TOC profiles

Fig. 7.8 Experimental (solid line) and calculated (dotted line) TOC profiles during the H2O2-UV treatment of a diluted aqueous solution of acetone (2-propanone) ff lcalculated ff acetone] + [fOQntermediates]) at irradiation time t redrawn from Stefan and Bolton (1999) Figure 3.

An additional effect, which is the most important of all the phenomena observed in these experiments, is the effect the Fe ions observe on the overall mineralization rate of phenol. The Fe not only enhances the rate of oxidation of phenol and changes the formation of its oxidation intermediates but also accelerates the rate of its overall mineralization. Figure 9a and b compare the TOC profiles for the oxidation of 20 and 30 ppm C of phenol in both impromoted PC and Fe-assisted PC systems. It can be seen that during the Fe-assisted PC reaction, the overall mineralization of phenol is faster than that for the impromoted PC reaction. One can also observe that for both cases, during the first part of the reaction time, the two profiles follow a similar trend. The TOC profile in the Fe-assisted PC systems, however, drops off faster than that in the PC system. More importantly, one can notice that in the last part of the reaction period, there is a considerable change on the slope of the TOC profile in the Fe-assisted PC reactions. 

Figure 9 (a) TOC profiles for both unpromoted PC reaction (20 ppm C in phenol) and... 

Kinetic Model 2 (KM 2) lumped acids and CO2 production The kinetic model 1 considers only the oxidation of the major aromatic intermediates. As shown in the previous section, when most of the major intermediates have been depleted, there is still a substantial concentration of other remaining organic intermediates, as the TOC profile indicates. Therefore, it is of particular interest to calculate and predict the total mineralization times. Also, with TOC measurements, it is possible to approximate the amount of CO2 produced in the course of the reaction. In this new series-parallel model, the formation and disappearance of carboxylic acids as well as the production of CO2 has been incorporated. 

The bioreactor effluent analysis showed an average removal efficiency of 99.6% for thiodiglycol and 90.6% for total organic carbon (TOC). Figure 2 shows the TOC profile and the results of MICROTOX luminescent marine bacteria toxicity testing... 

Figure 13.16 Down-core sediment profiles of (a) total organic carbon (TOC) and (b) atomic C N ratios at two locations in the York River estuary. (Modified from Arzayus...

Figure 15 Comparison between OCar and TOC for the unpromoted PC oxidation of 30 ppm C in phenol. TOC and CO2 profiles are in a different scale (six times higher than that shown on V-axis) (Ortiz-Gomez et al., 2008).

FIGURE 1. Oxygen uptake profiles for oxidation of 0.12 M methyl hnoleate in 0.5 M SDS micelles, initiated by 0.03 M of the thermal azo initiator di-tcrt-butylhyponitrite, comparing the effects of the retarder melatonin (R) with phenolic antioxidants U—uninhibited oxidation, R1— 8.72 X 10-5 melatonin, R2—87.2 x 10-5 melatonin, a-Toc—8.72 x 10-5 a-Toc, nib—8.72 x 10 5 M BHT [butylated hydroxytoluene (2,6-di-t-butyl-4-methylphenol)], Vc—8.72 x 10 5 M Trolox (2,5,6,7-tetramethyl-2-carboxy-5-hydroxychroman), Va—8.72 x 10-5 PMHC (2,2,5,6,7-pen-tamethyl-5-hydroxychroman). Reproduced by permission of Elsevier Science from Reference 283... 

FIGURE 5. Oxygen uptake profiles for inhibition of azo-bis-2,4-dimethylvaleronitrile (ADVN) initiated oxidation of 5.7 x mol DLPC at 37 °C. Va is 1.20 x lO mol PMHC (0.95 pmol ADVN), an analog of a-Toc without the long phytyl tail, which, compared to 5.04 x 10 mol a-Toc (3.17 pmol ADVN), shows a much sharper break and more rapid return to uninhibited rate. Ilia is 9.74 X 10 mol DBHA (3.05 pmol ADVN). Reproduced by permission of NRC Research Press from Reference 55... 

