Organic Model Pollutant Research Articles

Photocatalytic and Antibacterial Activities of a Nickel(II)-Bipyridine Complex-Modified Graphene Oxide Nanocomposite: Synthesis and Characterization

In this study, we aimed to synthesize and characterize a nickel(II) complex-modified graphene oxide (Ni-GO) nanocomposite with enhanced photocatalytic and antimicrobial properties. The nanocomposite was prepared through a modified Hummer’s method, followed by an adsorption technique using the precursor complex [Ni(bipy)3]Cl2·5H2O, which was preferentially adsorbed onto the graphene oxide (GO) surface. The surface interaction between the nickel complex ions and GO was characterized using various analytical techniques, including FTIR, XRD, SEM-EDX, DRS, and XPS analyses. Photoluminescence analysis demonstrated the fluorescence property of the prepared composite. The DRS spectra indicated that the adsorption of composite particles extended to the visible region, making it excitable by visible light. The photocatalytic activity of the Ni-GO nanocomposite was tested by studying the degradation of an organic model pollutant, Rhodamine B dye, under real sunlight irradiation. The introduction of the Ni(II) complex onto the GO surface matrix intensified the photocatalytic property, making it more efficient under direct sunlight exposure. Comparisons with pristine graphite and GO revealed that Ni-GO exhibited enhanced photocatalytic potential. Additionally, we have evaluated the antimicrobial property of the Ni(II) complex-modified GO against Klebsiella pneumoniae. The results demonstrated that both the Ni(II) precursor complex and Ni-GO nanocomposite possessed an excellent antimicrobial efficacy, suggesting their potential use in antimicrobial applications. The synthesis and characterization of the Ni(II) complex-modified GO nanocomposite presented in this study showed promising results for both ameliorative photocatalytic and antimicrobial activities. These findings indicated the potential utility of Ni-GO as an efficient photocatalyst and antimicrobial agent, surpassing the performance of pristine graphite and GO. This research opens up new avenues for the development of advanced nanocomposites with diverse applications in environmental remediation and biomedical fields.

Developing a photo-electric-field wireless electrochemical system for highly efficient removal of diazinon as an organic model pollutant as a next-generation electrochemical advanced oxidation process

Developing a photo-electric-field wireless electrochemical system for highly efficient removal of diazinon as an organic model pollutant as a next-generation electrochemical advanced oxidation process

Hierarchical Ultrathin Layered GO-ZnO@CeO2 Nanohybrids for Highly Efficient Methylene Blue Dye Degradation.

Highly efficient interfacial contact between components in nanohybrids is a key to achieving great photocatalytic activity in photocatalysts and degradation of organic model pollutants under visible light irradiation. Herein, we report the synthesis of nano-assembly of graphene oxide, zinc oxide and cerium oxide (GO-ZnO@CeO2) nanohybrids constructed by the hydrothermal method and subsequently annealed at 300 °C for 4 h. The unique graphene oxide sheets, which are anchored with semiconducting materials (ZnO and CeO2 nanoparticles), act with a significant role in realizing sufficient interfacial contact in the new GO-ZnO@CeO2 nanohybrids. Consequently, the nano-assembled structure of GO-ZnO@CeO2 exhibits a greater level (96.66%) of MB dye degradation activity than GO-ZnO nanostructures and CeO2 nanoparticles on their own. This is due to the thin layers of GO-ZnO@CeO2 nanohybrids with interfacial contact, suitable band-gap matching and high surface area, preferred for the improvement of photocatalytic performance. Furthermore, this work offers a facile building and cost-effective construction strategy to synthesize the GO-ZnO@CeO2 nanocatalyst for photocatalytic degradation of organic pollutants with long-term stability and higher efficiency.

Photocatalytic degradation of tetracycline antibiotic over a flower-like S-doped BiOBr: Performance, mechanism insight and toxicity assessment

A new catalyst of S-BiOBr flower-like morphology was synthesized by simple pyrolysis and further used for photocatalytic degradation of TC. Phase structure analysis, elemental analysis and micromorphological analysis confirmed that S doping has a reinforcing effect on the polarization between the [Bi2O2S]2+ and [Br2]2- layers and is conducive to interlayer polarization and rapid charge transfer. In addition, its unique petal morphology is more favorable to the adsorption of contaminants on its surface and accelerates the reaction of catalyst surfactant with contaminants. It was also found that S-BiOBr degrades TC significantly better than single BiOBr@HCs, with up to 99.1% in 60 min illumination. In addition, the S-BiOBr catalyst has good reusability in antibiotic degradation. The results of photocatalytic mechanism analysis show that free radical O2− plays a major role in the photodegradation of organic model pollutants. Intermediates in TC degradation were identified, and their potential degradation pathways were prospected, and the toxicity development of TC in the degradation process was analyzed by toxicity assessment software. The S-BiOBr photocatalytic system developed in this paper provides a new idea for effective modification of bismuth-based semiconductors and has important guiding significance for future water purification.

