School of Urban and Environmental Sciences, Northwest University, Xi'an 710127, China; Department of Chemistry, Nanchang University, 999 Xuefu Avenue, Nanchang 330031, China.
Department of Chemistry, Nanchang University, 999 Xuefu Avenue, Nanchang 330031, China.
J Colloid Interface Sci. 2017 Nov 1;505:168-177. doi: 10.1016/j.jcis.2017.05.087. Epub 2017 May 26.
In this paper, a novel strategy for the preparation of poly(levodopa) functionalized MgAl-layered double hydroxide (PDOPA-f-LDH) was developed based on the modified mussel inspired chemistry. The utilization of PDOPA-f-LDH for the removal of methylene blue (MB) from aqueous solution was also examined. Taken advantage of the self-polymerization of levodopa (DOPA) in alkaline solution and the strong affinity of catechol groups to the substrate surface, the LDH was covered homogeneously by a layer of polymer coating of DOPA, leading to the functionalization toward LDH. The structure, surface morphology, thermostability and elemental composition of as-prepared PDOPA-f-LDH were investigated by the transmission electron microscope, scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and X-ray photoelectron spectroscopy. Besides, the surface charge of the PDOPA-f-LDH was also investigated using zeta potential. The effects of various parameters, including contact time, initial MB concentration, solution pH and temperature, on the adsorption of MB onto PDOPA-f-LDH were systematically investigated. Results show that the adsorption capacity of functionalized LDH at 25°C could reach up to 102mg/g, which is much higher than that of pure LDH in the same experimental conditions. The adsorption kinetics and isotherm of MB adsorption were studied in batch experiments. The pseudo-second-order model is found to be the best to describe the adsorption kinetics. The isotherm result shows that the Freundlich isotherm is the better-fit-isotherm model to represent the equilibrium data. The values of thermodynamic parameters, including enthalpy change ΔH, entropy change ΔS and Gibbs free energy change ΔG, were also determined. All the ΔG values are negative; the ΔH and ΔS values of PDOPA-f-LDH were -7.824kJmol and -0.01562kJmolK, respectively. And the activation energy of system (E) is calculated as 24.69kJmol. The fact suggests that the MB adsorption on PDOPA-f-LDH is a spontaneous and exothermic process. These obtained results indicate that the prepared PDOPA-f-LDH could be used as an interesting adsorbent with great potential to adsorb the cationic dyeing pollutants from aqueous media.
本文基于改良的贻贝启发化学，开发了一种制备聚左旋多巴功能化 MgAl 层状双氢氧化物（PDOPA-f-LDH）的新策略。还考察了 PDOPA-f-LDH 用于从水溶液中去除亚甲基蓝（MB）的效果。利用左旋多巴（DOPA）在碱性溶液中的自聚合以及儿茶酚基团对基底表面的强亲和力，将 LDH 均匀地覆盖一层 DOPA 聚合物涂层，从而实现对 LDH 的功能化。通过透射电子显微镜、扫描电子显微镜、傅里叶变换红外光谱、热重分析和 X 射线光电子能谱研究了所制备的 PDOPA-f-LDH 的结构、表面形貌、热稳定性和元素组成。此外，还通过动电电位研究了 PDOPA-f-LDH 的表面电荷。系统研究了各种参数，包括接触时间、初始 MB 浓度、溶液 pH 值和温度，对 PDOPA-f-LDH 吸附 MB 的影响。结果表明，在 25°C 下，功能化 LDH 的吸附容量高达 102mg/g，远高于相同实验条件下的纯 LDH。在批量实验中研究了 MB 吸附的吸附动力学和吸附等温线。发现拟二级动力学模型最适合描述吸附动力学。吸附等温线结果表明，Freundlich 等温线是代表平衡数据的更好拟合等温线模型。还确定了热力学参数，包括焓变ΔH、熵变ΔS 和吉布斯自由能变ΔG 的值。所有ΔG 值均为负值；PDOPA-f-LDH 的ΔH 和ΔS 值分别为-7.824kJ/mol 和-0.01562kJ/mol·K。并且系统的活化能（E）计算为 24.69kJ/mol。事实表明，MB 吸附在 PDOPA-f-LDH 上是一个自发和放热的过程。这些结果表明，所制备的 PDOPA-f-LDH 可用作一种有趣的吸附剂，具有从水介质中吸附阳离子染料污染物的巨大潜力。
