Study On Pyrite Oxidation Activation Method By Persulfate Advanced Oxidation Technology

For the refractory gold ores,the gold is wrapped by pyrite,arsenopyrite and other sulfides,the traditional process is used to extract gold directly by cyanidation,and the leaching rate of gold is low,therefore,oxidation pretreatment is needed before cyanidation to improve the recovery rate of gold.In the early stage,the project team took low-grade micro-disseminated primary gold ore as the research object.Under the system of Fe SO₄-?NH₄?₂S₂O₈/K₂S₂O₈,the pretreatment technology of"advanced oxidization-alkali wet method"was adopted to study the thermodynamics and kinetics of oxidation dissolution of pyrite and the dissolution mechanism of gold-bearing quartz under alkaline conditions.In view of the low oxidation rate of oxidized pretreated pyrite in the previous Fe²⁺-S₂O₈^2-system,this paper proposes the research on the activation mode of advanced oxidation pretreated pyrite loaded with golden pyrite,and the research results provide a basis for the application of advanced oxidation pretreatment technology in low-grade micro-disseminated primary gold deposits.The effects of different activators?Fe OOH?Fe₂O₃?Fe₃O₄?Fe S?Fe O?Fe SO₄?nano iron powder?nZ???Mn O₂?Cu O?concentration,?NH₄?₂S₂O₈concentration,oxidation pretreatment time,oxidation pretreatment temperature,initial p H value and other factors on the oxidation pretreatment of pyrite were investigated.The heat flux in the oxidation pretreatment of pyrite in nZ??Fe O/Fe SO₄?-?NH₄?₂S₂O₈system was simulated by c80 microcalorimeter.A simple and rapid method for the determination of sulfate radical?SO₄^-??in the oxidation pretreatment of pyrite by nZ?-?NH₄?₂S₂O₈was developed.Finally,XRD?SEM-EDS?XPS?NMR and electron probe were used to characterize the morphology,crystal structure,element composition,pore size distribution and chemical oxidation state of partially oxidized pretreatment pyrite slag.The results of the study on the activation mode of oxidizing pyrite by advanced oxidation technology show that the oxidation rate of pyrite generally increases with the increase of the dosage of activator and?NH₄?₂S₂O₈.By activator and?NH₄?₂S₂O₈dosage results show that the change of oxidation pretreatment of pyrite?NH₄?₂S₂O₈dosage is greatly influenced by the change of pyrite oxidation rate,and the influence of the change of the activator dosage of pyrite oxidation rate is not very significant,when used alone?NH₄?₂S₂O₈or activator oxidation of pyrite,pyrite oxidation rate is very low,so that activator in pyrite oxidation pretreatment process only play a role.Under different oxidation systems,the effect of initial p H on the oxidation rate of pyrite is not significant.Under normal temperature and pressure,the effect of advanced oxidation pretreatment of pyrite by nZ??Fe O?-?NH₄?₂S₂O₈was obvious,and the maximum oxidation rate of pyrite reached 91.12%and 82.95%respectively within 0.5 h.With the increase of temperature,the advanced oxidation pretreatment of pyrite in the system of activators(Fe OOH?Fe₂O_3?Fe₃O₄?Fe S?Fe SO₄?Mn O₂?Cu O)-?NH₄?₂S₂O₈showed an overall rising trend,and the oxidation rate of pyrite was obvious when Fe SO₄was the activator.When the temperature was 60?,the maximum oxidation rate of pyrite within0.5 h was 57.31%.By XRD?XPS?SEM-EDS?NMR and electron probe analysis of partial oxidation pretreatment of pyrite slag characterization results show that the pyrite surface morphology before leaching rule,leaching after surface oxidization,gradually produce sag and cracks,voids,the formation of many holes,the oxidation process with intermediate generated,such as polysulphide?Fe S_n?,lack of iron sulfide(F_1-xS₂).In addition,no new inclusions were found in the pyrite slag after oxidizing pretreatment,and the oxidizing pretreatment only oxidized and dissolved pyrite.The results of c80 microcalorimeter showed that pyrite pretreatment by advanced oxidation of nZ??Fe O?-?NH₄?₂S₂O₈was an exothermic reaction,and pyrite pretreatment by advanced oxidation of Fe SO₄-?NH₄?₂S₂O₈was an endothermic reaction,with reaction heat of-3889.56 J/g?-692.56 J/g and 587.35 J/g,indicating that oxidation pretreatment was easier when the activator was nZ?.Finally,the relative concentration of SO₄^-?in the reaction process of pyrite oxidation between nZ? and?NH₄?₂S₂O₈within 1 hour was measured,and the analysis showed that the relative concentration of SO₄^-?increased rapidly with time,then gradually decreased,and finally approached zero.Moreover,the maximum relative concentration of SO₄^-?at 7 min was calculated to be 7.533 mmol/L,which indirectly proved that the oxidation rate of pyrite could reach 84.24%at 7 min.The results showed that the activation mode of pyrite was selected and optimized based on the previous study to obtain a more efficient and more significant initiator nZ? as an activator,which has certain reference value for the efficient application of the subsequent oxidation leaching of fine disseminated pyrite.