Degradation studies on paraquat malathion using tio2/zno based photocatalyst
Paraquat, a herbicide and malathion, an insecticide are pesticides that are always polluting our water system. Thus a lot of efforts has been conducted to treat the pollu ted water. The latest technology proposed is using photocatalyst. In this study, ZnO and TiO 2 w...
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| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
2008
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| Subjects: | |
| Online Access: | http://eprints.utm.my/18876/ http://eprints.utm.my/18876/ http://eprints.utm.my/18876/1/Rusmidah%20Ali2008_Degradation%20studies%20on%20paraquat%20malathion.pdf |
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| Summary: | Paraquat, a herbicide and malathion, an insecticide are pesticides that are always polluting our water system. Thus a lot of
efforts has been conducted to treat the pollu
ted water. The latest technology proposed
is using photocatalyst. In this study,
ZnO and TiO
2
were used as photocatalysts to degrade the pesticide in the presence of UV light (
λ
=354 nm). The
photodegradation rate was measured using UV-Visible spect
rophotometer and TOC analyzer. Malathion showed the
absorption peak at
λ
=210 nm while for paraquat at
λ
=258 nm. The best coupled photocatalyst for degrading malathion
solution is ZnO/TiO
2
with % weight ratio 1:0.05 and the best coupled
photocatalyst in degrading paraquat solution is
TiO
2
/ZnO with % weight ratio 1:
0.03. The result shows that Fe
2+
ion present in the reaction mixture was better than Fe
3+
ion
present as a dopant (which is added during the catalyst prep
aration). The opt
imum photocatalys
t calcinations temperature for
degrading paraquat and malathion were 550°C for TiO
2
and 500°C for ZnO. The physical prop
erties of the best catalyst were
characterized using SEM, XRD,
UV-Vis-NIR spectrophotometer and elipsometer.
By increasing the calcinations temperature
up to 600°C, XRD data showed the transformation of TiO
2
anatase to rutile phase while for ZnO, the increment of the
intensity of ZnO catalyst was observed, indicating that, the quali
ty of ZnO wurtzite crystal wa
s improved. The thicknesses for
ZnO, ZnO/TiO
2
1:0.05 and ZnO/TiO
2
doping with Fe
3+
thin film were 130.57 nm, 150.68
nm and 153.84 nm respectively.
The band gap energy values measured using UV-Vis NIR were in the range of 2.95 – 3.09 eV. |
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