Synthesis and characterizations of Ni-SnO2-TiO2 nanocomposite for photocatalytic application

A first attempt was made to synthesize a Ni-SnO2-TiO2 nanocomposite by a one-pot simple synthetic method. A [Ni(im)6]Cl2 precursor complex is preferably adsorbed on the solid surface forming nanocomposite: complex adduct, it simultaneously becomes a surface species (Ni-SnO2-TiO2). In this investigation, it has been found that surface interaction of nickel complex ions lead to the formation of surface species that are identified by XRD, FTIR, UV–vis DRS, SEM, EDX, HRTEM, XPS, and XANES analyses. The metal-loaded metal oxide coupled semiconductor solids find their applications as catalysts and in advanced electronics. We demonstrate the dopant induced changes in electronic density of states using DFT VASP calculations. The photocatalytic property of Ni-SnO2-TiO2 sample was tested, and the results showed that a small amount of nickel surface co-doped SnO2-TiO2, formed an anatase–rutile-cassiterite mixed phases with surface defects or oxygen vacancies, and had improved the photocatalytic activity. The organic model pollutant of Azo dye and methyl orange degradation property of TiO2 photocatalyst under visible light irradiation has greatly enhanced after the introduction of Ni into the SnO2-TiO2 surface matrix. This study points out a potential way to develop new and more active tin and nickel co-doped titania photocatalysts for organic pollutant degradation in water systems.

Sub-micro photocatalytic TiO2 particles for a water depollution: Comparable removal efficiency to commercial P25 and easy separation via a simple sedimentation

The sub-micrometer sized TiO2 particles (100–200 nm) were synthesized by a sol-gel and subsequent thermal annealing. The particle size, surface area, pore structure, and crystallinity were varied upon the annealing temperatures (450, 550, 650 °C). The photocatalytic activities of three TiO2 particles annealed at various temperatures (450-, 550-, and 650-TiO2) were examined by performing photocatalytic depollution of three organic model pollutants (methylene blue, methyl orange, and phenol) from aqueous solutions under the UV light irradiation. Among three samples, 550-TiO2 (~200 nm) exhibited the highest photocatalytic activity towards the removals of all three model pollutants. Photocatalytic activity of the 550-TiO2 was compared with a commercial TiO2 (P25, Evonik) at various conditions of loading amounts of particles dispersed in MB solution. Light scattering by dispersed particles at high sample loading conditions was less pronounced in the case of 550-TiO2. Therefore, the sub-micro 550-TiO2 particles can exhibit comparable activity to P25 at high sample loading conditions (2–4 g/L). In addition, the bigger size of 550-TiO2 made it possible to separate them via a simple sedimentation process, showing a potential of sub-micro TiO2 particles as an efficient photocatalysts for water depollution.

Preparation and characterization of the Cu, Fe co-doped Bi2Ti2O7/EG-g-C3N4 material for organic model pollutants removal under direct sun light irradiation

The following hindrances should be overcome to enhance the efficacy of photo-catalysts such as a poor-visible light response, high charge-carrier recombination rate, less surface area, and inappropriate band-edge alignment for photo-induced redox reaction. This study reported, visible light responsive Cu, Fe-co-doped Bi2Ti2O7/EG-g-C3N4 catalyst for photo-removal of organic pollutants. Series of characterization tools are used to testify and demonstrate the properties of formed material. The photo-removal efficiency of Cu, Fe-co-doped Bi2Ti2O7/EG-g-C3N4 hybrids are estimated to be 69.5 and 83.69% for ciprofloxacin and Rhodamine B organic molecules. Free radical trapping experiments were carried to predict active radical's participating in the reaction. The possible reaction mechanism was explained based on band edge potentials and trapping experiment results. This reporting Cu, Fe-co-doped Bi2Ti2O7/EG-g-C3N4 catalyst showed good durability. This work gives a new insight into coupling tactics of Cu, Fe-co-doped Bi2Ti2O7 and g-C3N4 material and which will helpful for designing efficient photocatalytic materials.

