Analogies and differences between photocatalytic oxidation of chemicals and photocatalytic inactivation of microorganisms

This study reports the analogies and differences found when comparing TiO₂ photocatalytic treatment for chemical oxidation and microorganisms inactivation, using methylene blue and Escherichia coli as references, respectively. In both processes the activation is based on the same physicochemical phenomena and consequently a good correlation between them is observed when analyzing the effect of operational variables such as catalyst concentration or incident radiation flux, both factors influencing common stages such radiation absorption and generation of reactive oxygen species. However, different microbiological aspects (osmotic stress, repairing mechanism, regrowth, bacterial adhesion to the titania surface, etc) makes disinfection kinetics significantly more complex than the first-order profiles usually observed for the oxidation of chemical pollutants. Moreover, bacterial inactivation reactions are found to be extremely sensitive to the composition of water and modifications of the catalysts in comparison with the decolorization of the dye solutions, showing opposite behaviors to the presence of chlorides, incorporation of silver to the catalysts or the use of different types of immobilized TiO₂ systems. Therefore, the activity observed for the photocatalytic oxidation of organics can not be always extrapolated to photocatalytic disinfection processes.     

Solar photocatalytic treatment of synthetic municipal wastewater

The photocatalytic organic content reduction of a selected synthetic municipal wastewater by the use of heterogeneous and homogeneous photocatalytic methods under solar irradiation has been studied at a pilot-plant scale at the Plataforma Solar de Almeria. In the case of heterogeneous photocatalysis the effect of catalysts and oxidants concentration on the decomposition degree of the wastewater was examined. By an accumulation energy of 50 kJL(-1) the synergetic effect of 0.2 gL(-1)TiO(2) P-25 with hydrogen peroxide (H(2)O(2)) and Na(2)S(2)O(8) leads to a 55% and 73% reduction of the initial organic carbon content, respectively. The photo-fenton process appears to be more efficient for this type of wastewater in comparison to the TiO(2)/oxidant system. An accumulation energy of 20 kJL(-1) leads to 80% reduction of the organic content. The presence of oxalate in the Fe(3+)/H(2)O(2) system leads to an additional improvement of the photocatalytic efficiency.     

Efficient electricity production and simultaneously wastewater treatment via a high-performance photocatalytic fuel cell

A great quantity of wastewater were discharged into water body, causing serious environmental pollution. Meanwhile, the organic compounds in wastewater are important sources of energy. In this work, a high-performance short TiO₂ nanotube array (STNA) electrode was applied as photoanode material in a novel photocatalytic fuel cell (PFC) system for electricity production and simultaneously wastewater treatment. The results of current work demonstrate that various model compounds as well as real wastewater samples can be used as substrates for the PFC system. As a representative of model compounds, the acetic acid solution produces the highest cell performance with short-circuit current density 1.42 mA cm⁻², open-circuit voltage 1.48 V and maximum power density output 0.67 mW cm⁻². The STNA photoanode reveals obviously enhanced cell performance compared with TiO₂ nanoparticulate film electrode or other long nanotubes electrode. Moreover, the photoanode material, electrolyte concentration, pH of the initial solution, and cathode material were found to be important factors influencing the system performance of PFC. Therefore, the proposed fuel cell system provides a novel way of energy conversion and effective disposal mode of organics and serves well as a promising technology for wastewater treatment.     

Solar and photocatalytic disinfection of protozoan, fungal and bacterial microbes in drinking water

The ability of solar disinfection (SODIS) and solar photocatalytic (TiO(2)) disinfection (SPC-DIS) batch-process reactors to inactivate waterborne protozoan, fungal and bacterial microbes was evaluated. After 8 h simulated solar exposure (870 W/m(2) in the 300 nm-10 microm range, 200 W/m(2) in the 300-400 nm UV range), both SPC-DIS and SODIS achieved at least a 4 log unit reduction in viability against protozoa (the trophozoite stage of Acanthamoeba polyphaga), fungi (Candida albicans, Fusarium solani) and bacteria (Pseudomonas aeruginosa, Escherichia coli). A reduction of only 1.7 log units was recorded for spores of Bacillus subtilis. Both SODIS and SPC-DIS were ineffective against the cyst stage of A. polyphaga.     

