Ultrasonic Pretreatment Of High Sulfur Residue From Zinc Smelting And Flotation Separation Of Elemental Sulfur

Recovering elemental sulfur from the high sulfur residue of zinc smelting by flotation method can realize the harmless and resource-based safe disposal of high sulfur residue,which has dual significance for environmental protection and resource recycling.However,the elemental sulfur is embedded in the coating with other minerals,it is difficult to effectively separate them,and the recovery efficiency is not high.To solve this problem,ultrasonic technology was used in this paper to pretreat high sulfur residue before flotation operation,which effectively improves the grade and recovery efficiency of elemental sulfur in the flotation concentrate.The density functional theory(DFT)was applied to illustrate the adsorption structure between collector and mineral,and the mechanisms of adsorption were analyzed by the electron localization function.This paper provides theoretical guidance for the efficient recovery of elemental sulfur from high sulfur residue.The XRD and XRF were used to analyze the main phases and elemental composition of the high sulfur residue,and the results showed that the high sulfur residue was composed of minerals such as elemental sulfur,sphalerite,pyrite,quartz,lead sulfate,galena,and silicate;the grade of elemental sulfur is 32.98%;the main elements of high sulfur residue are divided into three categories: valuable elements,gangue elements,and poisonous elements.After ultrasonic treatment at 30 ℃ for 6 min,the recovery efficiency and the grade of elemental sulfur in flotation concentrate were 80.98%and 73.61%,respectively.Compared with those without ultrasonic treatment,the recovery efficiency and grade of sulfur were increased by10% and 4% respectively.Ultrasonic pretreatment was mainly a physical action process,which would not change the functional groups,phases,and elemental composition of high sulfur residue.It could improve the distribution and wrapping state of elemental sulfur and other minerals to a certain extent,and increase the hydrophobicity of the surface of high sulfur residue,to improve the flotation efficiency.The optimal flotation process conditions are as follows: mine pulp concentration of 20%,gas flow rate of 80 L/h,flotation time of 12 min,pH value of 4,and temperature of 30 ℃.Under the optimal condition,the recovery efficiency of elemental sulfur reached 97% with a grade of 74%,and the Ag grade in the tailings was 520 g/t.Mine pulp concentration,flotation time,and pH value had a great influence on the flotation recovery efficiency,while gas flow rate,temperature,and grinding particle size had little effect.Therefore,it is crucial to control the appropriate mine pulp concentration,flotation time,and pulp pH value in the flotation process.The flotation concentrate was mainly composed of elemental sulfur and a small amount of sphalerite,pyrite,and quartz.The tailings were mainly composed of silicate,pyrite,quartz,lead sulfate,and galena.When the dosage of ethyl xanthate and calcium lignosulfonate were100 g/t and 150 g/t,respectively,the sulfur grade of the flotation concentrate was 78.53% and the recovery efficiency reached 95.19%.The molecular configuration and electronic structure of ethyl xanthate,elemental sulfur,pyrite,lead sulfate,and sphalerite were calculated by density functional theory(DFT).When the dosage of the ethyl xanthate was 100 g/t,the recovery efficiency of elemental sulfur,pyrite,lead sulfate,and sphalerite was 98.59%,20.09%,12.19%,and 8.45%,respectively.