Redox reaction in silicate melts monitored by "static" in-situ Fe K-Edge XANES up to 1180°C

Abstract

A new experimental setup to measure in-situ kinetics of redox reactions in silicate melts is presented. To study the progress of the Fe-redox reaction, the variation of the signal is recorded at an energy, where the difference between the spectra of the oxidized and reduced Fe in the melt is largest ("static XANES"). To control the redox conditions, the gas atmosphere could be changed between to types of gases using computer-controlled valves (N 2:H2 and air, respectively). In this way, a number of reduction/oxidation cycles can be monitored in-situ and continuously. Applied at the Fe K-edge in molten silicates, we obtained a set of high quality data, which includes the very first steps of the redox reaction. An Avrami-type equation is used to investigate rate-controlling parameters for the iron oxidation/reduction kinetics for two melts (basaltic and Na trisilicate) for temperatures up to 1180°C. © 2007 American Institute of Physics.