Abstract-Determining the degradation mechanism of phenol under illumination of titanium dioxide (TiO 2 ) is main task in this present work. The experiment carried out with 100 ppm of phenol solution and 0.9 g/L TiO 2 under UV-C light. The COD and UV-Vis measurement were applied in the present work to evaluate the efficiency of phenol removal. The results showed that photocatalysis removed effectively phenol from water after 24 hours of UV-C illumination. In the first 16 hours, there was a slight decrease in the COD value. However, it decreased dramatically after 24 hours of illumination. Similarly, the result from UV-Vis spectrophotometer also showed the same reduction of phenol peak. These proved that the photocatalytic degradation of phenol include two main phases. Phenol was transformed to by-products in the intermediate compound phase. Subsequently, these intermediate compoundss were removed from water under the form of carbon dioxide and water in the mineralization phase. Therefore, it is necessary to identify intermediate phase of phenol photodegradation in the further work.
WO3/CeO2 heterostructured nanocomposites
containing different WO3 ratios (0.1, 0.3, 0.5, and 1.0
wt %) were synthesized by a precipitation method. The coupling of
CeO2 and WO3 with a high specific surface area
noticeably enhanced the photocatalytic activity of indigo carmine
(IC) degradation under visible-light irradiation. The degradation
rate constants (k) of 0.5 wt % WO3/CeO2 nanocomposites reached 4 and 5 times higher than those of
CeO2 and WO3, respectively. Regarding the experimental
results, the X-ray diffraction (XRD) patterns of the CeO2 spherical nanoparticles and rod-shaped WO3 were assigned
to the cubic fluorite and orthorhombic phase structures, respectively.
The increasing photocatalytic activity of nanocomposite samples could
be attributed to the heterojunction of the photocatalysts with efficient
charge separation and strong oxidative ability, which were confirmed
by the photoluminescence spectra and diffuse reflectance spectrometry.
The staggered heterojunction of the nanocomposite promoted efficient
electron transfer and suppressed the recombination of photogenerated
electrons and holes during the process.
Higher concentrations of ammonium (NH(4)-N) and iron (Fe) than a standard for drinking are typical characteristics of groundwater in the study area. To remove NH(4)-N and Fe, the drinking water supply system in this study consists of a series of treatment units (i.e., aeration and sedimentation, filtration, and chlorination); however, NH(4)-N in treated water is higher than a standard for drinking (i.e., <1.5 mg NH(4)-N/L). The objective of this study, therefore, is to develop an attached growth system containing a fiber carrier for reducing NH(4)-N concentration within a safe level in the treated water. To avoid the need of air supply for nitrification, groundwater was continuously dripped through the reactor. It made the system simple operation and energy efficient. Effects of reactor design (reactor length and carrier area) were studied to achieve a high NH(4)-N removal efficiency. In accordance with raw groundwater characteristics in the area, effects of low inorganic carbon (IC) and phosphate (PO(4)-P) and high Fe on the removal efficiency were also investigated. The results showed a significant increase in NH(4)-N removal efficiency with reactor length and carrier area. A low IC and PO(4)-P had no effect on NH(4)-N removal, whereas a high Fe decreased the efficiency significantly. The first 550 days operation of a pilot-scale reactor installed in the drinking water supply system showed a gradual increase in the efficiency, reaching to 95-100%, and stability in the performance even with increased flow rate from 210 to 860 L/day. The high efficiency of the present work was indicated because only less than 1 mg of NH(4)-N/L was left over in the treated water.
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