Treatment Of Acidic Fluoride-containing Waste Water And Utilization Of Fluorine

In this paper,a comprehensive technology was explored to realize the dispose and resource utilization of 600t/d waste smelting acid containing 11490mg/L fluoride and2531mg/L total arsenic,which comes from the purification process of Acid-making with Smelting Gas in Daye Nonferrous Metal Company.The technology includes utilization of arsenic,utilization of fluorine and treatment of residual waste smelting acid containing fluoride,while the last two items were emphases.By the process of precipitation,reduction,crystallization,synthetic reaction,neutralization and flocculation,cryolite and arsenic trioxide can be obtained.In the utilization of fluorine,a fluidized crystallization reactor was designed to achieve continuous reaction and the preparation of high molecular ratio sandy cryolite while the core technology is fluidized induced crystallization.The waste acid after the utilization of fluorine contains 10260mg/L fluoride and 45.2mg/L total arsenic.The results show that when wastewater flow was 3L/h,precipitant flow was 0.3L/h,reflux flow was15L/h,dosage of seed was 150 g,wastewater pH was 4,dosage of aluminium sulfate was Al:F=1:6,reaction temperature was 40℃,the removal rate of fluoride can reach 94.9% and the residual concentration of fluoride was 480mg/L,while the molecular ratio of cryolite obtained was 2.82,which can reach the quality standards in GB/T 4291-2007.When the running time of reactor came to 10 h,the sandy cryolite was got from the reactor,while the average grain size was 120μm.In order to safely dispose the residual waste smelting acid containing fluoride,twostages of neutralization precipitation and flocculation precipitation was used to deal with the pollutants.The results show that in the first stage the dosage of ferrous sulfate was 2.0g/L and pH adjusted with lime milk was 10.0.In the second stage,the dosage of ferrous sulfate was 0.8g/L,pH adjusted with lime milk was 9.0 and the dosage of PAC was 0.3g/L.At last,the residual concentration of fluoride decreased to 5.4mg/L and the residual concentration of arsenic decreased to 0.27mg/L while the quality of final effluent can reach the standards in GB 25467-2010.On the basis of primary experiment,a simulant intermediate experimental device of300L/h(2628t/a)scale and its software was designed.According to investment estimate and economic evaluation,the cost was 321.38 thousand yuan and the income of products were351.11 thousand yuan in a year.As a results,this technology can get good enviromental and economic benefits when dealing with waste smelting acid containing fluoride.