Leaching And Separation Ofvaluable Metals From Spen Acrvlonitrile Catalyst

Nowadays spent catalyst produced all over the world is about 50-70 ton per year,while 10 ton per year in china.If these valuable metals in spent catalyst can't be recycled,a lot of resourse will be wasted,which may also cause enviromental pollution.Molybdenum,bismuth and nickel are important raw material for petro-chemistry and pharmacy industry.Mineral resources become less and less,so the utilization of secondary resources become more and more important.Recycling valuable metals from spent catalyst will help human get economic and environmental benefits.Various of recycling methods for valuable metals from spent catalyst are summarized.One kind of spent acrylonitrile catalyst is used for this research.Based orn the analysis of physicochemical property and chemical component,different methods are chosen to recycle different metals,which can provide reference for industrial application.The main research contents and results are as follows.Acid leaching and hydrolyzing is used to recycle bismuth and nickel from spent acrylonitrile catalyst in laboratory.Hydrolyzing of bismuth nitrate after acid leaching can separate bismuth and nickel in acid leaching solution.Factors like temperature,acid leaching time,acid concentration,the liquid to solid ratio and stirring condition is focused on during acid leaching,while temperature,hydrolyzing time and the liquid to liquid ratio is focused on during hydrolyzing.Under the optimal acid leaching condition of temperature 80oC,acid leaching time of 1.5 h,acid concentration of 3 mol/L,liquid to solid ratio 5,stirring condition 10,97.49%of bismuth and 82.81%of nickel can be dissolved by nitric acid.Under the optimal hydrolyzing condition of temperature 80?,hydrolyzing time of 60 min,liquid to liquid ratio 8,89.57%of bismuth precipitate while 94.86%of nickel remain in the hydrolyzing solution.In total,above 75%of bismuth and nickel can be recycled.The Bi/Ni value increase from 0.297(raw material)to 136.76(hydrolyzing residue),while the Ni/Bi value decrease from 3.37(raw material)to 0.007(hydrolyzing solution),which means the separation of bismuth and nickel is efficient.Acid leaching and alkali leaching is used to recycle molybdenum.Under the optimal acid leaching condition of bismuth and nickel,40%of molybdenum can leach out and the rest are in.the acid leaching residue.Factors like temperature,alkali leaching time,alkali concentration,the liquid to solid ratio and stirring condition is focused on during alkali leaching.Under the optimal alkali leaching condition of temperature 80?,alkali leaching time of 75 min,alkali concentration of 1 mol/L,liquid to solid ratio 5,stirring condition 10,86.06%of molybdenum can be dissolved by sodium carbonate.But in total,only about 50%of molybdenum can be recycled by this method,which is higher than the recovery rate of direct alkali leaching method.Roasting and water leaching is used to recycle molybdenum.High-temperature roasting change the properties of spent catalyst and lost some metal.Water leaching of roasting residue can recycle molybdenum,while most of the bismuth and nickel can't leach out.Factors like temperature,roasting time and the mole ratio is focused on during roasting,while temperature,water leaching time,the liquid to solid ratio and stirring condition is focused on during water leaching.Under the optimal roasting condition of temperature 800?,roasting time of 2 h,mole ratio 1 and the optimal water leaching condition of temperature 90?,water leaching time of 5 h,liquid to solid ratio 6,stirring condition 10,88.25%of molybdenum can be recycled.Less than 1%of bismuth and nickel is dissolved in water,while more than 99%of bismuth and 70%of nickel is recycled in the water leaching residue.This means the separation of molybdenum is efficient.So bismuth and nickel in this kind of spent acrylonitrile catalyst can be recycled by acid leaching and hydrolyzing method,while molybdenum can be recycled by roasting and water leaching method.