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In this study, preparation of Fe–TiO 2 was synthesized by sol–gel method using tetraisopropoxide and hand warmer waste as precursors. The manipulation parameters including different calcination temperatures (500 °C, 600 °C and 700 °C), Fe:Ti molar ratios (0.05%, 0.1%, 0.25%, 0.5% and 1%), the pH value (3, 5.5, 9) were evaluated by photodegradation of acid red 27 (AR-27) under visible light. Reusability of the catalyst was investigated by the optimal operating parameters. Characterization of prepared catalysts by FE-SEM, HR-XRD, BET, ESCA, Zeta potential, UV–vis was investigated. Fe:Ti molar ratio 0.1 mole% calcined at 500 °C showed strip shape and high surface area. Crystal structure exhibited anatase phase and pH zpc was 5.6. There was the same trend between actual proportion of iron-doped and theoretical values. The band gap decreased as the amount of iron increased and shifted the absorbance edge to the visible light region. The results demonstrated that the best photodegradation efficiency was 0.1 mole% Fe–TiO 2 calcined at 500 °C, 10 mg/L AR-27 and at pH 3. The color removal efficiency kept 89% after catalyst used for 4 times.

In this study, a fluidized bed reactor was used to compare heterogeneous and homogeneous crystallization for recovering magnesium ammonia phosphate (MAP) from the dewatering filtrate at a municipal water resource recovery facility. Investigating the factors affecting crystallization revealed that pH exerted a greater effect than the Mg/P molar ratio. The results of a heterogeneous crystallization experiment showed that removal efficiency of phosphate (RP%) and crystal efficiency of phosphate (CP%) were 68% and 66%, respectively, at a PO4-P concentration of 200 mg/L, pH of 8.0, and Mg/P molar ratio of 1.0 for 3 h. The reaction rate of heterogeneous crystallization was markedly higher than that of homogeneous crystallization. Those pellets produced through the heterogeneous crystallization exhibited a dense surface (particle size 0.5-1.0 mm; water content 8.7%). Through scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS), and X-ray diffraction (XRD) examination, the crystallized patterns of the needle-shaped pellets were identified as MgNH4PO4·6H2O.

Interest in pollution issues caused by synthetic dye wastewater is growing. For many years, researchers have attempted to develop more efficient treatment technology to solve this long-standing environmental problem. As many related studies have focused on advanced oxidation processes (AOPs), the plasma process is remarkable due to its high decolorization efficiency over a short time. This study applied a plasma process in the form of pulsed discharge to treat dye wastewater and to investigate the decolorization of dye wastewater over time by manipulating operation parameters. This method is expected to provide a rapid and highly efficient decolorization technology for wastewater treatment. The results indicate that 99%, 98%, 95% and 73% decolorization could be achieved for methylene blue solutions with initial concentrations of 1 ppm, 5 ppm, 10 ppm, and 20 ppm, respectively, after the experimental device was operated for one hour with operation parameters set at 100 mL min -1 for air inflow, an initial pH of 2.5 for pollutants, and 10 KV for output voltage, while other parameters were fixed.

Chlorophenols (CPs) is one of the organic pollutants and are most widespread in aqueous environment. Advanced oxidation processes (AOPs) have been extensively utilized for the decomposition of hazardous or recalcitrant pollutants in the environment. The study combined UV/TiO2 with ultrasonic procedure to degrade 2,4-dichlorophenol (2,4-DCP) wastewater. The effects of factors including pH value, initial concentration of 2,4-DCP and quantities of TiO2, Fe (II), and Fe (III) added on the removal efficiency of 2,4-DCP wastewater were investigated. Experimental results revealed significant additive effect attributed to the combination of two procedures, 13-watt UV irradiation and 10-watt ultrasound, under the pH 10 and 1g L-1 TiO2. In additional, the destruction removal efficiency (DRE) of 2,4-DCP was raised about 10 % when 250 μM of Fe (II) and Fe (III) were added and this phenomenon was suggested that the Fenton-like reaction occurred.

In this study, we utilized electrolytic catalysis technology and the concentrated brine from the Matsu Nankan Desalination Third Stage Plant to develop a brine resource utilization process, producing a multi-oxidant with disinfection efficacy, containing chlorine dioxide (ClO2), chlorine (Cl2), ozone (O3) and hypochlorous acid (HOCl). This experimental result is expected to achieve waste resource utilization by using the waste concentrated brine as an electrolyte material to produce disinfectants by an electrolysis procedure. The disinfectant generated can also be used in many sterilizing processes in the plant. In the study, the optimal operational conditions were controlled at 40 ℃ for temperature and 12 V for cell voltage. 6 % NaClO2 was added into the same brine. Under these optimum conditions, the major product became ClO2 with a maximum concentration of 1074 mg L-1. Comparing the disinfection efficacies between 1 ppm of commercial 10 % hypochlorous acid and the multi-oxidant produced in this study, the efficacies of hypochlorous acid and the multi-oxidant reached 28 % and 93 %. The latter was three times greater than the former. In conclusion, the multi-oxidant produced by recycling the brine from desalination plants was expected to have applicability and economic value.

