Redox reactions of structural Fe in 2:1-type phyllosilicate as a battery in environment

Abstract

2:1 type layered silicates such as smectite are ubiquitous in the environment and play a variety of roles in the material cycle. They are especially important as adsorbents of cations mainly due to their negative charge and large specific surface area of the layer structure. On the other hand, iron (Fe) in the octahedral layer structure of smectite can be both Fe(II) and Fe(III), and is known to contribute to redox reactions in the environment through its valence change. The valence change is also characterized by the fact that it varies over a wide range of redox states (Eh) and that the Eh range covered by the same smectite is different depending on the constituent elements and Fe concentration, such as montmorillonite, non-tronite, and saponite. Because the Fe(II)/Fe(III) ratio in smectite changes in response to different redox environments, we have been studying in parallel multiple phenomena in which iron in the same smectite acts as either an oxidant or a reductant, and we will present them to discuss the role of 2:1-type layered silicates as batteries in the environment and I would like to discuss the role of 2:1 type layered silicates as batteries in the environment.