Advanced oxidation of 4-chlorophenol via combined pulsed light and sulfate radicals methods: Effect of co-existing anions

Pulsed light (PL) technology, which is based on photonic technology involves the application of broadband emission of light with short and high-power pulses is beginning to emerge for the treatment of wastes via advanced oxidation processes (AOP). The present work investigates the efficiency of PL as a light source for persulfate (PS) activation (PL/PS) and 4-chlorophenol)4-CP) degradation, an organic model pollutant. The influencing parameters on 4-CP degradation such as solution pH, reaction time, initial concentration of 4-CP, PS dose, pulse intensity and frequency, and distance from PL source are systematically investigated. With increasing pH from 3 to 9, the 4-CP degradation decreased from 49.79 ± 2.49 to 33.12 ± 1.66%. The 4-CP degradation followed the first order kinetics that was improved with increasing reaction time, PS dose, pulse intensity, frequency of pulse, and decreasing pH, initial 4-CP concentration and distance from the PL source. The presence of sulfate, chloride, and carbonate anions in the solution has the inhibitory effects on 4-CP degradation, while nitrate anion improved the performance of PL/PS system. In addition, presence of humic acid had an inhibitory effect on the PL/PS system, which led to a decrease of reaction rate constant and 4-CP degradation was performed in PL/PS system with OH, SO4−, O2- and 1O2 radicals. The contributions of OH and SO4− radicals were 46% and 51%, respectively for the 4-CP degradation and synergistic effect of PL/PS system showed a significant influence on 4-CP degradation while using a combination of PL and PS, suggesting that PL is an effective activator of PS.

Visible Light Driven Degradation of Terephthalic Acid: Optimization of Energy Demand by Light Modulation Techniques

Aims: The aim of this work was to investigate the impact of light modulation parameters on the degradation of terephthalic acid, an organic model pollutant, within a heterogeneous photocatalytic system under visible light. For this purpose, a fixed bed photocatalytic reactor, irradiated by white-light LEDs matrix controlled by a system for light dimming, was used. The bed consisted of a nitrogen-doped titania photocatalyst deposited on polystyrene pellets. Background: Wastewater containing TPA can be treated into conventional aerobic biological units. However, the mineralization of TPA is slow and inefficient and its presence negatively influences the biodegradation efficiency because this pollutant inhibits microbial growth. Nowadays, innovative technologies named advanced oxidation processes (AOPs), such as heterogeneous photocatalysis with UV and visible light, ozonation, and Fenton oxidation, have gained popularity for effective organic destruction of TPA from wastewater. The heterogeneous photocatalytic oxidation process of the TPA under visible light is the most advantageous process in terms of both fixed and operating costs. Objective: In this work, the successful application of light modulation techniques for degradation of TPA using a photocatalytic system with supported visible active photocatalysts (N-doped TiO2) immobilized on polystyrene pellets is reported. In particular, sinusoidal lighting has been used analyzing the influence of the period of oscillation and the amplitude of light modulation on the reaction kinetics, in such a way as to minimize the times and energy costs for the process. Methods: To evaluate the influence of light modulation on the efficiency of the TPA removal, a discontinuous system composed of a Recirculating Photocatalytic Fixed Bed Reactor (RPFBR) irradiated by a matrix of white light LEDs was used. The flat geometry of the photoreactor guarantees the efficient excitation of the photocatalyst. An amount of 250 mL of aqueous solution with the initial TPA concentration of 12.5 ppm was applied in the photocatalytic tests lasting 180 min of irradiation fixed or sinusoidal modulated. Results: The results show that the variation of the oscillation period of the sinusoidal modulation has a pertinent influence on the photodegradation of TPA and a maximum value of the apparent kinetic constant, 0.0045 min-1 is found when the period of oscillation is 0.24 s. The sinusoidal modulation with optimal amplitude occurs with current between 50-200 mA, that shows the highest value of the apparent kinetic constant equal to 0.0046 min-1. The optimal sinusoidal modulation, as a consequence is with current between 50-200 mA and period of 0.24 s. From the data collected from the tests, it is possible to evaluate the energy cost necessary to obtain the reduction of 90% of the terephthalic acid in 1 m3 of polluted water for each modulation (E E/O), and compare these values with other tests for TPA degradation reported in the literature. The internal comparison with the three systems of literature shows that the optima sinusoidal modulation of LEDs matrix permits a strong reduction in the electrical energy consumption. Conclusion: Photocatalytic tests have demonstrated the improvement of the process energy efficiency using the light modulation technique. A further confirmation of the advantage of light modulation was obtained by comparing the energy costs required for the abatement of 90% of the terephthalic acid in 1m 3 of the photocatalytic system. Finally, a mathematical model for photocatalytic degradation of terephthalic acid within the recirculating fixed bed photocatalytic reactor, irradiated by white-light LEDs was developed.

