Adsorption of calcium(II), cadmium(II) and copper(II) ions from water by prepared silicon-aluminum-zirconium oxide using sol-gel process

Ternary oxide silica-alumina-zirconia (SiO₂/Al₂O₃/ZrO₂) obtained by the sol-gel process was applied as novel adsorbent of ions in aqueous solution. Batch isotherms were performed using standard CuII, CdII and CaII solutions at variable pH and different concentrations. Adsorption capacity was best at weakly acidic pH. The maximum adsorption capacities were 2.28 mg g^-1 for CaII, 9.89 mg g¹ for CdII, and 14.88 mg g^-1 for CuII. The adsorption data fitted well to the single and dual-site Langmuir-Freundlich isotherm models. However, since the adsorption is very low in the sites with high energy, the single-site Langmuir-Freundlich provided a good fit as well. Whereas, the site responsible for the most ion adsorption was assigned to the Zr-OH group. A real sample of produced water was also tested. The new adsorbent showed a wide ability to retain many metal ions (alkali-earth, transition, and p-block metals) and even some anions were also caught by the adsorbent. The ternary oxide silica-alumina-zirconia was found to be a promising alternative adsorbent for metal ions in aqueous media. (author)