Ni Zhe-Ming, Xia Sheng-Jie, Wang Li-Geng, Xing Fang-Fang, Pan Guo-Xiang
College of Chemical Engineering and Materials Science, Zhejiang University of Technology, Hangzhou 310032, PR China.
J Colloid Interface Sci. 2007 Dec 15;316(2):284-91. doi: 10.1016/j.jcis.2007.07.045. Epub 2007 Jul 27.
Adsorption of a weak acid dye, methyl orange (MO) by calcined layered double hydroxides (LDO) with Zn/Al molar ratio of 3:1 was investigated. In the light of so called "memory effect," LDO was found to recover their original layered structure in the presence of appropriate anions, after adsorption part of MO(-) and CO(2-)(3) (come from air) intercalated into the interlayer of LDH which had been supported by XRD and ICP. The results of adsorption experiments indicate that the maximum capacity of MO at equilibrium (Q(e)) and percentage of adsorption (eta%) with a fixed adsorbent dose of 0.5 g L(-1) were found to be 181.9 mg g(-1) and 90.95%, respectively, when MO concentration, temperature, pH and equilibrium time were 100 mg L(-1), 298 K, 6.0 and 120 min, respectively. The isotherms showed that the adsorption of MO by Zn/Al-LDO was both consistent with Langmuir and Freundlich equations. The adsorption process was spontaneous and endothermic in nature and followed pseudo-second-order kinetic model. The calculated value of E(a) was found to be 77.1 kJ mol(-1), which suggests that the process of adsorption of methyl orange is controlled by the rate of reaction rather than diffusion. The possible mechanism for MO adsorption has also been presumed. In addition, the competitive anions on adsorption and the regeneration of Zn/Al-LDO have also been investigated.
研究了锌铝摩尔比为3:1的煅烧层状双氢氧化物（LDO）对弱酸染料甲基橙（MO）的吸附性能。基于所谓的“记忆效应”，通过X射线衍射（XRD）和电感耦合等离子体发射光谱（ICP）证实，在吸附部分插入层状双氢氧化物（LDH）层间的MO(-)和CO(2-)(3)（来自空气）后，LDO在适当阴离子存在下可恢复其原始层状结构。吸附实验结果表明，当MO浓度、温度、pH值和平衡时间分别为100 mg L(-1)、298 K、6.0和120 min时，固定吸附剂剂量为0.5 g L(-1)时，MO的平衡最大吸附量（Q(e)）和吸附百分比（η%）分别为181.9 mg g(-1)和90.95%。等温线表明，Zn/Al-LDO对MO的吸附符合Langmuir和Freundlich方程。吸附过程本质上是自发的且吸热的，并遵循准二级动力学模型。计算得到的活化能（E(a)）值为77.1 kJ mol(-1)，这表明甲基橙的吸附过程受反应速率而非扩散控制。还推测了MO吸附的可能机制。此外，还研究了竞争性阴离子对吸附的影响以及Zn/Al-LDO的再生性能。
