Activated Carbon Adsorption To Pt,Pd,Rh In The Spent Auto-catalysts Chlorination Leach Liquor And The Effects On Leaching Rate Of Platinum Group Metals

The aqueous chlorination,because of the advantages of simple process,shorter recovery cycle,and less investment,has been used extensively as one of the most important methods recycling platinum group metals from spent auto-catalysts.At the present stage,this method has the disadvantage of the excessive amounts of precious metals in the leaching residue,which results in the slag can not be discarded.Aiming at exploring the possible reasons for this problem:the equilibrium of the platinum group metals in leach liquor and leaching residue,activated carbon adsorption to platinum group metals in primary and secondary aqueous chlorination leach liquor had been studied.On this basis,the effects of activated carbon adsorption on the leaching rate of platinum group metals had been researched in this thesis.The research results showed that activated carbon adsorption to platinum and palladium was related to the dosage of activated carbon,when the dosage of activated carbon was not seriously enough,the adsorption rate was high at first,and then slow,but the equilibrium of adsorption process could not achieve within the time of experiment design.When the dosage of activated carbon was basically enough,the adsorption rate increased and reached saturation state rapidly within the first 2 hours,adsorption rate and adsorption capacity did not change.When the dosage of activated carbon was excess,the adsorption could be finished in 2 hours(adsorption rate>99%).The activated carbon adsorption rule of rhodium was different from platinum and palladium,which was unstable.The adsorption rate of platinum and palladium improved with the increase of the dosage of activated carbon,the adsorption capacity was the opposite.The smaller the particle size of activated carbon was,the better the adsorption performance to platinum and palladium was.The adsorption rate of rhodium did not change obviously with the increase of the dosage of activated carbon.The different particle size of activated carbon was,the different the adsorption capacity of platinum group metals was,and the adsorption capacity was also influenced by the initial concentration.Within the study range of the temperature and concentration,adsorption process basically followed Langmuir equation and Freundlich equation.The introduction of activated carbon adsorption could significantly improved the leaching rate of platinum group metals in spent auto-catalysts and spent auto-catalysts pretreated,and the more the dosage of activated carbon was,the bigger the increase range of leaching rate was.