Release of uranium and other trace elements from coal ash by (NH4)2SO4 activation of amorphous phase

Due to the sintering phenomena of coal ash (CA), uranium is hardly leached even under high-concentration H2SO4 solution. It is difficult to collect and take advantage of those potential nuclear sources. In this study, the coal with high content of uranium (112.56 ug/g) was collected from Menwang, Yunan Province, Southwestern China. Sequential chemical extraction and leaching experiment were conducted. Based on X-ray diffraction and scanning electronic microscopy analysis, elements (U, V, Cs, Rb, Ga, and Sr) were surrounded by minerals during coal combustion when the temperature was over 700 degrees C. Therefore, thermochemical treatment with (NH4)(2)SO4 was used to activate the amorphous Al in CA, and led to the release of element at the following water leaching. The leaching contents of U, Cs, Rb, and Sr, under the thermochemical condition of the CA/(NH4)(2)SO4 = 2:4, 400 degrees C, and 1 h, were 1.89, 2.31, 8.39, and 1.74 times higher than directly leaching CA with 0.4 M H2SO4. Moreover, uranium was extensively leached by deionized water at the condition of solid to liquid ratio of 1:10, 60 degrees C, and 2 h, which was characterized by the advantages of the environment friendly, saving resources, and reducing equipment maintenance investment.