Cleaner production of ammonium poly-vanadate by membrane electrolysis of sodium vanadate solution: The effect of membrane materials and electrode arrangements

In this study, we put forward a clean and complete process of V2O5 production from vanadiumcontaining solutions. It features membrane electrolysis for V/Na separation and AMV precipitation. With the aid of membrane electrolysis, the vanadium and sodium in the leaching solution can be directly separated using membrane-electrolysis. Meanwhile, the NaOH in the cathode chamber can also be recycled for vanadium slag decomposition. The electrolysis systems and membrane types have been investigated. It was found that 3-chamber electrolysis was much more energy efficient than the traditional 2-chamber electrolysis, while F8080 membrane showed a better separation efficiency than N117, CMI7000, LF0014 membrane. The main electrolysis parameters were also investigated, and it appeared that high current density and electrolyte temperature, as well as low initial cathodic NaOH concentration were beneficial for the separation efficiency. Under the optimum electrolysis conditions the electricity consumption of producing 750 kg V2O5 and 1000 kg NaOH and was 2151 kW h, with a current efficiency of 92.9%. During the vanadium precipitation process, NH4VO3 was used as precipitant for the first time, avoiding the introduction of impurity ions, such as Cl-, SO42- or Ca2+, realizing zero waste generation by source. A low-sodium medium product of (NH4)(2)V6O16 was precipitated at pH between 2 and 4. The commercial quality V2O5 product could be obtained by calcination and the ammonium slat was recycled for precipitation. This method can achieve the clean production of V2O5 with no wastewater or solid waste generated through the whole process. (C) 2019 Elsevier Ltd. All rights reserved