Sonochemical Degradation of Benzothiophene (BT) in Deionized Water, Natural Water and Sea Water.

This paper deals with the sonochemical water treatment of polycyclic aromatic sulfur hydrocarbons (PASHs), one of the most common impurities found in waste water coming from petroleum industry. The best fit of the experimental data appears to be the kinetic parameters determined using the Michaelis-Mentonmodel in the concentrations range of the study. For the initial increase in the degradation rates, it is simply considered that the more the bulk concentration increases, the more the concentration in the interfacial region increases. This will be explained by Michaelis-Menton kinetics. The influence of organic compounds in the water matrix as a mixture with Benzothiophene (BT) was also evaluated. The results indicated that BT degradation is unaffected by the presence of bisphenol A (BPA). Finally, the results indicated that ultrasonic action is involved in oxidation rather than pyrolitic processing in the BT sonochemical degradation.

Sonochemical reactor characterization in the presence of cylindrical and conical reflectors.

Ultrasonic systems must be able to produce an acoustic field with the highest possible energy concentration in sonochemical reactors to accomplish maximum efficacy in the sonolytic degradation of water contaminants. In the present study, the impact of cylindrical and conical stainless-steel reflectors placed on the liquid surface on the sonochemical oxidation activity of ultrasonication reactors was investigated. The amount of effective acoustic power transferred to the ultrasonicated medium without and with reflectors was measured by calorimetric characterization of the sono-reactors at diverse ultrasonication frequencies in the interval of 300-800 kHz and different electrical powers in the range of 40-120 W. Iodide dosimetry without and with reflectors at diverse ultrasonication conditions (300-800 kHz and 40-120 W) and various aqueous solution volumes in the range of 300-500 mL was used to assess the sonochemical oxidation activity, i.e., the generation of oxidative species (mainly hydroxyl radicals). Sonochemiluminescence (SCL) imaging was used to study the active acoustic cavitation bubbles distribution in the sono-reactors without and with reflectors. Significant impacts of the position and shape of the reflectors on the active acoustic cavitation bubble distribution and the sonochemical oxidation activity were observed due to remarkable modifications of the ultrasonic field by directing and focusing of the ultrasonic waves. A significant augmentation in the triiodide formation rate was obtained in the presence of the conical reflector, especially at 630 kHz and 120 W (60.5% improvement), while iodide oxidation was quenched in the presence of the cylindrical reflector at all ultrasonication frequencies and powers. The SCL images show a noteworthy modification in the ultrasonic field and the acoustic cavitation bubble population when reflectors were used. The sonochemical oxidation activity was improved by the conical reflector when placed in the Fresnel zone (near field region).

Sonochemical formation of peroxynitrite in water: Impact of ultrasonic frequency and power.

There is a lack of literature on peroxynitrite formation due to sonolysis of aerated water. In this work, the impact of sonication parameters, frequency and power, on ultrasonic peroxynitrite production in aerated alkaline water was investigated. Peroxynitrite formation was clearly established with undeniable evidence at all the tested frequencies in the range of 516-1140 kHz with a typical G-value (energy-specific yield) of 0.777 × 10-10, 0.627 × 10-10, 0.425 × 10-10 and 0.194 × 10-10 mol/J at 516, 558, 860 and 1140 kHz, respectively. The ultrasonication frequency has a direct impact on the sonochemical peroxynitrite production. Increasing the ultrasonication frequency in the interval 321-1140 kHz reduces peroxynitrite formation. The most practical sonochemistry dosimetries, including hydrogen peroxide production, triiodide dosimetry, Fricke dosimetry, and 4-nitrocatechol formation, were compared with the sonochemical efficiency of the reactors used to produce peroxynitrite. The G-value, energy specific yield, for the tested dosimetries was higher than that for peroxynitrite formation, regardless of frequency. For all chemical dosimetries investigated, the same trend of frequency dependence was found as for peroxynitrite generation. The influence of ultrasonication power on peroxynitrite formation by sonication at diverse frequencies in the interval 585-1140 kHz was studied. No peroxynitrite was formed at lower acoustic power levels, regardless of frequency. As the frequency increases, more power is required for peroxynitrite formation. The production of peroxynitrite increased as the acoustic power increased, despite the frequency of ultrasonic waves. Ultrasonic power is a key factor in the production of peroxynitrite by sonolysis. Since peroxynitrite is uniformly distributed in the bulk solution, peroxynitrite-sensitive solutes can be transformed both in the bulk of the solution and in the surfacial region (shell) of the cavitation bubble. The formation of peroxynitrite should be taken into account in sonochemistry, especially at higher pH values. Ultrasonic peroxynitrite formation in alkaline solution (pH 12) can be considered as a kind of chemical dosimetry in sonochemistry.

