V₂O₅-WO₃/TiO₂ catalysts were synthesized from waste selective catalytic reduction (SCR) catalyst through oxalic acid leaching and impregnating with various V₂O₅ mass loadings. The denitration (deNO_x) activity and physiochemical properties of the catalysts were investigated. All the catalysts were characterized by N₂ adsorption/desorption, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and H₂-temperature programmed reduction. The evaluation result revealed that the deNO_x activity of newly synthesized catalyst with 1.0% V₂O₅ was almost recovered to the level of fresh catalyst, with NO conversion being recovered to 91% at 300 °C, and it also showed a good resistance to SO₂ and H₂O. The characterization results showed that the decrease of impurities, partial recovery of the V⁴⁺/V⁵⁺ ratio, and increased reducibility were mainly responsible for the recovery of catalytic activity.

High-alumina fly ash may potentially be a valuable source of Ga with a concentration of Ga at 80 mg/kg. Direct adsorption and enrichment of Ga from sulfuric acid leach liquor of high-alumina fly ash is developed in this study. The H-type chelating resin with two carboxy groups exhibited the best adsorption capacity for Ga. The maximum adsorption capacity for Ga was 55 mg/g resin with an adsorption time of 24 h, an initial Ga concentration of 500 mg/L, an adsorption temperature of 55 °C, and an initial acid concentration of 0.1 mol/L. The adsorption process of Ga was in good fit with the Langmuir isotherm and pseudo-second-order reaction kinetics model. The chemical adsorption rate was controlled by an internal diffusion mechanism. The resin had a high selectivity for Ga³⁺ with a K_d over 3600 compared with Fe²⁺, Al³⁺, K⁺, Ca²⁺, and Mg²⁺. The adsorption mechanism was found to be the ion exchange reaction between Ga and H of carboxy and hydroxyl groups. The concentration of Ga in sulfuric acid leach liquor from high-alumina fly ash achieved enrichment from 200 mg/L to 2 g/L. It is an attractive medium for large-scale Ga extraction from high-alumina fly ash.