Multi‐Site Chelation Enabled by 3D‐Printed TiO ₂ Hydrogel Monoliths for Dynamic Ge(IV) Recovery in Fixed Beds

ABSTRACT

Germanium is a critical dispersed metal, yet sustainable recovery from dilute solutions is limited by sorbents that are difficult to regenerate and operate in continuous mode. Here, we fabricate a regenerable 3D‐printed hydrogel monolith (3D‐ATO‐GS) by integrating hydroxyl‐rich amorphous TiO ₂ nanoparticles into an alginate/gelatin scaffold using direct ink writing followed by Ca ²⁺ crosslinking under low‐temperature aqueous conditions. The monolith features millimeter‐scale straight‐through channels coupled with a swollen nanoscale network, enabling shortened diffusion pathways and a stable fixed‐bed operation. In batch tests at pH 3, 3D‐ATO‐GS achieves a maximum Ge(IV) capture of 206.18 mg g ⁻¹ and retains > 75% adsorption efficiency after ten adsorption–desorption cycles using 0.1 mol L ⁻¹ NaOH. In continuous‐flow fixed‐bed experiments, the monolith delivers a breakthrough capacity of 56.1 mg g ⁻¹ at 1.0 mL min ⁻¹ , and maintains considerable capacity over three column regeneration cycles (56.1 → 45.6 → 43.3 mg g ⁻¹ ). Spectroscopic analyses combined with density functional theory and molecular dynamics simulations indicate that ‐COOH, Ti–OH, –OH, and –NH ₂ groups cooperatively chelate Ge(OH) ₄ via multi‐site coordination. These results demonstrate a monolithic regenerable platform that connects molecular binding design with fixed‐bed process requirements for Ge recovery.