Separation And Recovery Of Vanadium(Ⅴ) And Chromium(Ⅵ) From Vanadium-containing Chromate Solution

Abstract:Vanadium-titanium magnetite ore in Panxi area of China is a typical kind of ore containing vanadium accompanyed with chromium.In the steelmaking process,vanadium and chromium therein are enriched in vanadium slag.Using vanadium slag to extract vanadium,the upper liquor after vanadium precipitation remains low concentration of V(V) and Cr(VI) which are not only valuable metals elements but also harmful elements.In order to improve the comprehensive utilization of resources and protect the environment,separation and reclaimation of vanadium with chromium from vanadium-containing chromate solution has been systematically studied in this papaer using vanadium-containing chromate solution as the sorbent and the weak-base anion resin D314as well as strong-base anion resin D231as the separation medium. The main contents of this paper are as follows:(1) Separation of vanadium from chromate solution by static ion exchange.Static sorption of vanadium and chromium with anion exchange resins were studied to investigate affecting factors such as resin type,contact time and pH value. The experimental results show that separation of vanadium from chromate solution by ion exchange is feasible.The weak-base anion resin D314can be used to separate vanadium-contained solution at pH2.5-8.5,and the separation coefficient will increase with pH,but the capacity of resin will decrese inversely.Taking consideration of separation factor with capacity, the optimal pH for separation with D314is at2.5-6.5. To separate vanadium from chromate solution with strong-base resin D231, the change of separation factor with pH is complicated. And the separation of vanadium from chromium with strong-base anion resin is proper to operate at pH7.5-9.5.(2)Separation of vanadium from chromate solution by dynamic ion exchange.The weak-base resin is used to adsorp vanadium-containing chromate solution.The experiental results show that though D314can adsorp vanadium with chromium in the vanadium-containing chromate solution,the exchange potential of vanadium is greater than the exchange potential of chromium. When the sorption of resin approaches saturation, chomium loaded on resin can be stripped by vanadate soulution,and the resin bed is purified indicating that the vanadium is completely separated from chromium.(3)Recovery of vanadium and chromium.Although both vanadate anion and chromate anion will condense inordinately with the pH changes, it is found that the vanadic acid group and chromic acid group won’t condense with each other to form heteropoly-acid.The vanadium-containing sodium chromate solution can be effectively separated and recycled with anion exchange resin after two step adsorption.The solution is first adsorped to recycle vanadium and twice adsorpted to recycle chromium.After the peak solution stripped with sodium hydroxide solution from resin loaded on vanadium was precipitated with ammonium and filtered,the cake was roasted, the product V2O5with a purity of99.8%was obtained.The peak solution stripped with NaOH/NaCIO mixed solution from resin loaded on chromium was reducted, neutralized to precipitae chromium.The cake was roasted and then washed in distilled water,after drying,the product Cr2O3with purity of98.2%was obtained.