Leaching behavior of arsenic and selenium in coal fly ash by aging treatment and cement mixing

Abstract

In the use of coal fly ash (FA) mixed cement, the assessment of the leachabilities of toxic elements in FA is crucial. This study evaluated the leaching behavior of arsenic and selenium in 40 types of raw FA (R-FA), aging-treated FA (A-FA), and cement-mixed FA (C-FA). The mean leaching concentrations from R-FAs were 0.03 mg/L for arsenic and 0.09 mg/L for selenium. The leaching of arsenic and selenium was suppressed by the aging treatment, and more significantly suppressed by the cement mixing under 0.01 mg/L for both arsenic and selenium. The pH for R-FAs ranged from 7.6 to 12.9, and that for C-FAs ranged from 11.1 to 12.3 with a smaller pH range due to cement mixing. Furthermore, the results of the leaching experiment with time for R-FAs and C-FAs indicated that the leaching of arsenic and selenium was suppressed by the formation of secondary compounds with calcium due to the supply of calcium from the cement. These results indicate that the common FA cement and low alkaline cement used in the actual site can sufficiently suppress the leaching of arsenic and selenium because the ratio of cement amount to FA is higher than that examined in this study. GRAPHICAL ABSTRACT