Although phospholipid bilayers are better mimics of biomembranes than are micelles, there are few reliable quantitative data on flavonoid antioxidant activities in lipid bilayers. Terao and coworkers compared the antioxidant efficiency of quercetin and catechins (epicatechin and epicatechin gallate) with that of a-Toc in egg yolk PC liposomes using initiation by the water-soluble initiator, ABAP, and analysis of hydroperoxide formation and antioxidant consumption by HPLC. Based on the length of the induction periods and the profile of suppressed hydroperoxide formation, they concluded that quercetin and the catechins were more efficient antioxidants than a-Toc in these bilayers. Apparently the unique behavior of a-Toc in bUayers is responsible for these results (vide supra). In hexane and alcohols solution during suppressed peroxidation of methyl linoleate, the relative antioxidant activities reversed so that the flavonoids were 5-20 times less active... 

Figure la shows the product distribution vs. time during the oxidation of succinic acid (43 mmol 1 ) at 190°C and a total pressure of 5 MPa (partial oxygen pressure 0.7-0.8 MPa) on Ig of 5% Ru/C catalyst. Figure lb gives the TOC removal and the eorresponding pH profile for the same experiment. 

Figure 1. Oxidation of an aqueous solution of succinic acid (43 mmol.r ) over 5 wt% Ru/C a) yield of succinic acid and intermediate products vs. time and b) TOC removal and pH profile vs. time. Reaction conditions 190°C, air, 5 MPa total pressure.

In Figure 5, a TOC-normalized concentration profile of HHCB and AHTN along the river is plotted. In this case, AHTN concentrations showed partly different trends than HHCB and are therefore also discussed in detail. In sediments of the upper reaches from site 19 to site 9 both compounds had relatively low concentrations (< 2.6 pg/g HHCB and < 2.6 pg/g AHTN). At sites 16, 13, 11 and at the river source (site 19) they were not even detectable. An exception is site 18, where higher concentrations were observed (4.7 pg/g HHCB and 4.2 pg/g AHTN). However, the TOC content of this sediment was at the detection limit, so... 

Figure 3 - Concentration profiles of phenol ( ), catechol ( ), hydroquinone ( ) and TOC removal (A) during photocatalytic degradation of phenol using MWNT-Ti02 catalyst.

Fig. 3.1 Concentration profiles in the pore water fractions of sediments obtained off the estuary of the River Congo, at a depth of approximately 4000 m. The sediments contain a relatively high amount of TOC. Values ranging from 1 to 3.5 wt. % indicate that this sediment is characterized by the high reaction rates of various early diagenesis processes. These processes are reflected by diffusion fluxes over gradients and by reaction rates determined by gradient changes (after Schulz et al. 1994).

Fig. 12.9 Occurrence of nepheloid layers (based on beam attenuation and light scattering profiles) across the continental margin off Namibia at 25.5°S. As a result of the lateral particle transport, a TOC-rich depot center has develloped on the mid-slope (compiled from Inthorn et al. subm. a and b).

The distributions of various fractions of the TOC in many marine areas have been reported. In Table II, a summary of some of the reported particulate organic carbon (POC) results from various oceanic environments is presented. A survey of some of the geographic areas where analyses of dissolved (DOC) or total (TOC) concentrations have been reported is shown in Fig. 4. The depth and geographic relationships of TOC results which I have analyzed are summarized in Table III. In Fig. 5, depth profiles of averaged... 

Fig. 5. Depth-averaged profiles of volatile organic carbon (VOC) concentrations and its fraction of total organic carbon (VOC/TOC) measured in various geographic areas. Bars represent range of values measured = VOC O = VOC/TOC. A. Gulf of St. Lawrence. B. Nova Scotian shelf and slope. C. Sargasso Sea.

Figure 6(b) represents the same oxidation profiles in terms of TOC versus the number of coulombs passed rather than the time elapsed. Using the same electrocatalytic electrodes in each experimental run,... 

Table 2. Kinetic data from pseudo first-order analysis of organic cocktail oxidation (TOC-time) profiles...

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