石煤提钒反萃液中杂质离子对酸性铵盐沉钒的影响

Impact of Impurity Ions on Vanadium Precipitation Process of Stripping Solution from Vanadium Extraction of Stone Coal

以V_2O_5浓度为17.85 g·L^(-1)的模拟一步法石煤提钒反萃液为研究对象。以沉钒产品纯度及其中杂质离子存在状态、杂质离子存在时多聚钒酸铵(APV)晶体状况为指标,讨论了模拟反萃液中的Fe^(3+),Al^(3+),Ca^(2+),K^+等金属杂质离子对酸性铵盐沉钒效果的影响。研究结果表明:Fe^(3+),Al^(3+)妨碍沉钒过程的顺利进行且会降低产品V_2O_5的纯度,并造成沉钒母液的p H值改变,增加后续母液处理的成本和难度;而Ca^(2+),K^+仅会影响产品V_2O_5的纯度,对沉钒率和母液p H值的影响并不显著;4种杂质离子均会使产品多聚钒酸铵(APV)的晶体形貌发生改变,但是每种杂质改变APV晶体形貌的方式各异:Fe^(3+)会破坏APV晶体的完整性并改变其晶体颗粒大小,K^+破坏APV晶体的完整性;Ca^(2+)使APV晶体表面粗糙,晶体颗粒之间黏连,形成大块颗粒;Al^(3+)形成的杂多酸的非晶体状态阻碍APV晶体的顺利长大。同时得到了反萃液沉钒指标良好时,4种杂质离子浓度的控制范围:Fe^(3+)浓度应<0.1 g·L^(-1),Ca^(2+)浓度应<0.9 g·L^(-1),K^+浓度应<2.0 g·L^(-1),Al^(3+)浓度应<3.0 g·L^(-1).

Simulated stripping solution of one-step vanadium extraction from stone coal with V2O5 concentration of 17.85 g.L-1, was used as the object of the study. Based on the production purity, the existing status of impurity ions in production and the condition of APV crystal structure, when different ions existed of the impact of impurity ions in simulated stripping solution such as ICe3 ＋, A/a＋, Ca2 ＋, K ＋ on precipitation of vanadium by acidic ammonium was discussed. The result showed that with the existence of Fe3 ＋, Al3 ＋, the smooth process of the vanadium precipitation with acidic ammonium salt was influenced, and also the purity of the V2O5 was reduced. Meanwhile, the pH of mother liquor was changed by the existence of Fe3＋, Al3 ＋, which meant that the difficulty and cost of disposing of mother liquor would be increased. It also showed that only the purity of the V2 05 was influenced by the existence of Ca2 ＋, K ＋ , the precipitation rate and the pH of mother liquor were not changed remarkably. And the crystal morphology of APV was altered for the presence of Al3 ＋, Ca2＋, K ＋ , Fe3＋ though the principles of them were different. The crystal was destroyed and the size of crystal became smaller when Fe3＋ existed. And the integrity of crystal was destroyed by K ＋ . The effect of Ca2＋ in the aspect of crystal embodied in two sides： the surface of crystal was harshened and there were adhesions between crystals, followed by the growth of crystal particles. The growth of crystal of ammonium polyvanadate was impeded by Al3 ＋ which became amorphous heteropoly acid. Meanwhile, to get good vanadium precipitation effect, the four ions concentrations were optimized as Fe3＋ 〈0.1 g.L-1, Ca2＋〈 0. 9 g.L-1, K ＋〈 2.0 g.L-1, Al3＋〈 3.0 g.L-1.