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Research of the Aqua Regia Insoluble Residue Bearing Ruthenium Treated by the Alkaline Heat Pressure

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Tutor: YangTianZu
School: Central South University
Course: Non-ferrous metallurgy
Keywords: alkaline heat pressing oxidative leaching,oxidant,aqua regiainsoluble residue,re
CLC: TF838
Type: Master's thesis
Year:  2013
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Abstract:
ABSTRACT:The ruthenium in aqua regia insoluble residue is a rare precious metal and it is used to the extraction by the alkali fusion method.However,the crucible is easily corroded during the pyrometallur-gical smelting process,and this method has some disadvantages of high energy consumption,difficult to solve ruthenium completely and smelting slag cumbersome treatment and so on.In this work,the alkaline pressure oxidative leaching process is proposed to deal with aqua regia insoluble residue according to thermodynamic analysis for the current situation to treat it diffcultly.The main research content and conclusions are as follows:The method of alkaline heat pressing oxidation with sodium chlorate and sodium hypochlorite as oxidant is used to treat aqua regia insoluble residue in order to get alkaline leaching solution containing ruthenium and the oxidation residue bearing Lead and bismuth,which achieves the initial separation of ruthenium,lead and bismuth in the aqua regia insoluble residue.Meanwhile the stirring rate, reaction temperature, the concentration of leaching agents, reaction time and liquid-solid ratio etc have been investigated detailedly by experiment and the optimum conditions of aqua regia insoluble residue treated by alkaline heat pressing oxidation method relying on sodium chlorate or sodium hypochlorite as the oxidant in the case of stirring were respectively determined as follows:the reaction temperature being220℃,the reaction time being4h,the sodium hydroxide concentration being2mol/L,the sodium chlorate concentration being lmol/L,the liquid to solid ratio being120:1and the reaction temperature being200℃,the reaction time being4h,the sodium hydroxide concentration being2mol/L,the sodium hypochlorate concentration being0.485mol/L,the liquid to solid ratio being120:1.The leaching rate of ruthenium is able to achieve91.24%and99.75%respectively under their optimum conditions.When the amount of ethanol or hydrazine hydrate served for reducing agent is respectively10.13and50.51times of their theoretical amount,the reaction temperature of them25℃and80℃respectively,the time is in around120min and the initial pH of alkaline lixivium is approximately equal to13, the ruthenium contained alkaline lixivium will availably convert into dark brown precipitate and achieve effectualy the recovery of ruthenium based on chemical properties of ruthenium in the alkaline leaching solution easily revered to Ru(OH)4.The results have shown that the ruthenium of aqua regia insoluble substance treated through the alkaline heat pressing oxidation method is effectively dissolved, and the method can solve that the ruthenium isn’t completely melted out by the pyrometallurgical smelting process and equipment corrosion such as problems.
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