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| Cu2+ removal from wastewater using hydroxyapatite prepared from FGD gypsum |
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Abstract Hydroxyapatite (FGD-HA) was synthesized from waste FGD gypsum using hydrothermal method. FGD-HA was characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM) and investigated as adsorbent for removal Cu2+ from wastewater. The sorption kinetics, isotherms and thermodynamics of Cu2+ adsorption onto FGD-HA were investigated by batch tests. The kinetics was evaluated utilizing pseudo-first order and pseudo-second order models, and the experimental data agreed well with the pseudo-second order model due to its relatively high R2 value (0.9998). The equilibrium data were further analyzed by using the Langmuir, Freundlich and Dubinin-Radushkevich models. Equilibrium sorption of Cu2+ onto FGD-HA had best fitness with the Langmuir model. Response surface methodology (RSM) employed to optimize the adsorption process parameters. The optimum operating conditions were determined as dosage of 3.11g/L, pH of 4.96, temperature of 22.09℃, initial concentration of 24.75mg/g, and the removal efficiency for Cu2+ was found to be 100%. The verification experiment was also carried out at same conditions and the result was 97.4%, confirming that the model was effective.
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Received: 05 December 2013
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