Adsorption of reactive brilliant orange X-GN from aqueous solutions by layered mixed oxides
煅烧阴离子粘土(LDO)对低浓度活性艳橙X-GN的吸附研究

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 LDHat 773 Kfor 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 BETanalysis.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-GNby the 2:1 LDO and 4:1 LDO.The results showed that the optimum pHvalue of the dye adsorption was 3.0.At pH3.0 and 298 K,the adsorption capacities of reactive brilliant orange X-GNby 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 LDOwas 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 LDOwas mainly attributed to the structural "memory effect" of the LDO.Desorption of the reactive dye by 2:1 LDOand 4:1 LDO were also investigated,providing evidence to support the conclusions of the XRD and FTIRanalyses.