Environment
shima rahimi; Mehdi Irannajad
Abstract
In this study, Red Mud (RM) as a byproduct in alumina production process from bauxite was used as an adsorbent for sulfate contaminant adsorption from acid mine drainage (AMD). AMD discharge led to the acidification of water which has detrimental effects on aquatic life and human health. Analytical methods, ...
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In this study, Red Mud (RM) as a byproduct in alumina production process from bauxite was used as an adsorbent for sulfate contaminant adsorption from acid mine drainage (AMD). AMD discharge led to the acidification of water which has detrimental effects on aquatic life and human health. Analytical methods, laboratory studies and molecular simulations were conducted to investigate sulfate adsorption on RM. Thermodynamic calculations were performed after optimizing of existing metal oxide in RM structure with the Material Studio software using the dmol3 and DFT method. The adsorption energy results by Adsorption locator module determined -819.09, -561.7, -268.8, -105.4, and -314.7 kcal/mol for Fe2O3, Al2O3, CaCO3, TiO2 and SiO2, respectively. The most active compounds in RM structure (iron and aluminum oxides) account for 22.5% and 13.3% in the red mud structure, respectively. In addition, seawater washing was employed as RM modification methods, and it could decrease high rates of pH and improve the sorption capacity of raw RM. The effect of this modification was investigated by simulation of solvent in adsorption environment of sulfate on RM and the dielectric constant selection. For water as the primary solvent with a dielectric constant of 78.54, adsorption energy for RM was calculated to be -35.68 kcal/mol and it was increased to -56.69 kcal/mol for the seawater medium with a dielectric constant of 86. Therefore, RM can be considered as a potential sulfate adsorbent because of cost-effectiveness and alkaline pH that can lead to the neutralization of AMD.
Mineral Processing
Nooshin Navi; Mohammad Karamoozian; Mohammad Reza Khani
Abstract
Red mud is an important solid tailing with strong alkalinity that is obtained during the extraction of alumina in the Bayer process. The global reserve of red mud is more than 4 billion tons, and its disposal as tailing has always been a serious environmental problem. This tailing is considered as a ...
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Red mud is an important solid tailing with strong alkalinity that is obtained during the extraction of alumina in the Bayer process. The global reserve of red mud is more than 4 billion tons, and its disposal as tailing has always been a serious environmental problem. This tailing is considered as a potential source, due to its high content of valuable metal compounds including iron. In this research work, the extraction of iron in red mud is investigated by the method of reduction roasting. The main influencing factors are also investigated. These methods include reduction in muffle and tube furnace, and temperature, reduction agent, and additive type are as important factors. Reduction roasting of the samples in a tube furnace, with Argon gas and vacuum, a mixture of red mud, graphite, and sodium carbonate at 700–1000 °C results in the formation of Fe3O4. Magnetic measurements indicate that saturation magnetization increases from 0.239 to 38.205 emu/g due to the formation of Fe3O4. Applying the magnetic field intensity of about 1000 Gauss results in the iron recovery of 89.9%.
U. Yenial; G. Bulut
Abstract
Two common waste materials, red mud and fly ash, were used to produce a new nano-hybrid adsorbent by heat treatment with alkali addition. The new zeolitic structure formation of the hybrid adsorbent was revealed using the BET surface area, XRD, and SEM analyses. This hybrid adsorbent was utilized to ...
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Two common waste materials, red mud and fly ash, were used to produce a new nano-hybrid adsorbent by heat treatment with alkali addition. The new zeolitic structure formation of the hybrid adsorbent was revealed using the BET surface area, XRD, and SEM analyses. This hybrid adsorbent was utilized to remove arsenic from synthetic and real waste waters by batch and column adsorption experiments. The parameters such as the pH, contact time, and effect of the co-existing ions were investigated. Slightly acidic media favored arsenic adsorption by the hybrid adsorbent, the same as the individual use of fly ash and red mud. The effects of ions such as Fe3+, Cu2+, Cl-, SO42-, and PO43- were investigated as the co-existing ions. It was found that arsenic adsorption increased with cationic ions and decreased with anionic ions according to their valance charge. The intra-particle diffusion model showed that adsorption took place at three different rates depending on time. The hybrid adsorbent was formed as a pellet and utilized in a column for treatment of arsenic containing real waste water. The hybrid adsorbent derived from mineral wastes was more successful than their individual usages.
