Self-condensation route to Al₁₃-magadiite complex for arsenate removal

Al polycations like ε-Al₁₃ Keggin cluster [AlO₄Al₁₂(OH)₂₄(H₂O)₁₂⁷⁺] (referred to as Al₁₃) are promising for removal of arsenate from drinking-water. However, their practical applications are rather limited because mainly of difficulty in post-retrieving and of acute biotoxicity. Although complexation with clay minerals has been suggested to overcome these limitations, it led typically to appreciable inactivation of exposed OH groups. This study has attempted to fabricate Al₁₃-complexed magadiite by simple cation exchange reaction without any further treatments. Any noticeable back-release of Al₁₃ was not observed to confirm stable complexation between Al₁₃ and magadiite. Al₁₃-complexed magadiite exhibited maximum adsorption capacity of ~30.3 ​μmol ​g⁻¹ for arsenate predominantly by chemisorption. Furthermore, it was revealed that Al₁₃-complexed magadiite removed arsenate completely in a concentration level below 1 ​mg ​L⁻¹ (below detection limit of 0.52 ​μg ​L⁻¹). This study provides a new tailor-making approach to the adsorbents for complete removal of low-level aqueous arsenate.