PNNL

Abstract

Zn is an essential micronutrient that is often limited in tropical, lateritic soils in part because it is sequestered in nominally refractory iron oxide phases. However, erstwhile stable phases such as goethite and hematite can undergo reductive recrystallization without a phase change under benign pH conditions and release metal impurities such as Zn into aqueous solutions. Further, the process appears to be driven by defect chemistry or Fe vacancies. In this contribution, we used ab initio molecular dynamics (AIMD) informed EXAFS to show that Zn incorporated in the structure of hematite is associated with protonated Fe vacancies, providing a potential link between crystal chemistry and the bioavailability of Zn.