Equilibrium Modeling of Arsenic Adsorption in a Ternary Arsenic–Iron Oxide–Natural Organic Matter System

The effect of natural organic matter (NOM) on the adsorption efficiency of arsenic (As) species by iron oxide-based adsorbent (IBA) under different concentrations was investigated. To evaluate the sorption of As in the presence of humic materials, simple isotherm curves should be replaced by three-dimensional sorption isotherm surfaces. In this study, a modified Langmuir-type model was developed to describe the isotherm surfaces. The proposed model showed satisfactory predictions for the As uptake in different scenarios with the presence of As(V)/(III), organic matter fractions, and model adsorbent. The isotherms indicated a competitive uptake of the As species and humic substances, causing that less As was adsorbed on the adsorbent. The developed model for the ternary sorption system enabled quantitative estimation of As sorption onto iron oxide based adsorbents in complex natural water systems.