Study On Leaching Of Hematite From Roasted Cyanide Tailings

The roasted cyanide tailings is the residue of the refractory gold ore after roasting and cyanide leaching.Due to the melting and recrystallization of the iron phase in the process of roasting,part of the gold is wrapped by the dense hematite,and the leaching rate of wraped gold in it is low.A large number of studies have shown that destroying the wraped gold by hematite is the most effective way to increase the gold leaching rate.This paper proposed that H₂ox was used to leach the packed gold,and mainly studied the existence and distribution fraction of iron Fe（III）in the Fe³⁺-H₂ox-H₂O system and the process of H₂ox leaching hematite in cyanide tailings.The graphs of the existence form and distribution fraction of Fe（III）in Fe³⁺-H₂ox-H₂O system were drawn,and the effects of p H value and ox^2-/Fe³⁺molar concentration ratio on its existence form and distribution fraction were studied.The results show that the p H value and the ox^2-/Fe³⁺molar concentration ratio have a great influence on the existence and distribution fraction of Fe（III）,and the leaching effect of hematite is closely related to the leaching form of hematite.When ox^2-/Fe³⁺is greater than 3 and the p H is equal to about 3,hematite can be leached in the form of Fe（ox）₃^3-with a larger stability constant.Based on the analysis of the existence and distribution fraction of Fe（III）in the leaching solution,the effects of additive type,H₂ox/additive A molar ratio,ox^2-excess multiple,leaching temperature and leaching time on the leaching effect of hematite were studied.Based on the single-factor experiment,Design-Expert software was to used to optimize the conditions of leaching hematite,the relationship equation between iron leaching rate of and each factor is established,the main factors affecting the effect of iron leaching and the optimum conditions of iron leaching were obtained.Results show that the relationship between iron leaching rate and various influence factors is Y=88.95-3.43X₁+4.87X₂+4.86X₃+0.32X₄-1.54X₁X₂+3.47X₁X₃+0.20X₁X₄-0.42X₂X₃-0.25X₂X₄+0.11X₃X₄-5.36X₁²-0.97X₂²-1.72X₃²+1.91X₄²,and the H₂ox/A molar concentration ratio,leaching temperature,ox^2-adding amount and the interaction between the two factors have extremely significant effects on iron leaching rate,while the liquid-solid ratio and leaching time effect on iron leaching rate is not significant.Design-Expert software optimized the hematite leaching conditions is that ox^2-excess multiple of 1.2 times of theoretical amount,H₂ox/A molar ratio of 0.98,liquid-solid ratio of 4:1,leaching time of 65min,leaching temperature of 90℃.Under this condition,the leaching rate of iron is as high as 95%.In addition,the H₂ox system was used to leaching hematite in a sulfated roasting cyanide tailing from Shaanxi,a two stages roasted cyanide tailing from Shandong Guoda,and a sulfuric acid slag from Hunan,the leaching rate of iron reached more than 95%.Finally,the process of preparing iron red was explored from the leaching solution by ammonia iron precipitation-precipitation calcination.The results show that Fe（ox）₃^3-is destabilized and dissociated into ox^2-and Fe³⁺through adjusting the p H value of the leaching solution,and Fe³⁺and ox^2-are finally recovered in the form of iron red and（NH₄）₂ox·H₂O,respectively.In the process of ammonia iron precipitation,the precipitation time,precipitation temperature and the stirring speed have a great influence on the particle size and micro-morphology of iron red.The results will provide the theoretical and technical support for H₂ox used to leach hematite from the roasted cyanide tailings and sulfuric acid slag,recovery of iron and the regeneration of iron and H₂ox from the leaching solution.