Experimental design approach to the optimization of ultrasonic degradation of alachlor and enhancement of treated water biodegradability.

This work presents the application of experimental design for the ultrasonic degradation of alachlor which is pesticide classified as priority substance by the European Commission within the scope of the Water Framework Directive. The effect of electrical power (20-80W), pH (3-10) and substrate concentration (10-50mgL(-1)) was evaluated. For a confidential level of 90%, pH showed a low effect on the initial degradation rate of alachlor; whereas electrical power, pollutant concentration and the interaction of these two parameters were significant. A reduced model taking into account the significant variables and interactions between variables has shown a good correlation with the experimental results. Additional experiments conducted in natural and deionised water indicated that the alachlor degradation by ultrasound is practically unaffected by the presence of potential *OH radical scavengers: bicarbonate, sulphate, chloride and oxalic acid. In both cases, alachlor was readily eliminated ( approximately 75min). However, after 4h of treatment only 20% of the initial TOC was removed, showing that alachlor by-products are recalcitrant to the ultrasonic action. Biodegradability test (BOD5/COD) carried out during the course of the treatment indicated that the ultrasonic system noticeably increases the biodegradability of the initial solution.

Ultrasonic cavitation applied to the treatment of bisphenol A. Effect of sonochemical parameters and analysis of BPA by-products.

Bisphenol A (BPA), a chemical compound largely used in the plastics industry, can end up in aquatic systems, which it disturbs by its endocrine disrupting effect (EDE). This study investigated the BPA degradation upon ultrasonic action under different experimental conditions. The effect of saturating gas (oxygen, argon and air), BPA concentration (0.15-460 micromol L(-1)), ultrasonic frequency (300-800 kHz) and power (20-80 W) were evaluated. For a 118 micromol L(-1)-BPA solution, with the best performance obtained at 300 kHz, 80 W, with oxygen as saturating gas. In these conditions, BPA can be readily eliminated by the ultrasound process (approximately 90 min). However, even after long ultrasound irradiation times (9 h), more than 50% of chemical oxygen demand (COD) and 80% of total organic carbon (TOC) remained in the solution. Analyses of intermediates using HPLC-MS investigation identified several products: monohydroxylated bisphenol A, 4-isopropenylphenol, quinone of monohydroxylated bisphenol A, dihydroxylated bisphenol A, quinone of dihydroxylated bisphenol A, monohydroxylated-4-isopropenylphenol and 4-hydroxyacetophenone. The presence of these hydroxylated aromatic structures showed that the main ultrasonic BPA degradation pathway is related to the reaction of BPA with the *OH radical. After 2h, these early products were converted into biodegradable aliphatic acids.

Oxygen-induced concurrent ultrasonic degradation of volatile and non-volatile aromatic compounds.

Acoustic cavitation, induced by ultrasound, can be used to eliminate organic pollutants from water. This type of ultrasonic treatment of polluted water can be grouped with those generally referred to as advanced oxidative processes since it involves hydroxyl radicals. In this case these highly active species are generated from the dissociation of water and oxygen dissociation caused by cavitation bubble collapse. The cavitation induced degradation rates of organic compounds in water are mainly linked to their vapor pressure and solubility and here we will further explore these links by examining the degradation of a mixture of two materials with different physical properties, chlorobenzene and 4-chlorophenol. The results obtained when a dilute solution of a mixture of these compounds saturated with argon is subjected to sonication at 300 kHz, parallels previous observations achieved in an aerated aqueous medium at 500 kHz. The two compounds exhibit sequential degradation with the more volatile chlorobenzene entering the cavitation bubble and being destroyed first. The 4-chlorophenol degradation occurs subsequently only when the chlorobenzene has been completely destroyed. The two compounds exhibit different behavior when sonicated in water saturated with oxygen. Under these conditions the two compounds are degraded simultaneously, a remarkable result for which two explanations can be proposed, both of which are based on the formation of additional OH radical species: The ability to produce conditions for the simultaneous elimination of two organic compounds by the use of oxygen is of great importance in the developing field of ultrasonic water treatment.

