Kinetic Model Of Photocatalytic Degradation Research Articles

Kinetic modeling of the photocatalytic degradation of acetaminophen and its main transformation products

In this study, a kinetic model of the heterogeneous photocatalytic degradation of acetaminophen and its main transformation products is presented. Kinetic photocatalytic modeling and photon absorption rate modeling were included. Monte Carlo method was used to model the photon absorption process. Experiments were carried out in a reactor operated in batch mode and TiO2 nanotubes were used as photocatalyst irradiated with 254 nm UVC. Kinetic parameters were estimated from the experiments data by applying a non-linear regression procedure. Intrinsic expressions to the kinetics of acetaminophen degradation and its main transformation products were derived. Model, kinetics and photon absorption formulations and parameters proved to be affordable for describing the photocatalytic degradation of acetaminophen, but improvements should be done for better description of formation and oxidation kinetics of main transformation products. The model should be tested with other pharmaceuticals and emergent pollutants to calibrate it and evaluate its applicability in a wide range of compounds.

Novel kinetic modeling of photocatalytic degradation of ethanol and acetaldehyde in air by commercial and reduced ZnO: Effect of oxygen vacancies and humidity

A comprehensive kinetic model has been developed to address the factors and processes governing the photocatalytic removal of gaseous ethanol by using ZnO loaded in a prototype air purifier. This model simultaneously tracks the concentrations of ethanol and acetaldehyde (as its primary oxidation product) in both gas phase and on the catalyst surface. It accounts for reversible adsorption of both compounds to assign kinetic reaction parameters for different degradation pathways. The effects of oxygen vacancies on the catalyst have been validated through the comparative assessment on the catalytic performance of commercial ZnO before and after the reduction pre-treatment (10% H2/Ar gas at 500 °C). The influence of humidity has also been assessed by partitioning the concentrations of water molecules across the gas phase and catalyst surface interface. Given the significant impact of adsorption on photocatalytic processes, the beginning phases of all experiments (15 min in the dark) are integrated into the model. Results showcase a notable decrease in the adsorption removal of ethanol and acetaldehyde with an increase in relative humidity from 5% to 75%. The estimated number of active sites, as determined by the model, increases from 7.34 10−6 in commercial ZnO to 8.86 10−6 mol gcat−1 in reduced ZnO. Furthermore, the model predicts that the reaction occurs predominantly on the catalyst surface while only 14% in the gas phase. By using quantum yield calculations, the optimal humidity level for photocatalytic degradation is identified as 25% with the highest quantum yield of 6.98 10−3 (commercial ZnO) and 10.41 10−3 molecules photon−1 (reduced ZnO) catalysts.

Three-layer magnetic nanocomposite containing semiconductor nanoparticles as catalyst for dye removal from water solutions under visible light

In the present work, a three-layer magnetic nanocomposite containing ceria nanoparticles was synthesized as Fe3O4@SiO2@CeO2 by precipitation method and after characterization was used as photocatalyst for the degradation of malachite green dye from industrial wastewater under visible light. The influence parameters such as pH, initial dye concentration, photocatalyst amount and process time on the malachite green dye removal were investigated and optimized. Under optimum conditions (pH = 9, the photocatalyst amounts of 0.05 g, the reaction time of 40 min and the initial solution concentration of 10 ppm), the results indicated that the synthesized nanostructure has a desirable performance for dye. The removal percentage remained higher than 90% after 5 times of use and the photocatalyst could be quickly separated from aqueous solution with the assistance of the external magnetic field. According to the calculation, the second pseudo-model was selected as the kinetic model of photocatalytic degradation.

Kinetic modeling of the photocatalytic degradation of methyl ethyl ketone in air for a continuous-flow reactor

