A clean ammonia-free vanadium recovery process for titanium-white waste using D2EHPA extraction, hydrogen peroxide stripping, precipitation and calcination to produce V2O5

Traditional vanadium extraction process, which involves H2SO4 stripping after solvent extraction followed by ammonium vanadate precipitation, faced the issues of large amount of reagent consumption and discharge of ammonia contaminated wastewater. Hydrogen peroxide stripping and precipitation of vanadium products by heating process was considered as a novel alternative for H2SO4 stripping - ammonium vanadate precipitation route due to the ammonia-free wastewater and high efficiency. However, it was found that the V stripping efficiency was in the range of 54.9% similar to 97.7% during the pilot test of 3-stage counter-current stripping, which was extremely unstable, as the high stripping efficiency (>95%) could only be achieved in a very short operation time (within 30 s). To solve these issues, the ion species transformation and the stripping mechanism of V with H2O2 were systematically investigated. In this study, experimental results demonstrated that re-extraction led to a decrease of stripping efficiency. The use of D2EHPA alone without TBP as a modifier had a clear effect on prolonging the duration of maximum stripping efficiency at the optimal conditions so that the continuous operation of the pilot test was possible. The optimal stripping conditions were a molar ratio of H2O2:V of 4:1, phase ratio (O/A) of 3:1, temperature of 20 degrees C, stripping time of 8 min and the operation time of 3 min which resulted a similar to 98% V stripping efficiency. In addition, the precipitation of vanadium products by heating, proposed in this work was a cleaner and more efficient V precipitation procedure that didn't require any reagents and produced no wastewater. Eventually, heating the strip liquor at 100 degrees C for 1 h resulted a precipitation efficiency of 96% V. The intermediate precipitated products (V5O12 center dot 6H(2)O and V10O24 center dot 12H(2)O) were roasted to obtain V2O5 with a purity of >99%. Finally, the new process saves 885.2 $/t V2O5 compared with the traditional process according to the cost analysis. The research results provide an efficient, clean and economical process for recovering V2O5 from titanium-white waste.

Automated summary

The study proposes an efficient, clean, and economical process for recovering V2O5 from titanium-white waste through hydrogen peroxide stripping and precipitation of vanadium products by heating. Experimental results show that the use of D2EHPA as a modifier prolongs the duration of maximum stripping efficiency, enabling continuous operation.