Effect of sunlight irradiation on photocatalytic pyrene degradation in contaminated soils by micro-nano size TiO2

The enhanced catalytic pyrene degradation in quartz sand and alluvial and red soils by micro-nano size TiO₂ in the presence and absence of sunlight was investigated. The results showed that the synergistic effect of sunlight irradiation and TiO₂ was more efficient on pyrene degradation in quartz sand and red and alluvial soils than the corresponding reaction system without sunlight irradiation. In the presence of sunlight irradiation, the photooxidation (without TiO₂) of pyrene was very pronounced in alluvial and red soils and especially in quartz sand. However, in the absence of sunlight irradiation, the catalytic pyrene degradation by TiO₂ and the photooxidation (without TiO₂) of pyrene were almost nil. This implicates that ultra-violet (UV) wavelength range of sunlight plays an important role in TiO₂-enhanced photocatalytic pyrene degradation and in photooxidation (without TiO₂) of pyrene. The percentages of photocatalytic pyrene degradation by TiO₂ in quartz sand, alluvial and red soils under sunlight irradiation were 78.3, 23.4, and 31.8%, respectively, at 5 h reaction period with a 5% (w/w) dose of the amended catalyst. The sequence of TiO₂-enhanced catalytic pyrene degradation in quartz sand and alluvial and red soils was quartz sand > red soil > alluvial soil, due to different texture and total organic carbon (TOC) contents of the quartz sand and other two soils. The differential Fourier transform infrared (FT-IR) spectra of degraded pyrene in alluvial soil corroborate that TiO₂-enhanced photocatalytic degradation rate of degraded pyrene was much greater than photooxidation (without TiO₂) rate of degraded pyrene. Based on the data obtained, the importance for the application of TiO₂-enhanced photocatalytic pyrene degradation and associated organic contaminants in contaminated soils was elucidated.     

Surface modification of TiO2 by a ruthenium(II) polypyridyl complex via silyl-linkage for the sensitized photocatalytic degradation of carbon tetrachloride by visible irradiation

A new ruthenium(II) photosensitizer, [Ru(II)(py-pzH)(3)](2+) (where py-pzH=3-(2'-pyridyl)pyrazole), has been synthesized. The complex displayed outstanding excited state redox properties (estimated Ru(III)/Ru(II)* approximately -1.24 V vs. NHE) and was expected to sensitize the injection of electrons into the conduction band of anatase TiO(2) upon visible irradiation. The photosensitizer was anchored onto the surface of anatase TiO(2) particles via in situ silylation. The silyl-linkage displayed excellent stability in both aqueous media, over a wide pH range, and in common organic solvents. The resultant material, TiO(2)-[Ru(II)(py-pz-Si identical with )(3)], was found to be able to mediate degradation of CCl(4) in neutral aqueous medium under broad band visible irradiation (lambda>450 nm). The relation between the rate of degradation and concentration of substrate was explored and the mechanism of the photodegradation of the perhalogenated organic was discussed.     

Photocatalytic degradation of reactive black 5 in aqueous solutions: Effect of operating conditions and coupling with ultrasound irradiation

The degradation of reactive black 5 (RB 5), a representative diazo dye found in textile effluents, by means of ultraviolet irradiation (9W UVA) over TiO(2) suspensions, ultrasound irradiation (80kHz, 135W) and their combined application was investigated. Several commercial TiO(2) catalysts were screened and an anatase Hombicat UV 100 sample exhibited considerable activity in terms of solution decoloration, COD and ecotoxicity reduction. Photocatalytic degradation increased with increasing TiO(2) loading (in the range 0.05-1g/L) and decreasing dye concentration (in the range 120-20mg/L) and solution pH (in the range 9-2.6). At the typical conditions employed in this study (60mg/L dye, 0.25mg/L catalyst, ambient pH=5.8, oxygen sparging), complete decoloration was achieved after 60min of reaction. Addition of H(2)O(2) up to 0.01M hindered degradation, scavenging the photogenerated holes and hydroxyl radicals. Ultrasound irradiation resulted in low decoloration, e.g. less than 10% after 60min at 60mg/L dye and oxygen sparging and slightly improved under an argon atmosphere. The simultaneous application of ultraviolet and ultrasound irradiation resulted in increased decoloration compared to that achieved by photocatalysis and sonolysis operating separately; moreover, the overall sonophotocatalytic effect was greater than the additive effect of the two processes, implying possible synergy.     

