Physical and chemical characterization of red mud in terms of its environmental effects

Red mud coming from different sampling points of an abandoned disposal site was investigated in this research. We examined the physical and chemical properties of red mud in terms of environmental effects especially for the subsurface environment. Their particle size, consistency, compressibility, shear strength and hydraulic characteristics were measured. The compositions, pH and cation exchange capacity also had been analyzed and special leaching tests were performed to characterize its behavior in the subsurface environment. Horizontal and vertical inhomogenity in the material of the disposal site and the evidence of secondary mineral precipitation was found based on the main properties of the samples. Differences between the rates of basic minerals were found in some samples, but overall the red mud has a lot of hazardous elements such as As, Pb, Cr and Hg. The red mud has very fine particles, high water content, and it is hard to compact. Some samples showed thixotropic behavior during the compression and shear tests. At the same time it has low hydraulic conductivity, and high cation exchange capacity, but even with these favorable properties there is the potential environmental risk in long-term storage of red mud.