Assessment of environmental condition in the waste disposal site of an ex-alumina plant near Obrovac, Croatia

The waste disposal site of the abandoned alumina plant near Obrovac, Croatia, contains two basins filled with red mud and waste base in total amounts estimated at 0.85 x 10(6) and 0.65 x 10(6) m(3), respectively. The Red mud was analyzed for its major components, heavy metals content, free base content and leaching properties under different conditions of pH and temperature. Concentrations of 15 elements (Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Ga, As, Rb, Sr, Y, Zr, and Pb) were measured using tube excited EDXRF. The major compounds were determined by XRD, and AAS and XRF methods were used for elemental concentration determinations in different types of leachates. It was found that a possible threat to the environment from red mud under normal environmental conditions could be caused only by leaching of alkalis and V. On the other hand, the concentrations of V, Cr, Cu, As and Se in the waste base and the pH are much higher than allowed for technical waste waters discharged directly into the environment. Waste base treatment (neutralization and heavy metal removal) can be achieved in a one-step process. During this process, neutralization of acidic red mud would result in the production of a gel-like coagulant. Copyright (C) 2004 John Wiley Sons, Ltd.