Dephosphorization of Iron Ore through Bioleaching

Phosphorus, as phosphate, is frequently found as a constituent of many of the world iron resources. Phosphorus is an extremely harmful element found in iron ore used as a raw material in the steelmaking process because it will affect the quality of iron and steel products. Allowable phosphorus concentration in high quality steel is usually less than 0.08%. Dephosphorization of iron ore has been studied for a long time. Although there are described physical beneficiation and chemical leaching processes, involving inorganic acids, to reduce phosphorus content of iron ores, these processes have several limitations such as poor recovery, require high energy quantity, capital costs and cause environmental pollution. Use of microorganisms in leaching of mineral ores is gaining importance due to the implementation of stricter environmental rules. Microbes convert metal compounds into their water soluble forms and are biocatalysts of leaching processes. Biotechnology is considered as an eco-friendly, promising, and revolutionary solution to these problems. Microorganisms play a critical role in natural phosphorus cycle and the process of phosphate solubilization by microorganisms has been known for many years. This study was performed to analyze the possibility of using bioleaching as a process for the dephosphorization of an iron ore from Northeast of Portugal. For bioleaching, Acidithiobacillus ferrooxidans bacterium were used. For this study two experiments were done with different conditions, which lasts 6 weeks for first experiment and 5 weeks for second experiment. From the result of these preliminary studies, it was observed that for first experiment 6.2 % and for second experiment 3.7 % of phosphorus was removed from iron ore.

Solubility and solvation of monosaccharides in ionic liquids

Herein, solubility experimental data for six monosaccharides, viz. D-(+)-glucose, D-(+)-mannose, D-(-)-fructose, D-(+)-galactose, D-(+)-xylose and L-(+)-arabinose, in four ionic liquids (ILs), at temperatures ranging from 288.2 to 348.2 K, were obtained aimed at gathering a better understanding of their solvation ability and molecular-level mechanisms which rule the dissolution process. To ascertain the chemical features that enhance the solubility of monosaccharides, ILs composed of dialkylimidazolium or tetra-alkylphosphonium cations combined with the dicyanamide, dimethylphosphate or chloride anions were investigated. It was found that the ranking of the solubility of monosaccharides depends on the IL; yet, D-(+)-xylose is always the most soluble while D-(-)-fructose is the least soluble monosaccharide. The results obtained show that both the IL cation and the anion play a major role in the solubility of monosaccharides. Finally, from the determination of the respective thermodynamic properties of solution, it was found that enthalpic contributions are dominant in the solubilization process. However, the observed differences in the solubilities of monosaccharides in 1-butyl-3-methylimidazolium dicyanamide are ruled by a change in the entropy of solution.