This paper reports the study on kinetic modeling of photocatalytic degradation of methyl ethyl ketone (MEK) using TiO2 coated on silica fiber felts. Two different mathematical models, ideal plug flow model and axially dispersed plug flow model (dispersion model), were used to simulate the performance of the PCO reactor. Six kinetic rate equations on the basis of Langmuir-Hinshelwood (L-H) expression were examined to find the best model that fits the experimental data. Moreover, the light intensity distribution on the photocatalyst surface was simulated using the linear source spherical emission model (LSSE) and validated with the experimental data. The Beer-Lambert model was also applied to demonstrate the diminishment of light intensity in the PCO filter. For model prediction validation, a series of experiments was carried out in a bench-scale continuous flow reactor at different concentrations (0.1–1 ppm), relative humidities (17–67%), flow rates (10–30 L/min), and light intensities (7–23.5 W/m2). In addition, adoption tests with MEK at various concentrations (0.25–1 ppm) and relative humidities (15–50%) were conducted under dark condition. Formaldehyde, acetaldehyde, acetone, and propionaldehyde were identified (through HPLC analysis) as by-products of the MEK PCO reaction. Owing to higher concentrations of formaldehyde and acetaldehyde, aldehyde group was considered as the main by-products. The result of carbon balance indicated that 7.2% of MEK mineralized to CO2 (measured by GC-FID) and around 10.8% of that was converted to by-products (for 18.4% removal efficiency). Evaluation of different kinetic rate expressions revealed that the unimolecular L-H model considering inhibitive effect of water vapor and by-products for adsorption provided the best fit. The dispersion model combined with this rate expression had a higher accuracy at all operating conditions while the plug flow model failed to predict the PCO performance at various intensities and air velocities. Evaluation of mass transfer was also performed, and it was concluded that the mass transfer effect on the PCO process is not dominating step; consequently, the PCO reaction is the rate-limiting process.

Photocatalytic degradation of methylene blue dye in aqueous solution by MnTiO3 nanoparticles under sunlight irradiation

Nanophotocatalyst MnTiO3 powders were synthesized by sol-gel technique and characterized by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), as well as their thermal behavior has been studied by differential thermal and thermogravimetric analyses (DTA/TGA). Powders morphology was analyzed by means of Transmission electron microscopy (TEM). Effect of various process parameters like amount of photocatalyst, dye concentration, solution pH and irradiation time on the extent of removal of dye were studied in detail. The photo-degradation was relatively higher using lower amount (0.005 g) of semiconductor, reached rate of 75% and 70% after 240 min for mixed MnTiO3/TiO2 and pure MnTiO3 nanocatalysts. The kinetic model of photocatalytic degradation of MB follows pseudo-first-order kinetic with a high correlation coefficient values (R2 > 0.95). These results underline the use of effective, low-cost and easily available MnTiO3 photocatalyst for the decomposition of pollutants to water under natural sunlight.

Synthesis of Porous Octahedral ZnO/CuO Composites from Zn/Cu-Based MOF-199 and Their Applications in Visible-Light-Driven Photocatalytic Degradation of Dyes

In the present paper, a porous octahedral (ZnO/CuO) composite is synthesized from zinc/copper-based metal-organic framework-199, and its applications in visible-light-driven photocatalytic degradation of dyes are demonstrated. The precursors of Zn-BTC, Cu-BTC, and Zn/Cu-BTC (BTC: benzene-1,3,5-tricarboxylate) were synthesized using a microwave-assisted method. Benzene-1,3,5-tricarboxylate acts as a sacrificial template and was removed from the precursors via thermal decomposition to form CuO, ZnO, and ZnO/CuO. ZnO/CuO with a large specific surface area of 32.5 m2·g–1 is composed of porous octahedral particles of 5–10 μm in diameter. Methylene blue (MB) was utilized as the dye model for photocatalytic degradation reactions. The porous octahedral ZnO/CuO exhibits superior visible-light-driven photocatalytic degradation of MB compared with single CuO or ZnO. The kinetic model of photocatalytic degradation was proposed as 1/KL×lnC+C=−krt+1/KL×lnCe+Ce, where KL is the Langmuir equilibrium constant and Ce is the MB concentration at equilibrium. The model significantly fits the kinetic data. In addition, the acquired catalyst manifests excellent photocatalytic degradation for several other dyes including phenol red, methyl orange, and Congo red.

