Valence separation of Fe and removal of Sn2+ by solvent extraction as a potential method to determine Fe2+ in glass containing Sn2+

The amounts of Fe 2+ and Fe 3+ present in glass are important indicators of its optical properties because even small amounts have significant effects.However, it is challenging to use wet chemical analysis to determine the concentration and the ratio of Fe 2+ and Fe 3+ in glass when it contains Sn because of the redox reaction between Sn 2+ and Fe 3+ in the glass decomposition solution.A two-step approach was tested to determine the concentrations of Fe 2+ and Fe 3+ in a glass decomposition solution in the presence of Sn 2+ .In the first step, the redox reaction between Sn 2+ and Fe 3+ was suppressed by increased pH.In the second step, Sn 2+ was removed from the glass decomposition solution by solvent extraction.To understand the kinetics of the redox reaction between Sn 2+ and Fe 3+ , time-resolved dispersive X-ray absorption fine structure and ultraviolet-visible absorption spectroscopy (UV-vis) were used with standard chloride solutions of Sn and Fe in respective valences.We found that lowering the acid concentration suppressed redox reactions.The partitioning behaviors of Sn 2+ , Sn 4+ , Fe 2+ , and Fe 3+ by bis(2-ethylhexyl) hydrogen phosphate (D2EHPA) as an extractant in n-dodecane were investigated to see the removal ability of Sn 2+ from the glass decomposition solution.As a result, D2EHPA in n-dodecane could extract Sn 2+ , Sn 4+ , and Fe 3+ into the organic phase, and Fe 2+ remained in the aqueous phase.The simultaneous removal of Sn 2+ and Sn 4+ and the separation of Fe 2+ and Fe 3+ became possible.This method can potentially apply to the rapid analysis of the concentration of Fe 2+ and Fe 3+ in a glass containing tin oxide.