77
Figure 4. 4 H
2
O
2
profile during the UVH
2
O
2
process.
4.1.2 Effect of Initial Concentration of MDEA
The effect of initial MDEA concentration on the UVH
2
O
2
oxidation process was studied using eight different initial concentrations Figure 4.5. The concentrations
were varied from 500 ppm to 12000 ppm of MDEA. The other variables namely volume 400 ml, UV intensity 12.06 mWcm
2
, temperature 30ºC, pH 7, and ratio between concentrations of MDEA to oxidant H
2
O
2
2 moles of MDEA to 14.5 moles of H
2
O
2
were retained at constant values. In order to show a better clarity of the data on TOC removal, a plot of
TOC
t
TOC with time was made. Figure 4.5 shows the dependency of TOC
removal on the initial concentration of MDEA present in the solution. Based on the trends and the profiles seen in Figure 4.5, the degradation efficiency decreases with an
increase in the initial concentration of contaminant. This result is in good agreement with the reported literatures [133, 135
– 136].
78
Figure 4. 5 The degradation profile of organic carbon for different initial
concentration of MDEA
Haji et al. [135] reported that higher initial concentration of dye with excess H
2
O
2
took longer time to achieve a specific degradation, whilst, Behnajady et al. [133] reported that decolorization decrease with an increase in the initial concentration of
Malachite Green for a constant initial concentration of H
2
O
2
. Ochuma et al. [136] also reported a similar behavior for the degradation rate of 2,4,6-trichlorophenol
TCP, and concluded that at constant UV lamp intensity, the higher concentration of TCP required longer radiation time for complete degradation.
The percentage of TOC removal Figure 4.6 for all the different initial concentrations of MDEA was found to be approximately 40 at the end of reaction.
At the end of the reaction all H
2
O
2
has been consumed and hence no further organic carbon was removed.
79
Figure 4. 6 Effect of initial concentration of MDEA on TOC removal after 360
minute reaction time.
In this preliminary study on effect of initial concentration of MDEA, there was found no optimum concentration for degradation. However, based on the observed
results, the suitable initial concentration for this experiment was found to be 2000 ppm of MDEA =1000 ppm TOC. The maximum degradation occurs at 3 hours, and
for this concentration it was found to be accurate and easy to follow the TOC profile with time. Hence all the further experiments were conducted using 2000 ppm of
MDEA.
4.1.3 Effect of UV Intensity in Combination with H
Kategori