SYNTHESIS AND CHARACTERIZATION OF AMIDOXIMATED ZEOLITE-POLYACRYLONITRILE (Z-AMO) HYBRID MATERIAL INDUCED BY γ-RADIATION AND ITS APPLICATION AS Pb2+ ION ADSORBENT
Recently, chelating composite hybrid materials have attracted a lot of attention owing to its unique properties from chemical bonding between each component, which enables them to be effective adsorbents. These materials exhibit combined properties of chelating functional groups from organic polymer...
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Format: | Dissertations |
Language: | Indonesia |
Online Access: | https://digilib.itb.ac.id/gdl/view/24543 |
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Institution: | Institut Teknologi Bandung |
Language: | Indonesia |
Summary: | Recently, chelating composite hybrid materials have attracted a lot of attention owing to its unique properties from chemical bonding between each component, which enables them to be effective adsorbents. These materials exhibit combined properties of chelating functional groups from organic polymer with the good mechanical and thermal stability of inorganic matrix. Natural zeolites with clinoptilolite framework type are inorganic materials which have been known as efficient heavy metal ion adsorbents because of good ion exchange abilities, low cost, availability abundant in Indonesia and also easy to be modified. However, the adsorption capacity of zeolite is lower than that of organic resin-based polymer. Modification of zeolite using conventional composite i.e. physical mixture technique method, uses poly(acrylonitrile) (PAN) as a binding agent which results in an adsorbent which is chemically resistant with reduced adsorption capacity. Radiation-induced grafting can be used to produce hybrid materials between zeolite and PAN. In this technique, the grafting can be employed in situ effectively, simply, fastly without using a chemical initiator. <br />
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In this research, the synthesis of Zeolite-PAN (Z-PAN) hybrid material induced by γ – radiation followed by amidoximation of the grafted PAN, which resulted in amidoximated Zeolite (Z-AMO) with amidoxime group, and its application as Pb2+ ion adsorbent were investigated. The specific aims of this research are (i) to select natural zeolites which are originated from several areas in Indonesia (Nanggung, Bayah and South Lampung); (ii) to modify the selected natural zeolite via PAN grafting and characterization of its physicochemical properties; (iii) to functionalize the Z-PAN hybrid composites through amidoximation of nitrile group to obtain Z-AMO which possesses chelating agents and characterize its physicochemical properties; (iv) to study the adsorption capacity of Z-AMO onto Pb2+ ion. <br />
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The natural zeolite of Nanggung-Bogor (ZN), Bayah-Banten (ZB) and South Lampung (ZL) were characterized by means of FTIR, XRD, XRF, TGA and SEM. The result shows that ZL was dominated by clinoptilolite phase without impurity of dense silica (quartz), whereas ZN and ZB contained a significant amount of quarzt. The Si/Al ratio of ZL was 5.59 which lower than those of ZN and ZB with ratio of 5.75 and 6.25 respectively. The adsorption capacity of ZL towards Pb2+ ions was 4.270 mg/g which higher than those of ZN and ZB with adsorption capacities of 3.196 and 3.051 mg/g. Moreover the adsorption capacities of homoionic ZL (NH4-ZL and Na-ZL) towards Pb2+ ions were similar to the ZL. Therefore, ZL can be directly used for the grafting process with poliacrylonitrile (PAN) without cation uniformity process. <br />
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The synthesis of Z-PAN hybrid material induced by γ-radiation had been successfully performed in which ZL was used as zeolite substrate. The Tween-80 emulsion water could increase the compatibility between acrylonitrile monomer and zeolites thus intercalation could be processed simply in room temperature. The optimum monomer concentration was 30% (wt) with irradiation dose and dose rate of 100 kGy and 2kGy/h respectively. Under this condition, the degree of grafting reached 20%. The Z-PAN hybrid structure confirmed by FTIR spectroscopy which show wavenumber of 2250 cm-1 which is a characteristic peak of C≡N group. SEM and TEM images show the morphological changes on zeolite surface, while thermogravimetric analysis (TG) showed the thermal stability of the hybrid material was similar to the zeolite. <br />
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The functionalization of Z-PAN through amidoximation to obtain Z-AMO had been successfully performed, resulting in amidoxime density of 5.05mmol/g. The conversion of nitrile group to amidoxime (AMO) confirmed by the disappearance of nitrile peak at 2250 cm-1 concomitantly appearance of new peaks at 1300 cm-1 and 950 cm-1which correspond to the NH and NOH group respectively. The XRD patterns show that the crystallinity did not change with the irradiation and functionalization. The SEM mapping and EDX analyses showed the grafting and functionalization were successfully performed due to the increase of C and N which around 23 and 28 % respectively. This result intensity confirmed by N2 Physisorption isotherm which show surface area and micropores volume of Z-PAN and Z-AMO reduced compare to that of unmodified zeolite. The 27Al Magic Angle Spinning (MAS) NMR analysis showed that the FWHM value of Z-AMO reduced while peak position (Xc) increased sharply compared to that of zeolite and Z-PAN indicated that influence of amidoximation to the Al environment. <br />
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The adsorption capacity of Z-AMO towards Pb2+ ion was 24% higher than that of zeolite because the amidoxime group play an important role as chelating agent, whereas the adsorption capacity of Z-PAN was lower than that of zeolite due to the un-functionalized grafted PAN had covered zeolite porosity. Based on isotherms and kinetics studies, the information obtained were adsorption of Pb2+ ions on the zeolite and Z-AMO surfaces fitted with the Langmuir Isotherm model with qmax of 50 and 62 mg/g respectively and the adsorption kinetics well fits to the pseudo-second-order model. |
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