Persulfate-enhanced sonochemical degradation of naphthol blue black in water: Evidence of sulfate radical formation.

This work explores the effect of persulfate (PS) on the sonochemical degradation of organic pollutants taking naphthol blue black (NBB), an anionic diazo dye, as a substrate model. The sonolytic experiments were conducted in the absence and presence of PS under various experimental conditions including acoustic power (10-80W), frequency (20 and 585kHz) and saturating gas (argon, air and nitrogen). Experimental results showed that PS decomposition into sulfate radical (SO4-) takes place by sonolysis and increasing PS concentration up to 1g/L would result in an increase in the NBB degradation rate. It was found that the PS-enhanced effect was strongly operating parameters dependent. The positive effect of PS decreased with increasing power and the best enhancing effect was obtained for the lowest acoustic power. Correspondingly, the PS-enhanced effect was more remarkable at low frequency (20kHz) than that observed at high frequency ultrasound (585kHz). Nitrogen saturating gas gave the best enhanced effect of PS than argon and air atmospheres. Theoretical (computer simulation of bubble collapse) and experimental measurements of the yields of free radical generation under the different experimental conditions have been made for interpreting the obtained effects of PS on the sonochemical degradation of the dye pollutant. The experimental findings were attributed to the fact that radical-radical recombination reactions occur at faster rate than the radical-organic reaction when the concentration of free radicals is too high (at higher sonochemical conditions).

Sonolysis of 4-chlorophenol in aqueous solution: effects of substrate concentration, aqueous temperature and ultrasonic frequency.

The sonolysis of 4-chlorophenol (4-CP) in O2-saturated aqueous solutions is investigated for a variety of operating conditions with the loss of 4-CP from solution following pseudo-first-order reaction kinetics. Hydroquinone (HQ) and 4-chlorocatechol (4-CC) are the predominant intermediates which are degraded on extended ultrasonic irradiation. The final products are identified as Cl-, CO2, CO, and HCO2H. The rate of 4-CP degradation is dependent on the initial 4-CP concentration with an essentially linear increase in degradation rate at low initial 4-CP concentrations but with a plateauing in the rate increase observed at high reactant concentrations. The results obtained indicate that degradation takes place in the solution bulk at low reactant concentrations while at higher concentrations degradation occurs predominantly at the gas bubble-liquid interface. The aqueous temperature has a significant effect on the reaction rate. At low frequency (20 kHz) a lower liquid temperature favours the sonochemical degradation of 4-CP while at high frequency (500 kHz) the rate of 4-CP degradation is minimally perturbed with a slight optimum at around 40 degrees C. The rate of 4-CP degradation is frequency dependent with maximum rate of degradation occurring (of the frequencies studied) at 200 kHz.

Effect of potassium monopersulfate (oxone) and operating parameters on sonochemical degradation of cationic dye in an aqueous solution.

In this study, removal of Cresol Red (CR), a cationic triphenylmethane dye, by 300kHz ultrasound was investigated. The effect of additive such as potassium monopersulfate (oxone) was studied. Additionally, sonolytic degradation of CR was investigated at varying power and initial pH. RC can be readily eliminated by the ultrasound process. The obtained results showed that. Sonochemical degradation of CR was strongly affected by ultrasonic power and pH. The degradation rate of the dye increased substantially with increasing ultrasonic power in the range of 20-80W. This improvement could be explained by the increase in the number of active cavitation bubbles. The significant degradation was achieved in acidic conditions (pH=2) where the color removal was 99% higher than those observed in higher pH aqueous solutions. The ultrasonic degradation of dye was enhanced by potassium monopersulfate (oxone) addition. It was found that the degradation of the dye was accelerated with increased concentrations of oxone for a reaction time of 75min.

A combination of ultrasound and oxidative enzyme: sono-enzyme degradation of phenols in a mixture.

