61
Although an optimum FeSO
4
;7H
2
O dosage on DEA degradation was 8 gram, but the COD removal at 30 minute almost constant for both experiment see Figure
4.8. An intensive work to study this effect may need for extent work from this study.
Lodha B and Chaudary S 2007 reported the same result that the degradation of dye by Fenton’s reagent had critical concentration. Low ferrous ion gave low
removal and a still higher ferrous ions concentration after the critical concentration would decrease the removal of dye.
4.1.5 Stoichiometric amounts of H
2
O
2
and FeSO
4
;7H
2
O
Figure 4.8
Effect of FeSO
4
;7H
2
O on DEA degradation{16000 ppm DEA: 175 ml
H
2
O
2
30 at pH 3 at different amount of FeSO
4
;7H
2
O : 4g, 8g, 12g and 16g, respectively }
The degradation of alkanolamine was not complete even in excess of H
2
O
2
which is the source of hydroxyl radical. An experiment was conducted to study the
62
behavior if stoichiometric amount of reagent is used. The stoichiomentic amount of reagent was calculated based on theoretical amount of hydroxyl radicals enough to
remove the COD on the feed solution. In the 5000 mgL COD 700 ml of DEA needs 44.7 ml H
2
O
2
30 and 121.6 g FeSO
4
;7H
2
O. The experiment was performed at pH 3.
Figure 4.9 shows that only 60 COD was removed. As in other cases, the degradation was completed in a few minutes. The reaction consumes about 98 of
H
2
O
2
. Only traces of un-decomposed H
2
O
2
were remaining. This shows that the hydroxyl radicals form very fast in the initial time of reaction and then a part of it is
lost without taking part in the oxidation process. In addition, the partially degraded product like organic acid degrade slower even in strongly oxidizing environment
Jones, 1999.
Figure 4.9 COD and H
2
O
2
profile on equivalent concentration of DEA and Fent on’s
reagent with one time addition of Fenton’s reagent 5000 COD 700 ml + 44.7 ml
H
2
O
2
30 + 121.6 g FeSO
4
;7H
2
O pH 3.
63
Oxidation of partially degraded DEA using Fenton’s reagent was also
observed. Fresh Fenton’s reagent was added and COD concentration by time was measured. Degradation of partially degraded DEA by hydroxyl radical Fenton’s
reagent is less than that for ‘pure’ DEA. Only 17.02 COD removal achieved from
about 5700 mgL COD. Figure 4.10 shows the COD evolution vs. time for this experiment.
In a different experiment, degradation of glycine one of byproducts which was identified oxidation using Fenton’s regent was as well preformed. Figure 4.11
shows the glycine degradation by Fenton’s reagent. It was observed that glycine
removal was lower compared to the MEA.
Figure 4.10 Partially Degraded DEA with Fresh Fenton
’s Reagent 6050 mgL COD+ 26.5 ml H
2
O
2
30 + 1 gram FeSO
4
;7H
2
O pH 3
4.1.6 Different Modes of Addition of Fenton’s Reagent
