Mineral Processing
Sasan Mirshekari; Mehdi iranajad; Hossein Kamran Haghighi
Abstract
In recent years, the use of microorganisms in the flotation of sulfide minerals has gained significant attention, particularly in processes requiring reduced chemical consumption and the utilization of saline water. The targeted application of microorganisms can improve flotation process conditions. ...
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In recent years, the use of microorganisms in the flotation of sulfide minerals has gained significant attention, particularly in processes requiring reduced chemical consumption and the utilization of saline water. The targeted application of microorganisms can improve flotation process conditions. Halophilic bacteria, as salt tolerant species, can be beneficial in selectively depressing pyrite during flotation. This study aimed to investigate the effect of the halophilic bacterium Bacillus mojavensis on enhancing the separation of chalcopyrite from pyrite in froth flotation using seawater. Experiments were conducted at five pH levels, and changes in recovery, flotation kinetics, and contact angle were evaluated. The results showed that the presence of the bacterium improved process selectivity and enhanced chalcopyrite flotation behavior at pH values between 6 and 10, while bacterial performance decreased at pH 4 and pH 12. The maximum recovery improvement was observed at pH 8, where chalcopyrite recovery increased from 55.11% to 62.04%, and the kinetic constant K was higher than that of the bacteria free sample. Contact angle measurements indicated that the bacterium significantly reduced pyrite hydrophobicity (from 73.73° to 46.7°) without causing noticeable changes in chalcopyrite (~75.8°); this behavior was attributed to the selective adsorption of EPS and bacterial cells on the pyrite surface, leading to its surface deactivation. The findings suggest that Bacillus mojavensis, due to its salt tolerance and stability in neutral to alkaline pH ranges, is a suitable candidate for use in seawater-based flotation circuits and low chemical consumption processes involving pH regulators.
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.