The study combines the UV/TiO2and an ultrasonic procedure to degrade the azo dye wastewater of Acid Yellow 17 and investigates the effects of various factors including the quantities of TiO2and iron ions added on the efficiency of the removal of the azo dye wastewater of Acid Yellow 17. The experimental results reveal the a significant additive effects occurs through the combination of the two procedures under the 13 watts UV irradiations and 10 watts ultrasound. The analysis of the catalyst properties indicates that there are no evident changes of the appearance of the crystal and TiO2catalyst when UV/TiO2is combined with ultrasonic procedures. Since the formation of hydrogen peroxide (ND≦1 mg L-1) was not detected during the reactions, the additions of Fe (II) and Fe (III) are unable to induce the Fenton-like reaction effectively. Nevertheless, the additions of Fe ions significantly affect the degradation rate of the dye. Moreover, the effect of Fe (III) was found to be superior to that of Fe (II) under the same concentration.

In this study, we investigate the production of hydroxyl radicals in photo- and electro-catalytic systems. A model compound, 4-hydroxybenzoic acid (4-HBA), served as a trapping (scavenger) reagent for the determination of hydroxyl radical (OH ) concentrations in both systems. Experiments were conducted by controlling different operation parameters (i.e., reaction time, electrolyte, applied voltage, power, and solution pH) to understand their respective impact on OH production. The results show that a number of similar characteristics exist between the photo- and electro-catalytic systems, including the electrolytes Na2SO4 and NaNO3, which are both suitable for photo- and electro-catalysis and increase the applied energy, proportionally enhancing the OH yields. These alkaline conditions are beneficial for generating OH in either the photo- and electro-catalytic system. Notably, electrolyte Na2CO3 is a strong scavenger of OH , which induces the failure of the catalytic system. In summary, the electro-catalytic system demonstrates better OH production rates than those of the photo-catalyst system under the same applied energy and with respect to the catalyst surface area.

Owing to its higher efficiency and better control of disinfection by-products compared with chlorine (Cl2), chlorine dioxide (ClO2) have been widely applied to disinfectation in public water system, cooling system control and wastewater treatment in the past decades. ClO2 of high purity and high concentration can be electrochemically produced using anolyte composed of specific chemical compounds. Electrochemical process has the advantages of simple dosing, ease of operation and onsite continuous production. In this study, different parameters of membrane electrolysis are varied to determine the appropriate conditions for ClO2 generation. Experimental results show that at operation voltage of 12 V, membrane electrolysis using anolyte composed of 2% NaCl and 6% NaClO2 with initial temperature of 30 °C and NaOH catholyte of 0.5% concentration can yield ClO2 of 906.5 mg/L cocentration and 98.4% purity. Moreover, electrolytic reaction accelerates with increase in NaOH catholyte concentration and decrease in initial pH of anolyte. The production rate of ClO2 is also found to be positively correlated with initial temperature of anolyte.

In this study, a new catalytic oxidation technology, microwave/Fe3O4 system, was used to treat volatile organic carbons (VOCs) and dichloromethane (DCM) was selected to simulate industrial emissions of VOCs. This system comprises a household microwave oven modified as the reaction chamber, which was fitted with a vertical, cylindrical quartz reactor comprising a catalytic packed column filled with granular Fe3O4, a microwave catalyst of iron (II, III) oxide. Experimental results showed that the destruction and removal efficiency (DRE) of DCM by microwave alone was close to zero, but with the microwave/Fe3O4 system, the temperature of the catalytic packed column increased rapidly and reached thermal balance within 10-15 min. Analysis of the rear gas after combustion showed that most of DCM was thermal oxidized into CO2 and H2O. The successful application of the proposed microwave/Fe3O4 system to thermal destruction of DCM promises a new technology for treatment of VOCs.

The color elimination of real tea wastewater by the electrocatalytic system was investigated. The electrocatalytic system composed IrO2 electrode as the anode and DSA electrode as the cathode under the current density of 40 mA cm-2. Various concentrations of NaCl and wastewater volumes were tested to understand their effects. For the effect of NaCl addition, the color removal efficiency increased 25% under the condition of NaCl addition. The relatively proper operation was 0.25 M NaCl and 1.0 liter wastewater, which caused the color removal efficiency up to 85%. Based on this color removal efficiency, the tea wastewater of 1.0 L consumed the electricity of 0.03KWh.

