Volume 10, Issue 2

It has been demonstrated that Photo-Fenton process is feasible for the remediation of wastewater containing multiple organic pollutants. In order to promote its industrialization, control strategies have to be defined and tested. The objective of the present work is to describe a mathematical equation that fits the amount of COD abated regarding the dose of H 2 O 2 . UVA Laboratory-scaled and solar up-scaled experiments are compared. Also two H 2 O 2 supply strategies are compared; one in which H 2 O 2 is added at the beginning of an experiment; the second, H 2 O 2 is added in doses through an experiment. According to the results, simple equations have been found to fit experimental COD degraded depending on the amount of H 2 O 2 supplied. There is also a ratio of COD degraded per amount of H 2 O 2 consumed that fits a wide range of operating conditions. The ratio is estimated to be 0.51 (mg O 2 /mg H 2 O 2 ) which can be considered as a stoichiometry of Photo-Fenton process in the current conditions.

The paper describes a kinetic model of removal of nitrogen oxide oxidation process by an oxygenozone mixture. The kinetic model includes total of eight chemical reactions and six reagents participating in them. NO, O 2 and O 3 , are substrates for the process and its products are NO 2 , NO 3 , N 2 O 5 as well as NO, O 2 and O 3 that have not completely reacted or are reproduced. All the performed calculations, regardless of the conditions i.e. initial concentrations and the temperature, have shown that the NO 3 content in the post-reaction mixture is practically equal to zero. Some ozone quantities remain in the mixture only in the case of its overstoichiometric initial concentration with respect to NO.

The effect of the contaminated water feed mode on advanced oxidation performance, for a combined system, using ozonation with electrolysis (ozone-electrolysis) in a two-compartment electrolytic flow cell, was discussed for ozone injection to the cathodic compartment of the cell. When ozone-electrolysis was applied, removal of the chemical oxygen demand (COD) proceeded in the cathodic compartment. The overall COD removal rate increased with the increase in current density for direct feed of contaminated water to the anodic compartment (DFA mode). However, the overall COD removal rate decreased at high current density for direct feed to the cathodic compartment (DFC mode), although the overall performance for the DFC mode was better than the DFA mode. The difference in the dependency of the performance on current density was determined to be due to the difference in the advanced oxidation mechanisms for each mode.

We measured the dissociation degree of oxygen molecule in a microwave discharge oxygen plasma by optical emission spectroscopy measurement based on actinometry method. We generated an oxygen plasma in a cylindrical quartz tube (26 mm i.d.) with a discharge pressure 0.5 - 3.0 Torr. The microwave frequency was 2.45 GHz and the output power was set at 600 W. We monitored the oxygen atom density by actinometry using the 844.6 nm line of oxygen atom and the 811.5 nm line of argon. The dissociation degree was estimated at about a few percent. To discuss the validity of the measured dissociation degree, we calculated the population balance equations of the active spices and EEDF (electron energy distribution function) self-consistently. The theoretical calculations were in agreement with the experimental results. We discussed the validity of the dissociation degree of oxygen molecule and some reactions, which play an important role in the microwave discharge oxygen plasma.

We made an experimental study on Ti oxidation by microwave discharge oxygen plasma. We treated titanium sheets with 15 × 15 × 2 mm 3 in their size, and irradiated them by microwave discharge oxygen plasma with its discharge pressure several Torr. We applied XRD analysis to detect TiO2 formation after the plasma treatment, where we found only rutile pattern under the present discharge condition. To elucidate the relationship between the oxidation rate and the plasma parameters, we measured plasma parameters by probe and OES method. Measured plasma parameters were the following; electron temperature 1.8 - 5.1 eV, electron density 1.0 × 10 11 - 1.0 × 10 12 cm -3 , vibrational temperature determined by OH radical transition 0.21 - 0.25 eV, rotational temperature determined by OH radical 0.14 - 0.15 eV, and the Ti-substrate temperature during the plasma processing 550 - 1100 K, all of which were found to be less significant to the plasma oxidation of titanium. We examined the density of oxygen atoms by actinometry measurement to be (1 - 6) × 10 12 cm -3 . The titanium oxidation rate was monotonically increased with the number density of oxygen atoms, whereas other plasma parameters had little correlation with the oxidation rate. The density of atomic oxygen has a significant role in plasma oxidation of titanium.

