Effect of thermal treatment on the retention of chemical elements in the structure of lightweight aggregates manufactured from contaminated mine soil and fly ash

► Effectiveness of thermal treatment in the immobilization of elements. ► Lightweight aggregates (LWAs) manufactured with contaminated mine soil and fly ash. ► Heat treatment was totally effective in the immobilization of most of the elements. ► The elements have become part of the LWA residual fraction. ► Heat treatment is detrimental from the standpoint of arsenic leaching. This paper presents a study about the effectiveness of thermal treatment in the immobilization of different chemical elements within the structure of artificial lightweight aggregates (LWAs) manufactured with contaminated mine soil and fly ash. The heat treatment was totally effective in the immobilization of Cr, Ni, Cu, Zn, Pb, Be, Mn, Co and most of the rare earth elements. In the LWAs, they have become part of the residual fraction, probably forming the crystalline structure of neo-formed feldspars, of neo-formed minerals of the spinel group and the matrix. The thermal treatment was detrimental from the standpoint of arsenic leaching.