Solar photocatalytic thin film cascade reactor for treatment of benzoic acid containing wastewater

A solar photocatalytic cascade reactor was constructed to study the photocatalytic oxidation of benzoic acid in water under various experimental and weather conditions at HKUST. Nine stainless steel plates coated with TiO(2) catalyst were arranged in a cascade configuration in the reactor. Photolytic degradation and adsorption were confirmed to be insignificant total organic carbon (TOC) removal mechanisms. A turbulent flow pattern and, hence, improved mixing in the liquid film were achieved due to the unique cascade design of the reactor. The photoinduced consumption of oxygen during reactions was demonstrated in a sample experiment. The proposed rate equations provided good fits to 90 data points from 17 experiments. The regression results showed that the TOC removal rates averaged over 30 min intervals did not illustrate significant dependence on TOC(0) and that I(mean) was more important in affecting the photocatalytic process within the ranges of the data examined. The percentage removal of TOC in 7 l of 100 mg/l (or 100 ppm) benzoic acid solutions increased from 30% to 83% by adding 10 ml of hydrogen peroxide solution (30 wt%). Hydrogen peroxide was also shown to enhance the efficiency of the degradation process at elevated temperatures. Ortho-, meta- and para-hydroxybenzoic acids were identified by HPLC analysis as the intermediates of benzoic acid during reactions without the addition of hydrogen peroxide solutions.     

Application of nano TiO(2) towards polluted water treatment combined with electro-photochemical method

A novel composite reactor was prepared and studied towards the degradation of organic pollutants in this work. In the reactor, a UV lamp was installed to provide energy to excite nano TiO(2), which served as photocatalyst, leading to the production of hole-electron pairs, and a three-electrode electrolysis system was used to accumulate H(2)O(2) which played an important role in the degradation process. The reactor was evaluated by the degradation process of rhodamine 6G (R-6G), and the data obtained in the experiments showed that the combination of the photochemical and electrochemical system raised the degradation rate of R-6G greatly; the working mechanism of the reactor was also discussed in the article. The prepared reactor was also utilized to treat polluted water from dyeing and printing process. After continuous treatment for 0.5h, chemical oxygen demand biochemical oxygen demand, quantity of bacteria and ammonia nitrogen of the polluted water were reduced by 93.9%, 87.6%, 99.9% and 67.5%, respectively, which indicated that the method used here could be used for effective organic dyes degradation.     

Synergetic effect between photocatalytic degradation and adsorption processes on the removal of phenolic compounds from olive mill wastewater

The photocatalytic degradation of two phenolic compounds, p-coumaric acid and caffeic acid, was performed with a suspended mixture of TiO₂ and powdered activated carbon (PAC) (at pH = 3.4 and 8). Adsorption, direct photolysis and photocatalytic degradation were studied under different pH and UV light sources (sunlight vs. 365 nm UV lamps). The potential for reusing this catalyst mixture in sequential photocatalytic runs was examined as well. Quantum yields for the direct photolysis of caffeic acid under solar and artificial 365 nm light were calculated (for the first time) as 0.005 and 0.011, respectively.A higher removal rate of contaminants by either adsorption or photocatalysis was obtained at a low pH (pH 4). Furthermore, the addition of PAC increased the removal efficiency of the phenolic compounds. Fast removal of the pollutants from the solution over three sequential runs was achieved only when both TiO₂ and PAC were present. This suggests that at medium phenolic concentrations, the presence of PAC as a co-sorbent reduces surface poisoning of the TiO₂ catalyst and hence improves photocatalysis degradation of phenolic pollutants.The adsorption equilibrium of caffeic acid or p-coumaric acid on TiO₂, PAC and the combined mixture of TiO₂ and PAC follows the Langmuir isotherm model. Experiments with PAC TiO₂ mixture and olive mill wastewater (anaerobically treated and diluted by a factor of 10) showed higher removal of polyphenols than of chemical oxygen demand (COD). 87% removal of total polyphenols, compared to 58% of COD, was achieved after 24 h of exposure to 365 nm irradiation (7.6 W/m²) in the presence of a suspended mixture of TiO₂ and PAC, indicating “self-selectivity” of polyphenols.     