A new way of preparation of TiO 2 /C photocatalyst by a pressure technique has been proposed. Hydrolysed titania TiO(OH) 2 (supplied by Chemical Factory Police in Poland) was used as a source of TiO 2 . TiO 2 /C was obtained by treating of TiO(OH) 2 with ethanol under pressure of 10 bar in a pressure reactor for 4 hours at a temperature of 180 °C. The building of carbon structures in the form of the alkene groups was proved by FTIR/DRS measurements, a new vibration in the region of 1520-1380 cm -1 appeared on the FTIR spectrum of TiO 2 /C photocatalyst. The photocatalytic activity of TiO 2 /C photocatalyst was tested for the azo dyes decomposition (Reactive Red, Reactive Black and Direct Green) under either UV or artificial solar light irradiation. The decantability of the photocatalysts in dye solutions after the photocatalytic process was measured. The photoactivity of prepared TiO 2 /C was compared to the hydrolysed titania and a commercial TiO 2 Degussa P25. Introducing of carbon to TiO 2 improved both, the photoactivity of TiO 2 under UV irradiation and its ability for sedimentation. The both, hydrolysed titania and TiO 2 /C photocatalyst revealed a better photoactivity for dyes decomposition under artificial solar light irradiation than Degussa P25, Reactive Red spread on the surface of TiO(OH) 2 was decolourised after 4 hours of artificial solar light irradiation while on P25 surface this process took 72 hours.

Fe-C-TiO 2 photocatalysts were prepared by mechanical mixing of TiO 2 with FeC 2 O 4 and heating at 400-800°C in a pipe furnace under Ar atmosphere. Three different kinds of TiO 2 were used for preparation, P25 of Degussa Company (Germany), TytanpolⓇ A11 and hydrolysed titania (TiO(OH) 2 ), obtained from Police Factory in Poland. It was proved, that the higher carbon deposition through the carbonization of oxalate was achieved on TiO 2 having the higher BET surface area (TiO(OH) 2 ). The presence of rutile phase in TiO 2 P25 caused fast transformation of anatase to metallic iron and different iron titanate phases, such as: FeTiO 3 , Fe 3 O 4 and Fe 2 TiO 4 , no anatase phase was observed above 500°C. TytanpolⓇ A11 having anatase phase was rather chemically stable and has been poorly modified. In case of modification of the TiO(OH) 2 , anatase coexisted with Fe 3 O 4 and FeTiO 3 phases, in samples heated above 600°C insignificant amount of rutile appeared. High photodecomposition of AR under UV/H 2 O 2 was observed on Fe-C-TiO 2 photocatalysts prepared from TiO(OH) 2 at 500 and 600°C, consisted mostly from anatase, Fe 3 O 4 and FeTiO 3 phases. It is postulated that the presence of carbon in Fe-C-TiO 2 photocatalyst is important for combination of photocatalysis and photo-Fenton processes and preparation of Fe-C-TiO 2 having high photoactivity can be achieved by modification of small size TiO 2 particles through the heating with FeC 2 O 4 in inert atmosphere.

Studies on applying the UV/TiO 2 photocatalytic process to reduce color and trace organics remained in the treated effluent have been carried out using pellet form photocatalyst in a static photocatalytic decolorization system. The effluent was characterized by general parameters such as color, A 254 (the organics absorption at the wavelength of 254 nm), total organic carbon (TOC), chemical oxygen demand (COD) and by the analysis of organic compounds using high performance size exclusion chromatography (HPSEC). The effects of catalyst amount, initial volume of effluent, UV intensity, light source, as well as catalyst regeneration (reuse) on the process efficiency were investigated. The data obtained in this study demonstrate that the UV/TiO 2 photocatalytic process is effective in reducing the organic matters including color causing compounds in the treated effluent. Color removal is great than 80% after 2 h of reaction with the dosage of 20 g TiO 2 . The HPSEC profiles reveal that only very small amount of organic matters remained in the treated samples, suggesting an extensive mineralization which was corroborated by 77% A 254 , 54 % COD and 52% TOC removals. The catalyst amount and initial volume of effluent treated have a great impact on the process efficiency. The effects of UV light source and intensity, however, are relatively small in this study. The activity of used photocatalysts could be regenerated to a full extent by UV irradiation.