Assembly of mixed Bi4V1.4Nb0.6O11 phase and g-C3N4 photoactive material over rGO: Enhanced organic model pollutants removal under sun light irradiation

A novel efficient Bi4V1.4Nb0.6O11/g-C3N4 over the rGO ternary composite has been prepared by the cost effect method for diverse model organic molecule pollutants removal. The synergistic interaction between the materials has been investigated by the several characterization tools. The intimate contact between the ternary materials was explored by HRTEM analysis. The photo-catalytic degradation rate of the obtained ternary composite samples was examined for the removal of the MB dye and photo-reduction of the 4-Nitrophenol molecules in direct sun light irradiation. More interestingly, photo removal efficiency for MB molecule was achieved 93 % and the photo-reduction efficiency was 97 % for 4-Nitrophenol solution. The complete mineralization of the MB and 4-NP was further assessed by the LC-MS analysis, which shows the successful destruction of toxic molecules. The Z- scheme charge carrier transfer between the active materials was proposed and which is evidenced by the free radical trapping experiments and ESR trapping experiments.

Multi-functional photocatalytic fuel cell for simultaneous removal of organic pollutant and chromium (VI) accompanied with electricity production

It is of significant importance to realize the efficient wastewater treatment and energy recovery. This study presents a multi-functional photocatalytic fuel cell (PFC), which could reductively treat Cr(VI) contaminant and oxidatively degrade organic pollutant simultaneously along with electricity production in an economical strategy. TiO2 nanotube arrays (TNA) and graphite were used as photoanode and cathode in two separated chambers, respectively. The optimized PFC with open circuit voltage of 1.06 V, maximum power density of 1 W m−2 and short circuit current density of 3.7 A m−2 can be obtained by increasing Cr(VI) concentration and decreasing pH values in catholyte. Under optimized PFC conditions, more photogenerated electrons will be transferred to cathode for Cr(VI) reduction, and accelerating electron-hole separation in the photoanode, then facilitating the oxidation of organic pollutants on anode. More than 96.8% removal efficiency for 6.8 mM Cr(VI) with a cathodic efficiency of 95.1% can be achieved within 6 h. Methylene blue (MB), an organic model pollutant, is totally decolorized on photoanode, which is significantly improved compare to photocatalysis (61.5% removal efficiency). The stable cycle operation of this economical PFC has obtained owing to the stable and low cost materials of both photoanode and cathode. This work may provide an efficient and economical method to simultaneously remove two types of pollutants with electricity harvested in one cell.

Insights into the Kinetics of Intermediate Formation during Electrochemical Oxidation of the Organic Model Pollutant Salicylic Acid in Chloride Electrolyte

The present study investigated the kinetics and formation of hydroxylated and chlorinated intermediates during electrochemical oxidation of salicylic acid (SA). A chloride (NaCl) and sulfate (Na2SO4) electrolyte were used, along with two different anode materials, boron doped diamond (BDD) and platinum (Pt). Bulk electrolysis of SA confirmed the formation of both hydroxylated and chlorinated intermediates. In line with the density functional theory (DFT) calculations performed in this study, 2,5- and 2,3-dihydroxybenzoic acid, 3- and 5- chlorosalicylic acid and 3,5-dichlorosalicylic acid were the dominating products. In the presence of a chloride electrolyte, the formation of chlorinated intermediates was the predominant oxidation mechanism on both BDD and Pt anodes. In the absence of a chloride electrolyte, hydroxylated intermediates prevailed on the Pt anode and suggested the formation of sulfonated SA intermediates on the BDD anode. Furthermore, direct oxidation at the anode surface only played a subordinate role. First order kinetic models successfully described the degradation of SA and the formation of the observed intermediates. Rate constants provided by the model showed that chlorination of SA can take place at up to more than 60 times faster rates than hydroxylation. In conclusion, the formation of chlorinated intermediates during electrochemical oxidation of the organic model pollutant SA is confirmed and found to be dominant in chloride containing waters.

