Slurry Photoreactor Research Articles

Performance analysis of rGO-bridged g-C3N4/ZnV2O6 S-scheme heterojunction for CO2 photoreduction with H2O in an externally reflected photoreactor

The photocatalytic conversion of CO2 with H2O over rGO-bridged g-C3N4/ZnV2O6 S-scheme heterojunction using an externally reflected photoreactor has been investigated. The structure and properties of photocatalysts, prepared via the one-pot solvothermal method, were characterized by XRD, RAMAN, FESEM, EDX, HRTEM, UV–vis and PL spectrophotometry. The 4 % rGO-bridged g-C3N4/ZnV2O6 (1:1) nanocomposite registered the highest CH3OH yield. The maximum yield of CH3OH over 4 % rGO-bridged g-C3N4/ZnV2O6 (1:1) nanocomposite was 6246.1 μmol/g-cat; 1.34 and 1.51 folds higher than g-C3N4/ZnV2O6 (1:1) and ZnV2O6 photocatalysts, respectively. Significant enhancement in quantum efficiency of an externally reflected photoreactor over 4 % rGO-bridged g-C3N4/ZnV2O6 (1:1) nanocomposite was observed compared to the slurry photoreactor. This is obviously because of the greater mobility of charges with hindered recombination rate and higher photonic efficiency. The stability of 4 % rGO-bridged g-C3N4/ZnV2O6 (1:1) nanocomposite was partially reduced after several cyclic runs. It is believed that the photocatalyst consisting of three components has demonstrated improved photocatalytic activity through a S-scheme mechanism, utilizing rGO as an electron mediator to enhance the overall performance of the S-scheme heterojunction.

Constructing MAX dispersed Ni2P/TiO2 nanocomposite with investigating influential effect of parameters through design expert and kinetic study for photocatalytic H2 evolution

Well-designed Ni2P/TiO2 nanoparticles dispersed over 2D Ti3AlC2 MAX, were investigated for H2 evolution with parameter optimization and kinetic modelling in a liquid phase slurry photoreactor. The highest H2 production rate of 1300 µmol was obtained over MAX dispersed Ni2P/TiO2 nanocomposite. The H2 production was observed to be 3.80 times more than the H2 generated by pristine TiO2, based on the inhibited charge recombination, improved visible light response, and good redox potential of TiO2. The sacrificial reagents, catalyst loading, and reaction time were optimized through the design of experiment (DoE). The results revealed 10.5 CH3OH concentration, 0.11 g loading, and a 3.59 h reaction time as the optimum conditions for maximum H2 generation. Finally, for investigating the adsorption behaviour, a modified Langmuir-Hinshelwood (L-H) mechanism-based kinetic model was developed. According to the kinetic model, the lower CH3OH adsorption constant suggested low adsorption at lower concentrations, but the higher CH3OH value indicated more adsorption at higher reactant concentrations. Thus, structured photocatalysts with enhanced photoactivity and kinetic-model findings should help researchers to comprehend photocatalytic reaction engineering properly for solar energy applications.

Modeling and simulation of photocatalytic CO2 reduction into methanol in a bubble slurry photoreactor

One of the attractive but still challenging ways of CO2 utilization is photocatalytic conversion of CO2 into fuels. Since reactor design plays an important role in both the efficiency and quality of the product, moving towards modeling and simulation of the photoreactor is vital. Thus, in this work modeling and simulation of photoreactor has been conducted using appropriate hydrodynamic and kinetic modules. The obtained model has been thoroughly validated by the experimental data which can further be utilized to scale-up the photoreduction process. The important parameters in the reactor design including the number of spargers, inlet gas flux, average bubble diameter, and light intensity have been studied. The methanol concentration after 150 s of the reaction under irradiation with light intensity of 120 W/m2 where 12 spargers delivered carbon dioxide gas into the reactor has been reported and the results have been validated accordingly.