The significant yield of dissolved oxygen (DO) is one advanced advantage of the electrocatalytic technique for wastewater treatment. Here, we measure DO concentrations during electrocatalytic processing of Taiwanese municipal wastewater and landfill leachate. Chloride ion–containing electrolytes in the wastewater had the most deleterious effect on the production of DO. In contrast, other anions including carbonates, nitrates, sulfates, and phosphates improved DO yield. The Cl− effect can account for electrode erosion, because the anode surface will be impacted by chloride ions. This erosion results in the release of metal ions at the anode that react with DO to form species of metal oxides and deplete the DO in wastewater. However, other cations in the wastewater such as Na+, Ca2+, and Mg2+ are irrelevant with the DO yield in the electrocatalytic system. Results indicate that inert anodes such as dimensionally stable anodes can increase DO concentration, but the metal-related anodes such as stain...

The purpose of this research is to develop a photocatalytic TiO2that can be activated by visible light and can be conveniently recollected for reusing. This research synthesizes the 20 to 40 nm TiO2/Fe3O4particles with magnetization of 5.8 emu/g using the modified sol-gel method followed by 500°C calcinations. The experiment verified that visible fluorescent light (VFL, contains no UV-A) could activate the photocatalytic activity of TiO2/Fe3O4particles as did ultraviolet A light (UV-A, 360 nm). Regular magnets can be used to separate TiO2/Fe3O4particles from solution. The results indicate that VFL-sirradiated TiO2/Fe3O4particles could decompose isopropanol (IPA) in the absence of UV-A and the issue of TiO2/Fe3O4recollection from water for reusing is also resolved.

La–doped TiO2 thin films were synthesized using TTIP, IPA , Acetic acid ,and La2¬O3 as precursors by sol-gel method and dip-coating method. The different molar raitos of La/Ti ( 0.025,0.050,0.075 and 0.100 ) were supported on ITO glass to product photocatalytic electrodes. The properties of both TiO2/ITO and La- TiO2/ITO photocatalytic electrodes were characterized by FE-SEM,BET and XRD. The FE-SEM and BET analytical results demonstrate that La-TiO2/ITO particles have uniform shape and small size (＜10nm ) compared with TiO2/ITO. Anotherway, the XRD resultes show that when more molar raitos of La/Ti the crystallites become more percent to of rutile. The La-TiO2/ITO photocatalytic electrode with molar raito 0.05 shows the best photocatalysis with mineralization rate after four hours reaction. On this condition, different Acid Yellow 17 initial concentration and UV light intensity have been research. Applied potential 2.0V would effectively increase the decolonization rate under visible light irradiation.

The aim of this research was to investigate the removal of iron and manganese from groundwater by aeration, chlorine oxidation and microfiltration (MF). Pilot-scale experiments were performed at the Chang-Hua Water Treatment Plant in Taiwan. The raw waters contained soluble iron (0.4 mg/L) and manganese (0.5 mg/L) which were oxidized by chlorine and then filtered by hollow-fiber PTFE-MF. The oxidized particles on membranes under appropriate backwash were also investigated. The particle size and quality of treated water were examined. The experimental results indicated that the concentration of the residual manganese remained greater than 0.1 mg/L in treated water during the initial operation period. However, it decreased to below 0.01 mg/L after 2 weeks processing time. The scanning electron microscopy (SEM) energy dispersive spectroscopy analysis of oxidized metal particles under each process illustrated that the particles accumulated on membrane enhanced removal of iron and manganese, through autocatalytic activity in the accumulated layer on membrane. Moreover, the membrane operation pressure over 120 kPa was suggested for the active backwash process, where no structural damage on membrane was confirmed by SEM analysis.

The La/TiO2 photocatalyst was prepared by lanthanum into TiO2 structure in a sol-gel process. The catalyst was characterized by field-emission scanning electron microscope (FE-SEM), X-ray diffractometer (XRD), ESCA, and Brunauer Emmett Teller (BET) analyses. Photocatalytic activities of the supported catalysts were examined through decomposition process of azo-dye Acid Yellow 17 solution under UV irradiation. The results showed that the particle size of TiO2 is about 20 nm, and the particle of La/TiO2 is about 10 nm. The crystal structure is mainly in anatase phase, the contents of the rutile phase increase with the increase of the amount of doped lanthanum. The adsorption capacity of La/TiO2 catalysts increases with lanthanum dosage in the acidic solution. The contribution of actual photodecomposition was determined by desorption process, after the photocatalytic reaction. In the acidic solution, better photodecomposition efficiency is achieved than in the neutral or alkaline solution. The experiments demonstrated that the optimum doping of La at 10 mol %, the maximum photodecomposition in dye concertration at 15 mg L-1 and photocatalytic dosage at 0.75 g L-1, achieving the highest effect.