Synthesis of TiO2 (B) and High-temperature Stable Anatase TiO2 Nanowires by Hydrothermal Method and Investigation of Photocatalytic Activity.

In this study, TiO2 nanowires (TNWs) were synthesized through hydrothermal method and were characterized using X-Ray diffraction (XRD), transmission electron microscopy (TEM) and BET techniques. Monoclinic TiO2 (B) is the dominant phase of TNWs up to 600°C which is completely transformed into a highly crystalline anatase phase at 800°C. The photocatalytic activity of TNWs, prepared at various calcination temperatures, was investigated in the removal of Rhodamine B as an organic model pollutant. The results indicated that the photocatalytic activity of TNWs, prepared at 800°C calcination temperature, was better than that of other samples and even TiO2 -P25 nanoparticles.

The role of cobalt in bimetallic iron-cobalt magnetic carbon xerogels developed for catalytic wet peroxide oxidation

Three magnetic carbon xerogels were developed by inclusion of iron and/or cobalt precursors during the synthesis procedure. The synthesized materials were tested in the catalytic wet peroxide oxidation (CWPO) of aqueous solutions containing 4-nitrophenol (4-NP) − a refractory organic model pollutant, under a water treatment process intensification approach. For that purpose, the experimental runs were performed with high pollutant load (5gL−1), low catalyst dosage (2.5gL−1, corresponding to a fixed pollutant/catalyst mass ratio of 2), atmospheric pressure, 50°C, pH=3 and stoichiometric amount of hydrogen peroxide (H2O2).The bimetallic magnetic carbon xerogel catalyst (CX/CoFe) was more active than each of the monometallic catalysts (CX/Fe or CX/Co). The better performance was explained in terms of a synergic association of factors: (i) the enhanced accessibility to the active iron species at the surface of CX/CoFe promoted by the simultaneous incorporation of cobalt, (ii) the ability of metallic Co to catalyse H2O2 decomposition via hydroxyl radicals (HO) formation, and (iii) the efficient reduction of Fe3+ to Fe2+ promoted by metallic Co on the surface of CX/CoFe. A 4-NP conversion of 98.5% was determined after 30min of CWPO reaction. Leaching of the iron species in the bimetallic CX/CoFe was considerably reduced with relation to the monometallic iron catalyst. However, partial catalyst deactivation occurred due to lower stability of oxidized cobalt species.A detailed reaction mechanism is proposed for the surface catalytic reactions occurring over the CX/CoFe catalyst.

Cold sprayed WO3 and TiO2 electrodes for photoelectrochemical water and methanol oxidation in renewable energy applications.

Films prepared by cold spray have potential applications as photoanodes in electrochemical water splitting and waste water purification. In the present study cold sprayed photoelectrodes produced with WO3 (active under visible light illumination) and TiO2 (active under UV illumination) on titanium metal substrates were investigated as photoanodes for the oxidation of water and methanol, respectively. Methanol was chosen as organic model pollutant in acidic electrolytes. Main advantages of the cold sprayed photoelectrodes are the improved metal-semiconductor junctions and the superior mechanical stability. Additionally, the cold spray method can be utilized as a large-scale electrode fabrication technique for photoelectrochemical applications. Incident photon to current efficiencies reveal that cold sprayed TiO2/WO3 photoanodes exhibit the best photoelectrochemical properties with regard to the water and methanol oxidation reactions in comparison with the benchmark photocatalyst Aeroxide TiO2 P25 due to more efficient harvesting of the total solar light irradiation related to their smaller band gap energies.

Adsorption and regenerative oxidation of trichlorophenol with synthetic zeolite: Ozone dosage and its influence on adsorption performance

Regeneration of loaded adsorbents is a key step for the sustainability of an adsorption process. In this study, ozone was applied to regenerate a synthetic zeolite for the adsorption of trichlorophenol (TCP) as an organic model pollutant. Three initial concentrations of TCP in water phase were used in adsorption tests. After the equilibrium, zeolite loaded different amounts of TCP was dried and then regenerated with ozone gas. It was found that the adsorption capacity of zeolite was increased through three regeneration cycles. However, the adsorption kinetics was compromised after the regeneration with slightly declined 2nd order reaction constants. The ozone demand for the regeneration was highly dependent on the TCP mass loaded onto the zeolite. It was estimated that the mass ratio of ozone to TCP was 1.2 ± 0.3 g O3/g TCP.

