State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023, China.
Department of Environmental Science and Engineering, Nanjing Agricultural University, Nanjing 210095, China.
Water Res. 2021 Feb 1;189:116599. doi: 10.1016/j.watres.2020.116599. Epub 2020 Nov 2.
Adsorption is a viable technology to remove trace heavy metals from wastewater, but regeneration of adsorbents in an economic and environmentally friendly manner often represents a limiting factor of its application. Compared with traditional strong acid desorption, developing a chemical-free method is of great significance to both economic and the environmental welfare. Herein, we synthesized a novel thermoresponsive absorbent, A-MIL-121, which could effectively remove trace Cu(II) (> 95 %) from a high-salinity ([Na]/[Cu] = 20000) water at normal temperature. At elevated temperature, A-MIL-121 could quickly and efficiently desorb Cu(II), with over 90% desorption rate at 80°C within 3 h. Fourier transform infrared spectroscopy (FTIR) analysis revealed that two types of -COOH groups existed in the material. One was in free form and acted as the sites for Cu(II) adsorption; the other was in dimer connected by two H-bonds, which cleaved at elevated temperature. As a result, massive exchangeable protons were released to the solution, which caused the desorption of Cu(II). Similar temperature dependent adsorption-desorption behavior was also found to other heavy metals, such as Cd, Pb, Ni. No significant capacity loss was observed after 10 successive adsorption-desorption cycles. Finally, Column experiments using a real copper electroplating wastewater showed that a total of ~ 1650 mL of clean water was generated before breakthrough (Cu < 0.5 mg/L), while less than 45 mL of 80°C water was used for regeneration. This study indicates the potential of A-MIL-121 as a novel green adsorbent to address trace heavy metals in wastewater.
吸附是一种可行的技术，可用于从废水中去除痕量重金属，但以经济和环保的方式再生吸附剂通常是其应用的一个限制因素。与传统的强酸解吸相比，开发无化学试剂的方法对于经济和环境福利都具有重要意义。在此，我们合成了一种新型的温敏吸附剂 A-MIL-121，它可以在常温下有效地从高盐度（[Na]/[Cu] = 20000）废水中去除痕量的 Cu(II)（>95%）。在高温下，A-MIL-121 可以快速高效地解吸 Cu(II)，在 80°C 下 3 小时内解吸率超过 90%。傅里叶变换红外光谱（FTIR）分析表明，该材料中存在两种类型的-COOH 基团。一种以游离形式存在，作为 Cu(II)吸附的位点；另一种以二聚体的形式存在，通过两个氢键连接，在高温下断裂。结果，大量可交换的质子被释放到溶液中，导致 Cu(II)的解吸。其他重金属，如 Cd、Pb、Ni，也表现出类似的温度依赖的吸附-解吸行为。经过 10 次连续的吸附-解吸循环后，没有观察到明显的容量损失。最后，使用实际的铜电镀废水进行柱实验表明，在穿透（Cu < 0.5 mg/L）之前，共产生了约 1650 mL 的清洁水，而仅使用了不到 45 mL 的 80°C 水进行再生。这项研究表明，A-MIL-121 作为一种新型的绿色吸附剂，具有处理废水中痕量重金属的潜力。
