Experimental study on mixed acid synergistic leaching of vanadium from spent deNOx catalysts
According to the relevant provisions of Law of the People's Republic of China on the Prevention and Control of the Environmental Pollution of Solid Wastes,the waste vanadium and titanium catalysts generated in the process of flue gas denitrification are classified as hazardous wastes due to their toxicity and harmful effects on the ecological environment and human health (HW50772-007-50),and therefore the extraction of the valuable metals therein,especially vanadium metals,is a very important technological means and solution. In this paper,we investigated the leaching effect of different combinations of inorganic and organic acids on vanadium from spent vanadium and titanium catalysts,and a mixed acid consisting of sulphuric acid-oxalic acid was preferred under the same conditions of stirring speed of 500 r/min,liquid-solid ratio of 20 mL/g,reaction temperature of 110 ℃ and leaching time of 5 h. The process optimisation of this combination was carried out by using a mixture of sulfuric acid and oxalic acid to extract vanadium. The process optimisation of this combination was carried out,and the results showed that the maximum leaching rate of vanadium was 95.65％ when the liquid-solid ratio was 20 mL/g,the concentration of sulphuric acid was 20 wt％,the concentration of oxalic acid was 0.3 mol/L,the reaction temperature was 140 ℃,and the leaching time was 7 h. The leaching slag obtained under the optimal process conditions was mainly composed of anatase titanium dioxide,and the analysis of its specific surface area and pore structure after leaching showed that the specific surface area of the leaching slag had increased by 13.5％ and the average pore volume had also increased compared with the state before leaching,which indicated that it could be recycled as a raw material.
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