Study and simulation of the adsorption of dihydrogen phosphate ions on magnetite as a function of pH

The adsorption of dihydrogen phosphate ions on iron oxide surface is simulated at various values of pH, and the double electrical layer that appears at the iron oxide/electrolyte solution interface is shown to substantially influence the adsorption behavior. The hydrogen ion concentration and the potential at the iron oxide/electrolyte solution interface play a key role. To describe adsorption, it is necessary to take into account the acid–base equilibria that appear at the iron oxide/electrolyte solution interface. The adsorption behavior of dihydrogen phosphate ions is described with a set of the five equilibria that take place at the iron oxide/electrolyte solution interface and correspond to the triplet layer model (TLM). The simulation performed using TLM explains the dependence of adsorption on pH and the concentrations of a background electrolyte and dihydrogen phosphate ions.