Design and experimental analysis of a novel slant‐plate photoreactor

AbstractA novel slant‐plate photoreactor (SPR) immobilized with titanium dioxide (P25) was developed to address the disadvantage that the effluent on the backlight side of the corrugated plate photoreactor could not be treated. The SPR was tested and analyzed regarding the degradation of phenol under UV light. For comparison, a flat‐plate photoreactor, a slurry photoreactor, and a corrugated plate photoreactor were also examined. The performance of SPR in phenol degradation was higher than either corrugated plate photoreactor with the same angle or flat‐plate. Furthermore, SPR exhibited highest energy utilization efficiency compared to the corrugated plate photoreactor with the same angle and flat‐plate photoreactor in phenol oxidation. The superior performance of SPR was due primarily to the highly exposed catalyst surface area, high mass transfer coefficient, and multiple reuses of reflected light. In addition, the SPR was tested under natural solar light for its possible implementation in practice.

Performance of a C-containing Cu-based photocatalyst for the degradation of tartrazine: Comparison of performance in a slurry and CPC photoreactor under artificial and natural solar light

A carbon-containing Cu-based material (Cu@C) was used as photocatalyst for the degradation of a commonly food-industry azo-dye (tartrazine, also called Y5), under solar light at laboratory and pilot scale photoreactors. Important performance parameters such as dark adsorption capacity, catalyst́s loading and initial concentration of the dye were first optimized in a slurry photoreactor at laboratory scale under artificial solar light following the kinetics of degradation of the dye. Afterwards, the photocatalytic activity was investigated at pilot scale in a compound parabolic collector (CPC) photoreactor operating for 10 h of irradiation. The degradation of tartrazine is among the highest values reported for alternative metal oxide semiconductors, in both photoreactor configurations. Catalytic data revealed a 3 times faster degradation kinetics of tartrazine in the CPC photoreactor under natural solar light than in the slurry reactor under artificial solar light. This behavior indicates that a moderate photon flux in the CPC is more adequate to operate with the prepared photocatalyst, as it minimizes the recombination of charge carriers in the catalyst. This is important, since most of the photocatalytic tests designed to evaluate the activity of novel materials are frequently carried out under simulated solar light and disregard the impact of photon flux in outdoor conditions.

Synergetic Electrocatalytic Effects of Cu2O-TiO2 Heterostructures in a Solar Driven PEC Device for CO2 Reduction to >C1 Chemicals

A solar driven photo-electro-catalytic (PEC) device for CO2 reduction/water oxidation is here presented. The electrodes are engineered to be used in the n-type configuration, without using precious metals or rare/expensive raw materials. Specifically, the photoanode for water oxidation is made of TiO2 nanotube arrays prepared via controlled anodic oxidation, while Cu2O-TiO2 heterostructures, synthesised by ultra-sonicated assisted co-precipitation and then spray-coated over a carbon-based gas diffusion layer (GDL), are used as electrocathode materials for CO2 reduction. All the tests are performed without applying external bias or adding sacrificial donors, in a compact homemade PEC reactor in comparison with a conventional slurry photoreactor. The catalytic performances are evaluated in terms of formic acid and acetic acid production, the latter involving the formation of C-C bond. The effect of the presence of TiO2 is investigated in comparison with a bare cuprous oxide (Cu2O) film. Results for the bare Cu2O/GDL electrode (no TiO2) show 31.8 and 80.6 µmol h-1 gCu-1 as formic acid and acetic acid production rates, respectively. Cu2O-TiO2/GDL electrode, instead, shows more than one order of magnitude higher productivity (0.69 and 2.59 mmol h-1 gCu-1, respectively). The Faradaic efficiency (FE) to acetic acid is much higher for Cu2O-TiO2/GDL electrodes (61.9 %) considering the higher number of electrons involved for acetic acid with respect to formic acid (8 vs. 2). This behaviour can be ascribed to the synergetic electrocatalytic effects of the as-formed Cu2O-TiO2 heterostructures, favouring the formation of C-C bond for the sustainable production of >C1 chemicals and fuels.

