Kinetics of Activated Carbon Promoted Ozonation of Polyphenol Mixtures in Water
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- 作者：Fernando J. Beltrá ; n ; Iné ; s Girá ; ldez ; Juan F. Garcí ; a-Araya
- 刊名：Industrial & Engineering Chemistry Research
- 出版年：2008
- 出版时间：February 20, 2008
- 年：2008
- 卷：47
- 期：4
- 页码：1058 - 1065
- 全文大小：141K
- 年卷期：v.47,no.4(February 20, 2008)
- ISSN：1520-5045
文摘
The kinetics of the activated carbon ozonation of mixtures of three polyphenol compounds (gallic acid, tyrosol,and syringic acid) in water has been studied from the application of a double mechanism of reactions toexperimental data. These mechanisms involve direct ozone reactions with starting polyphenols and hydroxylfree radical reactions with intermediates and end reaction products, mainly saturated carboxylic acids (theconcentration being represented with the chemical oxygen demand, COD). The direct ozone reaction mechanismdevelops during the initial period (15-60 min) where polyphenols are removed. The kinetic regime of theprocess was fast of pseudo first order, and at 25 
C and pH 5 the direct rate constants of the reactions betweenozone and gallic acid, syringic acid, and tyrosol were determined from different kinetic methods. Oncepolyphenols disappear and saturated carboxylic acids (end reaction products) are present, the removal ofthese compounds goes through hydroxyl free radical oxidation. This second mechanism involves the reactionof ozone and the organic matter, through hydrogen peroxide formation, both in bulk water and on the carbonsurface, as the initiating step of hydroxyl radical formation. In the absence of activated carbon, the activationenergy of the bulk water ozone-organic matter reaction was found to be 36.3 ± 4.5 kcal·mol-1. In thepresence of activated carbon, at the conditions here applied in addition to bulk water chemical reaction, theprocess depends on mass-transfer resistances, and the values of the volumetric liquid-side and individualliquid-solid external mass-transfer coefficients were found to be 0.71 ± 0.05 min-1 and 1.19 ± 0.10 × 10-3m·min-1, respectively.
C and pH 5 the direct rate constants of the reactions betweenozone and gallic acid, syringic acid, and tyrosol were determined from different kinetic methods. Oncepolyphenols disappear and saturated carboxylic acids (end reaction products) are present, the removal ofthese compounds goes through hydroxyl free radical oxidation. This second mechanism involves the reactionof ozone and the organic matter, through hydrogen peroxide formation, both in bulk water and on the carbonsurface, as the initiating step of hydroxyl radical formation. In the absence of activated carbon, the activationenergy of the bulk water ozone-organic matter reaction was found to be 36.3 ± 4.5 kcal·mol-1. In thepresence of activated carbon, at the conditions here applied in addition to bulk water chemical reaction, theprocess depends on mass-transfer resistances, and the values of the volumetric liquid-side and individualliquid-solid external mass-transfer coefficients were found to be 0.71 ± 0.05 min-1 and 1.19 ± 0.10 × 10-3m·min-1, respectively.