| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 607210 | Journal of Colloid and Interface Science | 2014 | 9 Pages |
•Rod-like nanostructured hydroxyapatite (FGD-HAP) was firstly prepared from waste FGD gypsum.•The obtained FGD-HAP showed excellent adsorption performance for both Pb2+ and Cd2+.•The FGD-HAP had a higher affinity with Pb2+ than Cd2+.•The desorption efficiency of Pb2+ and Cd2+ by EDTA solution could reach 74.3% and 81.4%, respectively.
Flue gas desulfurization (FGD) gypsum, a familiar waste generated from coal-fired power plants, was successfully transformed to hydroxyapatite (FGD-HAP) by hydrothermal method. The obtained FGD-HAP was characterized by XRD, FTIR, TEM and BET methods and investigated as adsorbent for removal of Pb2+ and Cd2+ from wastewater. Batch experiments were performed by varying the pH values, contact time and initial metal concentration. The result of pH impact showed that the adsorption of two ions was pH dependent process, and the pH 5.0–6.0 was found to be the optimum condition. The achieved experimental data were analyzed with various kinetic and isotherm models. The kinetic studies displayed that the pseudo-second order kinetic model could describe adsorption processes well with high correlation coefficient, and the Langmuir isotherm model provided the best fit to the equilibrium experimental data. The maximum adsorption capacities calculated from Langmuir equation were 277.8 and 43.10 mg/g for Pb2+ and Cd2+, respectively, which can compete with other adsorbents. The thermodynamic parameters revealed the adsorption processes were endothermic and spontaneous in nature. In binary adsorption, the amount of Cd2+ adsorbed on FGD-HAP decreased by 46.0% with increasing concentration of Pb2+, which was higher than that of Pb2+(21.7%), demonstrating the stronger affinity between FGD-HAP and Pb2+. The highest amount of Pb2+ and Cd2+ desorbed from saturated FGD-HAP by EDTA solution confirmed the FGD-HAP was a promising alternative adsorbent in treatment of toxic Pb2+ and Cd2+ wastewater.
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