Studying On Leaching Gold With Non-Cyanide Reagents And Process Kinetics From Smelting Industrial Residue

To solve the problem of the contradiction between the increasing need of gold and its limited resources, it is necessary for us to make use of the secondary resources such as tail , waste slag, devil liquor and so on ,besides seeking for the new mineral resources. Cyanidation leaching gold can produce much cyanide waste water,which can do great harm to the enviornment,so the method is limited. Therefore to get the succedaneum for the cyanide is in great need .At present the reaserch of non-cyanidation leaching gold is mainly focusing on the methods of thiourea, thiosulfate,chlorine and bromine;These methods have the features that the speed of leaching gold is fast, furthermore, the environment polution is becoming little.The subject investigated of the reasearch task is industrial residue,aiming at setting up the operable technology way of extracting gold from the industrial residue using non-cyanidation,screening a effective method of leaching gold from industrial residue and ensuring the technology conditions, doing the kinetics experimental reserch of leaching gold in order to extract gold cleanly and change waste into treasure.In this thesis firstly the screened leaching agent is thiourea,and the aiming data point to leaching gold rate. The single element test and orthogonal test are used to observe and study how such factors as thiourea concentration, leaching time,H2SO4 dosage,liquid-to-solid ratio influence on leaching gold rate in industrial residue.From the variance analysis of orthogonal test we can get the result that the main factor is thiourea concentration,secondly the leaching time and liquid-to-solid ratio ,while the H2SO4 dosage have the least influence. The accompanying mineral such as copper,zinc may have the disadvantageous influence on the gold leaching, so the experiment of dilute sulfuric acid pre-leach and calcination anticipation have been made before leaching gold with thiourea,and the result shows that the gold leach rate after pre-leach goes up 0.32% , and that after calcination anticipation goes up 1.3%,so the existence of copper and zinc in industrial residue inflence little on leach gold .Eventually we know the fine technological conditions: thiourea concentration 15 g·L-1,H2SO4 dosage of 55ml,leaching time of 3h,liquid -to- solid ratio is 3. On the above conditions the gold leaching rate can go up to 93.50%.Secondly we screen ammonium thiocyante as leaching agent,and we study how the rate of leaching gold is affected by the factors of ammonium thiocyante concentration, manganese consumption accounts, pH value,liquid-to-solid ratio and leaching time in the conditional experiments. And the result shows that the best leaching condition is that ammonium thiocyante concentration is 6%,the manganese consumption accounts is 7.5% of minral powder,the ph value is 1,the liquid-to-solid ratio is 2 ,and the leaching time is 5h. On the condition the leaching gold recovery rate can reach 81%.Ammonium thiocyante is enventually chosen as leaching agent in the experiment to do the kinetics research of leaching gold on the basis of comprehensive thinking about the factors of leaching gold rate ,the difficult degree of reaction conditions control and production cost by the reaserch of leaching gold experiment using thiourea and ammonium thiocyante as non-cyanide leaching agent.In the experiment we observe and study that how ammonium thiocyante concentration and chemical reaction temperature affect the leaching gold rate ,and make sure that the order of reaction is 0.4. When the reaction activation energy is 15.80kJ·mol-1,we can get the chemical reaction rate constant of k=0.3113·e-1900/T in the reaction of ammonium thiocyante extracting the industrual waste slag.According to the reaction activation energy data we can originally judge that the rate determining step in the reaction of ammonium thiocyante leaching gold is solid-phase diffusion.Therefore, the kinetics equation of ammonium thiocyante leaching gold isThe thesis puts forward the rational technological way of extracting gold from smelted industrial residue using the ammonium thiocyante as leaching gold agent after the research on physicochemical property of waste slag,systematic leaching gold experiment ,leaching kinetics.We can get a program to put smelting tailing into rational use.