Abstract：
In this study, a high-efficiency strontium-doped hydroxyapatite (Sr-HAP) adsorbent was synthesized by a sol-gel method for removing cobaltous ions (Co(II)) from water. The effects of adsorbent dose, initial solution pH, initial Co(II) concentration and temperature on the removal performance of Co(II) were investigated. Experimental results indicated that the optimum Sr-HAP dose was 0.30 g/50 mL solution, the Sr-HAP adsorbent could effectively remove Co(II) in a wide pH range of 3-8. Increasing temperature was conducive to the adsorption, and the maximum Co(II) adsorption capacity by Sr-HAP reached 48.467 mg/g at 45 °C. The adsorption of Co(II) followed the pseudo-second-order kinetic model, indicating that the Co(II) adsorption by Sr-HAP was attributed mainly to chemisorption. The isothermal adsorption results showed that at lower Co(II) equilibrium concentration, the Langmuir model fitted the data better than the Freundlich model but opposite at higher Co(II) equilibrium concentration. Therefore, the adsorption of Co(II) was a process from monolayer adsorption to multilayer adsorption with the increase of the Co(II) equilibrium concentration. The diffusion analysis of Co(II) to Sr-HAP indicated that the internal diffusion and surface adsorption were the rate-controlled steps of Co(II) adsorption. Thermodynamic study demonstrated that the Co(II) adsorption process was spontaneous and endothermic. The mechanism study revealed that in addition to chemisorption, Sr-HAP also removed Co(II) ions from water via ion exchange and surface complexation.
摘要：
在这项研究中,通过溶胶-凝胶法合成了一种高效的锶掺杂羟基磷灰石（Sr-HAP）吸附剂，用于从水中去除钴离子（Co（II））。吸附剂剂量的影响，初始溶液pH值,研究了初始Co(Ⅱ)浓度和温度对Co(Ⅱ)去除性能的影响。实验结果表明,Sr-HAP的最佳剂量为0.30g/50mL,Sr-HAP吸附剂可以在3-8的宽pH范围内有效去除Co（II）。升高温度有利于吸附,45℃时Sr-HAP对Co(II)的最大吸附容量达到48.467mg/g。Co(II)的吸附遵循拟二级动力学模型,表明Sr-HAP对Co（II）的吸附主要归因于化学吸附。等温吸附结果表明,在较低的Co(Ⅱ)平衡浓度下,Langmuir模型比Freundlich模型拟合数据更好，但在较高的Co(II)平衡浓度下相反。因此,随着Co(II)平衡浓度的增加，Co(II)的吸附是一个从单层吸附到多层吸附的过程。Co（II）在Sr-HAP中的扩散分析表明，内部扩散和表面吸附是Co（II）吸附的速率控制步骤。热力学研究表明，Co（II）的吸附过程是自发的和吸热的。机制研究表明，除了化学吸附，Sr-HAP还通过离子交换和表面络合从水中去除Co（II）离子。
