چكيده به لاتين
The presence of phosphorus in iron ore can significantly impact the final quality of iron and steel products. If the phosphorus content in iron ore is high, it may necessitate certain purification processes to enhance the iron quality to a desirable level. This issue is crucial in iron and steel production as elevated phosphorus levels can affect the mechanical, corrosion, and oxidation properties of the product. Traditionally, iron ore with high phosphorus is chemically treated using inorganic acids for phosphorus removal. However, this process is not currently recommended due to high costs and environmental pollution concerns. Given the current trend towards developing cost-effective and environmentally friendly processes, reducing phosphorus from high-phosphorus iron ore through microbial processes is feasible. In this study, factors influencing the biological dissolution of phosphates from iron ore were investigated. Initially, acidic leaching of iron ore with organic acids at low concentrations, producible by microorganisms, was performed. Citric acid and lactic acid demonstrated the capability to dissolve phosphates in iron ore. Subsequently, the dissolution of insoluble phosphate salts by selective microorganisms was examined, and Aspergillus niger was chosen for further experiments. In the next stage, the effects of various factors on phosphate dissolution from iron ore, such as the mass/volume ratio of iron ore to the culture medium (0.05, 0.1 g/ml), inoculation type (spore and hyphal forms of Aspergillus niger) with inoculation percentages (5 and 10%), temperature (30 and 35°C), and initial phosphate concentration (25 and 50ppm), were investigated in a one-factor-at-a-time approach for 8 days. After determining suitable levels of the variables, factorial experiments were conducted, and optimal values were determined using Design Expert software version 13. The highest percentage of removed phosphates from iron ore on a 90% scale was achieved at a mass/volume ratio of 0.05 g/ml, a temperature of 30°C, and an initial phosphate concentration of 50 ppm. In the next step, the process was scaled up in a stirred-tank reactor using a mechanical stirrer under optimal operational conditions obtained from the small-scale experiments in the 90% scale Erlenmeyer flask. This led to an increase in the rate of phosphate dissolution from iron ore during the initial days. Additionally, kinetic models, including the logistic model for Erlenmeyer flask data and the Box-Lucas model for stirred-tank reactor data, were applied to the results to investigate the trend of phosphate dissolution over time. The difference between these two models was attributed to variations in the rate of phosphate dissolution from iron ore in the initial days of the experiment. In conclusion, the removal of phosphates from iron ore through microorganisms presents a promising method for improving the efficiency of phosphate removal while being environmentally friendly.
