三维有机LDH的制备及其对有机物的普适性吸附

以表面活性剂十二烷基硫酸钠(SDS)为软模板剂,制得有机三维花状层状双金属氢氧化物(3D-SLDH).采用X射线衍射(XRD)、扫描电子显微镜(SEM)、X射线能谱仪(EDS)和N₂吸附-脱附等表征手段对3D-SLDH的结构进行表征,确定最佳合成尿素浓度,并通过静态吸附实验考察了3D-SLDH对金橙Ⅱ(AO7)、罗丹明(RhB)以及萘(NAP)的吸附性能.结果表明,室温下,3D-SLDH对AO7、RhB和NAP的吸附容量分别为454.9,46.8和43.7mg/g,表明其对有机物的吸附具有普适性.3D-SLDH对AO7、RhB和NAP吸附过程均符合准二级动力学模型,对AO7和RhB的吸附等温线符合Langmuir模型,而对NAP的等温吸附行为符合partition-adsorption模型.升温有利于3D-SLDH对AO7和RhB的去除,不利于对NAP的去除.此外,结合反应前后固样XRD,FT-IR和XPS分析,可知3D-SLDH对AO7的去除机制主要是层间离子交换作用,对RhB的去除机制主要是疏水及表面吸附作用,而对NAP的去除机制主要为分配作用.

Synthesis of organic 3D flower-like layered double hydroxide and universal adsorption for organic pollutants

Organic 3D flower-like layered double hydroxide (3D-SLDH) was prepared by sodium dodecyl sulfate (SDS) under various urea concentrations. X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray energy dispersive spectral analysis (EDS), and Brunauer-Emmett-Teller (BET) were employed to determine the optimum synthesis condition. The adsorption performance of 3D-SLDH for acid orange 7 (AO7), rhodamine B (RhB), and naphthalene (NAP) was studied by static adsorption experiments. The results showed that the adsorption capacity of 3D-SLDH toward AO7, RhB, and NAP could reach up to 454.9, 46.8 and 43.7mg/g, respectively, indicating that 3D-SLDH is a universal adsorbent to organic pollutants. Adsorption kinetics demonstrated that all contaminants removal could be well described by the pseudo-second-order model. The adsorption isotherms of AO7 and RhB fitted the Langmuir model, while partition-adsorption model was suitable for NAP adsorption. Moreover, the elevated temperature benefited for both AO7 and RhB adsorption. By contrast, lower temperature is suitable for NAP removal. Combined with the analysis of XRD, FT-IR, and XPS, the removal mechanism of AO7, RhB and NAP on 3D-SLDH was investigated. Ion exchange and surface adsorption contributed to AO7 and RhB adsorption, respectively. Whereas partition played a dominant role in NAP removal.