The study combined UV/TiO2 with ultrasonic procedure to degrade azo dye wastewater of Acid Yellow 17. The effects of factors including pH value, initial concentration of dye, and quantities of TiO2, Fe (II), and Fe (III) added on the removal efficiency of azo dye Acid Yellow 17 were investigated. Experimental results revealed significant additive effect attributed to the combination of two procedures under 13-watt UV irradiation and 10-watt ultrasound. Analysis of the catalyst properties indicated no evident changes in the appearance of crystal and TiO2 catalyst by UV/TiO2 combined with ultrasonic procedure. However, the specific surface area was increased by approximately 53%. No effective formation of hydrogen peroxide (ND  1 mg/L) proved that the addition of Fe (II) and Fe (III) failed to induce the Fenton-like reaction effectively. Nevertheless, the addition of Fe ions affected significantly the initial adsorption and the degradation rate of the dye. Moreover, the treatment efficiency of Fe (III) was found to be superior to that of Fe (II) under the same concentration.

An integrated, online fouling monitoring technique that provides dynamic and real-time information of membrane fouling during a water treatment membrane process was developed. This technique has preliminarily been demonstrated for monitoring particulate fouling in a water treatment microfiltration process using a single photo sensor. The results of the online dynamic analysis suggest that this technique provides in situ measurement of fouling layer thickness, dynamic analysis of the fouling layer structure, and monitoring of water quality during the membrane filtration process.

In this study, the Taguchi method was used to optimize the preparation of titanium dioxide thin film reactor through modified chemical vapor deposition (CVD) method and then conversion ratio of toluene was evaluated at the optimal condition. The results indicated that optimal condition for preparation of TiO2 thin film reactor was as followings: water bath temperature of 80°C, Ti (OC3H7)4 / H2O ratio of 4, carrier gas flow rate of 1000 mL min-1, catalytic oxidation temperature of 400°C, oxidation time of 8 hrs, calcination temperature of 450°C, spraying speed of 30 rpm and furnace linear motion geared motor speed of 75 cm min-1. The conversion ratio of 56.56 ppmv toluene could be achieved up to 99.8% with the irradiation intensity of 3.76μW cm-2 at the flow rate of 300 mL min-1 after 120 minutes.

The different molar ratios of La/Ti (0.025, 0.050, 0.075 and 0.100) photocatalytic electrodes use in this study were synthesized by sol-gel method and dip-coating method. The XRD pattern of TiO2/ITO presents only anatase phases, [1] but for La-TiO2/ITO presents both anatase and rutile phases. The SEM image of the La-TiO2/ITO showed particles of regular shapes with smaller size (＜10nm) compared to the TiO2/ITO, which presented uniform particles of spherical structure and larger size （20nm）.The La-TiO2/ITO photocatalytic electrode with molar ratio 0.050 shows the best ability both on the absorbtion and photocatalytsis. Applied potential 2.0V would effectively increase the photoelectrocatlaytic activity under visible light irradiation.

In this study, the V-doped TiO2 was synthesized by sol-gel method and we evaluate the photocatalytic degrading efficiency of V-TiO2 complexes on azo dye wastewater under irradiation with visible light (λ= 419 nm). The results showed that the Anatase structure and nano size of V-TiO2 complexs were formed and they had better photo-response to visible light than pure TiO2. The efficiency of decoloriztion or destruction efficiency was less than 6 % using TiO2 alone but efficiency of 0.10VT-I was up to 90% after irradiated with visible light for 240 min. These evidences also reveal that the system of V-TiO2 complexes can directly utilize the sunlight and can be used to treat organic pollutants in the practical wastewate treatment factories.

In this study, a new, low cost and easy method, hydroxyl radical trapping method, was employed to investigate the photo-activity of UV/TiO2 photocatalytic reaction. The Taguchi method was utilized to optimize the preparation of titanium dioxide (TiO2) thin-film reactor through the modified chemical vapor deposition (CVD) method. The optimal yield of hydroxyl radicals was then evaluated by calculating the conversion ratio of salicylic acid under the optimal conditions. In the experiments, salicylic acid was used as the free-radical scavenger and the formation of three different intermediates were examined to shed light on the trend and kinetics of reaction of hydroxyl radical with organic substance under different operation conditions. The results indicated that the yield of hydroxyl radicals increased with increasing irradiation intensity and dissolved oxygen level. The optimal experimental conditions obtained in this study were irradiation with intensity of 2.9 mW cm(-2) on salicylic acid at concentration of 250 mg L(-1) by both agitation and aeration processes (dissolved oxygen level=8.2 mg O(2)L(-1)) at pH 5. Such conditions could achieve the optimal hydroxyl radical yield of 5.1 x 10(-17)M.

The use of TiO2 as photocatalyst to degrade the organic compounds is an effective method of oxidation process and has been widely studied in environmental engineering. However, TiO2 absorbed the UV light which is only small part of sunlight reaching earth surface to activate photocatalytic procedure effectively is a major disadvantage. Therefore, studies on the development of new TiO2 wherein its photocatalytic activity can be activated by visible light which is the major part of sunlight will be valuable for field application. In this study, we evaluate the photocatalytic degrading efficiency of porphyrins/TiO2 complexes on the organic pollutants under irradiation with visible light (λ = 419 nm). The results showed that the photodecomposition efficiency of 2,4-dichlorophenol (2,4-DCP) wastewater by using porphyrin/TiO2 irradiated under visible light for 4 h was up to 42–81% at pH 10. These evidences reveal that the system of porphyrin/TiO2 complexes has also significantly efficiency of photocatalytic degradation for some hazardous or recalcitrant pollutants under visible light irradiation.