Enhancement of photocatalytic activity by metal deposition: characterisation and photonic efficiency of Pt, Au and Pd deposited on TiO2 catalyst

Pt, Au and Pd deposited TiO2 have been prepared and characterised by surface analytical methods such as surface area, XRD, and scanning electron micrograph and photophysical characterisation by diffuse reflectance spectroscopy. The photocatalytic activity of the doped catalysts was ascertained by the photo-oxidation of leather dye, acid green 16 in aqueous solution illuminated with low-pressure mercury lamp ( approximately 254 nm). The effect of metal contents on the photocatalytic activity was investigated. The highest photonic efficiency was observed with metal deposition level of less than 1 wt%.     

Preparation and application of TiO2 photocatalytic sensor for chemical oxygen demand determination in water research

In this work, a TiO(2) photocatalytic sensor was prepared and utilized into flow injection analysis (FIA) for chemical oxygen demand (COD) determination. With a positive bias potential of 0.4V (vs. Ag/AgCl) applied to the sensor and a 12-W quartz UV lamp illuminating it, photocurrent, due to the charge transfer at the interface of TiO(2) sensor and the passing solution, was recorded and its change (deltaI(Photo)) caused by the detected sample was calculated to characterize the COD value of the sample. Under the optimizing conditions, the sensor responded linearly to the COD of D-glucose solution in the range of 0.5-235 mg/L, with a linear correlation coefficient of 0.9998. Its application in artificial wastewater analysis has achieved results in good agreement with those from the conventional dichromate method; meanwhile, the process requires no hypertoxic reagents and less analysis time, suggesting that it would be another appropriate method for COD determination in water assessment.     

A practical demonstration of water disinfection using TiO2 films and sunlight

The scope of this study is the assessment of the efficiency of solar disinfection by heterogeneous photocatalysis with sol-gel immobilized (titanium dioxide) TiO2 films over glass cylinders. The solar disinfection process known as SODIS was considered as a reference. Spring water naturally polluted with coliform bacteria was exposed to sunlight in plastic bottles with and without TiO2 over simple solar collectors and the disinfection effectiveness was measured. Total and fecal coliforms quantification was performed by means of the chromogenic substrate method in order to obtain the efficiency of each disinfection treatment. The disinfection with TiO2 was more efficient than the SODIS process, inactivating total coliforms as well as fecal coliforms. On a sunny day (more than 1000 W m(-2) irradiance), it took the disinfection with immobilized TiO2 15 min of irradiation to inactivate the fecal coliforms to make them undetectable. For inactivation of total coliforms, 30 min was required, so that in less than half the time it takes SODIS, the treated water complies with the microbial standards for drinking water in Mexico. Another important part of this study has been to determine the bacterial regrowth in water after the disinfection processes were tested. After SODIS, bacterial regrowth of coliforms was observed. In contrast, when using the TiO2 catalyst, coliforms regrowth was not detected, neither for total nor for fecal coliforms. The disinfection process using TiO2 kept treated water free of coliforms at least for seven days after sun irradiation. This demonstration opens the possibility of application of this simple method in rural areas of developing countries.     

Drugs degrading photocatalytically: Kinetics and mechanisms of ofloxacin and atenolol removal on titania suspensions

The conversion of the antibiotic ofloxacin and the β-blocker atenolol by means of TiO₂ photocatalysis was investigated. Irradiation was provided by a UVA lamp at 3.37 × 10⁻⁶ einstein/s photon flux, while emphasis was given on the effect of catalyst type and loading (50-1500 mg/L), initial substrate concentration (5-20 mg/L), initial pH (3-10) and the effect of H₂O₂ (0.07-1.4 mM) as an additional oxidant on substrate conversion and mineralization in various matrices (i.e. pure water, groundwater and treated municipal effluent). Conversion was assessed measuring sample absorbance at 288 and 224 nm for ofloxacin and atenolol, respectively, while mineralization measuring the dissolved organic carbon. Degussa P25 TiO₂ was found to be more active than other TiO₂ samples for either substrate degradation, with ofloxacin being more reactive than atenolol. Conversion generally increased with increasing catalyst loading, decreasing initial substrate concentration and adding H₂O₂, while the effect of solution pH was substrate-specific. Reaction rates, following a Langmuir-Hinshelwood kinetic expression, were maximized at a catalyst to substrate concentration ratio (w/w) of 50 and 15 for ofloxacin and atenolol, respectively, while higher ratios led to reduced efficiency. Likewise, high concentrations of H₂O₂ had an adverse effect on reaction, presumably due to excessive oxidant scavenging radicals and other reactive species. The ecotoxicity of ofloxacin and atenolol to freshwater species Daphnia magna was found to increase with increasing substrate concentration (1-10 mg/L) and exposure time (24-48 h), with atenolol being more toxic than ofloxacin. Photocatalytic treatment eliminated nearly completely toxicity and this was more pronounced for atenolol.     

