Reseach On Gold And Silver Recovery From Pyrite Cinder

Sulfuric acid from pyrite roasting is one of the main sources of sulfuric acid production.Pyrite cinder often contains valuable precious metals such as gold and silver.Industrial recovery of gold and silver commonly used methods such as flotation,gravity separation,magnetic separation,hydrometallurgy.Hydrometallurgy is often used to recover refractory minerals with fine grain size of gold and silver,wrapped with ore.However,cyanide extraction of gold and silver is serious to the environment.Acid thiourea method is a new environmentally friendly method for extracting gold and silver.It has high recovery rate of gold and silver and is capable of industrial production.In this paper,the gold and silver in pyrite cinder were recovered through acid thiourea leaching-resin adsorption-acid thiourea desorption-zinc powder replacement process test.A series of analytical methods were investigated for pyrite cinder,including chemical composition analysis,X-ray diffraction,semi-quantitative X-ray fluorescence spectroscopy,laser particle size,scanning electron microscopy,etc.The results show that the slag of a pyrite in Jiangxi province is mainly iron concentrate with low sulfur,low lead and low arsenic content,containing 1.16 g /t gold,2.21 g /t silver and65.78% iron.All of the gold,silver and iron have recycling value.The gold and silver in the slag have fine particle size,which are wrapped in the ore and difficult to dissociate.Gold and silver were recovered from pyrite cinder by acid thiourea leaching-resin adsorption-acid thiourea desorption-zinc powder replacement.The effects of ore particle size,thiourea concentration,liquid to solid mass ratio,slurry p H,stirring time and slurry temperature on gold and silver leaching rate were studied in small-scale acid thiourea agitation-leaching experiment.The optimal technological parameters are determined as follows: 89% grinding ore is less than 74 μm particle size,thiourea concentration is 15 g/L,p H value is 2-3,L/S=3.0,stirring time is 7.5-8 h,slurry temperature is 50 °C,the leaching rates of gold and silver are 84.8% and 72.1%,respectively.Before and after leaching,the pyrite cinder were analysed by the methods of chemical composition,SEM and XRD,showed that the physical and chemical properties of pyrite cinder did not change,and the cinder after leaching could be used as raw material for iron and steel smelting.Resin adsorption of gold and silver in leaching solution includes static adsorption and dynamic adsorption.The effects of resin type,adsorption time,resin dosage,adsorption temperature and adsorption times on the adsorption rates of gold and silver were studied by static adsorption test.The optimal technological parameters are determined as follows: the resin type is ICM001,the resin dosage is 10 g/L,adsorption temperature is 20 °C,adsorption time is 120 min,adsorption times are twice,the adsorption rates of gold and silver are 80.9% and 99.6%,respectively.The effects of flow rate of leach solution,column height of ion exchange and leach solution capacity on the adsorption rates of gold and silver were studied by dynamic adsorption test.The optimal technological parameters are determined as follows: the flow rate of leach solution is 0.5 m L/min,the column height of ion exchange is 4 cm,the leach solution capacity is 300 m L,the adsorption rates of gold and silver are 88.6% and 94.8%,respectively.The desorption of gold and silver in acid thiourea leaching solution include static desorption and dynamic desorption.The static desorption rates of gold and silver are 21.8% and 54.0%,respectively.The dynamic desorption rates of gold and silver are up to 99%.The replacement rates of zinc powder for gold and silver are 99.5% and 98.0%,respectively.Relenishing 300 kg 5% sulfuric acid and 6.67g/L thiourea to the adsorption solution,the experiments of leaching-adsorption-desorption-zinc powder replacement were carried out under the condition of adding20 kg/t zinc powder,the leaching rate of gold and silver were 89.1% and77.2% in acid thiourea solution,respectively.The adsorption rates were93.5% and 94.4% after the leaching solution was adsorbed by ICM001 resin.The elution rate of acid thiourea was 99% and the gold and silver replacement rates by zinc powder were 99.5% and 98.0% after the resin was eluted by acid thiourea solution.The combined recovery rate of gold and silver were 81.7% and 70.7%,respectively.30 figures,19 tables,and 132 references.