Environmental Engineering and Management Journal COMPARISON OF PHOTOCATALYTIC TREATMENT EFFECTIVENESS ON SEWAGE AND INDUSTRIAL WASTEWATERS (original) (raw)
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Photocatalytic Degradation of a Chemical Industry Wastewater: Search for Higher Efficiency
2017
15 Páginas, 8 Figuras, 3 TablasIn the present research, an annular photocatalytic reactor system was designed and operated to quantify the degradation of a real case chemical company wastewater. The photocatalytic degradation process was analyzed and optimized varying some critical operating variables such as pH, catalyst (TiO2) loading, H2O2 concentration (oxidant agent) and light intensity to find the best criterion warranting a high level of degradation. It was demonstrated that a pH of 7.0 and an amount of 2.0 g/L ofTiO2 resulted in a cleanup allowable level for discharge to river. Furthermore, photo-degradation by H2O2/TiO2/UV process was much more efficient (97%) with respect to the processes carried out individually by H2O2/UV(92%) orTiO2/UV (89%). It is remarkable that the optimum concentration of H2O2 was 11.6mM, and increasing the intensity of light accelerated degradation reaction. Careful selection of industrial wastewater reflected the capability predicting the level of...
TREATMENT OF PETROLEUM INDUSTRY WASTEWATER USING TiO 2 /UV PHOTOCATALYTIC PROCESS
Journal- Indian Chemical Society
In the present study, degradation of petroleum industry wastewater has been investigated through laboratory experiments by employing heterogeneous photocatalytic process. A photocatalytic reactor was used for the advanced oxidation. The industrial wastewater was characterized. Photocatalytic activity of semiconductor such as titanium dioxide (TiO 2) has been investigated. An attempt has been made to study the effect of process parameters through amount of catalyst, and operating pH on photocatalytic degradation of petroleum industry wastewater. The experiments were carried out by varying pH (2–11), amount of catalyst (0.25–1.5 g/L). Optimal suspended catalyst concentration, fluid pH and temperature were obtained at amounts of near 1 g/L, 3 and 50 0 C, respectively. The maximum rate of degradation was observed in acidic medium at pH 3 and maximum reduction in chemical oxygen demand (COD) of 60%.
Applied Catalysis B: Environmental, 2012
The photocatalytic degradation of a mixture of three compounds spiked in secondary treated wastewater by means of simulated solar radiation over titania suspensions was investigated. Bisphenol-A (BPA) and 17␣-ethynylestradiol (EE2) were chosen as representatives of emerging micro-contaminants, while phenol was chosen as a reference contaminant. Ten titania samples were synthesized and employed to evaluate the effect of doping with nitrogen, phosphorous, calcium, silver, sodium and potassium, as well as platinum dispersion on photocatalytic activity. The catalysts were characterized by X-ray diffraction, diffuse reflectance UV-vis spectroscopy, nitrogen physisorption and selective chemisorption of CO or hydrogen. A 0.5% Pt/TiO 2 catalyst (38 m 2 /g surface area, 72:28 anatase:rutile, 20 and 2 nm crystallite size for TiO 2 and Pt, respectively) was highly active for the degradation of the contaminants, whose reactivity increased in the order: phenol < BPA ≤ EE2; a commercially available Aeroxide P25 TiO 2 exhibited comparable activity. The effect of various operating conditions, such as 0.5% Pt/TiO 2 concentration (125-1000 mg/L), initial contaminant concentration (100-300 g/L each), photon flux (17.4 × 10 −8-58 × 10 −8 einstein/(L s) provided by a 150 W Xenon lamp) and the water matrix (wastewater and ultrapure water), on degradation was then assessed. Reaction rates increased linearly with catalyst concentration and photon flux, confirming the photo-induced nature of the activation of the catalytic process; likewise, a linear dependence of rate on initial concentration occurred denoting first order kinetics. Degradation in wastewater was slower than in pure water by an order of magnitude, implying the scavenging behavior of effluent's constituents against hydroxyl radicals. The implications for tertiary wastewater treatment (e.g. mineralization, disinfection and removal of estrogenicity) are also discussed.
Applied Sciences
Water resources are depleting, and the availability and supply of clean, potable water are a global concern. Advanced oxidation processes (AOPs) possess immense prospects in water and wastewater treatment settings. This study investigated and optimized the photocatalytic treatment of wastewater using titanium dioxide (TiO2) as the photocatalyst. The one-factor-at-a-time (OFAT) technique was employed to evaluate the effects of reaction time (20–100 min), mixing speed (20–100 rpm), and catalyst load (0.3–1.5 g/L) on pH, colour, turbidity, and chemical oxygen demand (COD) removal from actual municipal wastewater. Reaction time and catalyst load were then identified as the two key factors selected to be modeled and were optimized for turbidity and COD removal using the Central Composite Design (CCD) of response surface methodology (RSM). These statistical models were developed and used to optimize the operating conditions. The results obtained showed a desirability efficiency of 74.7% a...
