salt flocs and fluoride ions conforms to the Langmuir isothermal adsorption model,and the adsorption process is dominated by chemical adsorption;based on the Van’t Hoff equation,the fitting of experimental data revealed that the aluminum Salt sorbent concentration versus nonstandard Gibbs free energy change.The thermodynamic test results show that the adsorption effect of aluminum sulfate and polyaluminum chloride(PAC)is the best when the concentration is 1.3 g/L and 1.0 g/L respectively,and the optimal reaction pH is 6.0～7.0 and 6.0～7.5 respectively;PAC has Higher adsorption capacity and relatively wide pH value applicable conditions.(2)On the basis of thermodynamic experiments,the fluidized bed defluorination kinetic model established in the previous research was optimized,and the correction coefficient wasintroduced to obtain the fluidized bed defluorination correction model:C=C0β exp(-Kφt/H),the model was fitted with experimental data,and the correlation between process operating parameters and process operating effects was analyzed.(3)The kinetic test results show that when aluminum sulfate is used as a coagulant,when the concentration of fluoride ion in the raw water is 50 mg/L,the dosage of aluminum sulfate is 1300 mg/L,the residence time is 20 min,and the removal rate of fluoride ion It can reach more than 90%;when PAC is used as coagulant,the concentration of fluoride ion in raw water is about 50 mg/L,the dosage of PAC is 1000 mg/L,and the residence time is 20 min,the removal rate of fluoride ion can reach more than 80%.(4)According to the kinetic model and the results of laboratory experiments,the productive test was designed to determine the parameters of the productive test conditions,and the productive test was carried out with the production wastewater of a fluorine chemical enterprise as the research object.The optimal operating conditions for fluidized bed reactor fluoride removal are determined as follows:PAC dosing amount is 1900 mg/L,pH value is between 6.5 and 7.0,and the fluoride ion removal rate is 69%under these conditions;Under the condition that the fluoride ion concentration of the raw water is 30.2 mg/L,the first-stage fluidized bed can maintain the fluoride ion concentration of the effluent at 8-10 mg/L,and the second-stage fluidized bed can ensure that the fluoride ion concentration of the effluent is between 2.5-3.5 mg/L.(5)The cost estimation of the treatment of fluorine-containing wastewater by the fluidized bed process was carried out,and it was found that the chemical cost of the fluidized bed process for removing fluoride was much lower than that of using a fluoride removal agent to treat wastewater,and the effluent was more stable.In this study,the reaction kinetics and thermodynamic laws of aluminum salt defluorination in the fluidized bed reactor were tested and analyzed,the original fluidized bed defluorination process model was optimized,and the model fitting was carried out to determine the process It has certain application reference value and application prospect.