Removal Of Arsenic From Polluted Acid And Recycling Of Arsenic Removal Agents

The flue gas of nonferrous smelter will be washed and purified before acid making.During the washing process,the fluorine,chlorine,arsenic and other heavy metal elements in the flue gas will enter the acid and gradually enriched.so,the non-ferrous smelter will regularly discharge some dilute acids in the production process,which are "polluted acids".The composition of waste acid is complex and contains high-risk pollutants,so it can not be discharged directly to the water body,especially the arsenic,whose concentration is generally far higher than the discharge standard.Therefore,it is of great significance to develop a new process,which can not only meet the requirements of non-ferrous smelting enterprises for arsenic removal from waste acid,but also reduce the cost of the current process,as well as reduce the output of arsenic slag and the difficulty of subsequent treatment process.At present,there are some problems in the technology of arsenic removal from waste acid,such as high cost,low arsenic removal ability,secondary pollution and substandard effluent.In this paper,barium sulfide is used as the arsenic remover,and one-stage indirect and two-stage direct sulphurization and arsenic removal processes are used.The effect of these processes on the removal of arsenic from waste acid is studied.At the same time,the process of producing barium sulfide by carbothermal reduction of barium sulfate is also studied,and the process of "waste acid two-stage sulphurization treatment-regeneration and recycling of barium sulfide" is formed.The main research contents and conclusions are as follows:(1)The best technological conditions of one-stage indirect vulcanization method are as follows: the input of barium sulfide is 2.4 times of the theoretical value,the reaction temperature is 50?,the reaction time is 80 minutes,at this time,the arsenic content of one-stage tail liquid is reduced from 8810mg/L to below 50mg/L,and the arsenic removal rate is more than 99%.Among them,the most important factor is the amount of barium sulfide,the second is the reaction time,and the least is the reaction temperature;(2)The best technological conditions of the two-stage direct sulfurization method are as follows: the input of barium sulfide is 1.6 times of the theoretical value,the reaction temperature is 25?,the reaction time is 60 minutes,at this time,the arsenic content of the two-stage tail liquid is reduced from 50mg/L to less than 0.5mg/l,and the arsenic removal rate is more than 99%.Among them,the most important factor affecting the arsenic removal rate in the process of precipitation of waste acid by the direct sulfurization method of barium sulfide is the input of barium sulfide,followed by the anti arsenic method The temperature and reaction time have the least influence on the arsenic removal rate by indirect sulfurization;(3)The best technological conditions of carbothermal reduction of barium sulfate are as follows: the mass ratio of reductant to barium sulfate is 0.15,the reaction temperature is 1100?,the reaction time is 60 minutes,and the conversion rate of barium sulfate is 92.91%.Among them,the most important factor affecting the reduction rate of barium sulfate is the mass ratio of solid reductant to barium sulfate,the second is the reaction temperature,and the least is the reaction time.