In this study, a nano-class TiO 2 /Ti thin-film electrode was made using the atmospheric pressure chemical vapor deposition (APCVD). The electrode was combined with an external circuit and anode bias to study the efficiencies of silver ions reduction and acetic acid decomposition. Results of SEM images and XRD patterns of the TiO 2 /Ti thin-film electrode surface show that the thin-film electrode made using the APCVD method can be as size as 30 nm with the TiO 2 photoelectric catalyst in anatase crystal form. More obvious agglomeration of TiO 2 particles was observed for shorter APCVD sprayed times. Results of the light response study show that the electrode has a rapid response time to 365 nm UV light to produce electricity with 7 μA/cm 2 density. Additionally, results of the photocatalytic studies using the electrode combined with an external circuit in the photoelectrical catalytic studies to reduce silver ions reveal that with a reaction time of 180 min, the photocatalytic process will reduce 70% of silver ions in high-concentrated solution (1000 mg/l as Ag) and 93% silver ions in low-concentrated solution (108 mg/l as Ag). When the irradiation time is extended to 240 min, the silver reduction efficiency is as high as 99.8%. Higher solution pH is favorable to the photoelectrical reduction of silver while the anode bias does not benefit the silver reduction efficiency but favors the decomposition of acetic acid. However, the process decomposes less than 10% of acetic acid. The external circuit will transmit the photo-generated electrons to the cathode surface thus reducing the combination of electron and holes at the anode surface. As the reduction of precious metals is concerned, the external circuit is capable of avoiding the metal deposition at the catalyst surface to cause catalyst poison or light shielding that are know to reduce the photo utilization efficiency.

In this study, a TiO2 film was prepared in an annular reactor by the chemical vapor deposition (CVD) method. Results indicated that anatase crystals were formed, except for at a deposition temperature of 200°C without calcination. At a calcination temperature of 850°C, anatase crystal was the major species formed with a small amount of rutile crystals. After conducting a photocatalytic reaction of toluene, the best activity was found with a preparation temperature of 350°C for the deposition, and 550°C for calcination.

In this study, titanium dioxide thin film was prepared using the modified chemical vapor deposition. The parameters employed to control the preparation of the catalyst include the temperature of water bath, the Ti(OC3H7)4/H2O ratio, the flow rate of carrier gas, the oxidation temperature, the oxidation time, the calcination temperature, the rotating speed of furnace, and the speed of geared motor. The orthogonal arrays in the design of experimental method proposed by Taguchi were adopted to conduct the multiple-factor experiment. The conversion rate of salicylic acid in the aqueous or heterogeneous phase photocatalysis experiment was employed to identify the optimal conditions for assembly. The results indicated that a higher conversion ratio of the organic substance could be achieved under catalytic oxidation temperature of 400°C, calcination temperature of 550°C, and spraying speed of 30 rpm and the optimal experimental conditions obtained in this study were irradiation with intensity of 2.9 mW cm-2 on salicylic acid at concentration of 250 mg L-1 by both agitation and aeration processes (dissolved oxygen level = 8.2mg O2 L-1) at pH 5, which could achieve optimal hydroxyl radical yield of 5.1 ×10-17 M.

Increasing cycle of water circulation in industrial cooling water system caused accumulation of dissolving materials in circulating water. Subsequently, the problems including scaling, fouling, corrosion and slime occurred. The multiple oxidants including chlorine dioxide, ozone, peroxide hydrogen, and chlorine were prepared using diaphragm electrolysis method to alleviate the problems above in the cooling system. Meanwhile multiple oxidants can also inhibit the accumulation of biological dirt and erosion effectively. The efficiency of multiple oxidants to inhibit precipitation of magnesium carbonate and calcium carbonate can be increased by adjustment of pH value in the whole pipeline system to reduce corrosion rate of the pipeline and to achieve energy-water saving goal. The results showed that the high efficiency of chlorine dioxide mixture was an excellent bio-corrosion inhibitor and bio-accumulation bactericide. The residue concentration of mixture oxidants are at the range of 0.05 ~ 0.25 mg ClO2/L that is high enough to restrain the growth of micro-organisms.

A microwave/Fe3O4 catalytic system was proposed for treatment of volatile organic carbons (VOCs). This system comprises a household microwave oven modified as the reaction chamber, which was fitted with a vertical, cylindrical quartz reactor comprising a catalytic packed column filled with granular Fe3O4, a microwave catalyst of iron (II, III) oxide. Experimental results showed that the destruction and removal efficiency (DRE) of toluene by microwave alone was close to zero, but with the microwave/Fe3O4 system, the temperature of the catalytic packed column increased rapidly and reached thermal balance within 10-15 min. Analysis of the rear gas after combustion showed that most of the toluene was thermal oxidized into CO2 and H2O. The successful application of the proposed microwave/Fe3O4 system to thermal destruction of toluene promises a new technology for treatment of VOCs.

