Photomineralization kinetics of phenol in aq. solns. were studied in a lab.-scale reactor with cylindrical geometry and a 20 cm long high-pressure mercury arc lamp at 145 W of radiant power emitted. The whole vol. of the irradiated soln. was 4.00±0.005 L. Temp. was maintained at 308±3 K. The stoichiometric ratios R between phenol as substrate and hydrogen peroxide were 0.20, 0.50, 1.00, 2.00, 4.00, and ¥ (only dissolved oxygen at satn. with air). Under the latter conditions runs were also carried out in the absence of photocatalytic membrane. Kinetic modeling was carried out by considering only the formation of carbon dioxide from intermediates. By Langmuir-Hinshelwood treatment of the exptl. data two parameters, k and K, were obtained. Even if the latter is formally considered as an equil. adsorption const., K values were markedly dependent on R. This non-linear dependence is also obsd. in the sub-stoichiometric range, when R is increased from 1 to 2 and 4, resp. This shows a practical advantage to reduce costs, when operating with sub-stoichiometric concns. of H2O2, say 25% of the stoichiometric. Under the exptl. conditions of R = ¥, but in the presence of the photocatalytic membrane, several sets of kinetics runs were finally carried out with varying amts. of Fe (III), Fe (II) and SCN- ions in soln. A stationary equil. ratio of Fe (III)/Fe (II) concns., which amts. to 1.06±0.12, was measured at 288 K. The acceleration effect brought about by the presence of Fe (II) and Fe (III) thiocyanate during the photomineralization of phenol at R = ¥ has also been detd., with the aim of studying the mechanism of this photopromoting system. With 2.6 ´ 10-3 M of Fe (II) plus Fe (III) thiocyanate, by employing only air as oxygen supplier, the same rate of TOC redn. can be almost reached as that in the presence of a stoichiometric hydrogen peroxide quantity.

Influence of concentrations of iron(III) thiocyanate and hydrogen peroxide on photomineralization rate of phenol onto photocatalytic membranes immobilizing titanium dioxide / Mirco Bezzon, Marco Carminati, Claudio Lagrasta, Ignazio R. Bellobono, Maria Paola Tozzi. - In: FRESENIUS ENVIRONMENTAL BULLETIN. - ISSN 1018-4619. - 12:12(2003), pp. 1551-1557.

Influence of concentrations of iron(III) thiocyanate and hydrogen peroxide on photomineralization rate of phenol onto photocatalytic membranes immobilizing titanium dioxide

Claudio Lagrasta;Ignazio R. Bellobono;
2003

Abstract

Photomineralization kinetics of phenol in aq. solns. were studied in a lab.-scale reactor with cylindrical geometry and a 20 cm long high-pressure mercury arc lamp at 145 W of radiant power emitted. The whole vol. of the irradiated soln. was 4.00±0.005 L. Temp. was maintained at 308±3 K. The stoichiometric ratios R between phenol as substrate and hydrogen peroxide were 0.20, 0.50, 1.00, 2.00, 4.00, and ¥ (only dissolved oxygen at satn. with air). Under the latter conditions runs were also carried out in the absence of photocatalytic membrane. Kinetic modeling was carried out by considering only the formation of carbon dioxide from intermediates. By Langmuir-Hinshelwood treatment of the exptl. data two parameters, k and K, were obtained. Even if the latter is formally considered as an equil. adsorption const., K values were markedly dependent on R. This non-linear dependence is also obsd. in the sub-stoichiometric range, when R is increased from 1 to 2 and 4, resp. This shows a practical advantage to reduce costs, when operating with sub-stoichiometric concns. of H2O2, say 25% of the stoichiometric. Under the exptl. conditions of R = ¥, but in the presence of the photocatalytic membrane, several sets of kinetics runs were finally carried out with varying amts. of Fe (III), Fe (II) and SCN- ions in soln. A stationary equil. ratio of Fe (III)/Fe (II) concns., which amts. to 1.06±0.12, was measured at 288 K. The acceleration effect brought about by the presence of Fe (II) and Fe (III) thiocyanate during the photomineralization of phenol at R = ¥ has also been detd., with the aim of studying the mechanism of this photopromoting system. With 2.6 ´ 10-3 M of Fe (II) plus Fe (III) thiocyanate, by employing only air as oxygen supplier, the same rate of TOC redn. can be almost reached as that in the presence of a stoichiometric hydrogen peroxide quantity.
Iron(III) thiocyanate photopromoter; Phenol photomineralization; Photocatalytic membranes
Settore CHIM/03 - Chimica Generale e Inorganica
2003
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/33962
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