An effective and environment-friendly method for preparing NaVO 2 , which can be used as an energy storage material, from Na 2 CO 3 roasted vanadium-chromium slag was proposed using water as the leaching medium. Vanadium-chromium slag with 30 % Na 2 CO 3 was heated in air and argon atmospheres from 30 °C to 1000 °C, respectively. The results show that vanadium compounds converted to NaVO 3 while chromium compounds to Na 2 CrO 4 under air. NaVO 3 and Na 2 CrO 4 were water-soluble making the separation of vanadium and chromium complicated. NaVO 3 and Na 2 CrO 4 were water-soluble making the separation of vanadium and chromium complicated. Heating vanadium-chromium slag in an argon atmosphere caused Fe 2 VO 4 to react with Na 2 CO 3 , forming NaVO 2 and NaFeO 2 below 1000 °C. However, chromium compounds unreacted in argon. NaFeO 2 was insoluble, while NaVO 2 was water-soluble with a leaching efficiency exceeding 70 %. Notably, the characteristic peak of V(III) in NaVO 2 was first found to be −532.00 ppm by the liquid 51 V NMR spectrum. This method represents a novel, green strategy for the resource utilization of vanadium-chromium slag, involving Na 2 CO 3 roasting in an argon atmosphere to produce NaVO 2 . It offers a promising approach to reduce the cost of NaVO 2 battery production and support its commercialization.
Yongzheng Jia,Yu Qing,Baoyan Feng,Yiwei Zhong,Lei Dai,Mingyong Wang
Green separation and efficient extraction of vanadium and chromium from vanadium-chromium leaching solution are serious challenges for the utilization of chrome-vanadium slag. A green sucrose reduction-H 2 O 2 selective oxidation route is proposed for deep separation of vanadium and chromium from vanadium-chromium leaching solution based on different redox properties. Eh-pH diagram of V-Cr-H 2 O system and existence forms of vanadium and chromium ions are calculated. Obvious difference of redox properties between V(V) and Cr(VI) exists in acidic environment. The dependences of selective separation on pH for reduction, temperature, m (sucrose) /m (Cr(VI)) and n (H2O2) /n (V(V)) are studied. The concentration ratio of vanadium to chromium in solution after selective separation of chromium decreases from 1.6 to 0.06. The extraction ratios of Cr 2 O 3 and V 2 O 5 are 96.3% and 93.8%, respectively. The redox behavior of V(V) and Cr(VI) is revealed. Cr(VI) and V(V) are reduced to Cr(Ⅲ) and V(IV) by 5-hydroxymethylfurfural, a hydrolysate of sucrose, and then V(IV) is selectively oxidized to V(V) by H 2 O 2 . Cr 2 O 3 ·n(H 2 O) and ammonium polyvanadate obtained by hydrolysis and ammonium precipitation are calcined to Cr 2 O 3 and V 2 O 5 , respectively. Cr 2 O 3 with the purity of 99.4% can be used as high-quality pigment. The purity of V 2 O 5 meets the requirements of YB/T 5304–2011 for 98 V 2 O 5 .
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