The advanced oxidation process Catalyzed H 2 O 2 Propagations (CHP, or modified Fenton’s reagent) uses transition metal catalysts and hydrogen peroxide (H 2 O 2 ) to generate reactive oxygen species. Aqueous and simple heterogeneous systems were used to investigate the effect of reagent addition order in the effectiveness of CHP for the treatment of industrial waste streams and contaminated soils and groundwater. Several concentrations of H 2 O 2 were used in the CHP reactions, and probe compounds were used to monitor the relative generation rates of the reactive oxygen species hydroxyl radical, superoxide anion, and hydroperoxide anion. Statistical analysis showed that for each system and for each reactive species, there was no difference between reactions in which iron (III) was added first and those in which H 2 O 2 was added first. These results indicate that reagent addition order is not an important consideration in the process design for CHP treatment and remediation systems.

The volumetric mass transfer coefficient (K L a) for ozone was determined for various operational conditions in a novel ozonation-ceramic membrane system. Four operational parameters, water flow rate, gas flow rate, inlet gaseous ozone concentration and water temperature were considered. K L a values were higher at high water flow rates, because of the increased turbulence created under high flow conditions. K L a values were higher at high gas flow rates, because of the greater interfacial surface area of the bubbles at high gas flow and the increased turbulence created the air bubbles. Initially the K L a value found for the system increased with the ozone gas concentration, however, at the highest ozone gas concentration studied the K L a value decreased, possibly because the diffusion of gaseous ozone becomes rate limiting under these conditions. The water temperature had little effect on the K L a value over the temperature range from 10 ºC to 30 ºC. A mathematical model was developed to describe the concentration profiles of dissolved ozone in the ozonation-membrane system. Over a wide range of operating conditions there was a good agreement between the predicted and experimental data.

NO gas is directly decomposed using an intermittent DBD plasma generated by a one cycle sinusoidal power source. Previously, we have developed an ammonia radical injection system, where ammonia radicals were produced by a dielectric barrier discharge (DBD) in a chamber, called a radical injector, which is separate from the chamber in which NO gas flows. The radicals are injected into the mixing zone in the NO gas flow field to decompose NO gas. The power source for generating the DBD is a one-cycle sinusoidal (OCS) waveform so as to easily control the electrical power consumed in the DBD plasma. The fundamental frequency of the OCS power source is 150 kHz. In this paper, we used the same power source, but NO was decomposed directly by the plasma; that is, NO gas is in the DBD plasma. NO gas was varied from room temperature to approximately 400 C, where the effect of DeNOx characteristics were discussed. By optimizing parameters for DeNOx, an energy efficiency of 100 g/kWh was obtained.

In order to remove NO from diesel exhaust gas, non-thermal plasma methods have been expected so far. However it is known that one of the problems is a relatively large energy consumption of the De-NOx process. In this paper, we tried to solve this problem by using a combination method of exhaust gas recirculation and ozone injection. Using a 2.4kVA diesel engine generator, we investigated that how effective is the exhaust gas recirculation to reduce the NO concentration. NO removal experiments were carried out using ozone injecttion method, and a great reduction of discharge energy of De-NOx was confirmed. The optimal recirculation rate was discussed by evaluating the total energy consumption, and we obtained a conclusion that optimal recirculation rate is about 10%.

An ozone production using pulse voltage driven dielectric barrier discharge (DBD) reactor was investigated experimentally to clarify an influence of a duty factor of applied pulse voltage on ozone yield. A square of 10 kV applied voltage was generated using a pulse modulator. Insulated gate bipolar transistor (IGBT) switches were employed to generate the square pulse with 1 kHz in pulse repetition rate. Duty factor of the pulse voltage was controlled in range from 10 to 80% by timing of a gate signal to the IGBT switches. The output voltages of the power supply were applied to a multipoint electrode type DBD reactor in order to operate at low applied voltage. The ozone yield was obtained to be around 100 g/kWh at several thousands ppm ozone production in pure oxygen circumstance at 5 L/min. gas flow. The ozone yield decreased with increasing ozone concentration and was almost independent of the duty factor of square applied voltage under the present experimental condition. Power loss consumed in the pulse modulator was successfully reduced by decreasing duty factor of the output voltage without decrease of the ozone production.

