Selective adsorption of cationic dyes from aqueous solution by polyoxometalate-based metal–organic framework composite

• Published in: Applied surface science 2016-01, Vol.362, p.517-524
• Main Authors: Liu, Xiaoxia, Gong, Wenpeng, Luo, Jing, Zou, Chentao, Yang, Yun, Yang, Shuijin
• Format: Article
• Language: English
• Subjects: Adsorption; Aqueous solutions; Cationic dye; Cationic dyes; H6P2W18O62; Isotherms; Mathematical models; Metal organic frameworks; Metalorganic compounds; Selective adsorption; Selectivity adsorption; Surface chemistry
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2015.11.151

Selective adsorption ability of H6P2W18O62/MOF-5 toward MO (a), Rhb (b) and the removal rate of Rhb, MO and MB (c). •Using metal–organic framework (MOF) composite as an adsorbent was investigated.•Selective adsorption ability of the composite towards cationic dyes was proposed.•The removal rate of MOF was raised greatly by the modification of polyoxometalate.•The adsorption kinetic and isotherm were used to describe the adsorption process.•The thermodynamic parameters of the composite were investigated in detail. A novel environmental friendly adsorbent H6P2W18O62/MOF-5 was synthesized by a simple one-step reaction under solvothermal conditions and characterized by XRD, FTIR, thermogravimetric analyses (TGA) and N2 adsorption–desorption isotherms. The removal rate of H6P2W18O62/MOF-5 was quite greater (85%) than that of MOF-5 (almost zero), showing that the adsorption performance of porous MOF-5 can be improved through the modification of H6P2W18O62. Further study revealed that H6P2W18O62/MOF-5 exhibited a fast adsorption rate and selective adsorption ability towards the cationic dyes in aqueous solution. The removal rate was up to 97% for cationic dyes methylene blue (MB) and 68% for rhodamine B(Rhb) within 10min. However, anionicdye methyl orange(MO) can only reach to 10%. The influences including initial concentration, contact time, initial solution pH and temperature of MB adsorption onto H6P2W18O62/MOF-5 were investigated in detail. The kinetic study indicated that the adsorption of MB onto H6P2W18O62/MOF-5 followed the pseudo second-order model well. The isotherm obtained from experimental data fitted the Langmuir model, yielding maximum adsorption capacity of 51.81mg/g. The thermodynamic parameters analysis illustrated that the MB adsorption onto H6P2W18O62 immobilized MOF-5 was spontaneous and endothermic process. Besides, these results implied that designing a novel material polyoxometalate-based metal–organic frameworks is great potential for removing cationic organic pollutants and even extended to improve other specific application.