Fuente: Journal of applied polymer Lugar: RESEARCH ARTICLE Alginate/hydroxyapatite composite beads for dye adsorption.

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 Ca2+ 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.