Browsing by Author "Chou, SS"

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Application of a supported iron oxyhydroxide catalyst in oxidation of benzoic acid by hydrogen peroxide
(1999-05-01)
Chou, SS
;
Huang, CP
;
環境工程研究所
;
Institute of Environmental Engineering
Oxidation of benzoic acid was studied via Fenton-Like reaction using an innovative supported gamma-FeOOH catalyst. The decomposition kinetics of hydrogen peroxide was investigated first. Oxidation of benzoic acid by hydrogen peroxide was performed to understand the effects of initial pH and hydrogen peroxide dosage. The treatment efficiency of benzoic acid at an initial pH of 3.2 was higher than at initial pHs of 6.0 and 10.0; this can be partly explained by reductive dissolution of gamma-FeOOH. Therefore, the extent of heterogeneous catalysis was evaluated. We found that the majority of oxidation occurred on the catalyst surface, with some occurred in the solution due to iron dissolution of the catalyst. (C) 1999 Elsevier Science Ltd. All rights reserved.
Application of optical monitor to evaluate the coagulation of pulp wastewater
(1998)
Chou, SS
;
Lin, SC
;
Huang, CP
;
環境工程研究所
;
Institute of Environmental Engineering
Coagulation/flocculation process is an important part of the solid/liquid separation in a wastewater treatment plant. However, conventional methods to determine coagulant dosage have led to poor results in real-time dosing control for the highly changeable quality of influent. In this study, we employ the photometric dispersion analyzer (PDA) to assess the feasibility of monitoring pulp suspended solids coagulation in pulp wastewater by batch trials. The use of PDA in the batch system to monitor the coagulation of filamentous microorganisms is also included. Batch test results indicate that PDA monitoring is an effective technique to reflect the state of aggregation of filament- and fiber-type solids and, therefore, can provide as a reliable index for determining the optimal dosage. In addition, in our coagulant dosing control system, the monitoring point of PDA should be set at the effluent of the rapid mixing unit We also assess the feasibility using PDA monitoring in a continuous system simulating the wastewater treatment processes. Results demonstrate that stable PDA output can accurately reflect the changes of influent turbidity and coagulant dosage. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.
Decomposition of hydrogen peroxide in a catalytic fluidized-bed reactor
(1999-09-20)
Chou, SS
;
Huang, CP
;
環境工程研究所
;
Institute of Environmental Engineering
The decomposition of H2O2 by a novel supported gamma-FeOOH catalyst was performed in a continuous fluidized-bed reactor. This catalyst has been successfully used in the treatment of organic contaminants with H2O2 in our previous work. In this study, we attempted to determine the effects of pH, H2O2 concentration, and catalyst concentration on the decomposition of H2O2 An approach, we regarded this reactor as a continuous-flow stirred-tank reactor, was applied to investigate the kinetic behavior. At low H2O2 concentration, the decomposition rate of H2O2 was found to be proportional to both H2O2 and catalyst concentrations. At high H2O2 concentration, however, the rate decreased with the increasing H2O2 concentration. This can be explained by the substrate inhibition model. The large difference in the observed first-order rate constants under various pH values was also modeled. The model agreed well with the experimental results. (C) 1999 Elsevier Science B.V. All rights reserved.
Effect of Fe2+ on catalytic oxidation in a fluidized bed reactor
(1999-11-01)
Chou, SS
;
Huang, CP
;
Huang, YH
;
環境工程研究所
;
Institute of Environmental Engineering
The aim of this study was to investigate the effect of Fe2+ on the catalytic oxidation in the fluidized-bed reactor (FBR) applying supported gamma-FeOOH as the carrier. Processes without Fe2+ addition and with Fe2+ addition (FBR-Fenton method) were performed on the oxidation of benzoic acid (BA) by H2O2. When Fe2+ was not added in the FBR, the high COD removal at low pH was caused by homogeneous catalysis of Fe2+ formed via reductive dissolution of gamma-FeOOH. In the FBR-Fenton process, both mineralization of organics and crystallization of Fe(III) were simultaneously well performed under adequate condition. The reaction mechanism, including the reductive dissolution and crystallization of gamma-FeOOH as well as the oxidation of BA, was proposed based on the experimental results. (C)1999 Elsevier Science Ltd. All rights reserved.
Heterogeneous and homogeneous catalytic oxidation by supported gamma-FeOOH in a fluidized bed reactor: Kinetic approach
(2001-03-15)
Chou, SS
;
Huang, CP
;
Huang, YH
;
環境工程研究所
;
Institute of Environmental Engineering
Oxidation of benzoic,acid (BA) by H2O2 was performed with a never supported gamma -FeOOH catalyst in a circulating fluidized-bed reactor (CFBR).; This study focused mainly on determining the proportions of homogeneous catalysis and heterogeneous catalysis in this CFBR. Also studied herein was how pH, H2O2 concentration, and BA concentration affect the oxidation of BA. Experimental results indicate that the decomposition rate of H2O2 was proportional to its concentration and that the oxidation rate of BA depended on both H2O2 and BA concentrations. The change in the rate constant of heterogeneous catalysis by pH was described in terms of ionization fractions of surface hydroxyl group. From the mathematical deduction, we-can infer that the reaction rate associated with equivalent toF(III)OH(2)(+) is markedly higher than that with equivalent toF(III)OH. Conclusively, although heterogeneous catalysis contributes primarily to the oxidation of BA at pH 4.4-7.0, the homogeneous catalysis is of increasing importance below pH 4.4 because of the reductive dissolution of gamma -FeOOH.
Treatment of high strength hexamine-containing wastewater by Electro-Fenton method
(1999-02-01)
Chou, SS
;
Huang, YH
;
Lee, SN
;
Huang, GH
;
Huang, CP
A novel Electro-Fenton (EF-Fere) method, applied H2O2 and electrogenerated ferrous ion, was investigated for treating the hexamine-containing wastewater. The performance of Fe2+ generation in the electrolytic system was first evaluated, including the factors of the cathode material, initial pH, initial ferric concentration (Fe-i), and current density. When initial pH exceeded 2.5, the current efficiency dramatically decreased, which was due to the formation of Fe(OH)(3). Between 3000 and 10,000 mg/l of Fe-i, the initial current efficiency of Fe2+ generation was almost constant (85-87%), which dropped sharply to 39% at 1000 mg/l. In EF-Fere experiments, the COD removal efficiency attained above 94% after 5 h of reaction. The relationship between the temperature, dissolved oxygen, and COD was discussed. The changes in hexamine and its oxidation intermediates (methanol, formaldahyde, formate, ammonium and nitrate) during the reaction were also investigated. Three additional experiments using H2O2/Fe2+, H2O2/Fe3+, and direct electrolysis were also conducted to treat the hexamine-containing wastewater for comparison. The results showed that the EF-Fere method was the most efficient. (C) 1998 Elsevier Science Ltd. All rights reserved.