The influence of the technological parameters on the course of the epoxidation of 1-butene-3-ol (1B3O) over the TS-1 catalyst has been presented. A 30 wt% H 2 O 2 was used as an oxidizing agent in the presence of solvent (methanol). The epoxidation was carried both at elevated pressure (autogenic) and atmospheric pressure. The influence of temperature in the range of 20-120°C under the autogenic pressure and in the range of 20-60°C under the atmospheric pressure was investigated. Moreover, the effect of the molar ratio of 1B3O/H 2 O 2 (1:1-5:1mol/mol), solvent concentration (5-90 wt%), catalyst concentration (0.1-5.0 wt%) and the reaction time (0.5-5.0h) was determined. The process was describing by the following functions: the selectivity of transformation to 1,2-epoxy-3-butanol (1,2E3B) in relation to consumed 1B3O, the selectivity of transformation to the organic compounds in relation to consumed H 2 O 2 and the conversion of 1B3O and hydrogen peroxide. The major product of epoxidation was 1,2-epoxy-3-butanol (1,2E3B), the epoxide compound with various applications.

Recently industrial applications of ozone have increased in widely different areas including oxidation, sterilization, deodorization, bleaching and others. Especially, a demand of movable ozonizer for treatment of diesel exhaust gas has been growing up. Generally, a generation of ozone has been attained using ultra violet irradiation, electrolysis and electrical discharges such as a dielectric barrier discharge, a surface discharge, a pulsed streamer discharge and a superimposed silent and surface discharge. In the present situation, a ozonizer based on a dielectric barrier discharge has been commonly utilized in the world. However, a ozonizer based on a dielectric barrier discharge has disadvantages as a movable ozonizer since a discharge electrode, having a breakable dielectric layer and a sensitive gap separation, does not have enough resistance to vibration stress. In this study, the characteristics of ozonizer based on a pulsed streamer discharge were measured using a magnetic pulse compressor (MPC), which has a maximum output voltage of 60 kV, a maximum pulse repetition rate of 500 pulses per second and a pulse duration of about 130 ns, and discharge reactors with coaxial geometry. For the reactor of pulsed streamer discharges, an anode and a cathode electrodes are made by metallic material and a gap separation between electrodes has a little influence on a discharge condition. Therefore, this type of ozonizer has a merit to apply mobile situation. As the results, the ozonizer based on the pulsed streamer discharges has the better production yield of 150 g/kWh in the concentration range of 10 to 20 g/m 3 than dielectric barrier discharge ozonizers.

Two kinds of plasma-catalytic processes initiated by gliding discharges (GD) were examined: 1) nitrous oxide decomposition and 2) methane non-oxidative coupling to C 2 hydrocarbons. In the first case, the GD reactor with stationary catalyst bed was used. It was found that the selected catalysts CuO/Al 2 O 3 and Fe 2 O 3 / Al 2 O 3 may increase the conversion rate of N 2 O into N 2 and O 2 in the plasma-catalytic system, not affecting, however, its oxidation to NO. For the methane coupling, a new model of GD reactor has been developed with a mobile (spouted) bed of catalyst particles. In that process, C 2 hydrocarbons were the dominant reaction products, however, some amounts of non-volatile substances (e.g. soot) were also produced. When using alumina-ceramic particles, acetylene was the main product with none or traces of other C 2 hydrocarbons. In the presence of Pt/Al 2 O 3 , however, much more ethylene and ethane were produced.

In this study, an intercalation process was used for the synthesis of a photocatalyst that works in visible light. Amine molecules were intercalated in layered material H 2 Ti 4 O 9 by means of an intercalation reaction in liquid phase. After the intercalation reaction, the intercalated materials were heated in atmosphere for N doping. After the heat treatment, the crystal structure changed the layered structure into an anatase structure. The sample after heat treatment at 500 degrees C absorbed visible light. The photocatalytic performance of the sample after heat treatment at 500 degrees C indicated that the method used in this study is effective for the synthesis of a photocatalyst that works in visible light.

