Abstract

A simple and effective approach was introduced to modify natural calcium-rich sepiolite (SEP) by in situ deposition of nanosized hydroxyapatite (nHAP) to improve SEP’s surface properties and adsorption potential to aqueous As(III). The obtained SEP-nHAP nanocomposites were characterized by means of X-ray diffraction, FTIR, SEM-EDS, and BET analysis. Adsorption of As(III) on SEP-nHAP was evaluated as a function of pH, contact time, coexisting anions, initial As(III) concentration, and temperature. Results showed that modification of SEP by nHAP deposition significantly increased the surface area of the SEP from 3.05 to 76.56 m²/g, and As(III) removal by SEP-nHAP nanocomposite was optimal at a pH range of 6.0–8.5 and at 2 h equilibrium time. The adsorption isotherm data fitted well to the Sips and Langmuir models with a maximum adsorption capacity of 17.34 mg/g, which outperformed not only the pure SEP but also many other reported adsorbents. In addition, the kinetics analysis revealed that the As(III) adsorption process was well described by the pseudo-second-order kinetic model. The primary mechanisms for As(III) adsorption included electrostatic interaction, the formation of complexation among As(III) species, and surface hydroxyl groups of nHAP. Furthermore, the SEP-nHAP adsorbent could be easily regenerated and reused with only a slight reduction in the As(III) adsorption capacity. Therefore, SEP-nHAP can be a suitable candidate for removing As(III) from groundwater.

摘要

介绍了一种简单有效的方法，通过原位沉积纳米级羟基磷灰石 (nHAP) 来改性天然富含钙的海泡石 (SEP)，以改善 SEP 的表面性质和对水性 As(III) 的吸附潜力。通过 X 射线衍射、FTIR、SEM-EDS 和 BET 分析对获得的 SEP-nHAP 纳米复合材料进行表征。As(III) 在 SEP-nHAP 上的吸附被评估为 pH 值、接触时间、共存阴离子、初始 As(III) 浓度和温度的函数。结果表明，通过 nHAP 沉积对 SEP 进行改性显着增加了 SEP 的表面积，从 3.05 增加到 76.56 m ²/g，SEP-nHAP 纳米复合材料去除 As(III) 在 pH 范围为 6.0-8.5 和 2 小时平衡时间时效果最佳。吸附等温线数据与 Sips 和 Langmuir 模型非常吻合，最大吸附容量为 17.34 mg/g，这不仅优于纯 SEP，而且优于许多其他报道的吸附剂。此外，动力学分析表明，As(III) 的吸附过程可以用准二级动力学模型很好地描述。As(III) 吸附的主要机制包括静电相互作用、As(III) 物种之间络合的形成以及 nHAP 的表面羟基。此外，SEP-nHAP 吸附剂可以很容易地再生和重复使用，而对 As(III) 的吸附能力只有轻微的降低。因此，SEP-nHAP 可作为去除地下水中 As(III) 的合适候选物。