화학공학소재연구정보센터
Oil Shale, Vol.36, No.2, 226-249, 2019
HAZARDOUS TOXIC ELEMENTS MOBILITY IN BURNED OIL SHALE ASH, AND ATTEMPTS TO ATTAIN SHORT- AND LONG-TERM SOLIDIFICATION
Jordan has huge organic-rich oil shale resources. The exploitation of this resource for generating electrical power by direct combustion is eminent. This process will produce huge ash tailings that contain high concentrations of potentially leachable toxic elements (e.g. Cr+6, V+5, As+3, Cd+2). This ash is friable and eventually will interact with rainwater, forming a leachate rich in toxic elements that might reach soil, plants and surface and groundwater resources. Therefore, as a preventive measure, the current study analyzed the mobility of toxic elements in the ash of burned oil shale (BOS), in particular Cr+6, and aimed to fix them through mixing with other natural locally available materials such as phosphogypsum (PG) and red soil (RS). In addition, a study of the changes in mineralogy, petrography and engineering properties with time during a period of up to 12 months was conducted. The ageing results revealed that the ash + RS mixtures showed a lower leachability of toxic elements in the pH range of 5-9 in comparison with other mixtures. Besides, the said mixtures exhibited an increase in the values of unconfined compressive strength (UCS) and decrease in those of permeability (PE) unlike other mixtures. Moreover, ettringite and portlandite phases increasingly appeared in these mixtures with time, which explains the increase of UCS. The USC of the ash alone mixture was the second lowest and that of the ash + PG mixture the lowest. Therefore, mixing the produced ash with RS (3:1 ratio) under water saturation conditions would afford the best long-term solidification of harmful toxic elements.