Constructing LaxCoyO3 Perovskite Anchored 3D g-C3N4 Hollow Tube Heterojunction with Proficient Interface Charge Separation for Stimulating Photocatalytic H2 Production

LaxCoyO3 perovskite dispersed porous three-dimensional (3D) g-C3N4 hollow nanotubes to construct a Z-scheme nanocomposite were successfully synthesized via a wet impregnation assisted ultrasonic approach and were used for photocatalytic H2 generation in a liquid phase slurry photoreactor under visible light. A rhombohedral distorted LaCoO3 perovskite with 1.70 eV narrow band gap for improved optical properties was synthesized by the combination of coprecipitation and a hydrothermal method. Additionally, two-dimensional (2D) porous g-C3N4 with advantageous structural features was synthesized by a novel, facile, and cost-effective technique depicting exposed active sites with improved charge mobility and charge separation. A Z-scheme heterojunction by a wet impregnation assisted ultrasonic technique was constructed by LaCoO3 anchored onto hollow tubular porous g-C3N4 formed after the curling of flaked nanosheets into hollow tubes. Highest amount of H2 was generated by 15 wt % of LaCoO3 dispersed over porous g-C3N4 in the nanocomposite. The Z-scheme heterojunction generated H2 (800 μmol g–1) which was 1.41 and 1.77 times higher than pristine porous g-C3N4 and pristine LaCoO3, respectively, contributing to the improved visible light absorption and reduced band gap, mass transfer, charge mobility, and charge separation. The nanocomposite showed stability over three consecutive cycles. Also, the nanocomposite generated CH4 by the simultaneous occurrence of water splitting and photoreforming. The apparent quantum efficiency of the nanocomposite was also calculated and estimated to be 1.52 and 1.26 times improved over LaCoO3 and P-g-C3N4, respectively. Overall, this work gives insight into less costly and simple Z-scheme heterojunctions for solar to hydrogen conversion with high efficiency.

Synergistically improved charge separation in bimetallic Co–La modified 3D g-C3N4 for enhanced photocatalytic H2 production under UV–visible light

Synergistically improved Lanthanum (La) and Cobalt (Co) co-modified g-C3N4 was synthesized for photocatalytic H2 generation from methanol-water mixture under UV–visible light irradiation. The g-C3N4 was synthesized by thermal polymerization and co-modification was carried out by wet impregnation method. Photocatalytic H2 production by Co2/La1-g-C3N4 was carried out in a slurry photoreactor with the highest H2 production of 250 μmol g−1h−1, which was 2.5, 1.35, and 1.25 times increased as compared to pristine g-C3N4, La1-g-C3N4, and Co2-g-C3N4, respectively. The enhanced activity can be associated with the synergistic effect for proficient charge separation due to electron trapping ability of Co and La, and C–H bond cleavage ability of La for enhanced oxidation. Among the sacrificial agents, highest H2 generation rate was observed with triethanolamine which generated 8.1, 3.6, 1.7, 2.4, and 4.2 times boosted H2 generation than water, ethanol, methanol, ethylene glycol, and glycerol, respectivel, because of the effectual binding of triethanolamine onto amine-containing g-C3N4. Moreover, it also depicted good photostability towards photocatalytic H2 generation. Therefore, Co and La co-modification was proved to be effective for efficient charge separation and reduction of charge carrier's recombination and would be beneficial for other solar energy applications.

Investigating the performance of liquid and gas phase photoreactors for dynamic H2 production over bimetallic TiO2 and Ni2P dispersed MAX Ti3AlC2 monolithic nanocomposite under UV and visible light