Photocatalytic oxidation of ibuprofen, clofibric acid, diclofenac and naproxen were studied in near- UV illuminated (> 300nm) aqueous TiO 2 suspensions with emphasis on reaction rates, intermediates and oxidation pathways. First order rate constants for 0.1 mM compounds are in the order NP > IBN > CFA >DC over the range of 0.091 to 0.026 min -1 . The kinetics constants derived from the Langmuir-Hinshelwood preequilibrium absorption model have the same reactivity order. Two oxidation pathways were identified for these compounds: (1) low pH electron transfer from carboxyl group to the TiO 2 valence band hole giving ketone and alcohol from ibuprofen and naproxen and chlorophenol from clofibric acid; (2) HO● radical aromatic ring oxidation dominant at pH 5 and above for all compounds giving Cl ion from clofibric acid and diclofenac. Diclofenac oxidized only through HO● radical ring oxidation to form a phenol and quinone on one ring and Cl ion from the other ring.

We designed and assembled a photocatalyst module for water treatment (referred to hereafter as module-I). The module consists of a Pyrex cylindrical tube into which a photocatalyst coated black light (P-BL) tube was inserted, and the admission port for water is attached tangentially to the curved surface of the P-BL tube. The decomposition-rate constant that we obtained by using a 3-ppm methylene blue aqueous solution showed a drastic increase when the fluid velocity exceeded 2 L/min. We think that the fluid velocity of 2 L/min is the turning point at which the flow pattern changes from a laminar flow to a spiral flow turning around the P-BL. We found that module-I is also effective for decomposition of 50 ppb or less concentration levels of dissolved substances such as 4,4'- (1-Methylethylidene)-bisphenol. From the results of decolorization experiments conducted with module-I in which we used 1 L of amber colored reclaimed water (RW) from a circulation toilet system as real waste fluid, we found that RW became transparent within 2-hours of operation at the fluid velocity of 6.1 L/min.

Sol-gel coating that is commonly used in photocatalyst immobilization has low binding capacity with supporting materials and low photocatalytic efficiency due to reduction of surface area of catalysts. In addition, the recombination of electrons and holes is an important reason of low efficiency in photocatalytic reaction. To solve such problems, our study devised a TiO 2 film using anodization under various electrolyte concentrations, current densities, and potentials. Also, microcurrent was provided to the TiO 2 coated titanium plate to enhance the photocatalytic reactivity. The property of TiO 2 film was researched with XRD, FE-SEM, and the decomposition of methylene blue. With the increase of electrolytes’ concentration and voltage, pore size, film thickness, and amount of rutile was increased. For anodized TiO 2 prepared under 0.25M H 2 SO 4 , 180V, and 110mA/cm 2 , maximum decomposition rate of methylene blue showed 85%. Moreover, addition of microcurrent to anodized TiO 2 increase the decomposition rate of methylene blue up to 5 times.

Photocatalytic decomposition of isopropanol (IPA) in air stream in a continuous TiO 2 or Pt/TiO 2 catalyst-coated annular photoreactor was demonstrated to be effective at relatively short detention times. The increase of UV light intensity and retention time improved the decomposition of IPA. However, both the apparent quantum yield for IPA decomposition and CO 2 production were decreased. A mathematical model combining the continuity equations and Langmuir-Hinshelwood (L-H) kinetics was established to adequately describe the reaction behavior of IPA decomposition in the annular photoreactor with various photocatalysts. The apparent quantum yielded can be modeled and calculated for the decomposition of IPA by photocatalytic oxidation in the annular photoreactor coated with TiO 2 and Pt/TiO 2 .

The photocatalytic degradation of 4-Chlorophenol (4-CP) in aqueous solution has been carried out with TiO 2 nanoparticles, prepared by sol-gel method. The effects of various factors, such as different calcination temperatures of TiO 2 , amount of catalysts, and intensity of light sources were attempted for the efficient degradation of 4-CP. Pt doped TiO 2 photocatalysts were also prepared by photo-reduction method and applied for 4-CP degradation. Pt-TiO 2 catalysts showed higher rate of degradation of 4-CP than the P-25, commercially available TiO 2 . Multi-wall carbon nano-tubes (CNTs) were used as solid support for TiO 2 catalysts and proved to be useful materials to speed up the settling process within 1 h after the reaction was over. The intermediate products formed during the degradation of 4-CP were identified using LC-MS.

