Potentially useful elements (Al, Fe, Ga, Ge, U) in coal gangue: a case study in Weibei coal mining area, Shaanxi Province, northwestern China.

Coal gangue has become one of the largest industrial solid waste in China, but it is also a kind of reserve resources. Representative coal gangue samples from different coal mines (mainly in Permo-Carboniferous and Jurassic) in Weibei area in Shaanxi Province are collected, and potentially useful elements (Al, Fe, Ga, Ge, U) in coal gangue are analyzed. The results show that the reserves of Al and Fe in Chinese coal gangue are 262 million tons and 196 million tons, respectively, based on the geometric mean values of Al2O3 (15.18%, weight percent) and Fe2O3 (6.24%, weight percent). Meanwhile, the crude reserves estimation of Ga, Ge, and U are 55,282, 6867, and 32,981 tons, respectively, based on the weighted mean contents of Ga, Ge, and U in coal gangue at 17.55, 2.18, and 10.47 mg/kg, respectively. Furthermore, Ga and Al contents in quite a large number of coal gangue mines exceed the cutoff value, which has a prospect of development and utilization from coal gangue. The policy implications from this study may include that (1) recycling of useful elements in Chinese coal gangue should be treated as an integral part of sustainable development with professional legislations and (2) establishing a basic database of coal gangue and authoritative system with relevant departments for solid waste management may effectively improve comprehensive utilization of coal gangue in the future.