Monolithic TiO2 and Ni2P dispersed 2D Ti3AlC2 MAX nanocomposite synthesized by sol-gel method, was investigated for stimulating photocatalytic H2 production. The performance was tested in three types of photoreactors including visible light irradiated slurry, visible and UV light irradiated fixed-bed and monolith photoreactors in batch and continuous operation. Using TiO2/Ni2P/Ti3AlC2 highest H2 production was achieved, which was 1.13, 3.25 and 3.80 times higher compared to TiO2/Ti3AlC2, TiO2/Ni2P and TiO2 samples. Under visible irradiation, slurry photoreactor in continuous operation depicted the highest activity, which was 23.6 and 32.5 times increased than fixed bed and monolith photoreactor, respectively. Using monolith photoreactor operating under UV light, 136 times more H2 was produced compared to monolith photoreactor under visible-light and 1.73 times higher H2 production than slurry photoreactor under visible-light. This was evidently due to higher penetration power of UV irradiations inside the monolith channels. The light penetration was declined when monolith channel length was increased or visible light was employed. With increasing feed composition, H2 production was further increased due to efficient oxidation and reduction reactions. Fixed-bed and monolith photoreactors operating in batch mode under visible light revealed 301 and 20 times higher H2 production than fixed bed and monolith photoreactors under continuous operation. The highest photonic yield and space yield were achieved using slurry photoreactor, while under UV light illuminated monolith showed highest apparent photonic yield and space yield. The findings of this work would be helpful to maximize photocatalytic H2 generation performance using various reactors under visible and UV irradiations.

Photoproduction of hydrogen in microreactors: Catalytic coating or slurry configuration?

A quartz microreactor containing 28 microchannels of 500 μm width and 105 mm length has been used to photoproduce hydrogen from liquid water-ethanol using an Au/TiO2 photocatalyst and UV light. The photomicroreactor has been tested in two flow configurations: (i) as a catalytic wall photoreactor by coating the microchannels with the photocatalyst, and (ii) as a slurry photoreactor by dispersing the photocatalyst in the liquid mixture of water-ethanol. The catalytic wall photoreactor configuration shows superior performance, with hydrogen yields more than three times higher than those obtained with the best slurry configuration under the same operation conditions.

Photocatalytic degradation efficiency of hazardous macrolide compounds using an external UV-light irradiation slurry reactor.

The current work investigates the removal of two hazardous macrolide molecules, spiramycin and tylosin, by photodegradation under external UV-light irradiation conditions in a slurry photoreactor using titanium dioxide as a catalyst. The kinetics of degradation and effects of main process parameters such as catalyst dosage, initial macrolide concentration, light intensity and stirring rate on the degradation rate of pollutants have been examined in detail in order to obtain the optimum operational conditions. It was found that the process followed a pseudo first-order kinetics according to the Langmuir-Hinshelwood model. The optimum conditions for the degradation of spiramycin and tylosin were low compound concentration, 1 g L-1 of catalyst dosage, 100 W m-2 light intensity and 560 rpm stirring rate. Then, a maximum removal (more than 90%) was obtained after 300 min of irradiation time. Furthermore, results show that the selection of optimized operational parameters leads to satisfactory total organic carbon removal rate (up to 51%) and biochemical oxygen demand to chemical oxygen demand ratio (∼1) confirming the good potential of this technique to remove complex macrolides from aqueous solutions.

Strong effect of light scattering by distribution of TiO2 particle aggregates on photocatalytic efficiency in aqueous suspensions

This work examines the important role of light power absorbed by TiO2 on the photocatalytic degradation of dichloroacetic acid (DCA) in a semi-continuous slurry photoreactor with UV–Vis radiation. This system is an excellent model for understanding the light matter interaction, because DCA is transparent and the acid pH of the solution prevents the formation of large TiO2 aggregates. Under these conditions, the light power absorbed by four different commercial Titania photocatalysts, along the whole volume of the reactor, has been quantitatively calculated by assuming a Mie scattering model on a distribution of different particle sizes. Although the different chemical nature of the four considered samples (three of them provided by the Evonik Company, P25, P25/20 and P90, together with Hombikat UV 100), and the different catalytic efficiency based on weight, we have found that all the catalytic responses are fundamentally controlled by the absorbed radiation in the four samples. Therefore, in the studied samples, any difference in the catalytic behavior is only due to the light-matter interaction being of lesser importance other mechanisms, as space-charge blocking.

