Comparative study of divalent cation sorption on titania nanotubes using Co2+, Ni2+, Zn2+, and Sr2+

• Published in: Chemical Engineering Journal Advances
• Main Authors: Tomoyo Goto, Yoshifumi Kondo, Sung Hun Cho, Satoshi Seino, Tohru Sekino
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2022
• Subjects: Titania nanotubes; Sorption; Divalent cation; Water purification; Ion-exchange; Chemical engineering; TP155-156; Langmuir; Carbonic acid
• Online Access: https://doi.org/10.1016/j.ceja.2022.100388; https://doaj.org/article/c92f94af20d84230a1f355e108097bea

Developing environmental purification techniques for water resources is important for realising a sustainable society. Inorganic ion-exchanger is one of the research themes in technological development, particularly titania nanotubes (TNTs), which have been studied for the removal of cationic heavy metals and radionuclides. Although many studies have reported the adsorption properties of TNTs, the sorption behaviour and state of intercalated cations in the structure are still unclear. In this study, the sorption properties of Co2+, Ni2+, Zn2+, and Sr2+ on TNTs were investigated using the equilibrium isotherms, kinetics and detailed analysis of residues under simple batch conditions. The sorption isotherms of cations on TNTs were fitted with the Langmuir model, and the maximum sorption amount (Qmax) was in the order of Sr2+ (1.13 mmol/g) > Zn2+ (0.99 mmol/g) > Co2+ (0.85 mmol/g) > Ni2+ (0.78 mmol/g). The sorption kinetics data fitted well with pseudo second-order model. The X-ray analysis indicated that the Sr2+ sorption on TNTs resulted from the ion-exchange and formation of carbonate compounds. In contrast, the Co2+, Ni2+, and Zn2+ ions were estimated to be incorporated in an ionic state in the TNT interlayer by ion-exchange with Na+ and H+ via chelation with surface hydroxyl groups on TNTs. These results indicate that the crystallographic properties of TNTs, ionic size, and chemical property of the target cation, and reactivity with carbonic acid are important factors to consider in the design of water purification systems using TNTs.