A simple geochemical model for predicting Sb(V) partitioning: From iron oxides to complex soil systems.

Predicting the partitioning behavior of Sb(V), a global environmental pollutant, at the solid-liquid interface in soils is crucial for understanding its environmental transport. However, existing geochemical models exhibit significant limitations. In this study, batch adsorption experiments integrated with reported microscopic surface species, were used to develop the surface complexation models for Sb(V) adsorption on goethite and ferrihydrite. Then, these two sub-models were integrated, along with consideration of the presence or absence of P(V) and soil organic matter (SOM), to construct the multi-surface speciation model (MSM) for Sb(V) partition in soils. The SCM depicted the presence of both bidentate and monodentate complexes for Sb(V) on iron oxides under various hydrochemical conditions. The constructed MSM performed well in predicting Sb(V) adsorption on all twelve studied soils, while the comparisons of four MSM scenarios indicated that considering the presence of both P(V) and SOM simultaneously yielded best model performance. In addition, the competitive effect of the reactive organic matter component (RO) could be quantitatively estimated by establishing the relationships between the RO and both SOM and iron oxide content. This study presents an advanced yet simple geochemical model approach for the qualitative and quantitative prediction of Sb(V) partition in complex soil environments.