Comparison of Titanium Dioxides Prepared from Different Materials and its Photocatalytic Evaluation

Titanium dioxides were synthesized from two different titanium salts, which contained chlorine and sulfur respectively. Titanium dioxide prepared from TiCi4 and had a particle size of ca. 20nm and its phase transition from anatase to rutile stated at 500°C. Titanium dioxide from TiOSO4 had a particle size of ca. 50nm and retained its anatase and sperit structure until 700°C by calcination. For the photocatalytic evaluation of these titanium dioxides, photocatlytic oxidation of organic model pollutant, humic acid, have been conducted. UV absorbance decrease by titanium dioxides prepared from both from TiCi4 and TiOSO4 at room temperature showed very similar results, compared to titanium dioxide prepared from TiCi4 at higher temperature.

Photo-induced carbonation of lime-TiO2 mortars

In this work, titanium dioxide (TiO2) has been used as an additive in lime binder (Ca(OH)2), in order to benefit from its photocatalytic properties and study both the photocatalytic properties of the produced mixtures and the effect of photocatalytically produced carbon dioxide on the carbonation process of lime. TiO2 was added in three different portions (3, 6 and 10% w/w) in lime mixtures and their physicochemical and photocatalytic properties were studied and compared to those of a reference, made exclusively of lime. The photocatalytic properties of the mixtures were studied through the photo-oxidation of an organic model pollutant solution (methyl orange) to a colorless form, as well as by studying the microstructure and carbonation depth in different groups of mixtures subjected to photocatalysis cycles in the laboratory and exposed for a 2 month period in the open air (urban environment).Laboratory results confirmed that lime-TiO2 composite mixtures exhibit photocatalytic properties in both UV radiation conditions and direct exposure to sunlight. Moreover, analytical results indicated an enhanced carbonation of lime-TiO2 composites. TiO2 can be added to lime successfully and can have applications in lime-based mortars used in the conservation of architectural heritage, enhancing their performance against soiling and amenity loss.

Kinetic modeling of the photocatalytic degradation of air‐borne pollutants

AbstractThe photocatalytic conversion of organic model pollutants (acetone, acetaldehyde, and isopropanol) in a novel Photo‐CREC‐Air unit is considered. This photocatalytic unit features: (1) external near‐UV lamps placed in parabolic reflectors, (2) a basket supporting the irradiated glass mesh holding TiO2 loadings to achieve high photoconversion rates, and (3) a fluid flow pattern securing high gas velocities in the near‐mesh region. Given the high quantum efficiencies observed in Photo‐CREC‐Air and, as a result, the high prospects for this novel design, rate equations and associated mechanistic formulations are investigated. With this goal, a Langmuir–Hinshelwood model, involving a one‐site model pollutant mechanism, is considered. The associated kinetic parameters with the related statistical indicators are established, using least‐square nonlinear regression. It is found that this model is adequate for describing the photodegradation of acetone on both Degussa P25 and Hombikat UV‐100. It is also observed that the same type of reaction rate model is less adequate for the photodegradation of acetaldehyde and isopropanol, in particular, for predicting the formation of carbon dioxide. © 2004 American Institute of Chemical Engineers AIChE J 50: 1017–1027, 2004

Photooxidation of a model pollutant in an oscillatory flow reactor with baffles

The degradation of an organic model pollutant, salicylic acid, by means of heterogeneous photocatalytic oxidation in a pulsed baffled tubular photochemical reactor (PBTPR), has been studied. Our studies show that oscillatory flow in the PBTPR can efficiently produce uniform dispersion of catalysts of a wide range of catalyst particle sizes, ranging from 20– 150 μm , and completely mineralize organic compounds. An interesting observation is that using the PBTPR with excess hydrogen peroxide, a nearly 100% rutile titania (Aldrich) is more efficient in mineralizing organics than the anatase-rich Degussa P25. We attribute this to the enhanced mass transfer for the Aldrich catalyst due to chaotic mixing, which renders the hydrogen peroxide a more efficient electron acceptor and facilitates the rapid conversion of hydrogen peroxide to hydroxyl radicals. This simultaneously lowers the electron–hole recombination rate, which has been considered to be a major factor for the low oxidation efficiency of rutile titania catalysts.