Faculty of Fisheries and Marine Sciences & Technology
http://ir.lib.ruh.ac.lk/xmlui/handle/iruor/7344
2024-03-29T06:34:29Z
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Heterogeneous and homogeneous photocatalytic degradation of chlorophenols in aqueous titanium dioxide and ferrous ion
http://ir.lib.ruh.ac.lk/xmlui/handle/iruor/15972
Heterogeneous and homogeneous photocatalytic degradation of chlorophenols in aqueous titanium dioxide and ferrous ion
Doong, R-A.; Maithreepala, R.A.; Chang, S-M.
Photocatalytic degradation of 100 mg/l chlorophenols was studied using TiO2 and Fenton
reagent as catalysts. 2-chlorophenol, 4-chlorophenol, and 2,4-dichlorophenol were selected as the target
compounds. Results showed that direct photolysis of chlorophenols was faster than that in the
TiO2-amended system. The photodegradation of 2CP followed a first-order rate relationship and the rate
constants were 0.022 and 0.0103 min–1 in direct photolysis and TiO2/UV systems, respectively. The
apparent-first-order reaction rate for decomposition of 4-chlorophenol was higher than that for
2-chlorophenol and 2,4-dichlorophenol under acidic conditions, while 2,4-dichlorophenol was higher than
2-chlorophenol and 4-chlorophenol in an alkaline medium. Both the TiO2 catalyst system and direct
photolysis process were faster in basic medium than acidic and neutral medium processes. The Fenton
system is excellent for the degradation of chlorophenols and its activity has become low in high pH medium.
2000-10-01T00:00:00Z
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The influence of pH and cadmium sulfide on the photocatalytic degradation of 2-chlorophenol in titanium dioxide suspensions
http://ir.lib.ruh.ac.lk/xmlui/handle/iruor/15961
The influence of pH and cadmium sulfide on the photocatalytic degradation of 2-chlorophenol in titanium dioxide suspensions
Doong, Ruey-an; Chen, Chih-hua
The influence of pH and cadmium sulfide on the photocatalytic degradation of 2-chlorophenol
(2-CP) in titanium dioxide suspensions was investigated to evaluate the feasibility of mixed
semiconductors on the photodegradation of chlorinated organics in aqueous solution. Apparent first-order rate constants (kobs) and initial rate constants were used to evaluate the degradation efficiency of 2-
CP. Higher degradation efficiency of 2-CP was observed at higher pH values. The apparent pseudo-first-order rate constant was 0.036 min-1 at pH 12.5 in TiO2/UV system, while a 2- to 9-fold decrease in kobs
was observed over the pH range of 2.5–9.5. The addition of phosphate buffer solutions at different pH
values have different effects on the degradation of 2-CP. H2PO-
4 has little effect on the photodegradation
of 2-CP, while HPO2-
4 could inhibit the photodegradation efficiency of 2-CP. Chlorocatechol,
hydroquinone, benzoquinone and phenol were identified as the predominant aromatic intermediates for
the photocatalytic degradation of 2-CP. Moreover, less aromatic intermediates at higher pH were
observed. Direct oxidation contributed significantly to the photodegradation of 2-CP. An addition of a
semiconductor decreased the initial and apparent first-order rate constants of 2-CP. The cutoff of
wavelength of 320 nm could diminish the contribution of direct photolysis of 2-CP. The combination of
cadmium sulfide and titanium dioxide can lead to an enhanced rate of disappearance of 2-CP compared to
those in single semiconductor system. A 1.2 to 2.5-fold increase in rate constant in coupled semiconductor
system relative to the single semiconductor system was obtained. © 2001 Elsevier Science Ltd. All rights
reserved
2001-08-01T00:00:00Z
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Enhanced remediation of carbon tetrachloride by Fe(II)-Fe(III) systems in the presence of copper ions
http://ir.lib.ruh.ac.lk/xmlui/handle/iruor/15957
Enhanced remediation of carbon tetrachloride by Fe(II)-Fe(III) systems in the presence of copper ions
Maithreepala, R.A.; Doong, R.-A.
The effect of Cu(II) ion on the dechlorination of carbon tetrachloride (CT) by Fe(II) associated with
various iron oxides was investigated. Iron oxides including goethite, hematite, ferrihydrite and magnetite
were selected as the model compounds. CT was dechlorinated to chloroform (CF) by 3 mM Fe(II) in iron
oxide suspensions at pH 7.2. The dechlorination followed pseudo first-order kinetics and the pseudo first order rate constants (kobs) were 0.048 h–1, 0.0836 h–1, 0.0609 h–1 and 0.0144 h–1 in goethite-, hematite-,
ferrihydrite- and magnetite-amended systems, respectively. Addition of Cu(II) into systems increased the
kobs for CT dechlorination significantly. A 3- to 120-fold increase in kobs relative to the systems without Cu(II)
was observed when 0.5 mM Cu(II) was added to the Fe(II)-Fe(III) suspensions. The pH of the system is an
important factor controlling the dechlorination rate of CT. The increase in concentrations of Fe(II) and iron
oxides also enhanced the dechlorination efficiency and rate of CT. Moreover, a linear relationship between
the kobs and Cu(II) concentration ranging between 0 and 0.4 mM was observed. Results obtained
demonstrate the feasibility of using surface-bound iron species with Cu(II) for the detoxification of
chlorinated solvents in the contaminated aquifers.
2004-01-01T00:00:00Z
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Photodegradation of 3,4-dichloropropionamide in aqueous TiO2 suspensions
http://ir.lib.ruh.ac.lk/xmlui/handle/iruor/15904
Photodegradation of 3,4-dichloropropionamide in aqueous TiO2 suspensions
Maithreepala, R.A.; Pathirana, Hema M.K.K.
Results of the photodegradation of 3,4-DPA in the presence of TiO2 are discussed. 100% destruction of an aqueous solution of 3,4-DPA (265 ppm) occurred within 5 h when illuminated with a medium pressure lamp (λ ≈ 365 nm) in the presence of TiO2. During the photodegradation of 3,4-DPA, formation of Cl−, H+, NO3− and CO2 were observed. Application of solar energy instead of artificial illumination also gave successful results.
1997-01-22T00:00:00Z