Removal of cadmium (II) from aqueous solution by a new adsorbent of fluor-hydroxyapatite composites

·The study disposed waste with waste to achieve value added utilization of waste.·FHA was obtained with a rod-like and developed space connected structure.·FHA showed a high specific surface area and adsorption amount.·FHA was a low-cost and high efficient adsorbent for the removal of cadmium (II).

The excellent precursor of fluor-hydroxyapatite composites (FHA) was prepared by hydrothermal method using fluorine-contained silica (F-SiO2) and hydrated lime (HL) as raw materials. And a new adsorbent FHA was obtained and employed as an adsorbent for the removal of Cd2+ from aqueous solution. Series of adsorption properties of FHA for the removal of Cd2+ from aqueous solution were investigated at various conditions. The influence of different adsorption parameters, such as solution pH, initial concentration of Cd2+, temperature and contact time on the adsorption efficiencies of FHA for Cd2+ were studied and discussed. The results showed that the adsorption process was in agreement with the Langmuir isotherm model and pseudo-second-order kinetic model. The Langmuir adsorption isotherm constant corresponding to adsorption amount, qm, was found to be 236.41 mg/g. Various thermodynamic parameters such as △G0, △H0 and △S° were calculated, which indicated the spontaneous and endothermic nature of the adsorption process. At the appropriate conditions, FHA was an excellent adsorbent for the removal of Cd2+ from aqueous solution. And it was confirmed that the adsorption mechanism of Cd2+ by FHA was mainly determined by ion-exchange and monolayer chemical adsorption.

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