Tamura Kenji, Kawashiri Rina, Iyi Nobuo, Watanabe Yujiro, Sakuma Hiroshi, Kamon Masumi
National Institute for Materials Science , 1-1 Namiki , Tsukuba , Ibaraki 305-0044 , Japan.
Faculty of Bioscience and Applied Chemistry , Hosei University , 3-7-2 Kajino-cho , Koganei, Tokyo 184-8584 , Japan.
ACS Appl Mater Interfaces. 2019 Aug 7;11(31):27954-27963. doi: 10.1021/acsami.9b08719. Epub 2019 Jul 26.
Rosette-like layered double hydroxide (LDH) crystals with interlayer CO anions were synthesized by the reaction of Mg(NO), Al(NO), and hexamethylenetetramine (HMT) at 140 °C over 4 days. Crystals as large as 20 μm were produced when using a specific range of HMT concentrations. The substitution of CO interlayer ions with ClO or Cl anions was achieved by the addition of perchloric acid or hydrochloric acid, respectively, to dispersion of material in methanol. The products were denoted as COLDH, ClOLDH, and ClLDH, respectively. These LDHs were characterized using X-ray diffraction under controlled relative humidity, as well as by Fourier transform infrared spectroscopy and scanning electron microscopy. Adsorption experiment with anions such as phosphate (HPO) and nitrate (NO) was conducted by using ClOLDH and ClLDH. The results indicate that both anions were adsorbed through an ion-exchange mechanism. The maximum HPO adsorption capacity at equilibrium on ClOLDH was 1.6 mmol g (49.6 mg P g), which corresponds to approximately 75% of the total positive layer charge. ClLDH showed a similar adsorption capability. Commercially available platelike LDH particles were essentially impermeable to water flow due to clogging, while the LDH crystals showed excellent permeability, an order of magnitude higher than that exhibited by the platelike LDH synthesized using a homogeneous precipitation method with different growth conditions. Anion adsorption during batch and flow-through test with the ClOLDH (mean particle diameter ∼ 38 μm) in a packed bed showed good uptake of HPO and NO from aqueous solutions. These results demonstrate the potential of LDH materials to serve as a column filler adsorbent of the hazardous anions.
通过在140℃下使硝酸镁、硝酸铝与六亚甲基四胺（HMT）反应4天，合成了具有层间碳酸根阴离子的玫瑰花状层状双氢氧化物（LDH）晶体。当使用特定范围的HMT浓度时，可制备出尺寸达20μm的晶体。分别向材料在甲醇中的分散液中加入高氯酸或盐酸，可实现用氯酸根或氯离子取代层间碳酸根离子。产物分别记为COLDH、ClOLDH和ClLDH。这些LDH通过在可控相对湿度下的X射线衍射以及傅里叶变换红外光谱和扫描电子显微镜进行表征。使用ClOLDH和ClLDH对磷酸根（HPO）和硝酸根（NO）等阴离子进行了吸附实验。结果表明，两种阴离子均通过离子交换机制被吸附。ClOLDH上平衡时的最大磷酸根吸附容量为1.6 mmol g（49.6 mg P g），约占总正层电荷的75%。ClLDH表现出类似的吸附能力。市售的板状LDH颗粒由于堵塞基本上不透水，而LDH晶体表现出优异的渗透性，比在不同生长条件下使用均匀沉淀法合成的板状LDH高一个数量级。在填充床中对ClOLDH（平均粒径约38μm）进行间歇和流通试验时的阴离子吸附表明，其对水溶液中的磷酸根和硝酸根有良好的吸附。这些结果证明了LDH材料作为有害阴离子柱填充吸附剂的潜力。
