Abstract
The feasibility and kinetics of vanadium (V) recovery from oxidative leaching of low-grade stone coal using MnO2 were investigated. Oxidative leaching processes (OLPs) were designed using response surface methodology (RSM) based on the central composite design (CCD) model. The results show that the order of factors that influence OLPs is leaching temperature > H2SO4 concentration > leaching time > MnO2 dosage. The interaction between leaching temperature and H2SO4 concentration on the OLP is the most significant. Vanadium leaching efficiency was 89.3% using 31% H2SO4 and 3% MnO2 at 90 °C for 7.9 h. The kinetics of V leaching from stone coal show that the leaching rate is controlled by chemical reaction through a layer according to the shrinking core model and the activation energy is 55.62 kJ/mol. A comparison of the SEM-EDS results of minerals before and after leaching confirms that the muscovite structure was significantly destroyed and V and aluminum (Al) were effectively dissolved during the OLP.
Highlights
Vanadium (V) is commonly used in the production of alloy steels, catalytic agents, and vanadium batteries
central composite design (CCD) is more effective than Box–Behnken design (BBD) in reflecting the interaction of different variables while the numbers of variables and levels are high
The optimum condition for V leaching efficiency was obtained by applying the response surface methodology (RSM), as shown in Table 3 case (1)—three validation experiments confirmed that the V leaching efficiency was 88.7%, 90.1%, and 89.0% under conditions of 31% H2SO4 at 90 °C, leaching time of 7.9 h, and 3% MnO2, which are consistent with the predicted value of 90.2%
Summary
Vanadium (V) is commonly used in the production of alloy steels, catalytic agents, and vanadium batteries. Direct acid-leaching technology has become a research hotspot for extracting V from low-grade stone coal because of its simple process, environmental protection, solid experimental research foundation, and industrial application prospects [8,9]. Oxygen pressure leaching is not cost-effective for low-grade stone coal and is only applied to stone coal with a grade higher than 1% to generate an industrially recoverable value [6]. The characteristics of stone coal resources in China and terms of environmental protection and operation make V extraction feasible when assisted by oxidant leaching. Shrinking core models for spherical particles of a constant size based on the Arrhenius equation are empirically used to study the kinetics of leaching low-grade stone coal. The kinetic model provides theoretical guidance for the application of oxidants in V extraction from low-grade stone coal
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