Design and Characterization of Concave Hollow Double-Layer Nanospheres for Efficient Cd(II) and Pb(II) Adsorption

> 0.99), while Pb(II) adhered to the Langmuir model, suggesting monolayer and heterogeneous binding mechanisms, respectively. Kinetic studies further corroborated chemisorption dominance through pseudo-second-order fitting for Cd(II) and Elovich compatibility for Pb(II). We propose a synergistic mechanism involving ligand complexation and ion exchange, facilitated by the dual functionality of surface groups and structural advantages of the concave architecture. This work provides a blueprint for designing spatially engineered polymers for environmental remediation.