Exploring the role of hydrolyzed Nb2O5 surfaces in manganese ion adsorption

Abstract This work investigates the adsorption of Mn 2+ ions on hydrothermally synthesized Nb 2 O 5 nanoparticles obtained via an oxidant peroxo method, with particular emphasis on the role of functional groups present on the nanoparticle surface. Orthorhombic Nb 2 O 5 was formed at a mild temperature (100 °C), yielding nanocrystalline particles with high colloidal stability and a strongly negative surface charge. FTIR and zeta potential analyses reveal a carbonyl and hydroxyl-rich surface that promotes electrostatic attraction toward Mn 2+ species. Adsorption experiments demonstrate rapid Mn 2+ uptake, reaching equilibrium within minutes, with kinetics best described by a pseudo-first-order model, indicating a physisorption-dominated process. Equilibrium data are best fitted by the Freundlich and Redlich–Peterson isotherms, reflecting surface heterogeneity and multilayer adsorption, with an experimental adsorption capacity approaching 116.67 mg g −1 . These findings demonstrate that hydrolyzed Nb 2 O 5 is an efficient and tunable adsorbent for Mn 2+ removal, offering strong potential for water treatment and environmental remediation applications. Graphical abstract