The aim of this work is to determine paraquat adsorption capacity of zeolite NaX and Al-MCM-41. All adsorbents were synthesized by hydrothermal method using rice husk silica. For Al-MCM-41, aluminum (Al) was added to the synthesis gel of MCM-41 with Al content of 10, 15, 20 and 25 wt%. The faujasite framework type of NaX and mesoporous characteristic of Al-MCM-41 were confirmed by X-ray diffraction. Surface area of all adsorbents determined by N2 adsorption-desorption analysis was higher than 650 m2/g. Al content and geometry were determined by X-ray fluorescence and 27Al nuclear magnetic resonance, respectively. Morphology of Al-MCM-41 were studied by transmission electron microscopy; macropores and defects were observed. The paraquat adsorption experiments were conducted using a concentration range of 80-720 mg/L for NaX and 80-560 mg/L for Al-MCM-41. The paraquat adsorption isotherms from all adsorbents fit well with the Langmuir model. The adsorption capacity of NaX was 120 mg/g-adsorbent. Regarding Al-MCM-41, the 10% Al-MCM-41 exhibited the lowest capacity of 52 mg/g-adsorbent while the other samples had adsorption capacity of 66 mg/g-adsorbent.
Iron (Fe) was loaded on zeolite beta (BEA) in ammonium (NH 4 BEA) or proton (HBEA) forms by various methods. Fe/HBEA-LSIE and Fe/NH 4 BEA-LSIE were prepared by liquid state ion exchange (LSIE). This method resulted in low Fe loading and a good dispersion. The form of Fe was Fe 2 O 3 mainly located at the ion exchange position in the zeolite channels. Fe/HBEA-IWI and Fe/HBEA-PM were prepared by incipient wetness impregnation (IWI) and physical mixing (PM), respectively. Both catalysts had higher Fe loading and larger Fe 2 O 3 particles located on both external surface and in the zeolite channels. Despite the different loadings, all samples gave similar phenol conversion in phenol hydroxylation, around 60 % and yielded products catechol (CAT) and hydroquinone (HQ) with the CAT/HQ mole ratio 2:1. After the catalytic testing, all catalysts had a dark color from coking. A further investigation revealed a formation of coke and organic acids. According to temperature programmed oxidation (TPO), heavy coke was produced from Fe/ HBEA-LSIE and Fe/NH 4 BEA-LSIE. The coke from Fe/HBEA-LSIE was heavier than that from Fe/NH 4 BEA-LSIE. Only light coke was produced from Fe/HBEA-IWI and Fe/HBEA-PM.Electronic supplementary material The online version of this article (
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