The use of TiO2 as photocatalyst to degrade the organic compounds is an effective method of oxidation process and has been widely studied in environmental engineering. However, TiO2 absorbed the UV light which is only small part of sunlight reaching earth surface to activate photocatalytic procedure is a major disadvantage. Therefore, studies on the development of new TiO2 that its photocatalytic activity can be activated by visible light which is the major part of sunlight will be valuable for field application. In this study, we evaluate the photocatalytic degrading efficiency of porphyrins/TiO2 complexes on the organic pollutants under irradiation with visible light (λ= 419 nm). The results showed that the photodecomposition efficiency of methylene blue were up to 95% and 90% respectively after using NiTPP/TiO2 and ZnTPP/TiO2 irradiated with visible light for 6 h. These evidences reveal that the system of porphyrin/TiO2 complexes has significantly high efficiency of photocatalytic degradation under visible light irradiation.

In this study the photocatalytic decomposition of a synthetic dye, C. I. Acid Yellow 17, was investigated. The TiO2 photocatalyst prepared by chemical vapor deposition (CVD) for UV/TiO2 process was prepared by annealing at 550 C for 24 h and anatase type crystalline (under XRD and SEM analysis) was obtained. The more important factors affecting the dye wastewater treatment in terms of dye removal ratio, color removal ratio, and mineralization ratio in this study were pH value of the solution, initial concentration of the dye wastewater, flow rate of the wastewater inflow and light intensity. Chloride and sulfate were detected in C. I. Acid Yellow 17 decomposition process while ammonium and nitrate were not detected. 2005 Elsevier Ltd. All rights reserved.

Locally available manganese-coated sand, from packing and a by-product of the filtration process for water treatment plants in Taiwan, was found to be a low cost and promising adsorbent for the removal of Mn2+ from raw water. In this work, adsorption and desorption of Mn2+ in water have been studied by using batch techniques. The equilibrium adsorption level was determined to be a function of the solution pH, contact time and adsorbate concentration. The equilibrium adsorption capacity of Mn2+ was obtained by using a pseudo-Langmuir isotherm. Ion exchange is probably one of the major adsorption mechanisms for binding divalent manganese ions to the coated sand. The results provide a feasible hypothesis of adsorption mechanisms. This study also supplies significant plant operation capacity data for engineering design.

"Manganese-coated sand" is a type of silica medium coated with manganese oxides, formed from the sorption of manganese oxides during long-term filtration via the process of rapid sand filtration, followed by aeration in a water treatment plant. Locally available manganese-coated sand, both for packing and as a byproduct of filtration processes for water treatment plants in Taiwan, was found to be a low-cost and promising adsorbent for removal of Mn(2+) from raw water. This study was conducted to build the basic data for coating hydrated manganese oxide on the sand surface to utilize the adsorbent properties of the coating and the filtration properties of the sand. In this study, gas adsorption porosimetry and scanning electron microscopy analyses were used to investigate the surface properties of the coated layer. An energy dispersive X-ray (EDAX) technique of analysis was used to characterize metal adsorption sites on a manganese-coated sand surface. Results indicated that manganese-coated sand had more micropores and higher specific surface area, owing to attachment of manganese sand. Manganese ions penetrated into the micropores and mesopores of manganese oxide on a sandy surface; regeneration of manganese-coated sand could be achieved by soaking with pH2.0 acid solution. Results of EDAX analysis showed that the interfacial layer constructed the interface of manganese-coated sand. Acid and alkali resistance tests interpret a wide application range of pH for manganese-coated sand, and general temperature conditions do not affect the performance of this sand. Manganese-coated sand is potentially suitable for application as a packed bed for treatment of heavy metals from water. The results of this study can also benefit plant operational capacity data for engineering design.

The purpose of the investigation was to study the photocatalytic reaction of trichloroethane using a TiO(2) catalyst deposited in an annular reactor by the chemical vapor deposition (CVD) method. The experimental results indicated the highest decomposition rate of the trichloroethane was 2.71 micro mol/(sm(2)) and the conversion ratio reached a maximum of 99.9%. When the humidity was below 154 micro M, the reaction rate slightly increased with increasing humidity. However, the reaction rate decreased as the humidity increased154 micro M. Oxygen played a role as an electron acceptor in the reaction, and reduced the recombination of the photogenerated electron-hole pairs. Therefore, the reaction rate rose as the oxygen concentration increased. Nevertheless, after the oxygen concentration reached 12%, the reaction rate reached it maximum and was constant in spite of increasing oxygen concentration. As the initial reactant concentration increased, the reaction rate increased, but the conversion ratio dropped. An increase of light intensity resulted in an increase in the number of photons and thus increased the reaction rate. Accordingly the decomposition of trichloroethane could be fitted by the semi-empirical bimolecular Langmuir-Hinshelwood model. Moreover, the reaction rate was proportional to the 0.48-order of the light intensity.