Solar Fenton and solar TiO2 catalytic treatment of ofloxacin in secondary treated effluents: Evaluation of operational and kinetic parameters

Two different technical approaches based on advanced oxidation processes (AOPs), solar Fenton homogeneous photocatalysis (hv/Fe²⁺/H₂O₂) and heterogeneous photocatalysis with titanium dioxide (TiO₂) suspensions were studied for the chemical degradation of the fluoroquinolone ofloxacin in secondary treated effluents. A bench-scale solar simulator in combination with an appropriate photochemical batch reactor was used to evaluate and select the optimal oxidation conditions of ofloxacin spiked in secondary treated domestic effluents. The concentration profile of the examined substrate during degradation was determined by UV/Vis spectrophotometry. Mineralization was monitored by measuring the dissolved organic carbon (DOC). The concentrations of Fe²⁺ and H₂O₂ were the key factors for the solar Fenton process, while the most important parameter of the heterogeneous photocatalysis was proved to be the catalyst loading. Kinetic analyses indicated that the photodegradation of ofloxacin can be described by a pseudo-first-order reaction. The rate constant (k) for the solar Fenton process was determined at different Fe²⁺ and H₂O₂ concentrations whereas the Langmuir-Hinshelwood (LH) kinetic expression was used to assess the kinetics of the heterogeneous photocatalytic process. The conversion of ofloxacin depends on several parameters based on the various experimental conditions, which were investigated. A Daphnia magna bioassay was used to evaluate the potential toxicity of the parent compound and its photo-oxidation by-products in different stages of oxidation. In the present study solar Fenton has been demonstrated to be more effective than the solar TiO₂ process, yielding complete degradation of the examined substrate and DOC reduction of about 50% in 30 min of the photocatalytic treatment.     

Mechanism of phenol photodegradation in the presence of pure and modified-TiO(2): A review

In recent years, the application of heterogeneous photocatalytic water purification processes has gained wide attention due to its effectiveness in degrading and mineralizing the recalcitrant organic compounds as well as the possibility of utilizing the solar UV and visible-light spectrum. By far, titania has played a much larger role in this scenario compared to other semiconductor photocatalysts due to its costly effectiveness, inert nature and photostability. A substantial amount of research has focused on the enhancement of TiO₂ photocatalysis by modification with metal, non-metal and ion doping.This paper aims to review and summarize the recent works on the titanium dioxide (TiO₂) photocatalytic oxidation of phenol and discusses various mechanisms of phenol photodegradation (indicating the intermediates products) and formation of OH radicals. Phenol degradation pathway in both systems, TiO₂/UV and doped-TiO₂/Vis, are described.     

Electrochemically assisted photocatalytic degradation of Acid Orange 7 with beta-PbO2 electrodes modified by TiO2

Modification of beta-PbO(2) electrodes was carried out by TiO(2) co-deposition and characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The 2.0 g TiO(2) (the amount of TiO(2) used in 200 mL electrodeposition solution) modified beta-PbO(2) electrode was more compact and more uniform in comparison with the unmodified beta-PbO(2) electrode. TiO(2) particles were tightly attached on and between beta-PbO(2) crystals on modified beta-PbO(2) electrode. It was also used in electrochemically assisted photocatalytic degradation (EAPD) of Acid Orange 7. Compared with the total efficiency by a single application of ultraviolet irradiation and electrochemical procedure, application of a 1.5 V potential in EAPD improved the apparent first-order rate constant by 44.2% for 2.0 g TiO(2) modified beta-PbO(2) electrode even if it was not freshly used. A synergetic effect was significant. Within the amount of TiO(2) investigated, the more TiO(2) used in electro-deposition solution, the higher the degradation efficiencies were. Effects of initial dye concentration, initial pH values and applied potentials across the electrodes were investigated. Acidic condition and high potentials applied across the electrodes favored color or TOC removal of the dye. Decolorization rate decreased with an increase in the dye concentration in the range of 5-50mg/L. Experiments above demonstrate that TiO(2) modified beta-PbO(2) electrode, which realized TiO(2) immobilization successfully, performed well in EAPD of Acid Orange 7.     

