A novel and sustainable technique to precipitate vanadium from vanadium-rich solutions via efficient ultrasound irradiation

During the traditional acidic ammonium salt precipitation process of vanadium, a large amount of ammonium salt is commonly consumed, hence high-concentration ammonia nitrogen wastewater is inevitably produced, which poses a great threat to the environment. In this investigation, a novel and environmentally friendly technique adopting ultrasound to strengthen the ammonium salt precipitation process of vanadium is firstly put forward and investigated. Under the optimal conditions, the precipitation percentage of vanadium and V2O5 purity of the ultrasound precipitation (UP) products can reach 99.67% and 99.50%, respectively, which is similar to the results of the regular precipitation (RP) process. However, the most obvious advantages of the former are that the reaction time can be dramatically shorten from 25 min to 5 min and the amount of ammonium salt consumption can be decreased by as much as 87.5% with the intensification of ultrasound. Both UP and RP methods are capable of preparing pure (NH4)2V(6)O(10), but the UP products exhibit more uniform size distribution and smaller mean particle diameter (9.88 mu m vs 46.2 mu m) compared to the RP products. The microstructure analysis demonstrates that the UP products have more regular crystal shape, where the fine flake crystals intercalate with each other in comparison to the latter. The precipitation kinetics analysis demonstrates that the intensification of ultrasound mainly embodies in the increase of the collision frequency of NH4+ and vanadium, which further accelerates the nucleation and growth rate of the precipitated crystals. Particularly, the residual NH4+ concentration in the precipitated mother liquor can be observably reduced from 24449 mg/L to 1083 mg/L using the UP method. In short, the proposed technique can definitely promote the green and sustainable development of vanadium extraction industry.