Adsorption of nickel on synthetic hydroxyapatite from aqueous solutions |
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Authors: | O. Rosskopfová M. Galamboš L. Pivarčiová M. Čaplovičová P. Rajec |
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Affiliation: | 1. Department of Nuclear Chemistry, Comenius University in Bratislava, Faculty of Natural Sciences, Mlynská Dolina, 842 15, Bratislava, Slovak Republic 2. Department of Geology of Mineral Deposits, Comenius University in Bratislava, Faculty of Natural Sciences, Mlynská Dolina, 842 15, Bratislava, Slovak Republic
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Abstract: | The sorption of nickel on synthetic hydroxyapatite was investigated using a batch method and radiotracer technique. The hydroxyapatite samples used in experiments were a commercial hydroxyapatite and hydroxyapatite of high crystallinity with Ca/P ratio of 1.563 and 1.688, respectively, prepared by a wet precipitation process. The sorption of nickel on hydroxyapatite was pH independent ranging from 4.5 to 6.5 as a result of buffering properties of hydroxyapatite. The adsorption of nickel was rapid and the percentage of Ni sorption on both samples of hydroxyapatite was >98 % during the first 15–30 min of the contact time for initial Ni2+ concentration of 1 × 10?4 mol dm?3. The experimental data for sorption of nickel have been interpreted in the term of Langmuir isotherm and the value of maximum sorption capacity of nickel on a commercial hydroxyapatite and hydroxyapatite prepared by wet precipitation process was calculated to be 0.184 and 0.247 mmol g?1, respectively. The sorption of Ni2+ ions was performed by ion-exchange with Ca2+ cations on the crystal surface of hydroxyapatite under experimental conditions. The competition effect of Co2+ and Fe2+ towards Ni2+ sorption was stronger than that of Ca2+ ions. NH4 + ions have no apparent effect on nickel sorption. |
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