Synthesis of (Zn/Co)-based zeolite imidazole frameworks and their applications in visible light-driven photocatalytic degradation of Congo red

Zinc/cobalt (Zn/Co)-based zeolite imidazole frameworks (ZIFs) with varying Zn/Co molar ratios from 0/10 to 10/0 were synthesized by a microwave-assisted method, and the resulting materials were characterized by x-ray diffraction (XRD), nitrogen adsorption–desorption isotherms, scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS), and atomic absorption spectroscopy (AAS). The microwave-assisted approach required a very short synthesis time as well as yielded (Zn/Co)ZIFs with high specific surface areas (1637.3 m2 g−1). It was found that the introduction of zinc into ZIF-67 enhanced catalytic activity in visible-light region. (Zn/Co)ZIF with a Zn/Co molar ratio of 2/8 manifested an excellent photocatalytic degradation of Congo red (CGR). The kinetic model of photocatalytic degradation was proposed based on adsorption isotherms (Langmuir model) and a unimolecular reaction for the heterogeneous catalysis. Further, the reusability was also addressed.

Kinetic Modeling of Photocatalytic Degradation of an Azo Dye Using Nano-TiO2/Polyester

Photocatalytic degradation of Reactive Orange 16 (RO16) was investigated using immobilized TiO2 nanoparticles on polyester support in exposure of UV irradiation in recirculated tubular photoreactors. Utilization of the polyester as a support has several advantages, such as low price, remarkable surface area, flexibility, and durability. Moreover, the prepared TiO2/polyester was successfully applied for the photocatalytic degradation of RO16 in aqueous media for several times without any discernible diminution in its activity. Applied TiO2 nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). Experimental results indicate that the degradation rate of RO16 follows pseudo-first-order kinetics. With nonlinear regression, a model was developed for prediction of pseudo-first-order rate constants (kapp) as a function of operational parameters, including temperature (295–328K), flow rate (5–15 L·min−1), and initial concentration of RO16 (5–25 mg·L−1) as $$k_{\rm app} = 2.20 ( \exp { [- 7427 / \rm RT} ]) ( FR ) ^{0.5034} [ {0.112 / (1 + 0.112 [ \rm RO16 ] _0} )] .$$ Calculated data from the model are in good agreement with the experimental results. Electrical energies per order (EEO) were estimated from the calculated and experimental data show that EEO depends on the operational parameters, considerably. To monitor the mineralization of RO16, chemical oxygen demand (COD) measurements were carried out during the UV/TiO2 process. COD measurement results indicated that all organic substances were completely mineralized after 5 h of UV irradiation.

Kinetic modeling of azo dyes photocatalytic degradation in aqueous TiO 2 suspensions. Toxicity and biodegradability evaluation

A kinetic model of the photocatalytic degradation of the azo dye Acid Orange 7 (AO7) is presented. It is based on mechanistic reaction steps and includes the modeling of the radiation absorption effects. The evaluation of the radiation field inside the reactor was achieved by solving the radiative transfer equation for the heterogeneous system. The study was carried out in a slurry batch photoreactor with recycle, employing artificial UV light as the source of radiation and TiO 2 Degussa P25 as catalyst. The biodegradability and toxicity of the irradiated mixture was also assessed. The kinetic model satisfactorily represents the evolution of AO7 under different experimental conditions, with a root mean square error of the estimations of 13.9%. The biodegradability of the AO7 solution was considerably enhanced after the photocatalytic treatment. In addition, a clear reduction of the toxicity of the azo dye was achieved at the end of the experiments.

A new kinetic model of photocatalytic degradation of formic acid in UV/TiO2 suspension system with in-situ monitoring

The results show that a newly developed kinetic model can successfully explain the photocatalytic kinetics of formic acid in UV/TiO2 suspension system with in-situ monitoring and the apparent rate constant (k) is affected by the initial concentrations of formic acid, amounts of TiO2, UV intensity and pH.

Kinetic modeling of photocatalytic degradation of Acid Red 27 in UV/TiO2 process

The photocatalytic degradation of Acid Red 27 (AR27) was investigated using UV radiation in the presence of TiO2-P25 as a function of initial concentration of AR27 ([AR27]0), oxygen concentration ([O2]), TiO2-P25 amount, light intensity (Ia), pH and temperature. The activation energy of the photocatalytic degradation of AR27 was 8.24kJmol−1. The photocatalytic degradation rate follows pseudo-first order kinetic with respect to the AR27 concentration. The following rate of decolorization was achieved by kinetic modeling: rAR27=5.294Iaexp−8247RT0.79O21+0.79O24.23AR271+4.23AR270 The calculated results obtained from above equation were in good agreement with experimental data. This model predicts the concentration of AR27 during the photodegradation process at different temperatures, light intensities, AR27 and oxygen concentrations.