Abstract
A simple successive calcination-H2C2O4 leaching method was employed to recycle the W in spent V2O5-WO3/TiO2 catalyst with high efficiency. The results showed that W partially reacts with calcium and form CaWO4 after the first calcination. The CaWO4 was leached by diluted H2C2O4, during which the W was converted into the soluble chelate compound (H2[WO3(C2O4)H2O]), while the calcium remained in the solid in form of CaC2O4. After filtration, the chelate compound in the filtrate could be precipitated by adding HCl to obtain H2WO4, while the filter residues were roasted for the second time to increase the recycling ratio of W. During the second calcination, the CaC2O4 was decomposed into CaO and reacted with the residue W to form CaWO4, which can be further leached by H2C2O4 and recycled as H2WO4. Finally, the H2WO4 can be roasted at 773 K for 1 h to obtain the WO3. As a result, the leaching efficiency of W could reach 87%, while the purity of the final WO3 was as high as 91%.
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