Abstract This research presented six natural clay minerals (NCM) evaluated for the effectiveness of NH4+ adsorption from aqueous solution. For the first time, the NH4+ adsorption capacities of kaolinite, halloysite, montmorillonite, vermiculite, palygorskite, and sepiolite were examined and compared in the same study. All the NCM were fully characterized by XRD, SEM/EDS, XRF,FTIR, CEC, zeta potential and nitrogen adsorption-desorption isotherms to better understand the adsorption mechanism-property relationship. Adsorption kinetics showed that the adsorption behavior followed the pseudo-second-order kinetic model. The adsorption isotherms fitted by the Langmuir model illustrated that among all the NCM studied, vermiculite (50.06 mg/g) and montmorillonite (40.84 mg/g) showed the highest ammonium adsorption capacities. Our results revealed that the cation exchange is the main mechanism for the NH4+ adsorption. Additionally, negatively charged surface, water absorption process and surface morphology of NCM might also contribute to the high adsorption capacity for the NH4+. The maximum adsorption capacities for all NCM were rapidly obtained within 30 min with a dosage of 0.3 g/25 mL at pH of 7. The results illustrated that the NCM have significant potential as economic, safe and effective adsorbent materials for the NH4+ adsorption from the aqueous solution.

中文翻译：

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不同天然粘土矿物对铵的吸附：表征、动力学和吸附等温线

摘要 本研究介绍了六种天然粘土矿物 (NCM)，用于评估从水溶液中吸附 NH4+ 的有效性。在同一研究中，首次对高岭石、埃洛石、蒙脱石、蛭石、坡缕石和海泡石的 NH4+ 吸附能力进行了检查和比较。所有 NCM 都通过 XRD、SEM/EDS、XRF、FTIR、CEC、zeta 电位和氮吸附 - 解吸等温线进行了全面表征，以更好地了解吸附机制 - 性能关系。吸附动力学表明吸附行为符合准二级动力学模型。Langmuir 模型拟合的吸附等温线表明，在研究的所有 NCM 中，蛭石 (50.06 mg/g) 和蒙脱石 (40.84 mg/g) 显示出最高的铵吸附能力。我们的结果表明，阳离子交换是 NH4+ 吸附的主要机制。此外，NCM 的带负电荷表面、吸水过程和表面形态也可能有助于 NH4+ 的高吸附能力。在 pH 值为 7 时，用量为 0.3 g/25 mL 时，所有 NCM 的最大吸附容量在 30 分钟内迅速获得。结果表明，NCM 作为经济、安全和有效的吸附材料具有巨大的潜力，可用于从 NH4+ 吸附水溶液。