Mesoporous hydroxylapatite/activated carbon bead-on-string nanofibers and their sorption towards Co(II)

The present work aims to prepare mesoporous hydroxylapatite/activated carbon (meso-HA/AC) bead-onstring nanofibers and evaluate their sorption towards Co(II) via sorption kinetics and isotherms. Using polyvinyl alcohol/hydroxylapatite/glucose electrospun nanofibers as the precursor, meso-HA/AC nanofibers are prepared by a hydrothermal process. The nanofibers show bead-on-string structures with mesoporous characteristics, main pores around 29 nm in size, and a specific surface area of 30.014 m(2) g(-1). Moreover, the rod-like HA crystals assemble into bundles and insert into the two neighboring activated carbon beads. The sorption of Co(II) onto meso-HA/AC nanofibers is strongly dependent on pH and ionic strength. The pseudo-second-order model is valid to describe the sorption of Co(II) onto meso-HA/AC nanofibers, and the intraparticle diffusion is not the sole rate-controlling step. Both Langmuir and Freundlich models can well describe the sorption isotherms, and the Langmuir model is slightly better than the Freundlich model. Moreover, the thermodynamic parameters imply that the sorption process is spontaneous and endothermic. The meso-HA/AC bead-on-string nanofibers may have potential as a highly effective material for the removal of heavy metal ions from aqueous solution.