Influence of Organic Dye Ligands on the Photocatalytic Reduction of Copper Ions in Aqueous Solution Using UV-Nano TIO2 System

This study investigates the influence of some organic dyes on the photocatalytic reduction of Cu (II) ions in aqueous solution. The dyes of interest were Eosin red, Eriochrome black T, Bromothymol blue and Malachite green. Slurry photoreactor design, with nano-sized titanium dioxide photocatalysts, and illuminated by a 15 W UV light, was utilized. Results showed that the percentage reduction of Cu (II) ions altered from 44.7% (without dye) to 25.7% (with ER), 60.7% (with EBT), 15.2% (with BTB) and 17.8% (with MG) after 60 minutes reaction time at pH 5. This implies that EBT enhanced Cu (II) ions reduction while the other three dyes inhibited the photoreduction process. The kinetic study indicated that the photo-reduction of Cu (II) ions followed the pseudo-first-order kinetics, with the exception of Cu-MG reduction which gave the best correlation values in zeroth-order plot. Statistical analysis was carried out with the ANOVA, Dunnetts post-hoc and Tukeys post-hoc multiple comparison tests. Tukeys post-hoc multiple comparison test was effected to determine the pair of Cu (II) ions with significant difference in mean values while Dunnetts post-hoc was effected to compare the measured values with the initial values. Photoreduction of Cu (II) ions were considered significant at P< 0.05 and 95% confidence interval.

Fabrication of CuWO4/Bi2S3/ZIF67 MOF: A novel double Z-scheme ternary heterostructure for boosting visible-light photodegradation of antibiotics

A novel double Z-scheme CuWO4/Bi2S3/ZIF67 ternary heterostructure was synthesized through hydrothermal method. The catalysts were characterized by XRD, FTIR, SEM, EDX, BET, TEM, PL, and UV–vis DRS analyses. The degradations of Metronidazole (MTZ) and Cephalexin (CFX) antibiotics by ternary catalyst were investigated in the batch and continuous slurry photoreactor under LED illumination. The ternary heterostructure exhibited a remarkable improvement in photoactivity compared with CuWO4/Bi2S3, and pristine ZIF67. Indeed, higher surface area, photo-stability, bandgap suppressing as well as better charge separation based on the dual Z-scheme structure caused the enhancement. The optimum values of operating parameters were obtained by the central composite design as: catalyst dose = 0.3 g/L, pH = 7, illumination time = 80 min, and 20 ppm initial concentration of antibiotic. The maximum degradation efficiencies by the new ternary heterostructure were 95.6% and 90.1%, respectively for MTZ and CFX at optimum conditions in the continuous flow mode. Maximum total organic carbon (TOC) removal rates were 83.2% and 74% for MTZ and CFX, respectively. The degradations by ternary composite followed the first-order kinetic, by reaction rate of 9 times, 5.5 times, and 4 times higher than that obtained by Bi2S3, ZIF67, and the binary CuWO4/Bi2S3, respectively. The influences of temperature and light intensity were explored, revealing 25 °C and 400 W/m2 as the optimum values. The new ternary heterostructure demonstrated excellent reusability and chemical stability after six cycles. The dominant active species were explored by trapping tests, indicating OH. free radicals as the most primary oxidant.

TiO2-rGO photocatalytic degradation of an emerging pollutant: kinetic modelling and determination of intrinsic kinetic parameters

