磁性羟基磷酸盐复合材料可控合成及应用研究

发布时间：2019-03-12 13:30

【摘要】：近年来,污水的不恰当排放给人类生存及自然环境的保护带来了严峻的考验。羟基磷灰石作为一种廉价高效、环境友好的吸附材料而成为研究热点,其本身具备的离子交换特性有利于对水体中重金属离子的吸附,但其吸附性能仍有待进一步提高。制备方法的改善及材料的掺杂有助于提高吸附材料的综合性能。本文采用水热法可控制备了掺锶碳羟基磷灰石与磁性羟基磷酸锶复合材料,并深入探究了它们在去除水溶液中重金属Pb~(~(2+))的行为和机理。主要研究结果如下:1、利用水热法合成了单分散、由纳米片自组装而成的绣球花状Sr-CHAp,具有较大的比表面积(43.54 m2·g-1)。Sr-CHAp对重金属铅离子具有很强的吸附能力,在最佳pH值(pH=3.0)的溶液中其对Pb~(~(2+))的饱和吸附量达到985.1 mg·g-1,为获得酸性条件下高效的Pb~(~(2+))吸附剂提供可能。其吸附Pb~(~(2+))的等温线数据与Langmuir模型相符,动力学数据与伪二级动力学模型相符。在酸性溶液中SrCHAp对Pb~(~(2+))的吸附主要表现为溶解/沉淀机理。溶液pH值不同会导致处理Pb~(~(2+))后产物有所不同,强酸性有助于PbHPO4的生成,而pH值为3.0-6.0时生成的主要产物则是Pb10(PO4)6(OH)2。2、将Fe_3O_4/SrCO_3前驱材料作为硬模板合成了Fe_3O_4/SrHAp1磁性复合材料,该复合材料由有棱的梭形棒自组装而成,比表面积的大小是51.68 m2·g-1。另外,利用直接水热法合成了Fe_3O_4/SrHAp2磁性材料,该材料由Fe_3O_4纳米球和羟基磷酸锶纳米棒组合而成,其中Fe_3O_4平均粒径是~150 nm,羟基磷酸锶纳米棒平均长度是~800 nm,直径是~90 nm。3、相比于Fe_3O_4/SrHAp1,Fe_3O_4/SrHAp2具有更强的饱和磁化强度(20.6 emu·g-1),作为吸附材料更有利于磁性分离。而且Fe_3O_4/SrHAp2复合材料吸附Pb~(~(2+))的能力更佳,最大吸附量高达291.1 mg·g-1,其吸附铅离子的平衡时间为20 min。伪二级动力学方程能很好地描述Fe_3O_4/SrHAp2磁性复合材料吸附Pb~(~(2+))的动力学过程,其等温线实验数据符合Langmuir模型。Fe_3O_4/SrHAp2在弱酸性溶液中吸附铅离子的过程主要源于该材料的表面吸附以及Pb~(~(2+))与Sr~(~(2+))的离子交换反应;在强酸性条件下吸附机理主要表现为溶解/沉淀机理,其中pH值为2.5时,主要生成PbHPO4沉淀,而pH值达到3.0时,主要产物则是Pb10(PO4)6(OH)2。本研究制备的掺锶碳羟基磷灰石与磁性羟基磷酸锶复合材料用于去除酸性水溶液中重金属Pb~(~(2+))时展现出优良的吸附性能,具有很好的应用前景,其性能及机理研究在重金属污水处理领域具有一定的参考价值。
[Abstract]:In recent years, the improper discharge of sewage has brought a severe test to the survival of human beings and the protection of natural environment. Hydroxyapatite (HA), as a cheap, efficient and environmentally friendly adsorption material, has become a research hotspot. Its ion exchange properties are beneficial to the adsorption of heavy metal ions in water, but its adsorption performance needs to be further improved. The improvement of the preparation method and the doping of the materials are helpful to improve the comprehensive properties of the adsorptive materials. Strontium-doped carbon hydroxyapatite and magnetic strontium hydroxyphosphate composites were prepared by hydrothermal method and their removal behavior and mechanism of heavy metal Pb~ (2) in aqueous solution were investigated. The main results are as follows: 1. Monodisperse and self-assembled hydrangea-like Sr-CHAp, was synthesized by hydrothermal method. The specific surface area (43.54 m ~ 2 路g ~ (- 1) of Sr-CHAp was higher than that of Pb ~ (2 +), and the adsorption capacity of Pb ~ (2 +) was very strong. The saturated adsorption capacity of Pb~ (2) reached 985.1 mg 路g-1 in the solution of optimum pH value (pH=3.0), which provided a possibility for obtaining efficient Pb~ (2) adsorbent under acidic conditions. The isotherm data of the adsorption Pb~ (2) are consistent with the Langmuir model and the kinetic data are in agreement with the pseudo-second order kinetic model. The adsorption of Pb~ (2) by SrCHAp in acidic solution is mainly due to the mechanism of dissolution / precipitation. Different solution pH values lead to different products after treatment of Pb~ (2), strong acidity contributes to the formation of PbHPO4, while Pb10 (PO4) 6 (OH) 2.2 is the main product when pH value is 3.0-6.0. Fe_3O_4/SrHAp1 magnetic composite was synthesized by using Fe_3O_4/SrCO_3 precursor as a hard template. The composite was self-assembled with ribbed fusiform rods with a specific surface area of 51.68 m2 路g-1.The surface area of the composite was 51.68 m ~ 2 路g ~ (- 1). In addition, Fe_3O_4/SrHAp2 magnetic material was synthesized by direct hydrothermal method. The material was composed of Fe_3O_4 nanospheres and strontium hydroxyphosphate nanorods, in which the average diameter of Fe_3O_4 was ~ 150 nm,. The average length of strontium hydroxyphosphate nanorods is ~ 800 nm, diameter is ~ 90 nm.3, and has stronger saturation magnetization than that of Fe_3O_4/SrHAp1,Fe_3O_4/SrHAp2 (20.6 emu 路g-1). As a adsorptive material, magnetic separation is more favorable. Moreover, the adsorption capacity of Pb~ (2) on Fe_3O_4/SrHAp2 composites is better, the maximum adsorption capacity is up to 291.1 mg 路g-1, and the equilibrium time of lead ion adsorption is 20 min.. The pseudo-second order kinetic equation can well describe the dynamic process of Pb~ (2) adsorption on Fe_3O_4/SrHAp2 magnetic composites. The isotherm experimental data are in accordance with the Langmuir model. The adsorption of lead ions by Fe _ 3O_4/SrHAp2 in weak acid solution is mainly due to the surface adsorption of the material and the ion exchange reaction between Pb~ (2) and Sr~ (2). In the strong acid condition, the adsorption mechanism is mainly the dissolution / precipitation mechanism, in which the pH value is 2.5, the main formation of PbHPO4 precipitation, and when the pH value is 3.0, the main product is Pb10 (PO4) 6 (OH) 路2. In this study, strontium-doped carbon hydroxyapatite and magnetic strontium hydroxyphosphate composites show excellent adsorption properties for removing heavy metal Pb~ (2) in acidic aqueous solution, and have good application prospects. The study of its performance and mechanism has certain reference value in the field of heavy metal wastewater treatment.
【学位授予单位】：宁波大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB33

【参考文献】