This research used an ultra-membrane filtration system to divide raw water into four different organic groups with different molecular masses. The effects of each organic group on the quantity of disinfection by-products formed after a reaction with chlorine dioxide was investigated. The experimental results show that the four organic groups of different molecular masses were: 10 kD

In this study, titanium dioxide thin film was prepared using the modified chemical vapor deposition. The parameters employed to control the preparation of the catalyst include the temperature of water bath, the Ti(OC3H7)4/H2O ratio, the flow rate of carrier gas, the oxidation temperature, the oxidation time, the calcination temperature, the rotating speed of furnace, and the speed of geared motor. The orthogonal arrays in the design of experimental method proposed by Taguchi were adopted to conduct the multiple-factor experiment. The conversion rate of salicylic acid in the aqueous or heterogeneous phase photocatalysis experiment was employed to identify the optimal conditions for assembly. The results indicated that a higher conversion ratio of the organic substance could be achieved under catalytic oxidation temperature of 400 °C, calcination temperature of 550 °C, and spraying speed of 30 rpm and the optimal experimental conditions obtained in this study were irradiation with intensity of 2.9 mW cm−2 on salicylic acid at concentration of 250 mg L−1 by both agitation and aeration processes (dissolved oxygen level = 8.2 mg O2 L−1) at pH 5, which could achieve optimal hydroxyl radical yield of 5.1 × 10−17 M.

This investigation used wastewater from manufactured fiber plant for studying the effect of controlling variables on the COD removal efficiency by photocatalyzed degradation of organic pollutants in the presence of titanium dioxide catalyst. By using BOD/COD ratio as index, the treatment of raw wastewater was evaluated for its change of biodegradability as a feasibility in the pre-treatment of biological treatment. The experimental results indicated that with the Janssen Chemica TiO2 as catalyst, the optimal addition was 0.25 g/L with increasing COD removal for decreasing pH value. Both increased light intensity and continuous aeration increased COD removal efficiency, particularly under continuous aeration for significantly raising the ratio of BOD/COD to improve efficiency of subsequent biological treatment.

This investigation concerned the photocatalytic decomposition of cis-dichloroethylene (cis-DCE) with titanium dioxide under irradiation of 365 nm wavelength UV light. The feasibility studies involved initial concentration of reactant, humidity, oxygen content and light intensity on the effect of the heterogeneous photocatalytic reaction along with the development of reaction kinetic model based on above parameters. Under experimental conditions, the maximum reaction rate for decomposing DCE was 0.959 μmole/s-g and quantum yield of 0.297. The concentration effect was in proportion to reaction rate but inversely to conversion ratio. As oxygen being a good electron accepter, the reaction rate increased with increasing oxygen content, but for higher than 15%(v/v), the reaction rate no longer increased. The functions of water were twofold: one being the source of hydroxyl free radicals, and the other for competing with DCE on adsorption sites. For lower moisture content, reaction rate increased with increased moisture content, but reversed under high moisture content. Stronger light intensity increased reaction rate with proportion to 0.6 order of light intensity. The kinetic expression could be represented by Langmuir-Hinshelwood bimolecular reaction model.

This investigation concerned the use of titanium dioxide irradiated with UV light of 365 nm wavelength in a jacketed cylindrical glass reactor for the removal of organic pollutants from the final settling tank of wastewater from manufactured fiber production. The controlling factors of the feasibility studies included the amount of titanium dioxide, pH value, light intensity, and aeration on the decomposition. The results indicated that, with 0.25 g/L TiO2, optimum decomposition could be attained. An excess amount of TiO2 could block the light passage and lower the efficiency. The lower the pH value, the better the decomposition. The decomposition of organic pollutants was in proportion to the light intensity, while aeration was a decisive controlling factor, with dissolved organic carbon (DOC) removal efficiency from 30% without aeration to 75% with aeration.

This investigation used a specifically built jacketed cylindrical type reactor with suspended titanium dioxide under UV-light of 365 nm for feasibility studies of decomposition of mono-substituted phenols. The factors to be studied were the effects of pH, anion additives and the influence of co-existing reactants competing for reaction. Finally, the degree of mineralization of reactants was conducted in order to survey the effectiveness of treatment. From experimental results, under the condition of 7.5 g/l TiO2, pH 3, and light intensity of 2.25 mW/cm2, 0.1 mM of substituted phenol could be completely decomposed in 2 h. The reaction was found to be apparent first-order following Langmuir–Hinshelwood model. In the presence of chloride ions, a significant inhibition of reaction was found at pH 3, but not at higher pH levels. At pH 3, a slight inhibition was found for nitrate ions, but uncertain for sulfate ions. For the experiment with co-existing 2-chloro and 2-nitrophenol, the result differed from that of the individual specie. In the mineralization experiments, substitution in the phenol ring had no applicable influence on the reaction rate, however, complete mineralization to carbon dioxide could not be completed within 9 h.

