| In this study the chemical-coagulation precipitation method was used for the arsenic and fluoride wastewater treatment in the electronics industry.Single factor experiment was used to study the effects of different influencing factors on the removal of arsenic and fluorine to meet the national standard for industry wastewater which is the concentration of As is lower than 0.01 mg/L and the concentration of F is lower than 10.0 mg/L,and the optimal reaction conditions were further determined in the arsenic-containing fluoride wastewater treatment.The real industry wastewater from an electronic panel plant was set as example,the optimal experiment and field debugging were applied to fulfill the modification works of the treatment of wastewater containing F.The influencing experiments of arsenic removal solution selection,physical and chemical factors and dosing mode were applied for the treatment of simulated wastewater prepared by GaAs.Results showed that ferric chloride had the advantages of good treatment effect and low cost,FeCl3 was chosen as the main arsenic removal chemical.In the wastewater containing As(V)of 100 mg/L,ferric chloride was divided into three batches,the reaction pH was 7.0,the total dosage of FeCl3·6H2O was 560 mg/L,fast stirring for 2 min,slow stirring for 30 min,coagulant PAM dosage was 2 mg/L.In this condition results showed the best treatment effect,after the reaction,the arsenic removal rate in water can more than 99%,the residual As(V)concentration in the water is 8.5 ?g/L.A multi-stage coagulation combined process which can meet the national standard for industry wastewater containing As was put forward based on above researches.The single factor experiment and the orthogonal experiment were carried out on the fluorine-containing wastewater.The experiment was carried out by using the CaCl2-PAC two-stage fluorine removal method.The experimental results showed that,during the calcium chloride treatment on the wastewater containing 100 mg/L F',calcium chloride was added twice,the dosage of CaC12 was 300 mg/L,the reaction pH was 5.5,the mixture was stirred at 200 r/min for 2 min,and stirred slowly at 50 r/min for 20 min,the dosage of PAM was 2 mg/L,the removal rate of F' can reach to 85.7%,and the residual F-concentration in water can be reduced to about 14.3 mg/L.In the wastewater after calcium chloride treatment,the PAC of 150 mg/L was added,and pH was adjusted to 6.5.Other parameters were the same as before.The final F-removal rate can reach 93.8%,and the residual F'concentration in water was reduced to 6.2 mg/L.A multi-stage coagulation combined process which canmeet the national standard for industry wastewater containing F" was put forward based on above researches.The dosage and pH optimization experiments were carried out with the real fluorine production wastewater containing F-.Results showed that in the actual production wastewater the F' concentration was 100 mg/L,the dosage of anhydrous calcium chloride was 300 mg/L,the pH is about 5.5,the mixture was stirred at 200 r/min for 2 min,and stirred slowly at 50 r/min for 20 min,the dosage of PAM solution was 2 mg/L,during this stage,the removal rate of F-can reach 85.7%,the residual F' in water can be get 14.3 mg/L.After this stage,150 mg/L PAC was added,pH was adjusted to 6.5,other parameters were the same as before,after this stage,the final removal rate can get 93.8%and the residual F-in water was 6.5 mg/L.A multi-stage coagulation combined process which can meet the national standard for industry wastewater containing F-was put forward based on above researches.Field debugging was applied for the real production wastewater containing F-in an electronics panel plant.A Ca(OH)2 removal fluorine was applied in the previous reaction.In the modified process CaC12 was used to replace CaC12 because Ca(OH)2 can cause blocking of door and flowmeter,the chemical was added in different points,pH and dosage were optimized.The results showed that,in the wastewater containing F-102 mg/L,the total dosage of CaCl2 was 1050 mg/L,the reaction pH was 5.5;the dosage of 10%PAC was 600 mg/L,the reaction pH was 6.5,concentration of F-was lower than the relevant standard.After the 80-day treatment,the system ran stably and the water can reach the national standard for industry wastewater.In this paper,the treatment of arsenic and fluorine-containing wastewater by chemical coagulation precipitation method was studied.The optimal treatment conditions were optimized by single factor experiment and orthogonal experiment,and the whole process of arsenic and fluoride containing wastewater treatment was finally given.The process was applied for the real production wastewater.This work provides systematic theoretical guidance for the treatment of arsenic and fluorine-containing wastewater,and has significant practical application meaning in actual wastewater treatment. |
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