LAUSR

Abstract The reduction in phosphorus content using microwave energy as a heating source has recently received remarkable attention due to the possibility of high heating rates and fracture generation in the particles. Such advantages can lead to a potential increase in productivity in the process of reducing the phosphorus content of iron ore particles, thereby increasing the reuse of large volumes of sterile with a high phosphorus content. Thus, it is highly relevant to understand how the interaction between the phosphate structure and the reaction medium occurs. Thus, this paper deals with the study of a possible kinetic model aiming at the process of reducing the phosphorus content using microwave energy to heat iron ore particles in contact with concentrated sulfuric acid (acid baking). This model treats the microwave oven as a multiphase reactor and two phases are considered simultaneously: liquid and granular or fine solids (crude or comminuted iron ore). First, a basic case consists of the ore/sulfuric acid mixture, in a ratio of 2:1. After heating, the mixture is added to a specific volume of water and then the system is stirred at a speed of 620 rpm. After the leaching process, the liquid was filtered and taken for chemical analysis, which was performed using an ultraviolet spectrometer at a wavelength of 420 nm for phosphorus and 473 nm for iron. Through the scanning electron microscopy (SEM) technique, it was possible to observe the structure of the iron ore particles after their treatment with microwave energy and leaching. Kinetic models of diffusional and chemical control were used to understand the interaction phenomena of sulfuric acid inside the particles. The mixed control kinetic model was also evaluated, in which it was possible to evaluate different parameters regarding the interaction between mineral structure and sulfuric acid as leaching medium. The obtained results indicated that the developed process has relevant utility. The kinetic modeling results contribute to a better understanding of heating phenomena using microwave energy, and also to the development of new cleaner technologies to improve the efficiency of the acid baking/leaching process to reduce particulate phosphorus content in iron ores.