Synthesis of a Quaternized Beta Cyclodextrin-Montmorillonite Composite and Its Adsorption Capacity for Cr(VI), Methyl Orange, and p-Nitrophenol

Abstract

In this paper, quaternized β-cyclodextrin–montmorillonite composite (QCD-MMT) was obtained and absorption properties of Cr(VI), methyl orange and p-nitrophenol were studied. QCD was prepared by 2,3-epoxypropyltrimethylammonium chloride and β-cyclodextrin (β-CD). QCD-MMT was obtained by reaction between QCD and montmorillonite suspensions, which could be attributed to the montmorillonite cation ion exchange properties. β-CD cavities of this composite were expected to capture organic molecules through inclusion, while montmorillonite units acted as the adsorption sites for metals. QCD-MMT was characterized by FT-IR, elemental analysis, XRD, SEM-EDX, and TGA. Adsorptions of Cr(VI), methyl orange, and p-nitrophenol were highly dependent on adsorbent dose, initial concentration, temperature, contact time, and pH. Adsorption kinetics of Cr(VI), methyl orange, and p-nitrophenol followed the pseudo-second-order model. Meanwhile, adsorption of Cr(VI) fit better in the Freundlich model, inferring a multilayer adsorption, while the adsorption of methyl orange and p-nitrophenol fit better in Langmuir model, inferring a monolayer adsorption. Thermodynamic analysis showed that the adsorptions were all endothermic process and could be spontaneous at given temperature range, except for Cr(VI), of which adsorption should be at much higher temperature. Overall, QCD-MMT exhibited potential for practical applications in the treatment of both metal ions and organic pollutants.