Characterization of Settled Particles of the Red Mud Waste Exposed to Different Aqueous Environmental Conditions

Red mud waste is generally transferred to the storage area in a slurry form with solids content varying from 15 to 40%. Due to arise of a variety of environmental and climatic conditions in the due course of time, settling behaviour of particles as well as properties of settled particles changes. Thus, understanding of the settling behaviour of waste particles becomes essential after disposing the waste into the pond. In addition, studies related to the settling behaviour of particles become important during the extraction of alumina from bauxite ore (i.e. in settlers). In the present study, efforts are made to investigate the settling behaviour of red mud waste particles when exposed to different aqueous environmental conditions. For testing purpose, a series of differential free swell tests were conducted considering aqueous environmental conditions such as tap water, distilled water, kerosene, NaCl solutions of 1.71 and 3.42M, and HCl solutions with a pH range from 1 to 4, respectively. In addition, efforts are also devoted to characterizing the post-exposed sediment samples to ascertain possible changes in the mineralogical, morphological, and elemental compositions of the particles. Results reveal that aqueous environment has a considerable effect on the settling behaviour of particles, while the effect of pH found to be trivial. The analyses of characterization studies disclose a marginal to considerable changes in elemental, phase compositions and morphological characteristics of the post exposed particles.