Tipplook Mongkol, Sudare Tomohito, Shiiba Hiromasa, Seki Arisa, Teshima Katsuya
Research Initiative for Supra-Materials (RISM), Shinshu University, Nagano 380-8553, Japan.
Department of Materials Chemistry, Faculty of Engineering, Shinshu University, Nagano 380-8553, Japan.
ACS Appl Mater Interfaces. 2021 Nov 3;13(43):51186-51197. doi: 10.1021/acsami.1c13706. Epub 2021 Oct 21.
Layered double hydroxides (LDHs) have attracted significant attention as adsorbents for the removal of anions from wastewater. However, it is challenging to develop a simple, economical, and environmentally friendly method for fabricating efficient LDH adsorbents. In this paper, we present an alternative approach for preparing a superb NiFe LDH adsorbent via a single-step topochemical synthesis method based on density functional theory (DFT) calculation. The NiFe LDH adsorbent [NiFe(OH)]·(CO)·0.25HO was obtained via the topotactic transformation of an oxide precursor (NaNiFeO), which was prepared by utilizing the high-temperature flux method, in ultrapure water. When the oxide precursor was soaked in ultrapure water, the host layer valence state changed from Ni and Fe to Ni and Fe, and carbonate (CO) ions were simultaneously intercalated in the interlayer. Thereafter, the CO ions were deintercalated by Cl ions to increase the adsorption capacity. The adsorbent exhibited high crystallinity, cation state, and porosity, and unique particle shape. In addition, it showed superior adsorption capacities of approximately 194.92, 176.15, and 146.28 mg g toward phosphate, fluoride, and nitrate ions, respectively. The adsorption capacity toward all the anions reached over 70% within 10 min. The adsorption behavior was investigated by performing from adsorption kinetics, isotherm, and thermodynamics studies. The results showed that the anions were endothermically and spontaneously chemisorbed through an ion exchange process onto the adsorbent in a monolayer. In addition, the as-prepared NiFe LDH adsorbent showed high stability after multicycle testing.
层状双氢氧化物（LDHs）作为从废水中去除阴离子的吸附剂已引起广泛关注。然而，开发一种简单、经济且环保的方法来制备高效的LDH吸附剂具有挑战性。在本文中，我们基于密度泛函理论（DFT）计算，通过单步拓扑化学合成法提出了一种制备优质NiFe LDH吸附剂的替代方法。通过高温助熔剂法制备的氧化物前驱体（NaNiFeO）在超纯水中进行拓扑转变，得到了NiFe LDH吸附剂[NiFe(OH)]·(CO)·0.25HO。当氧化物前驱体浸泡在超纯水中时，主体层的价态从Ni和Fe变为Ni和Fe，同时碳酸根（CO）离子插入层间。此后，Cl离子将CO离子脱嵌以提高吸附容量。该吸附剂具有高结晶度、阳离子状态、孔隙率和独特的颗粒形状。此外，它对磷酸根、氟离子和硝酸根离子分别表现出约194.92、176.15和146.28 mg g的优异吸附容量。对所有阴离子的吸附容量在10分钟内达到70%以上。通过吸附动力学、等温线和热力学研究对吸附行为进行了考察。结果表明，阴离子通过离子交换过程以吸热且自发的方式化学吸附在吸附剂上形成单层。此外，制备的NiFe LDH吸附剂在多循环测试后表现出高稳定性。
