Ramachandran, Muggundha Raoov (2015) Synthesis and characterization of cyclodextrin functionalized ionic liquid polymer for the extraction of phenols / Muggundha Raoov a/l Ramachandran. PhD thesis, University of Malaya.
Abstract
β-Cyclodextrin functionalized ionic liquid polymer (βCD-BIMOTs-TDI) was first synthesized by functionalized β-cyclodextrin (CD) with 1-benzylimidazole (BIM) to form monofunctionalized CD (βCD-BIMOTs), and was further polymerized using toluene diisocyanate (TDI) as a linker to form insoluble βCD-BIMOTs-TDI. The βCDBIMOTs- TDI was characterized using various tools and the results obtained were compared with those derived from the native β-cyclodextrin polymer (βCD-TDI). The scanning electron microscope (SEM) results showed that the presence of ionic liquid (IL) increased the pore size, while the thermo gravimetric analysis (TGA) results showed that the presence of IL increased the stability of the βCD-BIMOTs-TDI. Meanwhile, Brunauer-Emmett-Teller (BET) result showed that βCD-BIMOTs-TDI had 1.254 m2/g surface area, and the Barret-Joyner-Halenda (BJH) pore size distribution result revealed that the polymer exhibited macropores with a pore size of 77.66 nm. Preliminary sorption experiments were carried out and the βCD-BIMOTs-TDI polymer showed enhanced sorption capacity and high removal towards phenols. Based on preliminary sorption experiment, 2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TCP), and 2,4-dinitrophenol (2,4-DNP) were selected for batch adsorption study. The removal was found to be pH dependent, and therefore, pH 6 was selected for the adsorption process of 2,4-DCP and 2,4,6-TCP since optimum removal was observed at this range. In comparison, pH 4 was selected for the adsorption of 2,4-DNP. A kinetic analysis showed that the pseudo-second-order equation provided better fit for the adsorption of the studied phenols (correlation coefficient (R2) values ranged from 0.9996-1) with 120 min as the equilibrium time. The adsorption process on βCDBIMOTs- TDI was found to be in the order of 2,4-DNP > 2,4,6-TCP > 2,4-DCP. Meanwhile, external and intraparticle diffusion simultaneously occurred during the iv adsorption process of 2,4-DCP, 2,4,6-TCP, and 2,4-DNP onto βCD-BIMOTs-TDI, but it was not a rate determining step. As for the study of isotherm, Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich’s models were studied, and Freundlich’s isotherm was found to fit well for the adsorption of 2,4-DCP, and 2,4,6-TCP with R2>0.97 for all studied temperatures. On the other hand, Langmuir’s model was found to fit well with the adsorption of 2,4-DNP on βCD-BIMOTs-TDI. Besides, the thermodynamics results showed that the adsorption process of 2,4-DCP was exothermic since a negative value of ΔH° (-18.10) was obtained, while the positive values of ΔH° (40.27, and 2.38) indicated that the adsorption process of 2,4,6-TCP, and 2,4-DNP had been endothermic. In addition, adsorption mechanism was studied and was proposed by considering inclusion complex and π-π interaction between modified β-CD functionalized IL (βCDBIMOTs) with one selected phenol compound (2,4-DCP). Apart from that, a new method was developed by applying βCD-BIMOTs-TDI as an adsorbent material for solid phase extraction (SPE) of phenols in water samples by using Gas Chromatography–Flame Ionization Detector (GC-FID). Six different types of phenols; 2-chlorophenol (2-CP), 2-nitrophenol (2-NP), 2,4-dichlorophenol (2,4-DCP), 4- chlorophenol (4-CP), 4-chloro-3-methylphenol (4-CMP), and 2,4,6-Trichlorophenol (2,4,6-TCP) as model analytes, were extracted on a βCD-BIMOTs-TDI SPE cartridge. The optimum experimental condition was 15 mL of sample volume (sample at pH 6), and 2 mL of methanol containing 1% acetic acid as an eluent solvent. The developed method (βCD-BIMOTs-TDI-SPE) was then compared with other adsorbents and the obtained results showed that the βCD-BIMOTs-TDI exhibited higher extraction recovery due to the unique structure and properties. High sensitivity (detection limits 0.23-0.35 μg/L) and good recoveries (87%-116%) were achieved with satisfactory relative standard deviation (RSDs) (0.1-1.7%). Finally, under optimized condition, v βCD-BIMOTs-TDI was applied as an SPE sorbent for determination of phenols in river and tap waters, prior to GC-FID separation.
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