Research On Deselenium Of Copper Anode Slime By Microwave Sulfation Roasting

Copper anode slime is the metallurgical intermediate product produced by copper electrolytic refining,and it is the main source of recycled rare metal and precious metals such as selenium.At present,the traditional pyrometallurgy and hydrometallurgy process mainly used in industry to recover selenium,but the traditional recovery methods have some problems such as poor operating environment,long working cycle,low recovery efficiency,difficult wastewater treatment and so on.Aiming at the shortcomings of the existing process,this paper studies the new technology of microwave sulfuric acid roasting and selenium removal by using the characteristics of microwave selective heating and energy saving and green,in order to provide a new idea for the recovery of selenium from copper anode slime.?1?The microwave dielectric characteristics and heating behavior of copper anode slime were studied.The effects of temperature and acid ratio on dielectric properties of slime and the effects of different power,material quality and acid ratio on microwave heating characteristics of slime were investigated.The results show that in the 25⁶00?range,the dielectric constant and loss of slime go through three stages of rising-decreasing-recovery,corresponding to the temperature range of 25²00?,250⁴00?and 450⁶00?respectively.The maximum and minimum values of dielectric constant and loss were 9.289,2.84 and 3.0,0.06 respectively,and in the study of acid ratio 0.5¹.0,the dielectric constant and loss increased with the regularity.The larger microwave power and material quality,the faster the microwave heating rate,while the acid ratio increases,compared with the same material volume and power conditions,the heating time of adding acid is reduced to 1/3.?2?The thermodynamic analysis of the roasting process of copper anode slime was carried out,and the changing trend of each reaction free energy??G?under the combined action of oxygen,sulfuric acid and oxygen-sulfuric acid was analyzed respectively.Under oxygen conditions are exothermic reactions,and at low temperature selenium is easy to oxygen to produce selenate or selenite;under sulfuric acid conditions,copper selenide will give priority to the reaction of silver selenide,and tend to produce more stable sulfate;under the combined action of oxygen and sulfuric acid,oxygen is found to have a significant effect on the reaction.?3?Based on single factor experiment design,the optimization of copper anode slime response surface method was studied.The experimental factors and response values were roasting temperature?₁?,microwave action time?₂?,acid ratio?₃?and selenium removal rate???,and the quadratic polynomial model of the process condition of microwave sulfuric acid roasting was established.The results of response surface analysis show that microwave roasting time and acid ratio have significant effects on selenium removal under this experimental condition.The optimum technological conditions were:acid ratio 0.9:1,roasting time 28min,roasting temperature 400?,removal rate of 95.35%.In this optimization condition,3 groups of experiments were repeated,the average selenium removal rate of the test value was 96.12%,and the difference between the predicted selenium rate was 0.77%,which indicated that the test value matched the predicted value well.?4?The kinetic study of copper anode slime roasting was carried out.The analysis of thermogravimetric curve shows that the first stage is the removal of crystalline water and the evaporation of oxides,followed by oxidation and weight gain in 400⁵10?,followed by the decomposition reaction of selenate or selenite after 510?and weightlessness.The apparent activation energy calculated by FWO increases gradually with the increase of?and the change value of activation energy is larger,and the average apparent activation energy is 76.72kJ/mol.