Deep removal of iron from jarosite residue after acid mixing,microwave roasting and water leaching

A method combining microwave sulphation low-temperature roasting-water immersion and goethite processes was used to gain clean and valuable metals, such as Zn and Cu enriching to the leach liquor and Pb and Ag enriching to the leach residue. The process conditions to remove iron by using water immersion were optimized, and the iron removal effect was investigated when the pH value, the added amount of the leach liquor every time and the iron concentration in the leach liquor changed. X-ray diffraction and scanning electron microscopy were used to characterize the iron precipitates. It is found that with 200 mL of 0.01 mol·L^-1 ZnSO₄ solu-tion as a base solution, the iron removal rate can be reach to 99.3% and the residual iron concentration in the solution is about 0.065 g·L^-1 under the optimum conditions that the dosage of the goethite crystal seed is 20 g·L^-1, the pH value is 3, the temperature is 90℃ and 3 mL leach solution is added per 5 min (to keep the iron concentration in the solution 〈1 g·L^-1). In the iron removal process, the loss rate of Zn is only 4.1%.