The productivity of industrially important aqueous oxygen leaching processes is limited by gas-liquid mass-transfer rates of a sparingly soluble solute, usually oxygen. The low productivity of aqueous oxygen leaching processes is usually improved through operation at elevated temperatures and pressures. However, these processes become economically viable only at large capacities due to their high capital cost. In the Becher process for the manufacture of synthetic rutile, an aqueous oxygen leaching step at near neutral pH is employed to remove the metallic iron component from reduced ilmenite. However, the oxygen leaching step suffers from a serious drawback of low productivity due to limitations imposed by the sluggish mass transport rates of oxygen from the gas phase to liquid phase. In this specific case, the use of elevated pressures has been shown to be technically impossible due to low conversions brought about by the phenomenon of passivation.The present work reports an alternate strategy for the intensification of this process at ambient conditions and ensuring environmental compatibility of the process. The results are interpreted based on the theory of gas-liquid mass-transfer enhancement. The manufacture of synthetic rutile from ilmenite mineral is carried out in two major steps. First, ilmenite is reduced through carbothermal reduction at high temperature such that the iron component is converted to the metallic phase. Reduced ilmenite (RI) resulting from this step is then subjected to oxygen leaching in an electrolyte medium to remove the iron fraction through an accelerated corrosion reaction. The oxygen leaching step, alternately known as the aeration step in the Becher process, involves electrochemical dissolution of metallic iron by cathodic reduction with dissolved oxygen in a 0.1 M ammonium chloride solution followed by liquid-phase oxidation of the Fe~(2+) accompanied by hydrolysis and precipitation of ferric ions as hydrated iron oxides.
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