Study On The Separation And Extraction Performance Of Cobalt,Nickel And Copper With The New Extraction Systems

The technology of removing the impurities of Fe,Cu,Cr and Al is relatively easy by neutralization,while the simultaneously separating Ni and Co from Mn,Mg and Ca is rather difficult when using the leach solution of Cu-Co ores and nickel laterite ores.Compared with a single system,the synergistic extraction system is more effective in the simultaneously separating Ni and Co from Mn,Mg and Ca.Among them,the separation performance of carboxylic acid/hydroxyl oxime co-extraction system is particularly excellent,but this co-extraction system is limited by its slow nickel stripping kinetics.The extraction and separation performance of Mextral 6103H/naphthenic acid co-extraction system for Co purification from leach solution of Cu-Co ores was studied in this paper based on the difference of Ni and Co stripping kinetics with carboxylic acid/hydroxyl oxime co-extraction system.The Mextral6103H/Versatic acid/Aliquat 336 and Mextral 6103H/naphthenic acid/TOPO synergistic systems which were suitable for nickel extraction and purification with leach solution of nickel laterite were obtained via adding modifier to carboxylic acid/hydroxyl oxime co-extraction system to improve the nickel stripping kinetics.The main results are as follows:（1）Results indicate that Mextral 6103H has a significant positive synergistic effect on Co extraction by naphthenic acid when Mextral6103H/naphthenic acid/isooctanol（MNI）system was used to extract and separate cobalt from impurities with leach solution of Cu-Co ores.However,the difference of stripping kinetics between Co and Ni is significant,which is benefit for the selective separation of Co over Ni.At p H=4.0,the extraction rate of Co with MNI system can reach 99%,and the separation factors of Co over Mn,Mg and Ca areβ_Co/Mn=15360,β_Co/Mg=261403 andβ_Co/Ca=67727,respectively.The slope method was used to investigate the mechanism of Co extraction by MNI system.The results show that one Co²⁺ion combined with two naphthenic acid molecules and release two H⁺,while Mextral 6103H plays a role of synergistic extraction.Based on FT-IR and ¹H NMR spectra,Co L₂（HB）₂ was inferred as the structure of cobalt complexes.The reason why cobalt is easy to be stripped is explained according to the results of mechanism study.（2）Trialkyl phosphine oxide（TOPO）could significantly improve the Ni stripping kinetics of Mextral 6103H/naphthenic acid/TOPO（abbreviated as MNT）system.The stripping rate can reach 96%after 3min.This indicated that MNT system has the great potential of industry application on separating and recovering Ni from leach solution of Ni-laterite.In theory,nickel can be completely extracted via 3-stage of extraction based on the Mc Cabe-thiele diagram.At p H=5.5,the single extraction of Ni can reach 97%,while the co-extracted Mn,Mg and Ca is only 6.0%,0.08%and 0.24%,respectively.The separation factors of Ni over Mn,Mg and Ca were as follows:β_Ni/Mn=553,β_Ni/Mg=43387,β_Ni/Ca=14463.（3）The performance of Ni stripping kinetics of Mextral6103H/Versatic 10 acid/Aliquat 336（abbreviated as MVA）system was studied,results showed that Aliquat 336 could also improve the nickel stripping performance of MNT system.The nickel stripping efficiency reached 95%after 2 min.At p H=5.0,the single extraction of nickel was95.2%,the co-extracted Mn,Mg and Ca is lower than 0.5%.This indicated that MVA system has excellent performance of separating Ni from Mn,Mg and Ca.In theory,nickel can be completely extracted via 2-stage of extraction based on the Mc Cabe-thiele diagram.The results of material balance analysis showed that the comprehensive recovery rates of Ni was91.8%.（4）The semi-continuous counter current tests with the selected systems were studied with mixer-settler.More than 99%of nickel was extracted after 2～3 stages of extraction with a p H range of 5.0～5.5.80～98%of the co-extracted Mn,Mg and Ca could be scrubbed at p H 5.0.A good stripping efficiency（>98%）of nickel could be obtained at room temperature via two stages of stripping.The results show that MNT and MVA have the potential of industrial application.（5）The slope method was used to investigate the relationship between lg[extractants]and lg D,lg[H⁺]and lg D of MNT and MVA synergistic system.The extraction mechanism of nickel with MNT and MVA systems were studied based on the FT-IR and ¹H NMR spectrum analysis.Results showed that the structure of the Ni-complex was most probably the Ni L₂（HB）₂,Among them,One nickel ion bonded with two carboxylic acid and released two hydrogen ion.During the extraction process,carboxylic acid played the role of extractants and Mextral 6103H as the synergistic reagent.Aliquat 336 and TOPO have no direct interaction with nickel and cobalt in the extraction process.The slow nickel stripping kinetics of the carboxylic acid and hydroxyl oxime synergistic extraction system most probably depends on the interfacial properties of the solutions based on the results of the mechanism study.Therefore,the improvement of the Ni stripping kinetics of the co-extraction systems is mainly attributed to the fact that TOPO and Aliquat 336 significantly reduced the interfacial tension of the selected extraction systems.（6）The effect of the mixture of TBHQ and styrolfenol on the degradation of the copper extractants were studied.The degradation rate of copper extractants decreased by 50%～60%when adding the TBHQ and styrolfenol（1:2,w/w）to the extractants.Results showed that the phenol modified reagent can reduce the degradation of the copper extractants if there was nitrate existed in the leach solutions.