Magnetic Alginate-Based Composite Beads Incorporating Cu/TiO2: Synthesis, Structure-Property Relationships, and Catalytic Applicability.

Magnetic alginate-based composite beads integrating Cu/TiO2 and magnetite (Fe3O4) were fabricated as polymer-inorganic hybrid systems for magnetic recovery. These composite beads were generated via ionotropic gelation, a method that enabled efficient encapsulation of inorganic constituents within the sodium alginate matrix while preserving the crystalline structures of Fe3O4 and anatase TiO2. The impact of Fe3O4 loading on the beads' structural and physicochemical attributes was systematically investigated, revealing specific structure-property relationships that dictated encapsulation efficacy, swelling behavior, bulk density, and internal morphology. Among the formulations examined, the S-1.0Fe3O4-SA beads demonstrated a favorable balance between structural integrity and mass-transfer accessibility. The efficacy of the composite beads was evaluated via their employment in the hydrogenation of glacial acetic acid, a representative liquid-phase reaction. Examination of the reaction products indicated the formation of ethanol and ethyl acetate; the precise product distribution depended on the Cu loading in the Cu/TiO2 component. A moderate Cu content was observed to facilitate product formation, concurrently maintaining the structural stability of the beads. The S-1.0Fe3O4/SA-1.8Cu/TiO2-0.4 catalyst exhibited the highest ethanol production (18.69 mg L-1). Lower Cu loading resulted in insufficient active sites, whereas higher loading led to aggregation and reduced catalytic efficiency. Recycling tests revealed a gradual decrease in ethanol formation upon reuse, indicating partial catalyst deactivation, likely due to surface fouling and Cu leaching. Therefore, this study highlights the promise of alginate-based magnetic composite beads as a versatile polymer-supported platform, in which the macromolecular structure is crucial for dictating functional performance.