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Zinc oxide-hydroxyapatite nanocomposites were prepared from a natural phosphate ore via a solvent-free method and evaluated for the photodegradation of two antibiotics in solution. The in situ growth of ZnO followed by thermal treatment allowed for the formation of photocatalytic nanocrystals homogeneously dispersed in the apatite phase. Nanocomposites exhibited higher rates of sorption of ofloxacin and ciprofloxacin compared to the individual phases. At high ZnO loadings, photodegradation performances of the nanocomposites under UV irradiation were equivalent or greater than that of the photocatalytic particles alone, depending on the considered antibiotic. This dependency reflects distinct degradation pathways that were attributed to different affinities of the antibiotics for the nanocomposite particles. Because of its simplicity and versatility, the here-described approach appears very promising for the development of multifunctional platforms for water remediation. [ABSTRACT FROM AUTHOR]

The retention of four antibiotics, ciprofloxacin, ofloxacin, amoxicillin and sulfamethoxazole by a natural phosphate rock (francolite) was studied and compared with a converted hydroxyapatite powder. The maximum sorption capacities were found to correlate with the molecular weight of the molecules. The mechanisms of sorption depended mostly on the charge of the antibiotic whereas the kinetics of the process was sensitive to their hydrophobic/hydrophilic character. The two materials showed slightly distinct affinities for the various antibiotics but exhibited similar maximum sorption capacities despite different specific surface areas. This was mainly attributed to the more pronounced hydrophobic character of the francolite phase constituting the natural phosphate. These data enlighten that the retention properties of these mineral phases depend on a complex interplay between the inter-molecular and molecule-solid interactions. These findings are relevant to understand better the contribution of calcium phosphates in the fate and retention of antibiotics in soils. [ABSTRACT FROM AUTHOR]