Abstract
Rutile decomposition by sulfuric acid, including the formation of two salts, Ti(SO4)2/TiOSO4, is thermodynamically modelled. It is shown that TiO2 can spontaneously dissolve in H2SO4 solutions. However, titania is considered as an inert (ballast) phase component of titanium-containing raw materials due to the decelerated separate nature of such chemical transformations. It is concluded that the hampered related kinetics of dissolution can be attributed to the lability of Ti(IV) cations/the specific engineered features of the hierarchical crystalline structure. It is suggested that the breaking of Ti–O–Ti bonds without additional mechanical strains in crystal lattice geometry becomes more advantageous when smaller negative anions/fluoride ions can be used. The analysis of sulfate-fluoride extraction leaching of titanium confirmed that a decrease in the Gibbs energy in the presence of F occurs. It is indicated by kinetic research studies that the addition of corrosive sodium reagent (NaF) reduces the activation by 45 kJ/mol, which results in intensification. A mechanism is proposed for the interactions involving the Ti–O–Ti cleavage on the surface/the H2SO4-induced Ti dioxide degradation on the sites of defects. Moreover, F acts as a homogeneous/heterogeneous bifunctional catalyst.
Highlights
The global yearly production of titanium dioxide is approximately 6 million tons, and its demand grows continuously by an average of 2.5% per year [1]
The composition of titanium sulfates does not remain constant in sulfuric acid leaching of altered ilmenites; this was experimentally proved by the authors in the previous work [52]
The experimentally proven inhibition effect of such reactions forces technologists to consider rutile as an inert component of titanium-bearing raw materials
Summary
The global yearly production of titanium dioxide is approximately 6 million tons, and its demand grows continuously by an average of 2.5% per year [1]. Ilmenite is a widespread raw material for the production of titanium dioxide by both the chloride [2,3,4] and sulfate methods. Ways to intensify this leaching method are sought for using three activation methods: mechanical, thermal and chemical. The mechanical activation of raw materials significantly increases the rate of dissolution of solid minerals, as reported in a number of works [5,6,7,8,9,10,11,12,13]. It was shown in several publications that the mechanical dispersion of raw material can either change or remain constant, depending on various factors—among them, the ore grinding method (“dry” or in a solution medium), different process duration, etc
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