| High-chromium vanadium-bearing titanomagnetite in Hongge District is a giant iron-polymetallic deposit containing vanadium,titanium,chromium and other valuable elements.For processing high-chromium vanadium-bearing titanomagnetite,the existing technologies are unsuitable due to their low recoveries of valuable metals,high energy consumption,and serious environmental pollution.Therefore,a new process for comprehensive exploitation of high-chromium vanadium-bearing titanomagnetite concentrates has been developed by our research group.The new process involves several steps:partial reduction of the concentrates,magnetic separation,hydrochloric acid leaching of the titanium-bearing tailing.The obtained leach solution from the new process is the high-acidity chloride solution containing high concentrations of many impurities.The separation of V,Cr,and Fe as the valuable metals from the chloride solution which contains many impurities such as Ca,Mg,Al,Mn,Ti and Si has not been reported.In this thesis V,Cr,and Fe in the chloride solution selectively separated from impurities was systematically investigated.A novel process for the effective recovery of iron,vanadium and chromium from the chloride solution was developed.The research reults are listed as follows:1)The selective separation of vanadium and chromium has been studied.D2EHPA was selected as the extractant for the vanadium separation from iron and chromium.The effects of various parameters on vanadium separation were investigated.Under the optimal extraction conditions,the extraction of vanadium,iron,and chromium under two stages was 97.1%,9.8%and 7.9%,respectively.Vanadium could be partially separated from iron and chromium.As the concentration of iron is higher than that of chromium,the separation of chromium from iron has been investigated.The solvent extraction method was investigated and the effects of extractant,pH,concentration of iron,reducing agent and masking agent on chromium extraction were studied.The precipitation methods were also investigated.However,the investigation shows that chromium could not be separated from the chloride solution containing 36?39 g/L iron.2)As the existence of large amounts of iron in leaching solution adversely affected the subsequent recovery of vanadium and chromium,iron was firstly removed.A synergistic extraction system for removing iron from the high-acidity chloride leach solution was developed.TBP-MIBK synergistic system was suitable for iron removal due to its high extraction efficiency,fast phase separation,and negligible extraction of other metal ions.The effects of various parameters on the extraction of iron were investigated.Under the optimum extraction conditions,the extraction of iron under one stage was 86.7%.The effects of various parameters on the stripping of iron were investigated.Under the optimum stripping conditions,the stripping of iron under one stage was 91.6%.The mechanism of iron extraction using synergistic system was studied,and the extraction ability was significantly improved due to the solvating ability of MIBK.3)After iron was removed,a synergistic extraction process for recovering vanadium from the high-acidity chloride leach solution was developed.Aliquat 336-TBP synergistic system was suitable for vanadium recovery due to its fast extraction kinetics,negligible extraction of other metal ions,and ready stripping of vanadium.The effects of various parameters on the extraction of vanadium were investigated.Under the optimum extraction conditions,the extraction of vanadium under three stages was 90.2%.The effects of various parameters on the stripping of vanadium were investigated.Under the optimum stripping conditions,the stripping of vanadium under one stage was 92.4%.The mechanism of vanadium extraction using synergistic system was studied,and the extraction ability was significantly improved due to the solvating ability of Aliquat 336.4)After iron was removed and vanadium was recovered,a synergistic extraction system for recovering chromium from the chloride leach solution was developed.D2EHPA-isooctanol synergistic system was suitable for chromium removal due to its high extraction efficiency,fast phase separation,and ready stripping of chromium.The effects of various parameters on the extraction of chromium were investigated,and the optimum extraction conditions were obtained.The effects of various parameters on the stripping of chromium were investigated,and the optimum stripping conditions were obtained.The mechanism of chromium extraction using synergistic system was studied,and the extraction ability was significantly improved because isooctanol destroyed the dimer structure of D2EHPA,providing more extraction sites.5)After iron was removed and vanadium was recovered,in the real chloride leach solution,some components such as Ca,Mg,Al,Mn,Ti and Si were leached together with chromium.D2EHPA-isooctanol synergistic system shows high extraction ability of chromium.However,chromium can not be selectively separated by the D2EHPA-isooctanol synergistic extractant.Nitrate ion was added to form the complex compound with chromium,changing the species of chromium.Therefore,chromium can be selectively separated by Cyanex 923.The effects of various parameters on the extraction of chromium were investigated,and the optimum extraction conditions were obtained.The effects of various parameters on the stripping of chromium were investigated,and the optimum stripping conditions were obtained.Ca,Mg,Al,Mn,Ti and Si could not decrease the extraction of chromium,and chromium could be effectively stripped from the loaded Cyanex 923. |
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