Mechanism of oxalate ion adsorption on chromium oxide-hydroxide from pH dependence and time evolution of ATR-IR spectra

A chromium (III) oxide-hydroxide colloid film has been used to model the passive surface of stainless steel in in situ ATR-IR studies of oxalate ion adsorption from aqueous oxalate solutions over a wide pH range. Studies of time and pH dependence of adsorption have been used to reveal a mechanism of adsorption proceeding through ionic, hydrogen bonded and coordinated oxalate species. A Langmuir adsorption constant of 4.5×104 M−1 was determined for the surface coordinated oxalate from an adsorption isotherm at pH=3.