Abstract

The adsorption of praseodymium using hydroxyapatite was evaluated. The hydroxyapatite (HAP) was characterized by X-ray diffraction (JCPDS 01-04-3708), scanning electron microscopy, BET specific surface area (54.2 m²/g), and point of zero charge (6.5). Adsorption kinetics and isotherms were evaluated at pH of 3 and ¹⁴²Pr was determined using a gamma spectrometer. The adsorption of praseodymium was fast (1 min of contact) with an adsorption capacity of 1.68 mg/g and the data were best adjusted to the pseudo-second-order model, whereas the data of adsorption isotherm were best adjusted to the Langmuir model with a maximum adsorption capacity of 39.16 ± 0.20 mg/g. The thermodynamic parameters indicated that a physicochemical mechanism took place in the adsorption of praseodymium by HAP (adsorption enthalpy = 31.65 kJ/mol), the randomness of the system increased (adsorption entropy = 0.16 kJ/mol), and according with Gibbs free energy, the adsorption process was spontaneous at high temperature. The praseodymium in the hydroxyapatite is stable, it could not be desorbed using different solutions (ammonium sulfate, calcium chloride, sodium chloride, hydrochloric acid, and sodium hydroxide).

摘要

评价了使用羟基磷灰石对镨的吸附。羟基磷灰石 (HAP) 通过 X 射线衍射 (JCPDS 01-04-3708)、扫描电子显微镜、BET 比表面积 (54.2 m ² /g) 和零电荷点 (6.5) 进行表征。^{在 pH 值为 3 和142}时评估吸附动力学和等温线Pr 使用伽马光谱仪测定。镨的吸附速度很快（接触 1 分钟），吸附容量为 1.68 mg/g，数据最好调整为准二级模型，而吸附等温线数据最好调整为 Langmuir 模型最大吸附容量为 39.16 ± 0.20 mg/g。热力学参数表明，HAP对镨的吸附发生了物理化学机制（吸附焓= 31.65 kJ/mol），体系的随机性增加（吸附熵= 0.16 kJ/mol），并且根据吉布斯自由能，吸附过程在高温下是自发的。羟基磷灰石中的镨是稳定的，使用不同的溶液（硫酸铵、氯化钙、氯化钠、盐酸、