Development of solar-driven electrochemical and photocatalytic water treatment system using a boron-doped diamond electrode and TiO2 photocatalyst

A high-performance, environmentally friendly water treatment system was developed. The system consists mainly of an electrochemical and a photocatalytic oxidation unit, with a boron-doped diamond (BDD) electrode and TiO₂ photocatalyst, respectively. All electric power for the mechanical systems and the electrolysis was able to be provided by photovoltaic cells. Thus, this system is totally driven by solar energy. The treatment ability of the electrolysis and photocatalysis units was investigated by phenol degradation kinetics. An observed rate constant of 5.1 × 10⁻³ dm³ cm⁻² h⁻¹ was calculated by pseudo-first-order kinetic analysis for the electrolysis, and a Langmuir-Hinshelwood rate constant of 5.6 μM⁻¹ min⁻¹ was calculated by kinetic analysis of the photocatalysis. According to previous reports, these values are sufficient for the mineralization of phenol. In a treatment test of river water samples, large amounts of chemical and biological contaminants were totally wet-incinerated by the system. This system could provide 12 L/day of drinking water from the Tama River using only solar energy. Therefore, this system may be useful for supplying drinking water during a disaster.     

Cross-flow microfiltration with periodical back-washing for photocatalytic degradation of pharmaceutical and diagnostic residues-evaluation of the long-term stability of the photocatalytic activity of TiO2

The combination of semiconductor photocatalysis with cross-flow microfiltration accompanied by periodical back-washing was investigated in a pilot plant. The investigation included the testing of membrane materials because the membrane must resist the abrasion and the periodical back-washing. Another objective of this investigation was to assess the potential of two different TiO(2) materials (Hombikat UV100 and P25) for continuous photocatalytic degradation of persistent organic pollutants. The study focused on the long-term stability of the photocatalytic activity of TiO(2) during its continuous application. The combination of photocatalysis and cross-flow microfiltration allowed the separation and reuse of TiO(2) after the photocatalytic degradation of clofibric acid, carbamazepine and iomeprol. The investigations showed that the photocatalytic activity of P25 and Hombikat UV100 was constant during continuous usage over several days. This study indicates the high potential of the combination of heterogeneous photocatalytic oxidation processes with cross-flow microfiltration accompanied by periodical back-washing of the membrane. Thus environmentally relevant pharmaceuticals and X-ray contrast media can be transformed and mineralized in a continuous water treatment process.     

Investigation on photocatalytic degradation of ethyl violet dyestuff using visible light in the presence of ordinary rutile TiO2 catalyst doped with upconversion luminescence agent

To use solar irradiation or interior lighting efficiently, a new photocatalyst with high catalytic activity in visible light was sought. In this work, an upconversion luminescence agent, 40 CdF(2).60 BaF(2).1.0 Er(2)O(3), was synthesized and its fluorescent spectrum was determined. It is found that this upconversion luminescence agent can emit five upconversion fluorescent peaks below 387nm under the excitation of 488nm visible light. The upconversion luminescence agent has revealed an improvement over ordinary titanium dioxide (TiO(2)) in photocatalytic activity under visible light irradiation for the photocatalytic degradation of ethyl violet in aqueous solution as a model compound. The TiO(2) photocatalyst doped with upconversion luminescence agent was characterized by X-ray diffraction (XRD) and transmission electron microscope (TEM). The photocatalytic degradation of ethyl violet was tracked by UV-vis and (1)H-NMR spectra, and the influences of irradiation time, initial concentration of ethyl violet, addition amount of TiO(2) catalyst and initial pH value were also investigated. To affirm the complete mineralization, the total organic carbon (TOC) was also tested. The degradation rate of ethyl violet in the presence of doped rutile TiO(2) photocatalyst reached 87.08% at 4.0h visible light irradiation, which was obviously higher than the corresponding degradation rate (35.42%) in the presence of undoped rutile TiO(2) powder. The research results show that the upconversion luminescence agent is necessary to transform visible lights into ultraviolet lights and thus make the best use of visible lights. By calculation, the upconversion efficiency of the emission peak at 380nm was estimated to be about 0.78%. The TiO(2) powder doped upconversion luminescence agent under visible light irradiation is able to decompose the ethyl violet in aqueous solution efficiently, therefore, this method may be envisaged as a technology for treating dyes wastewaters using solar energy, especially at textile industries in developing countries.