New Technology And The Mechanism Of Recycling Silver From The Jarosite Slag In Zinc Hydrometallurgy

In order to recycle silver from the jarosite slag, muti-elments analysis, Original particle size analysis, the condition test of direct flotation and reduction roasting flotation were studied. We determined the flowsheet of silver recovery of the jarosite slag. We confirmed the structure and properties of the jarosite slag by the chemical phase analysis, XRD analysis, optical microscope, scanning electron microscope analysis. The mechanism on silver recovery of reduction roasting flotation was studied by the way of XRD analysis of silver sulfate reduction roasting, thermodynamic calculation and solution chemistry calculation. The results of this work can provide theoretical and practical guideline for recoverying silver from jarosite slag.The flotation test showed that direct flotation can’t recycle the silver from the jarosite slag effectively, but the reduction roasting-flotation did it. The best test conditions of reduction roasting-flotation test:reduction roasting temperature600℃, roasting time1hour, reducing agent carbon content10%, flotation pH5.0, pulp concentration25%, sodium sulfide dosage5000g/t, the vulcanizing time to20min, collector HD and SN-9#dosage400g/t,100g/t.Research results showed that:through reduction roasting decarburization-washing-two rough three cleaning three scavenging flotation process, the grade of silver concentrate reached7515.62g/t, silver concentrate recovery rate reached81.49%.Most of the mineral grains are under0.025mm.The grade of silver is very low, and the main silver element is the silver in the jarosite slag. The silver mineral grains were not seen under the optical microscope and scanning electron microscope. The jarosite become ferric oxide and lead sulfate after reduction roasting, the silver mineral become the elemental silver and silver sulfide.Differential thermal analysis showed that there are four steps in the roasting of jarosite slag. The end products are ferric oxide, sulfur dioxide, oxygen, sulfate minerals. Pure silver sulfate mineral reduction roasting test showed that the composition of silver sulfate reduction eventually product is silver but not silver sulfide.