Study On Comprehensive Recovery Of Valuable Metals In Zinc Leaching Residue

The comprehensive recovery of the valuable metals in zinc leached residue has theimportant economic environment and social significance, because there have a lot ofvaluable metals contained in zinc leached residue, such as lead, silver, copper, indium,germanium and gold. The zinc leached residue used in this research containing lead4.42%, silver185.7g/t, zinc5.62%, and has a higher recovery value. Based on literaturematerials investigation and analysis of characteristics for zinc leached residue, a newprocess for comprehensive recovery of valuable metals in zinc leached residue is putforward. This process consists of leaching by chloride, purification of impurity andmetals separation.It selected NaCl+HCl and NaCl+H₂SO₄as the two leaching agent throughcompared experiment. The effects of temperature on leaching rate of lead, silver, andzinc was studied. The temperature for leaching should be95. The leaching tests withNaCl+HCl and NaCl+H₂SO₄as leaching agent were optimized respectively byorthogonal. The leaching rate of lead, silver, and zinc were98.17%,93.05%and94.75%respectively at the optimal conditions. When taking NaCl+H₂SO₄as leachingagent, the leaching rate of lead, silver, and zinc could be reached93.65%,92.42%and81.75%respectively at the optimal conditions.The results of dynamics had shown thatleaching process of lead and sliver were all diffusion control and apparent activationenergy of lead, sliver were1.043kJ/mol and8.913kJ/mol respectively.Neutralizing hydrolysis process and jarosite process were used in purification ofimpurity for removing iron. The iron removal rate could reach more than97%when thepH=2at95and the loss rate of lead, silver, zinc were little using neutralizinghydrolysis process. Under the condition of pH=1.5, the optimum temperature of jarosite process was95and the iron removal rate was96.87%.The precipitating of lead, silver and zinc using sulfide agent was research in metalsseparation and enrichment test and the test condition was optimized by orthogonal. Theprecipitation rate of lead and silver were95.11%and97.61%respectively in theoptimum experimental condition. Percentage of lead concentrate obtaining by sulfideprecipitation process was67.5%which met the national secondary standard and thecontent of silver was2266.07g/t. The influence of pH and addition of Na2S on zincprecipitation rate was researched. The result showed that optimum pH was3.5andaddition of Na2S was1.4times as much as theoretical amount and the precipitation rateof zinc was closed to99%.The study about NaCl solution regeneration and recycling was showed that NaClin system could be recycled.