Simultaneous stripping and regeneration of chelate structure of vanadium through vanadium reduction and conversion in vanadium-bearing shale extraction

Chelating extractants have shown excellent selectivity in vanadium extraction. Nevertheless, the resulting extraction complex is stable, making the stripping of chelating extractant a challenge. The H2C2O4-H2SO4 system was proposed to stripping vanadium from the loaded organic phase of chelating extractant Mextral 984 H. The effects of process parameters of H2C2O4-H2SO4 system on the vanadium stripping percentage was investigated. The results show that the single-stage vanadium stripping percentage reached 93.12%, and the vanadium concentration in the single-stage stripping solution reached 13.44 g/L under optimum conditions: the H2SO4 concentration of 1.87 mol/L, the H2C2O4 concentration of 0.16 mol/L, the temperature of 80 degrees C, the time of 30 min, and phase ratio(O/A) of 4:1. In addition, the high extraction efficiency (>85%) was maintained after 10 cycles, indicating that the developed system can be used in the Mextral 984 H stripping system. The mechanism of stripping was also analysed using FT-IR and H-1 NMR combined with thermodynamic and quantum calculations. It was summarized that after H2C2O4 reduces V(V) to V(IV), H+ can replace V(IV), the free V(IV) in organic phase is more prone to coordinated with C2O42- and SO42- and then goes into aqueous phase. Thus the stripping and regeneration of the loaded organic phase of Mextral 984 H can be occurred simultaneously. Meanwhile, the introduction of H+ can speed up the stripping process. The innovative method of the reduction stripping of vanadium is proposed in the black shale extraction field.

Automated summary

In this study, a stripping method was proposed for vanadium extraction using the H2C2O4-H2SO4 system to strip vanadium from the chelating extractant. The results showed that under optimized conditions, a high vanadium stripping percentage and concentration in the stripping solution could be achieved. Furthermore, the extraction efficiency remained high even after multiple cycles, indicating the feasibility of this method. The mechanism of stripping was analyzed, and it was found that H2C2O4 and H+ played important roles in the reduction and replacement of V(IV).