煅烧阴离子粘土(LDO)对低浓度活性艳橙X-GN的吸附研究

Adsorption of reactive brilliant orange X-GN from aqueous solutions by layered mixed oxides

以不同Mg/Al比(物质的量比)的合成阴离子粘土为原料,在500℃条件下煅烧制备了煅烧阴离子粘土(LDO),研究其对低浓度活性艳橙X-GN的吸附行为,并用XRD、FTIR、XRF、BET等对LDO进行表征,通过研究解吸行为验证其吸附机理.实验表明,Mg/Al比为4:1的LDO的吸附效果比2:1的LDO好,Mg/Al比为2:1和4:1的LDO的吸附容量分别为195.66mg·g-1和492.75mg·g-1,最佳pH为3.0.吸附动力学研究表明,限制LDO吸附活性艳橙X-GN的主要步骤是化学吸附.吸附等温线拟合结果表明,LDO与活性艳橙X-GN之间的吸附主要为单层吸附.XRD、FTIR表征及解吸实验结果表明,活性艳橙进入到了LDO层间,成为阴离子粘土的组成部分,LDO与活性艳橙X-GN之间的吸附机理主要为离子交换和LDO的结构"记忆效应",其中,Mg/Al比为2:1的LDO以离子交换为主,Mg/Al比为4:1的LDO以结构"记忆效应"为主.

Layered double hydroxides （LDH） with Mg/Al molar ratios of 2：1 and 4：1 were prepared by co-precipitation.The mixed oxides,also called calcined layered double hydroxides （LDO）,were obtained by calcining the LDH at 773 K for 4 h.The obtained materials were characterized by powder X-ray diffraction （XRD） spectra,Fourier transform infrared （FTIR） spectra,X-ray fluorescence （XRF） spectra,and BET analysis.Batch experiments were carried out to investigate the effects of contact time,pH,and initial dye concentration on the adsorption of reactive brilliant orange X-GN by the 2：1 LDO and 4：1 LDO.The results showed that the optimum pH value of the dye adsorption was 3.0.At pH 3.0 and 298 K,the adsorption capacities of reactive brilliant orange X-GN by the 2：1 LDO and the 4：1 LDO were 195.66 mg·g-1 and 492.75 mg·g-1,respectively.The kinetics of the dye adsorption fit the Pseudo-second-order model.The adsorption equilibrium data were analyzed by the Langmuir,Freundlich,and Redlich-Peterson models.The Langmuir and Redlich-Peterson models provided better correlations to the equilibrium data than the Freundlich model,indicating that the mechanism of dye adsorption on the LDO was mainly due to monolayer adsorption.XRD and FTIR analysis after dye adsorption showed that the adsorption on the 2：1 LDO was mainly due to ion exchange and the adsorption of 4：1 LDO was mainly attributed to the structural ＂memory effect＂ of the LDO.Desorption of the reactive dye by 2：1 LDO and 4：1 LDO were also investigated,providing evidence to support the conclusions of the XRD and FTIR analyses.