Comparison of the kinetic laws of the dissolution of bauxite and aluminum and iron(III) oxides and hydroxides in hydrochloric acid

The influence of the temperature and concentration of a hydrochloric acid solution on the dissolution kinetics of aluminum and iron(III) oxides and hydroxides and a natural sample of aluminum-containing raw materials, bauxite, is studied. The rate W of the transition of iron(III) ions from bauxite is higher than the rate of aluminum ion transition. The dependence of the fraction of a dissolved solid phase on time τ of dissolution of the oxides and hydroxides is determined, α = 1 — exp(-Asinh(Wτ)). The solubility of iron(III) chloride increases and that of aluminum chloride decreases as the HCl concentration increases. An empirical equation is proposed for the description of the dependence of the process rate on a series of parameters, $$W = W_0 \left( {\frac{{\left[ {H^ + } \right]}} {{\left[ {H^ + } \right] + K}}} \right)\left( {\frac{{\left[ {A^ - } \right]}} {{\left[ {A^ - } \right] + K_2 }}} \right)\exp \left( {\frac{{E_a }} {{RT}}} \right)$$.