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This research used solar irradiation as the UV source to
degrade 2,4-dichlorophenol in water. The solar photocatalytic
reactor was constructed by packing four types of supported
catalysts (1 wt% TiO2/glass beads, 1 wt% TiO2/silica gel, 1 wt%
Pt/TiO2/silica gel, and 1 wt% Pt/TiO2/glass beads) into quartz
tubes. To investigate the influence on the destruction rates of
2,4-dichlorophenol (2,4-DCP), the following factors were
examined: (a) supported catalyst type, (b) solar irradiance, (c)
hydraulic loading, (dinfluent 2,4-DCP concentration, (e) pH
effects,and (f) degree of mineralization.
Experimental results showed that the supported catalyst of 1 wt%
Pt/TiO2/silica gel had the highest degradation efficiency. Under
the same operating condition, 2,4-DCP de-gradation increased
while solar irradiance increased, Hydraulic loading directly
influenced the retention time of 2,4-DCP in the photocatalytic
reactor. While hydraulic loading increased, the retention time
decreasedand reduced the degradation efficiency of 2,4-DCP. The
initial reaction rate increased with the influent concentration
of 2,DCP; but in terms of the total reaction rate, the higher
reaction rate was due to the lower initial concentration of
2,4-DCP. The effect of pH was not obvious. In the mineralization
experiment, we used the supported catalyst of 1 wt% Pt/TiO2/
silica gel to degrade 2,4-DCP under the following conditions :
solar irradiance=3.2 mW/cm2, hydraulic loading=21.2 m/hr and
influent 2,4-DCP concentration=20 mg/L. For a retention time of
2.83 min, we found that about 80% 2,4-DCP was degraded and 60%
chloride ions was ssociated; however, 40% chloride ions still
existed as the intermediate which contained chloride ion. Almost
30% TOC was completeiy mineralized to water and CO2, but 70% TOC
residue remained in the water. Thus, solar irradance can be used
as a reliable UV source to remove 2,4-DCP but limited in
itsability to mineralize TOC.
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