Influence of Inorganic Carbon

Inorganic carbon can also influence the total reaction rate by acting as a scavenger for hydroxyl radicals, whereas ozone itself does not react with carbonate or bicarbonate (Hoigne, 1984). The reaction of OH° with inorganic carbon proceeds according to the following mechanisms  

Not much is known about reactions of the carbonate radical with organic compounds they seem to be almost unreactive. The carbonate radical, though, has been found to react with hydrogen peroxide (Behar et al., 1970)  

The reaction rate constants for the inorganic carbon reactions are summarized in Table 4-4. A comparison of both reactions shows that carbonate is a much stronger scavenger than bicarbonate. This indicates that the pH-value, which influences the form and concentration of inorganic carbon present (pKa (HC037C032 ) = 10.3), is of major importance in determining the effect inorganic carbon has on the reaction rate. 

The effect on the reaction rate is relatively high at low concentrations of inorganic carbon. However, above 2 mmol L l for ozonation and about 3 mmol L-1 for the ozone/hydro-gen peroxide process, the decrease in the reaction rate is negligible (Gottschalk, 1997). Fomi et al. (1982) found this plateau at 1.5 mmol L 1 of inorganic carbon for ozonation. 

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The potentiometric titration was carried out in order to determine the functional groups present in the biomass surface. During the titration experiments, the C02-free condition was always maintained to avoid the influence of inorganic carbon on the solution pH. Detailed potentiometric titration procedure and estimation method of functional groups are available in the previous reports [4,6]. 

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