Observation of chemical reactions at the solid-water interface by quick XAFS combined with a column reactor.

A simple method for the observation of the kinetics of the reactions at the solid-water interface was developed using quick X-ray absorption fine structure combined with a column reactor. We applied the method to the oxidation reaction of As(III) by manganese oxide, a strong oxidizer in natural systems. A reliable reaction rate constant k', 3.9 x 10(-4) %(-1) min(-1) at pH 7.1, was obtained, where the effect of photooxidation under X-ray beam can be eliminated. Considering the average Mn/As molar ratio in the system, the value is reasonable compared with other reported values. Since this method is very simple, we can apply it to various elements and reaction systems at the solid-water interface as a tool to understand the kinetics of various reactions in detail.