Adsorption Studies of Methylene Blue And Malachite Green Dyes From Aqueous Solution Using Calix[4]arene – Polyurethane

Abstract

Calix[4]arene-polyurethane (C4PU) polymer was used as an alternative adsorbent for the adsorption of methylene blue (MB) and malachite green (MG) dyes, from the aqueous solution. C4PU was synthesised by reacting p-tert-butyl calix[4]arene with hexamethylene diisocyanate (HMDI) as the cross-linking agent. A preliminary study was carried out to determine the best ratio of calix[4arene and HMDI in the adsorption of dyes and C4PU-4 shows a better adsorption compared to the synthesized C4PU in other ratios. The polymer was characterised by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), Brunauer-Emmett-Teller (BET) analysis and point of zero charge (pHPZC). The isotherms and kinetics of the adsorption of MB and MG were studied under a range of experimental conditions, including pH, adsorbent dosage, initial dye concentration, and contact time. The adsorption was determined by the adsorption percentage of MB and MG dyes from the solution. The adsorption process for both dyes is best described by the Langmuir isotherm model, and it follows the pseudo-second order kinetic model, with the maximum adsorption capacity (qmax) of MB and MG, respectively, was found to be 1.619 mg.g− 1 and 2.192 mg.g− 1.