Modulating the structure of organofunctionalized hydroxyapatite/tripolyphosphate/chitosan spheres for dye removal

International audienceHybrid materials based on amino hydroxyapatite (NH2-HA) and chitosan (CS) were prepared by reticulation in the presence of sodium tripolyphosphate. NH2-HA having different weight percentages (10–75%) was used in the synthesis. The resulting solids were used for the removal of reactive violet 5R—an organic dye—from an aqueous solution. The synergy among the adsorptive properties of the precursors was assessed for the hybrid biomaterials by X-ray diffraction, thermogravimetry, CHN elemental analysis, infrared spectroscopy, and 13C nuclear magnetic resonance spectroscopy. The crosslinking mechanism was also elucidated. The effects of adsorbent dosage, time, pH, and initial dye concentration were investigated. The adsorption capacities of the resulting hybrids were proportional to the CS content in the hybrids and the surfaces were positively charged at pH 1–7. The optimal dye-removal capacity of 350 and 365 mg g-1 was achieved at pH 3 for the solids containing 10 and 25% silylated HA, respectively. Kinetic data were evaluated for the pseudo-first-order, pseudo-second-order, and Elovich models. At equilibrium, various systems were adjusted to the Langmuir models. The amino groups were blocked via the reaction with acetyl chloride, which demonstrated the contribution of different active sites in the prepared hybrids toward dye removal. The Artemia salina tests demonstrated the low toxicity of the prepared hybrids irrespective of their composition. The data indicated that the prepared hybrids were capable of achieving rapid and high dye removal. Additionally, the reuse tests suggested the formation of stable-loaded-dye substrates after adsorption