International Conference on Radiation Application – RAP2019, Belgrade, Serbia And Montenegro, 16 - 19 September 2019, pp.1
Bauxite residues (red mud) produced by digestion of bauxite ore during the production of alumina contain naturally occurring radionuclides such as 238U, 232Th and 40K and toxic elements such as Al, Cr, Co, Mn and Ni. In this research, red mud collected from Eti Seydisehir Aluminium Plant in Turkey was studied to determine the concentration of natural radionuclides and some toxic elements. Furthermore, short-term leaching tests of elements and radionuclides were undertaken on the red mud by Toxicity Characteristic Leaching Procedure (TCLP)-1311 method to evaluate in terms of the environmental impact. The activity concentrations of 234,235,238U, 232Th and 40K, and toxic elements contents in red mud and leachate samples were determined by neutron activation analysis and Compton suppression methods. The method was tested with certified reference materials such as SRM 1632d, 1633c and 2709a from the National Institute of Standards and Technology (NIST). Elemental calibration for NAA was done using NIST traceable liquid standards from Inorganic Ventures with the exception of barium and strontium (NIST 1632d) and cesium and potassium (NIST 2709a). Liquid standards and leachate samples were hermetically heat sealed in polyethylene vials for neutron irradiation. The results which are obtained from reference materials indicated that the method can be successfully applied for the determination of multiple elements. We observed from the obtained results that the major elements in red mud are Fe, Al, Na, Ti and Ca. The concentration of these elements in red mud sample was found significantly high. Other elements such as Th, Zr, Cr, Ni, Ce, V, Nd, Mn, La, Sc and As observed in red mud were found in smaller concentrations compare to the major elements. The results from potential ecological risk factors of red mud except Arsenic were found below the threshold value that indicates these metals (Ni, Cr, Mn and Co) have a low risk to the surrounding environment. On the other hand, it can be observed from the results of both of the leachate samples that there is no significant mobility in elements of under-investigated conditions. The results demonstrate that these elements are not easily mobile under environmental conditions. However, it is required to obtain further information about the leaching behaviour of these elements for estimating the magnitude of the red mud’s environmental impact.