A hydroxyapatite-carbon adsorbent with the hierarchical porous microstructure of sugarcane stems (SS-HAP/C) was prepared by carbonizing stem internodes of sugarcane tops and subsequent doping with the saturated limewater solution and 0.02 mo1/L (NH4)2HPO4 solution in turn for three times. The morphological character of SS-HAP/C was inherited from the bio-precursors of sugarcane top stems, which mainly included the macropores from the storage parenchyma thin-walled cells of 30~115 μm in width, the parallel and densely packed vessels of 20~85 μm in width, the sclerenchyma thick-walled cells of ~30 μm in width, and the pits in the vessel and cell walls of about ~4.0 μm in width. The specific surface area through the mercury porosimetry method and the Brunauer–Emmett–Teller (BET) surface area were estimated to be 5.63 m2/g and 8.52~28.44 m2/g, respectively. The SS-HAP/C showed an excellent removal performance as an adsorbent for Cd(II) ions. For the test at the initial Cd(II) concentrations of 10, 20 and 50 mg/L, the removal capacities were determined to be 10.89, 18.00 and 51.93 mg/g, respectively, which were comparable to the adsorption capacities of the synthetic nano-hydroxyapatite. The experimental data could be very well fitted with the pseudo-second-order kinetic model and the Langmuir isotherm. The formation of the (CdxCa1-x)5(PO4)3OH solid solution through the coexisting ion exchange and dissolution-precipitation (x=0.03~0.17) processes was the main mechanism for the Cd(II) uptake by SS-HAP/C.

Preparation of a hierarchical porous hydroxyapatite-carbon composite with the bio-template of stem internodes of sugarcane tops and its removal of cadmium from aqueous solution

256th National Meeting (2018)

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