羟基磷灰石与天然磷灰石去除铀的效果和机理研究

Study on Removal Effect and Mechanism of Uranium by Hydroxyapatite and Natural Apatite

  • 摘要: 通过静态实验分别研究了反应时间、温度、pH值、铀初始质量浓度、磷灰石用量等条件对羟基磷灰石与天然磷灰石去除铀的影响,并根据热力学和动力学原理进行了分析。结合红外光谱、扫描电镜、X衍射等分析结果探讨了羟基磷灰石与天然磷灰石去除铀的机理。羟基磷灰石去除铀的结果表明:铀的去除量随着铀初始浓度的增大而增大;在pH=4~5的铀溶液中,羟基磷灰石用量为0.75 g时,去除效果最好,铀的去除率达85%。天然磷灰石去除铀的结果表明:铀的去除率随铀初始浓度的增大而增大;在pH=3、天然磷灰石用量为1.0 g时去除效果最好,铀的去除率高达80%。二者的去除反应均在120 min时基本达到平衡,反应过程均既符合二级动力学方程又符合Langmuir热力学方程。红外分析结果表明,二者主要是通过磷酸根与UO2+2的络合作用去除铀。X衍射分析结果表明,羟基磷灰石基本符合纯物质的组成与构成,而天然磷灰石主要成分为Ca5H2(PO4)3F、Ca8H2(PO4)6H2O。扫描电镜对比分析显示,羟基磷灰石外观呈球状且开有孔,孔内有一含大量絮状物的空腔,羟基磷灰石在去除铀后表面变得光滑且微孔也被封闭,这是由于吸附了UO2+2使羟基磷灰石表面分子间发生了链接;而天然磷灰石去除铀前后皆呈现棱角分明的矿物外形,说明被吸附天然磷灰石上的UO2+2,形成了矿物晶体。

     

    Abstract: By the static experiments, the effects of reaction time, pH value, initial concentration of uranium, dosage of apatite on adsorption of hydroxyapatite and natural apatite for uranium were studied respectively. The adsorption process was analyzed by thermodynamics and kinetics, and the adsorption mechanism was analyzed by infrared spectroscopy, X-ray diffraction and scanning electron microscope. The results of hydroxyapatite show that the removal capacity of uranium increases with the initial concentration of uranium, and the adsorption rate of hydroxyapatite on UO2+2 reaches 85%, when the pH value is 4 to 5 and dosage of hydroxyapatite is 0.75 g. The results of natural apatite show that the removal capacity of uranium increases with the initial concentration of uranium, and the adsorption rate of natural apatite on UO2+2 is up to 80%, when the pH value is 3 and dosage of hydroxyapatite is 1.0 g. Similarly, at 120 minutes both of the removal reactions by hydroxyapatite and natural apatite substantially reach equilibrium. Moreover, both of the reactions by hydroxyapatite and natural apatite are in line with quasi secondary dynamics equation, and follow the Langmuir adsorption isotherm. Infrared spectra indicate that the removal of hydroxyapatite for uranium depends on the complexation of phosphate, which is almost the same as that of natural apatite. X-ray diffraction analysis shows that hydroxyapatite has the composition and structure of pure material, whereas the natural apatite is mainly composed of Ca5H2(PO4)3F and Ca8H2(PO4)6H2O. In addition, scanning electron microscope demonstrates that hydroxyapatite has the appearance of spherical with a hole and the hole has a cavity containing a large amount of floc, while the surface becomes smooth and pores are closed after removal of uranium, which is due to the adsorption of UO2+2 leading a link between molecules on hydroxyapatite surface. But for natural apatite, it depicts the angular mineral shape before and after the removal of uranium, which means that UO2+2 is adsorbed on the natural apatite and the mineral crystal is formed.

     

/

返回文章
返回