An intrinsic kinetic model, derived from a suggested reaction photo-mechanism and with an explicit dependence on the local volumetric rate of photon absorption (LVRPA), was developed to simulate the photocatalytic degradation of clofibric acid and the main reaction intermediates, with a new titania-reduced graphene oxide nanocomposite (TiO2-rGO), The proposed reaction mechanism takes into account that graphene behaves as an electron acceptor and, therefore, this effect was included in the derivation of the reaction rate expressions and in the parameters estimation of the kinetic model. The photodegradation of clofibric acid was performed in a slurry photoreactor under different irradiation levels and using several loadings of a TiO2-rGO nanocomposite, prepared by hydrothermal method with a 0.5 wt. % of GO. Absorbed radiation profiles inside the photoreactor were obtained by solving the radiation model with the Monte Carlo method. A photocatalyst loading of 100 mg L−1 gave place to the best photodegradation results. Mass balances were proposed for the main pollutant and their main detected intermediates: p-benzoquinone and 4-chlorophenol. The intrinsic kinetic parameters were obtained for the complete (6-parameters) and simplified (5-parameters) models by comparing the experimental and the theoretical concentration values of all the organic compounds detected. The model proved to be able to predict with good accuracy the concentration evolution of clofibric acid, 4-chlorophenol and p-benzoquinone under several photocatalyst concentrations and irradiation levels. Finally, a very good correlation between calculated and experimental values of clofibric acid concentration was obtained with root-mean-square errors below 11%.

Engineering approach to enhance photocatalytic water splitting for dynamic H2 production using La2O3/TiO2 nanocatalyst in a monolith photoreactor

In this study, photocatalytic activity of La loaded TiO2 NPs was enhanced by engineering approach using monolithic honeycomb assisted photo-reactor system for dynamic hydrogen production. La/TiO2 NPs loaded over monolithic honeycomb support were characterized by XRD, XPS, FESEM, RAMAN, HRTEM, BET, UV–Vis and PL-spectroscopy. The photocatalytic activity of La/TiO2 NPs was enhanced by 1.8 folds higher than using pristine TiO2 in a slurry photoreactor system. This enactment was due to larger surface area, faster charge carrier separation and decreased surface recombination centers due to the presence of oxygen vacancies. Moreover, using monolithic honeycomb support loaded with La/TiO2, H2 generation rate of 165.5 ppm/h was obtained, 9.19 folds higher than using La/TiO2 in a slurry phase. Moreover, apparent quantum yield and space yield of monolith photoreactor was 1.4 and 4.5 folds higher than the slurry phase photoreactor, respectively. The superior efficiency of monolith photoreactor was due to adaptable arrangement of reactor which permits most utilization of illuminated surface area and processing volume with effective mass transport which is restricted in a slurry phase photoreactor. Also, stability comparison of slurry and monolith photoreactor for hydrogen production reveals, reusability of La/TiO2 loaded over monolithic support was 4.18% higher than the catalyst suspended in slurry phase photo-reactor. Therefore, enhanced efficiency of catalyst can be obtained using monolith photoreactor for photocatalytic H2 production compared to suspended slurry system and can be employed for other energy applications.

La-modified TiO2/carbon nanotubes assembly nanocomposite for efficient photocatalytic hydrogen evolution from glycerol-water mixture

Lanthanum (La) modified TiO2 embedded over carbon nanotubes (CNTs) to develop nanocomposite for enhanced photocatalytic hydrogen evolution from glycerol-water mixture has been investigated. The samples, synthesized by sol-gel assisted hydrothermal method, were characterized by XRD, FESEM, HRTEM, FTIR, BET, UV–Visible, Raman and PL spectroscopy. La/TiO2 anchored CNTs has larger surface area with uniform distribution of La3+ ions. The performance of hybrid assembly was evaluated in a continuous flow slurry photoreactor system under UV–visible light irradiations. The highest H2 evolution rate of 17265 ppm g-cat−1 h−1 was obtained over 5% La-5% CNTs/TiO2 NRs, 1.14 folds the amount produced over 5% La-5% CNTs/TiO2 NPs, 1.53 time than 5% La/TiO2 and 4.10 folds than using pure TiO2 NPs. This significant improvement in the photo-activity was obviously due to synergistic effect between La and CNTs, larger BET surface area, cleavage of glycerol by La, appropriate band structure, and hindered charges recombination rate. Among the sacrificial reagents, highest H2 evolution was obtained using glycerol due to the presence of α-hydrogen atoms attached to carbon atoms. A correlation between BET surface area and photonic flux in terms of photocatalytic H2 production rate was established to understand the performance of hybrid nanostructures. It was observed that BET surface area and photo-flux utilization for the generation of charge carriers with their efficient separation has significant contribution towards improved H2 production rate. More interestingly, catalyst persisted prolonged stability with a steady H2 production in cyclic runs. This study provides promising pathway for constructing composite of La/TiO2 coupled CNTs for efficient H2 production under visible light.

