The reaction kinetics and Sn isotope fractionation of Sn(IV) chloride hydrolysis

Abstract

Hydrolysis of Sn is a pivotal step during the precipitation of cassiterite, the primary Sn-bearing mineral and thermodynamically stable Sn-oxide on Earth's surface. In this contribution, we investigated the reaction kinetics of Sn(IV) chloride hydrolysis by systematic experiments at temperatures of 6.4 °C to 28.6 °C. Experimental results show that the hydrolysis reactions of Sn(IV) chloride follow a first-order kinetics model, with rate constants (0.12 h⁻¹ to 5.5 h⁻¹) strongly controlled by temperature. Based on the obtained reaction constants at different temperatures and the Arrhenius equation, the activation energy of the Sn(IV) chloride hydrolysis reaction is calculated to be 26.05 ± 2.25 kcal/mol, indicating a surface-controlled reaction mechanism. Additionally, the Sn(IV) chloride hydrolysis rate increases with the ionic strength. No significant Sn isotope fractionation between aqueous Sn(IV) and the solid hydrolysis product was observed during the Sn(IV) hydrolysis experiments in this study. The activation energy data and Sn isotope behavior associated with Sn(IV) chloride hydrolysis may be used to better understand the behavior of Sn during various mineralization and weathering processes.