Green separation and recovery of molybdenum from tungstate solution achieved by using a recyclable vulcanizing agent
2021
Du, Jiawei | Li, Jia | He, Dongmei | Xu, Miaoyang | Zhang, Guiqing | Cao, Zuoying | Wu, Shengxi
Separation of molybdenum (Mo) from tungstate solution has become a bottleneck issue in tungsten (W) metallurgy and did hinder the development of high purity tungsten materials. The traditional Mo removal methods using Na₂S, NaHS as vulcanizing reagent are suffering the environmental issues of toxic H₂S gas and molybdenum trisulfide (MoS₃) sludge. To achieve the green separation of Mo from tungstate, a recycle vulcanizing reagent, ethyl thioglycolate (ET) was introduced for the vulcanization of molybdate (MoO₄²⁻) from tungstate solution. The vulcanization of Mo by ET, the selective extraction of vulcanized MoO₄²⁻ from tungstate and the recycling of ET were systematically investigated. The results demonstrated that a high vulcanization efficiency of >98% for MoO₄²⁻ was achieved and more than 97% of Mo was removed and recovered via vulcanization followed by single-stage solvent extraction, producing a purified tungstate solution with Mo < 5 mg/L (Mo/WO₃ < 1 × 10⁻⁴) and a byproduct of molybdate solution with 4.1 g/L Mo and <0.01 g/L WO₃ under optimal conditions. Additionally, ET exhibited an ideal cycling performance, the regeneration efficiency and the recycled vulcanization efficiency were >95% and >98%, respectively. Compared with traditional vulcanizing reagents, introduction of ET eliminates the emission of toxic H₂S gas, significantly decreases the cost caused by the unrecyclable reagent, and transferred the MoS₃ sludge into a valuable crude Mo byproduct, which provides an alternative for the green separation and recovery of Mo from tungstate.
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