Cellulose bridged carbonate hydroxyapatite nanoparticles as novel adsorbents for efficient Cr(VI) removal

Abstract

Removal of Cr(VI) from aquatic environment is crucial due to its bioaccumulation, high mobility and strong toxicity. In this work, a novel nano-adsorbent consisting of carbonate hydroxyapatite (CHAP) and carboxymethyl cellulose (CMC) was designed and successfully synthesized by a simple route for the uptake of Cr(VI). The synthetic CMC bridged CHAP (CMC-CHAP) material exhibited higher surface area (122.90 m2/g) and adsorption capacity for Cr(VI) (13.45 mg/g) than other apatite based adsorbents. The adsorption process of Cr(VI) by CMC-CHAP was in line with the Langmuir isotherm model and pseudo-second-order kinetic model. The calculated thermodynamic parameters showed that the adsorption of Cr(VI) on CMC-CHAP was a spontaneously endothermic process. In addition, CMC-CHAP had good ability to remove Cr(VI) under the interference of coexisting ions, and possessed remarkable reusability. Based on the pH-effect experiment and x-ray photoelectron spectroscopy characterization, the removal of Cr(VI) by CMC-CHAP was considered to be synergistic processes of electrostatic attraction, reduction reaction and chelation. This work provided new insights into performance optimization and application potential of CMC-CHAP on Cr(VI) removal from water.