方解石负载羟基磷灰石复合材料去除水中铀离子的PRB活性介质研究

铀污染地下水分布于世界多国,其危害备受关注。本文基于溶胶-凝胶法制备方解石负载羟基磷灰石复合材料(CLHC),通过静态与动态对比试验,探讨了PRB活性介质对水中铀离子的吸附机理和去除效果。试验结果表明,制备的CLHC表面被羟基磷灰石覆盖,对铀离子具有较强的吸附能力。当U的初浓度为5.0 mg/L、试验周期为2 h、溶液pH值为4、CLHC用量为0.5 g/L时,CLHC可以吸附水中所有的铀离子。CLHC对铀离子的吸附过程可以用Langmuir等温吸附模型、粒子内扩散吸附动力学模型和准二级吸附动力学模型较好地进行描述。石英砂负载羟基磷灰石与CLHC相比,后者具有更强的吸附能力,而且具有更长的使用寿命。CLHC在吸附铀的过程中没有价态变化,其对铀离子的吸附主要为离子交换的化学吸附。本研究的成果可为可渗透反应墙被应用于铀污染地下水修复提供试验依据。

An activated calcite-loaded hydroxyapatite PRB media for uranium ion removal from aqueous solution

Through static and dynamic tests, this paper investigated the removal efficiency and mechanism of uranium ion adsorption by calcite-loaded hydroxyapatite composites (CLHC) that was synthesized by the sol-gel method. The experimental results show that the CLHC surface was covered by hydroxyapatite after synthesis and had a strong affinity for uranium ions. The removal rate could reach 100% under the conditions of additive concentration of 0.5 g/L, solution pH of 4, initial uranium concentration of 5.0 mg/L, and experimental period of 2 hours. The adsorption processes of uranium can be described by a langmuir isotherm adsorption model, an intraparticle diffusion-adsorption dynamics model, or a quasi secondary adsorption kinetics model. CLHC has better adsorption ability and longer service life than quartz sand-loaded hydroxyapatite. Uranium ions were always hexavalent during adsorption, mainly by means of chemical adsorption via ion exchange. The results of this study provide a theoretical basis for the application of permeable reactive wall to groundwater remediation.