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Synthesis and Characterizations of Metal Oxide-Sulfonic Acid Functionalized ZSM-5 for Photocatalytic Degradation and Adsorption of
Dimethylarsenic Acid
Alias Mohd Yusof1, a, Nur Nadira Sulaiman 1, b and Hadi Nur 2, c 1Department of Chemistry,Universiti Teknologi Malaysia, Malaysia
All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP,www.ttp.net. (ID: 161.139.220.14, Universiti Teknologi Malaysia, Skudai, Malaysia-27/11/14,09:35:03)
996 Sustainable Energy and Development, Advanced Materials
Fig. 3. shows the diffractogram of ZnO-ZSM5-SH. The existence of ZSM-5 has a huge impact
on the intensity of the peaks recorded. Several peaks seem to interfere one another. The Expected
peaks for ZnO appeared but similar to TiO2, it has been shifted due to the effect of ZSM-5
introduced in the complex.
Scanning Electron Microscopy (SEM).The morphology of the complex TiO2-ZSM5-SH is clearly
shown in Fig. 4 while ZnO-ZSM5-SH shown in Fig. 5.
Fig.4. SEM image for TiO2-ZSM5-SH Fig. 5. SEM image of ZnO-ZSM5-SH
The shapes resemble those of non-uniform sphere-like particles. The average diameter for TiO2-
ZSM5-SH is 2.398 µm slightly longer than the diameter of ZnO-ZSM5-SH with an average of
1.8067 µm. Both TiO2-ZSM5-SH and ZnO-ZSM5-SH appeared as amorphous materials as both
metal oxides were incorporated into the ZSM-5 pores.
High Resolution Transmission Electron Microscopy (HR-TEM).The images obtained from HR-
TEM analysis shows the cross-section of both synthesized catalyst complexes.
Fig. 6. HR-TEM images of TiO2-ZSM5-SH
Fig. 6 shows the micrographs of TiO2-ZSM5SH. The appearance of a straight lattice line indicates
the existence of Ti crystal lattice line. The gradient colors appeared from black to grey showing the
difference between the crystalline TiO2 particles as indicated by the dark area and the bright area
which has no specific line structure portraying the degree of amorphous and mesoporosity of ZSM-
5. It can be clearly seen that there are several crystals lattice line appearing in the TiO2-ZSM5SH
complex.
Applied Mechanics and Materials Vol. 699 997
Fig. 7. HR-TEM images of ZnO-ZSM5-SH
Fig. 7 shows the images of the synthesized ZnO-ZSM5-SH. The image proves the mesoporousity of
the catalyst complex. Similar to TiO2-ZSM5-SH, the dark shade shows the existence of crystalline
metal which in this complex is the ZnO while the brighter shade shows the existence of amorphous
silica from the ZSM-5.
Degradation of Dimethylarsenic acid. Photocatalytic degradation of DMA was carried out in a
batch process for 2 h with 50 mg of each catalyst complex added into a 100 mL DMA and left for
24 hours dispersion before the reaction started under UV radiation. Samples were injected out at
one hour, half an hour and two hours and were further analyzed using GF-AAS and UV-Vis.
Fig. 8. Percentage of arsenic adsorption by catalyst complexes.
Fig. 8 shows the percentage of arsenic adsorption by each catalyst complex by analyzed using GF-
AAS technique. Results from GF-AAS prove that TiO2-ZSM5-SH holds the best adsorption
characteristics as compared to ZnO-ZSM5-SH within a 1.5 h of reaction time. The amount of
arsenic species being adsorbed by TiO2-ZSM5-SH are higher compared to ZnO-ZSM5-SH. Both
catalyst complexes gave the same trend. The percentage of adsorbed arsenic increase from 1 h to
1.5 h but as the time of reaction proceeded, the adsorbed arsenic species would be released back
into the medium as evident from the increase in the amount of arsenic species detected after 2 h. It
can be concluded that the optimum time required for efficient arsenic adsorption by both catalyst
complexes is 1.5 h.
998 Sustainable Energy and Development, Advanced Materials
Fig. 9. Percentage of DMA Concentration Reduction
Results from UV-Vis analysis show similarities to the trends observed from GF-AAS results. Fig. 9
portrays the results obtained from UV-Vis. Wavelength from DMA was detected at 197 nm which
interfering with wavelength from the other arsenic species such as As (III) and As (V) and
monomethyl arsenic acid (MMA). From UV-Vis data obtained, it shows that the ability of TiO2-
ZSM5-SH to degrade DMA is better as compared to ZnO-ZSM5-SH. The concentration of DMA
decreasing as time but the optimum time for best reduction of DMA concentration is 1.5 h. As time
is prolong, the percentage of DMA concentration reduction decreased.
Summary
A dual function photocatalyst namely TiO2-ZSM5-SH and ZnO-ZSM5-SH was successfully
synthesized having the abilities to degrade toxic pollutant; DMA and to adsorb the remaining
arsenic species in the degradation by-products. Both photocatalyst complexes were amorphous and
sphere-like shape composing of titanium dioxide, zinc oxide and silica from the zeolite introduced;
ZSM-5. The ability of TiO2-ZSM5-SH was proven to give better performance to degrade and
adsorb toxic pollutant since the percentage of DMA degradation and arsenic adsorption are higher
as compared to ZnO-ZSM5-SH.
References
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Applied Mechanics and Materials Vol. 699 999
Sustainable Energy and Development, Advanced Materials 10.4028/www.scientific.net/AMM.699 Synthesis and Characterizations of Metal Oxide-Sulfonic Acid Functionalized ZSM-5 for
Photocatalytic Degradation and Adsorption of Dimethylarsenic Acid 10.4028/www.scientific.net/AMM.699.994