Hydrogen sulfide is a widespread pollutant responsible for foul odors and severe damage to health and materials. However, current removal technologies have serious drawbacks. Photocatalysis seems to be a good alternative technology for eliminating H 2 S gas. Destruction efficiencies up to 100% have been achieved, and although the catalyst is deactivated, its regeneration by simple rinsing with water has been demonstrated. Experiments with different initial concentrations and residence times were carried out to define the dependence of conversion on these parameters. The effect of relative humidity, which noticeably influences the photocatalytic process, was also tested. Glass “Raschig” rings with different numbers of TiO 2 -ZrO 2 and TiO 2 layers deposited by a dip-coating procedure were used as the photocatalyst. The reaction rate increased with the number of oxide layers in the coating but no benefit from adding ZrO 2 was found.

Photodegradations of benzo[a]pyrene (B[a]P) on Ag-loaded BiVO 4 and TiO 2 (P25) photocatalysts as well as on a direct photolysis under UV or visible light irradiation have been investigated using the Ames mutagenicity assay to assess the possibility of producing active mutagens in the degradation processes. The Ames test was performed for residues after evaporating acetonitrile from the treated solutions, and evaluated by counting the revertant colonies grown on minimal glucose agar plates in the presence and absence of rat liver enzymes and cofactors (S9mix). In the case of the TiO 2 photocatalysis and the direct UV photolysis, the number of the revertant colonies of TA100 with S9mix decreased to the control level (100 - 150 counts) with decreasing B[a]P concentrations during the UV irradiation. No increase was observed for the revertant colonies of TA98 and TA100 in the presence and absence of S9mix. Thus, the B[a]P degradation by the above two methods does not induce mutagenic activities on both TA98 and TA100. On the other hand, for Ag-BiVO 4 , the number of TA98 revertant colonies gradually increased from the control level (ca. 60 counts) with visible light irradiation and reached ca. 400 counts after 10 h in the absence of S9mix. This result clearly indicates that some active mutagens inducing the frame-shift direct acting mutation were produced in the B[a]P degradation by the use of Ag-BiVO 4 .

Water quality monitoring throughout the United States has shown that atrazine is ubiquitous in surface and groundwater supplies. Once it is transported to adjacent streams and/or leaches to groundwater, it poses a potential threat to humans and wildlife. A photocatalytic reactor employing a highly pure nano-sized anatase TiO 2 (7 nm) was designed for the photocatalysis of atrazine. Light was delivered to the reactor by an 8 mm corediameter, liquid core optical fiber (LCOF) from a light source. Radiation wavelengths varied from 305 nm to 450 nm. The LCOF was connected to a 40 cm long quartz tube, which was coated with DuraflectⓇ coating material that reflected > 90% of the light between 300 nm and 1,200 nm. Openings, 2 mm wide, were provided by removing the coating around the circumference of the quartz tube every 1.8 cm to allow illumination through the quartz tube into the reactor. A 2 3 factorial design was conducted to determine significant effects of three primary design factors, i.e., pH (6, 7, 10, 12), illumination intensity, and the surface-to-volume (S/V) ratio or diameter (D) of the reactor (5 cm, 7.5 cm, 10 cm, 15 cm), and their interaction on atrazine removal rates. Analysis of variance (ANOVA) of the experimental data indicated that all three factors significantly (α = 0.05) affected the atrazine degradation rate. Increasing the illumination intensity (from 6.5 W/m 2 to 65 W/m 2 ) greatly enhanced the initial degradation rate of the atrazine from 0.2 ppb/min to 10.2 ppb/min. As the reactor surface-tovolume ratio increased from 0.27 cm -1 to 0.8 cm -1 , there was an increase in kinetic rate from 0.23 ppb/min to 10.22 ppb/min. Solution pH influenced the TiO 2 surface charge and the ionic form of atrazine in solution, which resulted in electrostatic repulsion of atrazine from the catalyst surface in the pH range of 5-10. Low initial degradation rates of 0.2-3 ppb/min were obtained at pH levels 10 and above. The adsorption isotherm experiments at pH levels from 5 to 10 indicated that no significant (α = 0.05) adsorption was observed on the TiO 2 surface. The results indicated that atrazine photocatalytic degradation was not a surface phenomenon. Degradation products were also measured by the liquid chromatography/electrospray ionization-mass spectrometry/mass spectrometry (LC/ESI-MS/MS) with time at optimal operating conditions: pH = 7, I = 65 W/m 2 , and D = 5 cm.

