Recovery of tungsten and titanium from spent SCR catalyst by sulfuric acid leaching process. (1st January 2023)

• Record Type: Journal Article
• Authors: Zhao, Chen; Wang, Chenye; Wang, Xingrui; Li, Huiquan; Chen, Yan; Wu, Wenfen
• Is Part Of: Waste management. Volume 155(2023)
• Page Start: 338
• Page End: 347
• Publication Date: 2023-01-01
• Subjects: Spent selective catalytic reduction catalyst -- Acid leaching -- Recycling -- Titanium-Tungsten powder -- Denitration; Hazardous wastes -- Periodicals; Refuse and refuse disposal -- Periodicals; 363.728
• DOI: 10.1016/j.wasman.2022.11.013
• Languages: English
• ISSNs: 0956-053X

Abstract

Graphical abstract: Highlights: A new route for recovering spent SCR catalyst by acidolysis-hydrolysis was proposed. The recovery efficiencies of Ti and W in a single process were 91.11% and 89.42%. Highly purified Ti-W powder containing 93.22% TiO2 and 4.27% WO3 was obtained. The transfer mechanism of Ti and W elements was analyzed. Abstract: The widespread use of selective catalytic reduction (SCR) catalysts has resulted in a large accumulation of spent SCR catalysts. These spent catalysts present a significant risk of environmental hazards and potential for resource recovery. This paper presents a feasible process, which works using atmospheric pressure leaching, of tungsten and titanium recovery from spent SCR catalysts. In this new method, titanium and tungsten are simultaneously leached with sulfuric acid as the leaching agent. After hydrolysis and calcination, titanium-tungsten powder with low impurity and reconstructed pore properties was obtained. The optimal conditions for the leaching of Ti and W were as follows: temperature, 150 °C; reaction time, 60 min; H2 SO4 concentration, 80 %; mass ratio of H2 SO4 /TiO2, 3:1; and diluted H2 SO4 concentration, 20 % after reaction. With these optimum conditions, the leaching efficiency of Ti and W were found to be 95.92 % and 93.83 %, respectively. The ion speciation and reaction mechanism of W were studied by Raman spectroscopy, FTIR, and UV–vis. The formation of heteropolytungstate with a Keggin structure is essential for the synergistic leaching of Ti and W, as the heteropolytungstate can be stably dissolved in the acid solution. During the hydrolysis process, heteropolytungstate gradually decomposed into Ti 4+ and WO4 2− due to the formation of insoluble Ti(OH)4 from Ti 4+ in the solution. This study demonstrated an effective method for synergistic recovery of titanium and tungsten from the spent SCR catalyst.