Modeling Competitive Adsorption of Molybdate, Sulfate, and Selenate on γ-Al2O3 by the Triple-Layer Model

• Published in: Journal of colloid and interface science Vol. 233; no. 2; pp. 259 - 264
• Main Authors: Wu, Chung-Hsin, Lo, Shang-Lien, Lin, Cheng-Fang, Kuo, Chao-Yin
• Format: Journal Article
• Language: English
• Published: San Diego, CA Elsevier Inc 15.01.2001; Elsevier
• Subjects: Chemistry; competitive adsorption; Exact sciences and technology; General and physical chemistry; molybdate; selenate; Solid-liquid interface; sulfate; Surface physical chemistry; triple-layer model; triple-layer model; competitive adsorption; sulfate; molybdate; selenate; Surface complex; Liquid solid interface; Liquid solid adsorption; Binary system; Experimental study; Molybdates; Sulfates; Modeling; Competitive fixation; Aluminium Oxides; pH; Selenates; Kinetic parameter
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1006/jcis.2000.7223

Competitive adsorption of molybdate, sulfate, and selenate onto γ-Al2O3 was investigated in the present study. Binary solute systems of MoO2−4+SO2−4, MoO2−4+SeO2−4, and SO2−4+SeO2−4 and a ternary solute system of MoO2−4+SO2−4+SeO2−4 were evaluated to determine their relative effects on competitive adsorption on the γ-Al2O3 surface. Anionic competitive adsorption efficiency was pH dependent. The higher the pH, the lower the efficiency of MoO2−4 in preventing SO2−4 and SeO2−4 adsorption; similar results were found in SeO2−4 depressing SO2−4 adsorption. This research found that more sites are occupied in mixed anionic adsorbate systems than when either ion is present alone. The results suggest that the γ-Al2O3 surface is composed of many groups of binding sites. Because of the heterogeneity of adsorption sites, the triple-layer model (TLM) predicted the competitive effects qualitatively but not quantitatively. TLM gave reasonable descriptions of molybdate adsorption in the presence of sulfate and selenate, indicating that the model may be useful in predicting molybdate adsorption on γ-Al2O3.