Microbubble Oxidation for Fe²⁺ Removal from Hydrochloric Acid Laterite Ore Leachate

After the atmospheric hydrochloric acid leaching method is used to treat laterite ore and initially purify it, the extract that results often contains a significant amount of Fe²⁺ impurities. A novel metallurgical process has been proposed that utilizes microbubble aeration to oxidize Fe²⁺ ions in laterite hydrochloric acid lixivium, facilitating subsequent separation and capitalizing on the benefits of microbubble technology, including its expansive specific surface area, negatively charged surface attributes, prolonged stagnation duration, and its capacity to produce active oxygen. The study examined the impacts of aeration aperture, stirring speed, oxygen flow rate, pH value, and reaction temperature. Under optimized experimental conditions, which included an aeration aperture of 0.45 µm, stirring at 500 rpm, a bubbling flow rate of 0.4 L/min, pH level maintained at 3.5, and a temperature range of 75-85 °C, the oxidation efficiency of Fe²⁺ surpassed 99%. An analysis of the mass transfer process revealed that microbubble aeration markedly enhances the oxygen mass transfer coefficient, measured at 0.051 s^-1. The study also confirmed the self-catalytic properties of Fe²⁺ oxidation and conducted kinetic studies to determine an apparent activation energy of 399 kJ/mol. At pH values below 3.5, the reaction is solely governed by chemical reactions; however, at higher pH values (>3.5), both chemical reactions and oxygen dissolution jointly control the reaction.