A Study of Silicate Adsorption on Gibbsite (Al(OH)3) by X‐Ray Photoelectron Spectroscopy (XPS)

Abstract

Abstract X‐ray photoelectron spectroscopy (XPS, ESCA) was utilized to investigate the mechanisms of adsorption of silicates and phosphates on a surface of synthetic gibbsite. Unbuffered solutions of CaSiO 3 Ca(H 2 PO 4 ) 2 , Si(OH) 4 , and Ca(NO 3 ) 2 at low concentrations, were adsorbed onto powdered Al(OH) 3 . The samples were dried, leached with large volumes of water, redried, pressed into a pellet, and examined by XPS. The following observations were made: When CaSiO 3 was the adsorbate, both Ca and Si were detected on the adsorbent surface by means of the Ca2p, Si2s, and Si2p photoelectron peaks. No Si was detected on the Al(OH) 3 surface in the Si(OH) 4 treatment which suggests weak adsorption of Si on gibbsite in the absence of Ca. Ca and P were both present on the adsorbent after Ca(H 2 PO 4 ) 2 treatment. Atomic concentration ratio estimates calculated from peak intensities, kinetic energies, and photoelectron cross‐sections, showed that Ca/Si exceeds Ca/P on the alumina surface.