School of Materials Science and Engineering, Tongji University, Shanghai, China.
Water Environ Res. 2010 Nov;82(11):2279-84. doi: 10.2175/106143010x12609736966405.
The goal of this study was to synthesize use of hydroxyapatite as a high-efficiency adsorbent for Ni(II) ions, and to study its adsorption behavior. Three tests--Fourier-transform infrared spectroscopy, transmission electron microscopy, and Brunauer-Emmett-Teller were carried out to determine the chemical functionality of the hydroxyapatite powders, to observe its crystal morphology, and to measure the specific surface area. Results indicate that proves the n-HA synthesized by chemical precipitation is an effective adsorbent for the removal of Ni(II) ions from water solution. The synthesized, needle-like nano-hydroxyapatite (n-HA) have a uniform average size of 31.9 X 21.3nm, a large specific surface area (135 m2/g), and typically is a weak crystal with a broad pore distribution. The adsorption isotherm shows the Langmuir model is applicable only when the initial Ni2+ concentration is lower than 0.1 mol/L. Multilayer adsorption was attributed to uneven pore distribution that occurred at higher Ni2+ concentration. The adsorption of Ni2+ onto n-HA was attributed to electrostatic attraction, ion exchange, and dissolution-precipitation reaction. As the result, Ni2+ substitutes Ca2+ and binds with the oxygen atom on the surface, which resulted from the change in crystal-phase composition and in the binding energy of surface elements of n-HA before and after adsorption.
本研究的目的是合成羟基磷灰石作为高效吸附剂用于去除 Ni(II)离子，并研究其吸附行为。通过傅里叶变换红外光谱、透射电子显微镜和 Brunauer-Emmett-Teller 对羟基磷灰石粉末的化学官能团进行了测试，以观察其晶体形态并测量比表面积。结果表明，化学沉淀法合成的 n-HA 是一种从水溶液中去除 Ni(II)离子的有效吸附剂。合成的针状纳米羟基磷灰石（n-HA）具有均匀的平均尺寸为 31.9 X 21.3nm，大的比表面积（135 m2/g），通常是具有宽孔分布的弱晶体。吸附等温线表明，Langmuir 模型仅适用于初始 Ni2+浓度低于 0.1 mol/L 的情况。在较高的 Ni2+浓度下，出现了不均匀的孔分布，导致多层吸附。Ni2+在 n-HA 上的吸附归因于静电吸引、离子交换和溶解-沉淀反应。结果，Ni2+取代了 Ca2+并与表面上的氧原子结合，这是由于 n-HA 吸附前后晶体相组成和表面元素结合能的变化所致。
