Reaction kinetics of shearing-enhanced goethite process for iron removal from zinc solution

A shearing-enhanced goethite process for iron removal is proposed to overcome the difficulties in process reaction control and non-uniform mass transfer. The reaction kinetics of the oxidation of Fe2+ to α-FeOOH and crystal growth of α-FeOOH were studied in a ZnSO4-FeSO4 system. Oxidation and crystal growth experiments were performed under the following conditions: shearing speed = 1000–4000 rpm, flow rate of oxygen = 0.3–1.5 L min−1, and reaction temperature = 70–90 °C. The results show that the oxidation rate increases with increasing shearing speed and reaction temperature, owing to the increase in oxygen mass transfer. The degree of crystallization of goethite improves and the needle-like structure is further refined as the shearing speed increases and the temperature decreases. The activation energy of nucleation is about 54 kJ mol−1. The rate equations are derived for the oxidation and oxygen mass transfer processes. The oxidation kinetics parameters are calculated by data fitting. The rate equations of oxygen mass transfer and Fe2+ oxidation are m O 2 = 54.01 k LO ∙ P O 2 H O 2 − C O 2 ∙ M O 2 ∙ v g ∙ n 0.4 and r = 47.08 C Fe 2 + 2 ∙ C O 2 C Fe 2 + + 0.001865 , respectively.