In this investigation, a packed bed filled with coated titanium dioxide glass beads to study the kinetics of photocatalytic degradation of trichloroethylene under irradiation of 365 nm UV light. In the range of 100–500 ml/min of flowrate, the reaction rate for 6 μM TCE increased with an increasing flowrate upto 300 ml/min, while was not affected by the flowrate at the values higher than 300 ml/min. For moisture in the range of 9.4–1222.2 μM, the reaction rate of TCE was decreased with an increasing humidity. The adsorbed water on the catalyst surface could compete with the adsorption of TCE on the sites. The reaction rate of 6 μM TCE increased as the light intensity increased, and was proportional to the 0.61 order of the light intensity. Among the three L–H bimolecular form models, the experimental data had the best fit for one of models: r=k[K 1 C r /(1+K 1 C r +K 2 C w )][K 4 C w /(1+K 3 C r +K 4 C w )]

This investigation used a packed-bed reactor filled with coated titanium dioxide glass beads which was activated by a 365 nm UV light for heterogeneous photocatalytic decomposition of trichloroethylene under different conditions of flowrate, oxygen content, moisture and light intensity. For the flowrate of feed gas between 100–500 mL/min, the reaction rates increased with an increasing flowrate below 300 mL/min. When the flowrate was more than 300 mL/min, the reaction rate was not affected by the flowrate. For the oxygen content in the range of 0–20 %(v/v), it indicated that under 10 %(v/v) oxygen content the reaction rate increased as the oxygen content increased. The increase of moisture content lowered the reaction rates in the range of 230–30000 ppmv. The reaction rate of 6μM TCE increased as the light intensity increased, and was proportional to the 0.61 order of the light intensity. The deactivation of the TiO2 described in the literature was not observed in this study.

This investigation was initiated to study the heterogeneous photocatalytic reactions of cresols and nitrophenols with ultraviolet light/titanium dioxide (UV/TiO2) system. The experimental parts consisted of pH effect, determination of intermediates and mineralization. At pH 7 and a concentration of 0.1 mM, cresols and nitrophenols nearly disappeared after 2.5 h of reaction time. Under various pH levels, the pseudo first order rate constants of Langmuir–Hinshelwood model was found satisfactory. From the results of GC/MS analysis, most intermediate products were hydroxyl derivatives of parent compounds as a result of photocatalyzed hydroxylation. In the mineralization of o-nitrophenol, about 89.6% of the compounds were mineralized in 9 h of reaction time with initial formation of nitrite and nitrate ions, indicating denitration followed by subsequent degradation.

This investigation used a packed-bed reactor filled with titanium dioxide catalyst. It was activated by a 365 nm UV light source, for heterogeneous photocatalytic decomposition of trichloroethylene (TCE) under different conditions of flow rate, moisture, and light intensity. At a constant temperature of 30°C, the concentration of 6.5 μM for TCE decreased with increasing time, and reached an equilibrium state in 9 min. For the flow rate of feed gas between 100–900 mL/min, the conversion decreased with an increasing flow rate. The decomposition of TCE at 900 mL/min was only 2.22%, indicating feed gas rapidly passing through the catalyst layer without a reaction. For moisture in the range of 3000-20 000 μL/L, the conversion of TCE decreased with increasing humidity, and the decomposition of this could be inhibited by excessive moisture. The adsorbed water on the catalyst surface could compete with the adsorption of TCE on the sites. By adjusting light intensity in the range of 0.085-0.5 mW/cm 2 , the stronger the illumination, the more the conversion of TCE, due to the increased supply of photons for reaction.

In the presence of ions with various hydrolysis characteristics, the water-molecule structure and surface charge on iron sludge colloids can be changed and the dewaterability of iron sludge will also be affected. Such effects were studied in the laboratory through determinations of zeta potentials and specific the resistance of Fe2O3 sludge particles. It was found from experiments in the presence of ions with various hydrolysis characteristics in the iron sludge solutions, that the dewaterabilities of iron sludges showed the orders Cl− > Br− > I− and IO3− > BrO3− > C1O3− for anions, and Li+ > Na+ > K+ > Rb+ > Cs+ and Mg2+ > Ca2+ > Sr2+ ∼ Ba2+ for cations. In the presence of ions of different concentrations, the change in zeta potentials and the improvement of dewaterabilities of iron sludge particles followed the order lO−2M > 10−3M > lO−M for both IO3− and Li+; although the change in zeta potentials increased with the ion concentration for I− and Cs+, the dewaterabilities of iron sludges were depressed with increasing ion concentrations.