Crystalline TiO 2 nanoparticles were synthesized by hydrolysis of titanium (IV) isopropoxide (TTIP) in the docusate sodium salt (AOT) -cyclohexane microemulsion at controlled temperature. The influence of various reaction conditions, such as agitation speed (ε), [AOT]/[H 2 O] molar ratio (W), [TTIP]/[H 2 O] molar ratio (R), temperature (T), and aging (t) on the particle size were investigated. The nano-TiO 2 particles were characterized for specific surface area (Brunauer-Emmett-Teller, BET) in addition to X-ray diffraction (XRD) and X-ray spectroscopy (XPS) as to determine the particle size, crystalline state, chemical composition, surface charge, and binding energy. The photocatalytic activity was assessed using methylene blue as probe. Results showed that the particle size was in the range from 13.7 to 31.4 nm based on BET measurements. The size of the particle grows with agitation speeds until log (ε) = 1.9; further increase in mixing rate caused particle breakup. In micelle solution, the particle size decreased with increase in W. In true solution the particle size increased with W. However, increase in R increased the particle size which reached a maximum value at a critical value of log R = -0.26, then decreased upon further increase in R. The activation energy (Ea) was calculated using Arrenhius plot and a value of -3.69 kJ/mol was obtained. Results of particle size analysis from XRD and BET were consistent with each other. Crystalline pattern was proved to be anatase. Furthermore, the photocatalytic activity appeared to optimum with particle size between 22.0 and 25.1 nm.

The novel CuO-SnO 2 nanocomposite oxide photocatalysts were prepared by simple co-precipitation method, and characterized by X-ray diffraction, transmission electron microscopy, N 2 adsorption-desorption measurement and UV-Vis diffuse reflectance spectroscopy. The photocatalytic activities of CuO-SnO 2 , evaluated using the photodegradation of acid blue 62 as a probe reaction under the irradiation of Xenon light, were also found to be related to the calcination temperature and the molar ratio of Cu to Sn. The maximum photocatalytic activity of the CuO/SnO 2 photocatalyst was observed to be calcined at 500°C for 3h (with the molar ratio of Cu to Sn is 1:1) due to the samples with good crystallization and high surface area. It also showed much higher photocatalytic activity in treatment dye wastewater under simulated sunlight irradiation compared to Degussa P25 TiO 2 .

In this work, the effect of six variables: sustrate concentration, initial pH, peroxide/substrate molar ratio, bubbling rate, recirculation rate, and irradiation wavelength on the photocatalytic degradation of chloramphenicol (CAP) using TiO 2 immobilized on glass Raschig rings was studied. The analysis was planned as a fractional factorial design, in order to determine the best affordable experimental conditions to diminish the energetic cost of treatment of this antibiotic, used for the plague treatment in salmon allevines from fish cultures in the southern zone of Chile. For a given sustrate concentration, the best results were obtained at 360 nm irradiation, adding H 2 O 2 and O 2 at the higher pH.

The photocatalytic hydrogen production from aqueous solutions of two diacids, i.e., oxalic acid and fumaric acid, was performed using the mixtures of TiO 2 and single walled carbon nanotubes (SWNTs) under UV light irradiation. The highest hydrogen evolution rates from aqueous oxalic acid and fumaric acid were found to be 15.7 and 2.6 μmol h -1 , respectively. In the absence of SWNTs, however, a negligible amount of hydrogen gas was observed. The content of SWNTs was changed from 1 to 20 wt% and the optimum hydrogen production was observed around 5 wt% for fumaric acid and 7 wt% for oxalic acid. The experiment was also performed to find the pH effect on the hydrogen production. The highest hydrogen evolution rate was observed around pH 3.5 for both acids. The influence of added inorganic anions on the hydrogen production was also studied.

