Study On Extraction And Separation Of Cobalt, Nickel And Manganese From Residue Of Benzoic Acid Production Process

The metals of Co, Ni and Mn in the residue are mainly come from the catalyst added during the benzoic acid production process. Considering the shortage of metal resources and the urgent requirement for environmental protection in China, the separation and recovery of the metals in the residue is very necessary. In this paper, comprehensive utilization of residue from the industrial production of benzoic acid was explored.The amounts of Mn, Co and Ni in the residue were determined and the effects of acid type, acid concentration and H2O2 mass fraction on the extraction recovery efficiency of Mn, Co and Ni were studied. Mn was separated through the ammonia complexing precipitation, while Co and Ni in the filtered solution were extracted by extraction agent P507. Moreover, the influences of pH of equilibrium aqueous phase, saponification ratio of P507, volume fraction of P507 and phase ratio (A/O) on metal extraction efficiency, separation factor β and the best stripping conditions of the organic phase cobalt were investigated.The residue from industrial production of benzoic acid was treated by using dry and wet digestion methods, separately The results showed that the wet digestion is better than the dry. Then the metal contents were determined by using atomic absorption spectrophotometer, and the mass fraction of Co, Ni,Mn was 0.3071%,0.0155% and 0.0850% respectively.The Co, Ni and Mn in the residue from the production process of benzoic acid were recovered by solvent extraction. Effects of acid, H2SO4 concentration, H2O2 concentration on the extraction recovery of Mn, Co and Ni were studied.The results showed that, when the concentration of H2SO4 was 2.0mol/L and the mass fraction of H2O2 is 25%, the recovery efficiency of Co, Ni and Mn was reaching 87.77%、86.50% and 88.59% respectively.The three metals of Co, Ni and Mn were separated step by step.First of all, with excess ammonia to the extraction, the Mn was formed to Mn(OH)2 which can be separated from Co and Ni. The precipitation rate of Mn can reach 93.67%, and the recovery rates of Co and Ni in the filtrate are 92.08% and 98.52%. P507 was chosen as the primary extractant to separate Co and Ni, using kerosene as solvent, adding a small amount of TBP to reinforce the phase effect. By comparing the multi-group experiments, the finally optimal conditions for separation of Co and Ni is 15% P507+5% TBP+80%, pH=4, saponification rate of 60%, A/O=1:1.In this study, the effective separation of Co and Ni was realized, with the extraction rate higher than 80%. The optimal conditions for stripping cobalt in organic phase are as follows:sulfuric acid concentration at 2.0 mol/L, anti-extraction ration of 1:1, and the stripping rate of cobalt was higher than 94%.