Sono-degradation and sono-enzyme degradation of phenols were performed on the mixtures of double compounds (phenol, p-chlorophenol; phenol, p-cresol; phenol, p-nitrophenol; and p-chlorophenol, p-cresol) in aqueous medium. Sono-degradation of phenol and its substituted compounds individually behaved approximately the same, but in the case of mixture behaved differently. Sono-degradation of substituted phenols was easier than phenol in a mixture, but there was an exception in the combination of phenol and p-nitrophenol that the degradation of phenol was faster than substituted compound. This behavior was the same in sono-enzyme degradation, but with higher degradation rate. Between these mixtures, the combination of phenol and p-cresol presented a significant different behavior in case of single and double compounds solutions. In this system, the sono-degradation of phenol in mixture was more difficult than phenol alone but, the sono-degradation of p-cresol in mixture was easier in comparison with p-cresol alone. In sono-enzyme degradation, p-cresol as a more reactive compound facilitated the remove of phenol in mixture in compare of the individual case.

Enhancing sonochemical activity in aqueous media using power-modulated pulsed ultrasound: an initial study.

Relatively little is known about the effects of pulsed ultrasound on the facilitation of chemical reactivity. Previous studies have indicated that sonochemistry using pulses is generally less effective than continuous ultrasonic irradiation. However, the pulse trains employed were such that the peak power of the pulses was the same as the maximum power used in continuous irradiation. As a result, less acoustic energy was transmitted to the solutions over the same period of time. The effectiveness of ultrasound when the pulse is adjusted so that the same amount of acoustic energy is input compared to continuous irradiation over a given time has not been previously explored. In this study we have embarked on an examination of the efficacy of power-modulated pulsed (PMP) sonochemistry. Specifically, we have explored the effects of pulse type and pulse frequency on the oxidation of potassium iodide and the degradation of acid orange, a common industrial colorant. A rate increase by a factor of three was observed compared with continuous irradiation under conditions of equivalent acoustic input power.

Ultrasound enhancement of near-neutral photo-Fenton for effective E. coli inactivation in wastewater.

In this study, we attempt for the first time to couple sonication and photo-Fenton for bacterial inactivation of secondary treated effluent. Synthetic wastewater was subjected to sequential high-frequency/low power sonication, followed by mild photo-Fenton treatment, under a solar simulator. It was followed by the assessment of the contribution of each component of the process (Fenton, US, hv) towards the removal rate and the long-term survival; sunlight greatly improved the treatment efficiency, with the coupled process being the only one to yield total inactivation within the 4-h period of treatment. The short-term beneficial disinfecting action of US and its detrimental effect on bacterial survival in long term, as well as the impact of light addition were also revealed. Finally, an investigation on the operational parameters of the process was performed, to investigate possible improvement and/or limitations of the coupled treatment; 3 levels of each parameter involved (hydraulic, environmental, US and Fenton) were tested. Only H2O2 increased improved the process significantly, but the action mode of the joint process indicated potential cost-effective solutions towards the implementation of this method.

Enhancement and inhibition effects of water matrices during the sonochemical degradation of the antibiotic dicloxacillin.

The sonochemical degradation of dicloxacillin (DXC) was studied in both synthetic and natural waters. Degradation routes and the effect of experimental conditions such as pH, initial DXC concentration and ultrasonic power were evaluated. Experiments were carried out with a fixed frequency (600kHz). The best performances were achieved using acidic media (pH=3) and high power (60W). The degradation process showed pseudo-first order kinetics as described by the Okitsu model. To evaluate water matrix effects, substrate degradation, in the presence of Fe(2+) and organic compounds such as glucose and 2-propanol, was studied. A significant improvement was achieved with Fe(2+) (1.0mM). Inhibition of the degradation process was observed at a relatively high concentration of 2-propanol (4.9mM), while glucose did not show any effect. Natural water showed an interesting effect: for a low concentration of DXC (6.4µM), an improvement in the degradation process was observed, while at a higher concentration of DXC (0.43mM), degradation was inhibited. Additionally, the extent of degradation of the process was evaluated through the analysis of chemical oxygen demand (COD), antimicrobial activity, total organic carbon (TOC) and biochemical oxygen demand (BOD5). A 30% removal of COD was achieved after the treatment and no change in the TOC was observed. Antimicrobial activity was eliminated after 360min of ultrasonic treatment. After 480min of treatment, a biodegradable solution was obtained.

A combination of ultrasound and oxidative enzyme: sono-biodegradation of substituted phenols.

