| The traditional vanadium extraction process by means of sodium roasting-water leaching seriously pollutes the environment with a large amount of gas emissions such as Cl2and HCl. What’s more, this process has stricter requirements to the quality of vanadium raw material, for example, the recovery rate of vanadium is low when it is used to treat the vanadium slag with high calcium content, and the waste water and residue after vanadium extraction costs highly to be treated comprehensively.In order to solve above problems, a novel process of calcium roasting-acid leaching-hydrolyzed precipitation from vanadium slag is proposed in this paper. This process achieves comprehensive utilization of waste residue for no sodium salt contained in the slag after acid leaching, and the solution can be recycled since there is not ammonium salt in solution after vanadium precipitation. Additionally, there is no waste discharging during the entire vanadium extraction process. Hence, this technology ultimately reaches the goal of clean vanadium extraction.Calcified roasting experiment indicates that additive amount of CaO, roasting temperature and roasting time have great influence on vanadium leaching rate. The appropriate conditions are6%CaO, roasting temperature of900℃, roasting time of2h, roasting vanadium particle in the range of48～75μm. Under these conditions, vanadium leaching rate can reach91.25%.In acid leaching process, experiment studies focus on the effects of particle size, leaching acidity, temperature, time, liquid-solid ratio and stirring speed on vanadium leaching rate. It comes to the conclusion that the leaching rate is favorable under the state of particle size of roasted slag48～75μm, pH2.5, temperature65℃, liquid-solid ratio4for90min, and the effect of stirring speed on vanadium leaching rate is not obvious.The study on phosphorus removal in the acidic leaching solution is not reported in the previous literature. This paper comes up with a method of phosphorus removal in acidic solution. Addition amount of phosphorus removal agent, temperature and time have been investigated. It comes to appropriate conditions:the addition amount4g of per100mL leaching solution, temperature55℃, time30min. Under these conditions, phosphorus removal rate and vanadium loss rate are48%and1.82%respectively.This paper uses hydrolysis precipitation of vanadium process, and the effect of the amount of starting vanadium solution, acidity, temperature and time on the rate of precipitating vanadium are investigated. It comes to appropriate conditions:addition amount of vanadium solution25%, temperature95℃, pH=1.8, time180min. After calcining the hydrolyzing product to remove crystalline water, the final product purity of vanadium pentoxide is95.48%, and vanadium recovery of the entire process is83.44%. |
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