TiO 2 and TiO 2 /SiO 2 films were supported on polyester granules using a grafting procedure and controlled temperature deposition under the generated autogenous pressure. For the TiO 2 films, tetraisopropyl orthotitanate, propan-2-ol and water were used; for the TiO 2 /SiO 2 films titanium tetrachloride, propan-2-ol and silica were employed. The precursors of the two gels were mixed in different amounts to determine the influence on the mechanical stability, nature and photocatalytic activity of the films. The films were characterized by UVvis, FTIR, SEM, DTA, and titanium composition, while their photocatalytic activity was tested in by the removal of methanol in air. Results show the production of uniform and stable films and a high efficiency in the methanol photodegradation as well as a strong relation between the photocatalityc activity and the physico chemical properties of the films and of these with the initial gel compositions.

Oxalic acid is common used in industry. It is also found to be the main reaction product in many advanced oxidation processes (AOPs), especially in the Fenton degradation process. In light, it may be mineralized via Fe(III)-catalyzed photoreaction (i.e. Photo-Fenton reaction). In this study, we found a novel electrochemical oxidation reaction called Fered-Fenton method to mineralize oxalic acid. We investigated the effects of anion and cathode material on the mineralization of oxalate. It was found that Ti-DSA cathode and ferric chloride solution showed the better results than those cathodes made of stainless steel and solutions prepared by ferric sulfate and ferric nitrate. COD could be completely removed in 3 hours when used Ti-DSA cathode and 30 mM ferric chloride solution to treat 20 mM oxalate. On the other hand, only 91% COD could be removed when used stainless steel net cathode instead of Ti-DSA one, and only 55% COD removal was obtained when further used ferric sulfate instead of ferric chloride. We also found that COD and TOC removals made little difference when reduced ferric chloride concentration from 30 mM to 6.67 mM. It could reduce the reagent cost of Fered-Fenton method.

Cryptosporidium parvum oocysts and helminth eggs are among the waterborne pathogens that resist the most to traditional chemical disinfection processes. Since the application of high doses of chlorine, ozone or other chemical disinfectant is not possible in practice because of the subsequent formation of disinfection byproducts, alternative processes for water disinfection have been investigated. This study investigated the potential of catalyzed-solar radiation to control the occurrence of C. parvum oocysts and helminth eggs in drinking water and wastewater, respectively. Bacillus subtilis spores were used as surrogate microorganisms for C. parvum oocysts. Experimental results indicate that 1.5 hours of exposure to ~1 sun-intensity solar radiation, in the presence of 5 mM ferrous ion and 70 mM hydrogen peroxide, decrease egg and spore viability by 49 and 96 percent, respectively. These results suggest that solar photocatalysis may represent an effective and economic alternative for water disinfection in rural communities and for developing countries.

This study investigated the degradation of an organic compound (an azo dye, Acid Red 4) in a synthetic wastewater by using dielectric barrier discharge (DBD) tube comprised of a hollow quartz cylinder and a coaxial copper rod. The DBD tube was immersed in the wastewater that was connected to the ground electrode. When AC high voltage was applied to the copper electrode, the electrical discharge occurred inside the quartz cylinder to produce ultraviolet (UV) light and reactive species such as ozone. The photocatalytic degradation of the organic compound with the UV emitted from the DBD tube was carried out in the presence of aluminum meshes coated with titanium oxide. The system further comprised a gas diffuser that distributed the ozone-containing gas produced in the DBD tube into the wastewater, such that the organic compound were degraded by reacting with ozone. The contributions of the photocatalysis and the ozonation to the degradation were separately assessed, and then combined effect on the degradation was examined. The results clearly revealed that the present system capable of degrading the organic compound in two ways (DBD-induced photocatalysis and ozonation) was very effective for the treatment of the wastewater.

Batch processes were carried out for the photocatalytic degradation of Acid Red 151 from its aqueous solution using ZnO catalyst at different initial dye concentrations. The process was found to be diffusion controlled for the first 15-20 minutes (before irradiation) with an average diffusion coefficient of 6.759 × 10 -6 cm 2 /s. The photocatalytic degradation kinetics was analyzed using the first order, second order and Langmuir-Hinshelwood expressions by linear and non-linear method. The four types of second order kinetic and Langmuir-Hinshelwood kinetic models were also discussed. Non-linear method is a better way to obtain the kinetic parameters. The photocatalytic degradation process was found to follow first order kinetics at lower substrate concentrations and second order kinetics at higher substrate concentrations.