Sorption of iodide on cuprite (Cu2O)

The interactions of iodide ions with cuprite (Cu2O) surfaces were studied b y combining batch experiments and surface analyses. The evolution of iodide uptake with pH was investigated. The thermodynamical calculations and surf ace analyses (X-ray photoelectron spectroscopy, scanning electron microscop y, Raman spectroscopy, and electrochemistry) were used to show that two dif ferent pH-dependent mechanisms are responsible fbr the accumulation of the iodide species on Cu2O. At pH values lower than 6.5, the precipitation of C uI occurs on the cuprite surface, while in more alkaline medium, the iodide adsorption takes place by substituting the surface hydroxyl groups of Cu2O . The sorption processes were not affected by a 1000-fold excess of chlorid e ions, but they were limited to the potential range corresponding to the s tability domain of Cu2O (i.e., between -10 and +190 mV/ENH at pH 8); thus n o accumulation was observed either on metallic copper or on CuO.