(335g) Comprehensive Utilization of Selenium Resources in Black Shales of Enshi

Comprehensive utilization of selenium resources in black shales of Enshi

Qin Shuai^1*, Shengrui Xu¹, Yu Tang¹, Yunjie Huang¹, Sen Yan², Zhengyu BaO^1,2

¹ Faculty of Material Science and Chemistry, China University of Geosciences, Wuhan, 430074, China

² Faculty of Earth Sciences, China University of Geosciences, Wuhan, 430074, China

Selenium (Se), as an important industrial material, has been extensively applied in many fields such as electronic metallurgical and petroleum industry.[1] However, selenium is a typical dispersed element with a low crustal concentration (0.05-0.09 μg g^-1). Interestingly, the huge independent deposit of selenium with 5 billion tons of selenium resources has been found in Enshi region (Hubei Province, China) and thought as the only site in the world till now. [2] The selenium with high concentration of more than 80000 μg g^-1 locates in the black shale which is called stone coal. [3] The stone coal is popularly utilized through combustion process. By this way, a significant portion of selenium in the vapors will escape into atmosphere and then lead to air pollution and waste of the scarce resources. Therefore, it is significant to increase the comprehensive utilization efficiency of selenium in the Se-rich stone coal during the combustion process.

Our work was focused on the adsorption and recovery of Se in the vapors from Se-rich stone coal combustion processes. Various calcium-based sorbents were firstly developed and evaluated for the Se adsorption at 700°C-1000°C. It was found that adsorption efficiency of selenium could reach 90.6% at 800°C with CaO/nano-ZnO as sorbent. This adsorption effect was from the formation of CaSeO₄ species. Then, the recovery of the Se from CaSeO₄ species were also studied with the reducing agent of Na₂SO₃. High percents of 98.17% and 69.78% were obtained for the reduction of Se from simulation and real experiments, respectively. The developed adsorption and recovery methods had potentials to be used for the utilization of Se resources from stone coal.