Trivalent ion-exchanged magadiite: structural and textural modifications accompanied by spontaneous nanoparticle formation

Abstract

Ion exchange with metal cations and the related adsorption mechanisms have been widely investigated for magadiite, despite limited knowledge of their complexation reactions. This study has successfully described the possible distinct adsorption reactions along with the structural and textural behavior of Na⁺-magadiite with trivalent metal cations (M³⁺ = Fe, In, and Al). Ion-exchange reactions of Na⁺ with M³⁺ led to deterioration of the layered structure, eventually to the H-form, suggesting subsequent additional reactions with adsorbed M³⁺. Further structural changes and successful grafting of M³⁺ in the interlayers were evidenced based on the distortion of the layered structure, the thermal stability, and the formation of interlayer micropores resulting in increased surface area. All M³⁺-magadiites exhibited uniform spherical-shaped nanoparticles whose size and population varied depending on the type and concentration of M³⁺ in solution. This study provides an initial comprehensive explanation of the ion exchange and complexation behavior of M³⁺ (Fe³⁺, In³⁺, and Al³⁺) with magadiite, detailing the resulting structural distortions, nanoparticle formation, and interlayer grafting, with implications for catalytic and environmental applications. Trivalent ion exchange in magadiite results in more extensive structural modifications than divalent exchange, as characterized by the framework disruption, H-form generation, and M³⁺ grafting. These unique effects highlight the enhanced tunability of trivalent ion-exchanged magadiites, underscoring their potential for advanced applications in adsorption, separation, and catalysis. These remarkable changes in the structural and textural properties of magadiite upon ion-exchange reactions with M³⁺ provide new insights into nanomaterial fabrication applicable to catalysis, environmental remediation, and related fields.