An extended X-ray absorption spectroscopy study of copper(II) sorption by oxides

Many important sorption parameters have been determined by isothermal sorption batch experiments; however, only macroscopic and indirect results were obtained. The objective of this study was to derive the species and structural environment of Cu(II) on the surface of gibbsite (Al(OH)3), pyrolusite (MnO2), and amorphous silica (SiO2), using the technique of extended X-ray Absorption Fine Structure (EXAFS) spectroscopy. Results show that the equilibrated pH of suspension affects significantly the species of Cu sorbed on the surface of these oxides. Sorbed species (Cu2+) were present below pH 5.73 and precipitated (Cu(OH)2) phases above 5.63. On the other hand, there is no EXAFS evidence that sorbent types and concentrations affect the local chemistry environment and species of Cu(II).