Synthesis, characterization of visible active MO hallow spheres by combustion technique


 
 
 A simple method to synthesize nano-sized hallow sphere such as Zn-Ce metal oxide (MO) by combustion technique. The product was characterized by X-ray diffraction (XRD), Field emission-scanning electron microscope (FE-SEM), Fourier transform infrared spectroscopy (FT-IR), Thermo gravimetric analysis (TGA), Diffuse Reflectance Spectroscopy (DRS) and Transmission electron microscope (TEM). The photocatalytic activity of Zn-Ce MO nano-sized hallow sphere was examined by studying the degradation of direct blue 71 (DB71) under visible light irradiations in a slurry photoreactor. The effect of parameters such as the catalyst dosage, concentration of the dye, pH and kinetics on photocatalytic degradation of DB71 is also studied. Degradation of dye was confirmed by UV-VIS spectrum, chemical oxygen demand (COD) and ESI-Mass.
 
 

Degradation of 2,4-dichlorophenoxyacetate isopropyl amine (2,4-D IPA) by O3/AC/UV in an internally slurry airlift photo-reactor

ABSTRACTAn externally illuminated slurry airlift reactor (ALR) was used to decompose 2,4-dichlorophenoxyacetate isopropyl amine during catalytic ozonation with activated carbon. The effect of superficial gas velocity (0.05–0.15 cm/s), UVAB irradiation (0–60 W), treatment period (10–30 min) and amount of activated carbon (0–0.8 g/l) on removal efficiency was investigated using response surface methodology (RSM) based on the Box–Behnken surface statistical design. Well-defined circulation pattern in the ALR allowed all the fluid elements to be exposed to high light intensity zone and achieve sufficient contact between the solid catalyst and the pollutant. Treatment period appeared as the most influential variable followed by the amount of activated carbon, superficial gas velocity and UV irradiation. A kinetic study was also carried out to evaluate the degradation efficiency versus the O3, O3/AC, O3/UV and O3/AC/UV combinations in which the last one had the highest impact. Efficient suspensions of AC in the ALR resulted in the high efficiency of the O3/AC system. No significant difference was observed between the overall kinetic constants determined in O3/AC and O3/AC/UV systems due to the light transmission obstacle of solid suspension.

Solar degradation of contaminants in water: TiO2 solar photocatalysis assisted by up-conversion luminescent materials

Solar energy, along with other renewable resources, could potentially solve environmental problems, as demonstrated by recent developments in the use of solar energy, such as solar photocatalysis. Solar photocatalytic technology has been demonstrated to be effective for treating groundwater, drinking water, wastewater and air and soil pollution. In this study, a solar photocatalytic application for wastewater decontamination is presented. Luminescent material has been evaluated as up-conversion material for enhancing the photocatalytic activity. Wastewater decontamination by heterogeneous photocatalysis has been developed in a slurry photo-reactor, using TiO2 as a photocatalyst. The photoactivity of TiO2 under several sun irradiation conditions was investigated. The up-conversion luminescence agent ZBLAN, a rare-earth (Yb-Er-Tm) co-doped fluoride glass (ZrF4– BaF2–LaF3–AlF3–NaF), was incorporated to enhance the solar-driven activity of TiO2 because this material could transform the unused near-infrared sunlight tail into UV–vis radiation available for photoreaction activation. The use of ZBLAN has demonstrated an improvement over ordinary titanium dioxide photocatalytic activity under sunlight irradiation for the photocatalytic degradation of pollutants in wastewater. Our results demonstrating the contribution of up-conversion luminescence to the improved photoactivity of titanium dioxide suggest that it can be used to develop new technologies for treating wastewater using solar light.