Sonolysis, enzyme treatment, and a combination of the two processes were tested for the degradation of substituted phenols (phenol, p-chlorophenol, p-bromophenol, p-iodophenol, p-methoxyphenol, p-cresol and p-nitrophenol) in aqueous medium. These organic pollutants are divided into three groups according to their degradation behaviour. In group (I), p-nitrophenol, horseradish peroxidase (HRP) in presence of hydrogen peroxide had a negligible effect on its decomposition. The combined method showed the same effect as sonolysis. Therefore, it is convenient to degrade p-nitrophenol by ultrasonic waves alone. In group (II), p-methoxyphenol and p-cresol, the combined method was approximately the same as enzyme treatment. It means that, the ultrasound had a negligible effect and the enzyme treatment alone was more favourable. Phenol and its halogenated compounds (choloro, bromo and iodo) were placed in group (III) and showed different behaviour than the two mentioned cases. The combined method was more efficient than the sonolysis and enzyme treatment individually. It should be noted that the effect of enzyme on this group (III) was in the medium level in compare of the two other groups (I and II) which the enzyme had a lower and higher effects respectively.

Kinetics and mechanisms of ultrasonic degradation of volatile chlorinated aromatics in aqueous solutions.

Ultrasonic decompositions of chlorobenzene (ClBz), 1,4-dichlorobenzene and 1-chloronaphthalene were investigated at 500 kHz in order to gain insight into the kinetics and mechanisms of the decomposition process. The disappearance of ClBz on sonication is almost simultaneously accompanied by the release of chloride ions as a result of the rapid cleavage of carbon-chlorine bonds with a concomitant release of CO, C2H2, CH4 and CO2. The intermediates resulting from attack of HO. radicals were detected but in a quite low yield (less than 2 microM). The generation of H2O2 on sonolysis is not significantly affected by the presence of aqueous ClBz while the generation of NO2- and NO3- is inhibited initially due to the presence of ClBz which diffuses into the gas-bubble interfaces and inhibits the interactions between free radicals and nitrogen. Moreover, brown carbonaceous particles are present throughout the ultrasonic irradiation process, which are consistent with soot formation under pyrolytic conditions. These important features suggest that, at the relatively high initial substrate concentrations used in this study, ultrasonic degradation of ClBz takes place predominantly both within the bubbles and within the liquid-gas interfaces of bubbles where it undergoes high-temperature combustion. Under these conditions, the oxidation of ClBz by free radical HO. outside of bubbles is a minor factor (though results of recent studies suggest that attack by HO. is more important at lower initial substrate concentrations). The sonochemical decomposition of volatiles follows pseudo-first-order reaction kinetics but the degradation rates are affected by operating conditions, particularly initial substrate concentration and ultrasonic intensity.

Sonochemical degradation of phenol in water: a comparison of classical equipment with a new cylindrical reactor.

Cavitation due to ultrasonic waves produces highly reactive oxidising species in water. As a result, it can be used to oxidise organic pollutants such as aromatic compounds in dilute aqueous solutions. Recent studies have demonstrated that reactors operating in the high frequency range (e.g. 500 kHz) are more efficient than reactors working at lower frequency (20 kHz) for the destruction of these kinds of contaminants. Our study describes the degradation of phenol with the help of a cylindrical ultrasonic apparatus that operates at 35 kHz (Sonitube-SODEVA). To date, the use of this type of reactor has not been reported. The reaction rates thus obtained were compared to those obtained at the same ultrasonic power (50 W) with more classical devices operating at 20 and 500 kHz. The general result is that in aqueous solution, the rate of phenol destruction is higher at 500 kHz than at 35 or 20 kHz. Addition of hydrogen peroxide and copper sulphate to the medium provides a different oxidative system that proceeds more efficiently at 35 kHz; the time of destruction was about one-third of the time needed at 500 kHz. It was also observed that the intermediate organic compounds are eliminated much faster at 35 kHz in comparison with the two frequencies. The observation of such different behaviour is not necessarily a pure frequency effect, but can be due to a response to other parameters such as the acoustic field and intensity.

Effect of pH on the ultrasonic degradation of ionic aromatic compounds in aqueous solution.

