Slag Modulation and Trapping Mechanisms for the Recovery of Platinum Group Metals via Iron:A Theoretical Study
The recycling of platinum group metals(PGMs)from spent catalysts not only alleviates the contradic-tion between supply and demand,but also guarantees the demand for metals in the national strategic reserve,which is of great strategic significance.Automotive spent catalysts have complex compositions,and the process of capturing PGMs by pyrometallurgical methods requires a large number of experiments in order to obtain the opti-mal slag and thus improve the recovery of PGMs.In this work,the theoretical calculations of FactSage were used to simulate the slag reaction equilibrium for the purpose of slag optimization.The results of FactSage calculations showed that when the additives CaO,SiO2,Na2CO3,and CaF2 were added at 40%,15%,30%,and 5%of the mass fraction of the spent catalyst,respectively,the slag properties were optimal,i.e.,the complete temperature of the slag phase was 1 330℃,and the viscosity was 1.92 Pa·s.We also investigated the mechanism of iron trapping of PGMs in spent automobile catalysts in conjunction with DFT calculations.The results showed that Rh forms an alloy structure with δ-Fe in a substitution-doped type at high temperatures exceeding 1 390℃;Pd can only form an alloy with γ-Fe in a substitution-doped manner in the temperature interval from 912℃to 1390℃;and most of the Pt is trapped and alloys with γ-Fe in a substitution-doped manner in this temperature interval.When the temperature is lower than 912℃,Rh and Pt are again trapped by α-Fe and form an alloy.However,γ-Fe-Pd alloys form α-Fe-Pd with decreasing temperature,and the alloy structure of α-Fe-Pd is unstable,which leads to the precipitation of Pd from the Fe phase and reduces the recovery rate of Pd.In sum-mary,the present study provides an efficient slag optimization method for the pyrometallurgy capture of PGMs.
spent automotive catalystsplatinum group metal recoveryiron trapslag designmechanistic study
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维普
