Impact of Filler Phase Processing of Hydroxyapatite/Alginate Nanocomposite Beads on the Removal of Reactive Dye From Aqueous Solution

ABSTRACT Polymer–ceramic nanocomposites combine biopolymers' unique physical properties with inorganic fillers that have significant adsorption capacity, yet the influence of filler‐phase processing is rarely compared. This study investigates the physicochemical properties and batch adsorption performance of alginate (AL)/hydroxyapatite (HA) composite beads made from three different HA formats: fresh precipitate (B1), aged dense slurry (B2), or preformed dried powder (B3). Beads were made with all three forms by dropwise gelation in Ca 2+ solution and characterized using x‐ray diffraction (XRD), Fourier transform infrared (FT‐IR) spectroscopy, scanning electron microscopy and transmission electron microscopy (SEM/TEM), energy‐dispersive x‐ray spectroscopy (EDX), thermogravimetric analysis (TGA), and BET analysis. In batch tests to remove Reactive Blue 21 (RB21), the maximum removal of dye was found to be 87.8% (B2), which had the highest monolayer adsorption capacity (1.724 mg g −1 ) and a rapid dye uptake process. Kinetics revealed that all samples fit pseudo‐second‐order models and exhibited Langmuir isotherm model behavior. The initial results of this study indicate that aged slurry‐based HA (B2) offered superior interactions with the matrix and mineral content, resulting in higher adsorption. These results suggest filler‐phase processing is critically important for governing sorption efficiency beyond surface area characteristics.