Photocatalysis as a tertiary treatment for petroleum refinery wastewaters
Brazilian Journal of Chemical Engineering, 2006
Photocatalysis has been used as tertiary treatment for petroleum refinery wastewaters to comply with the regulatory discharge limits and to oxidize persistent compounds that had not been oxidized in the biological treatment. The wastewater is generated by the refinery and directly discharged into the Guanabara Bay (Rio de Janeiro). Although BOD removal is high, a residual and persistent COD, besides a somewhat high phenol content remains. Three photocatalysts were tested-TiO 2 (Aldrich), ZnO (Aldrich), and TiO 2 (P25, Degussa)-the third being the most active. The optimized conditions obtained with an experimental design were 3.0 g L-1 TiO 2 and pH 6.3. The use of hydrogen peroxide (H 2 O 2) showed no beneficial effect. Removal of 93% of phenols, 63% of dissolved organic carbon (DOC), and more than 50% of oil and grease (OG) were achieved in the photocatalytic process, improving the quality of the treated wastewater.
Catalysts
In the present study, methylene blue (MB) removal from aqueous solutions via the photocatalytic process using TiO2 as a catalyst in the presence of external ultra-violet light (UV) was investigated. The results of adsorption in the absence of UV radiation showed that adsorption reached an equilibrium state at 60 min. The experimental kinetic data were found to be well fitted by the pseudo-second-order model. Furthermore, the isotherm study suggested that dye uptake by TiO2 is a chemisorption process with a maximum retention capacity of 34.0 mg/g. The photodegradation of MB was then assessed under various experimental conditions. The related data showed that dye mineralization decreased when dye concentrations were increased and was favored at high pH values and low salt concentrations. The simultaneous presence of organic and inorganic pollution (Zinc) was also evaluated. The effect of the molar ratio Zn2+/MB+ in the solution at different pH values and NaCl concentrations was also m...
Water Science and Technology, 2012
Simultaneous Escherichia coli inactivation and oxidation of pharmaceuticals in simulated wastewater treatment plant effluents has been investigated using a photocatalytic treatment with TiO2 in suspension and immobilised onto a fixed-bed reactor. Non-photocatalytic reference experiments of dark adsorption and photolysis showed a higher sensitivity of E. coli towards the chemical composition of water in comparison with the concentration of pharmaceuticals that remains unaffected. Moreover, it must be underlined that the presence of pharmaceuticals (including antibiotics) did not seem to affect the bacterial viability at such low concentrations. Concerning photocatalytic experiments, both suspended and immobilised TiO2 were able to simultaneously inactivate and oxidise both kinds of pollutants (bacteria and pharmaceuticals). The fixed-bed reactor showed similar activity to that of the slurry without deactivation after several cycles of reuse. That makes TiO2 photocatalysis a quite int...
Photocatalytic degradation employing semiconductors as photocatalyst is a promising and attractive method for the removal of pollutants in wastewater. TiO2 has been identified as the most effective and useful photocatalyst. However, the applications of TiO2 has been retarded by fast recombination of electron-hole pairs and their wide band gap which corresponds to the UV light. Therefore, the study with modifying TiO2 in order to reduce the electron-hole recombination and sensitization towards visible light is one of the current hotspots in the photocatalyst research.Photocatalytic degradation experiments were carried out using E. coli, UV light was mainly used as photon source. Theproposed study aims at investigating the above mentioned aspects by conducting an in-depth study of E. coli degradationusing commercially available, sol-gel synthesized and doped TiO2. Experimental runs were carried out with varying inoculum levels of 1 ml/L, 10 ml/L, 20 ml/L and this was fixed at 20 ml/L and also with varying concentrations of commercially available TiO2 i.e. 0.05 g/L, 0.1 g/L, 0.5 g/L, 0.7g/L, 1 g/L and 2 g/L in 100 ml and 1L total volume where 0.5 g/L was found to be optimum catalyst concentration for which the time taken was 2 h to degrade. Degradation studies were also conducted with sol-gel synthesized TiO2 and Ag doped TiO2 which took 9 and 6 min respectively for the optimum 0.5g/L catalyst concentration. Also Ag doped TiO2 was tested under sunlight for which the degradation time was 30 min. Keywords: Photocatalytic degradation
The photocatalytic disinfection of urban waste waters
Chemosphere, 2000
In this paper we present the results of the photocatalytic disinfection of urban waste water. Two microbial groups, total coliforms and Streptoccocus faecalis, have been used as indexes to test disinfection eciencies. Dierent experimental parameters have been checked, such as the eect of TiO 2 , solar or UV-lamp light and pH. Disinfection of water samples has been achieved employing both UV-lamp and solar light in agreement with data shown by other authors. The higher disinfection rates obtained employing an UV-lamp may be explained by the stronger incident light intensity. Nevertheless no consistent dierences have been found between TiO 2-photocatalysis and direct solar or UV-lamp light irradiation at natural sample pH (7.8). At pH 5 the presence of TiO 2 increases the relative inactivation rate compared with the absence of the catalyst. After the photocatalytic bacterial inactivation, the later bacterial reappearance was checked for total coliforms at natural pH and pH 5, with and without TiO 2. Two h after the photocatalytic treatment, CFU increment was almost nill. But 24 and 48 h later an important bacterial CFU increment was observed. This CFU increment is slower after irradiation with TiO 2 at pH 5 in non-air-purged samples.