The sonolysis of 4-nitrophenol (4-NP) and aniline in O2-saturated aqueous solutions was performed at 610 kHz with ultrasonic power of 25 W and aqueous temperature of 15 +/- 1 degrees C. The initial rate of degradation of both 4-NP and aniline in sonolysis of aqueous media follows pseudo-first-order reaction kinetics. Investigation of the H2O2 generation rate in phosphate buffer media (0.01 M) over the range of pH 2-9 revealed a maximum yield at pH approximately 3.2. The pH, which results in modification of the physical properties (including charge) of molecules with ionisable functional groups, plays an important role in the sonochemical degradation of chemical contaminants. For hydrophilic substrates, the neutral species more easily diffuse to and accumulate at the hydrophobic interface of liquid-gas bubbles in comparison with their corresponding ionic forms. As a consequence, the degradation rate of 4-NP under ultrasonic irradiation decreases with increasing pH. In contrast, the disappearance rate of aniline exhibits a maximum under alkaline conditions due to the high solubility of the ionic anilinium ion and the (potentially) preferential movement of the uncharged form to the interface. Additionally, the rate of reaction of the uncharged aniline molecule (which dominates at pH > 4.6) with hydroxyl radicals is reported to be about three times as fast as the rate of reaction of the cationic anilinium species.

Ultrasonic degradation of acetaminophen in water: effect of sonochemical parameters and water matrix.

This paper deals about the sonochemical water treatment of acetaminophen (ACP, N-acetyl-p-aminophenol or paracetamol), one of the most popular pharmaceutical compounds found in natural and drinking waters. Effect of ultrasonic power (20-60 W), initial ACP concentration (33-1323 µmol L(-1)) and pH (3-12) were evaluated. High ultrasonic powers and, low and natural acidic pH values favored the efficiency of the treatment. Effect of initial substrate concentration showed that the Langmuir-type kinetic model fit well the ACP sonochemical degradation. The influence of organic compounds in the water matrix, at concentrations 10-fold higher than ACP, was also evaluated. The results indicated that only organic compounds having a higher value of the Henry's law constant than the substrate decrease the efficiency of the treatment. On the other hand, ACP degradation in mineral natural water showed to be strongly dependent of the initial substrate concentration. A positive matrix effect was observed at low ACP concentrations (1.65 µmol L(-1)), which was attributed to the presence of bicarbonate ion in solution. However, at relative high ACP concentrations a detrimental effect of matrix components was noticed. Finally, the results indicated that ultrasonic action is able to transform ACP in aliphatic organic compounds that could be subsequently eliminated in a biological system.

Starch nanoparticles formation via high power ultrasonication.

Nano-sized starch particles (NSP) were prepared from starch granules using a purely physical method of high-intensity ultrasonication. Particle size distribution, Field Effect Scanning Electron Microscopy (FE-SEM), Raman spectroscopy, and Wide-Angle X-ray Diffraction (WAXD) were used to characterize the morphology and crystal structure of the ensuing nanoparticles. The results revealed that ultrasound treatment of the starch suspension in water and at low temperature for 75 min results in the formation of starch nanoparticles between 30 and 100 nm in size. An attempt to explain the generation of starch nanoparticles was made on the basis of WAXD, Raman analysis and FE-SEM observation. Compared to acid hydrolysis, which is the most commonly adopted process, the present approach has the advantage of being quite rapid, presenting a higher yield and not requiring any chemical treatment.

Low-frequency ultrasound induces oxygen vacancies formation and visible light absorption in TiO2 P-25 nanoparticles.

Low-frequency ultrasound (LFUS) irradiation induces morphological, optical and surface changes in the commercial nano-TiO(2)-based photocatalyst, Evonik-Degussa P-25. Low-temperature electron spin resonance (ESR) measurements performed on this material provided the first experimental evidence for the formation of oxygen vacancies (V(o)), which were also found responsible for the visible-light absorption. The V(o) surface defects might result from high-speed inter-particle collisions and shock waves generated by LFUS sonication impacting the TiO(2) particles. This is in contrast to a number of well-established technologies, where the formation of oxygen vacancies on the TiO(2) surface often requires harsh technological conditions and complicated procedures, such as annealing at high temperatures, radio-frequency-induced plasma or ion sputtering. Thus, this study reports for the first time the preparation of visible-light responsive TiO(2)-based photocatalysts by using a simple LFUS-based approach to induce oxygen vacancies at the nano-TiO(2) surface. These findings might open new avenues for synthesis of novel nano-TiO(2)-based photocatalysts capable of destroying water or airborne pollutants and microorganisms under visible light illumination.