Evaluation of hydroxyapatite-chitosan-magnetite nanocomposites for separation of pharmaceuticals from water: A mechanistic and comparative approach

Abstract

Binary and ternary composites of hydroxyapatite (HAP), chitosan (CT) and magnetite (MNP) were fabricated to assess the individual role of each constituent and to estimate their optimized proportion for maximizing the adsorption of pharmaceuticals (PCs) from aqueous phase. Batch studies carried out with model ibuprofen (IBU) reveal the significant role of HAP in enhancing the adsorption to binary composites (HAP@CT, HAP@MNP, CT@MNP). Among the HAP@CT composites fabricated with varying proportion, CT proportion of ≧ 50% showed improved adsorptive performance. Highest adsorption of IBU was achieved by the ternary composite of NC6 having a HAP: CT: MNP of 2:5:3. FTIR, VSM, Fe-SEM, TEM studies revealed NC6 to possess magnetic properties, better aqueous phase stability, higher surface area, higher crystallite sized nanoparticles with less agglomeration, and adequate surface functionality as compared to its precursors. The high efficiency and fast kinetics for Ibuprofen (IBU), Deflazacort (DEF), Methylprednisolone (MET) and Norfloxacin (NOR) could be corelated with the structural and physico-chemical nature of the PCs in aqueous phase. Langmuir adsorption capacity of 535.6 mg/g, 833 mg/g, 625 mg/g and 714 mg/g for NOR IBU, MET and DEF respectively was reported with NC6 dosage of 0.01 g/L. NC6 demonstrated faster equilibration time of 30–90 mins with > 85% PCs removal as compared to other reported composites. The results of this study reveal the efficacy of NC6 for fast and high adsorptive removal of diverse types of PCs from both model and hospital wastewater. Also, the reusability and biogenic nature of NC6 is established.