A kinetic study for the Fenton and photo-Fenton paracetamol degradation in an annular photoreactor (original) (raw)
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Applied Catalysis B: Environmental, 2015
A new model is proposed for the photo-Fenton oxidation of water contaminants including the effect of photon absorption (volumetric rate of photon absorption, VRPA), the effect of the geometry of the reactor and the illuminated volume to total volume ratio (R i) in the reaction system. Fe(III) was found to be the main species in the aqueous solution responsible for photon absorption provided that hydrogen peroxide was not totally consumed. Paracetamol was used as model pollutant at a concentration of 1 mM to validate the model. The illuminated part of the raceway reactor configuration (total length of 80 cm) was operated at two liquid depths (5.0 and 2.5 cm) equivalent to two irradiated reactor volumes (2 and 1 L) and using R i ratios in the range 0.30-0.65, which changed the dark reactor volume. These values are commonly found in photo-Fenton pilot plants for water treatment and purification. The model successfully fitted the temporal evolution of the dissolved oxygen (O 2) and the hydrogen peroxide (H 2 O 2) concentrations and the evolution of the total organic carbon (TOC) in solution in both reactor geometries and for different illuminated volume to total volume ratios. The model can be easily extended to model other water contaminants and provides a robust method for process design, process control and optimization.
A CFD study of an annular pilot plant reactor for Paracetamol photo-Fenton degradation
Chemical Engineering Journal, 2021
This work studies in detail the photo-Fenton degradation process of Paracetamol (PCT) on an annular pilotplant reactor using Computational Fluid Dynamics (CFD). A cylindrical lamp emission model was originally implemented over the structure of the OpenFOAM(R) platform and a multicomponent reaction mixture model was used to compute the temporal evolution of the different species at each point of the reactor. Once the proposed model was experimentally validated, the influence of different operating conditions (i.e. different strategies for hydrogen peroxide (H 2 O 2) dosage, use of low recirculation flow rates (Qr), and a completely uncovered lamp setup) was studied. The results of the analysis showed that a double addition of H 2 O 2 (50% before the tank and 50% before the reactor) significantly reduces the reaction times of the process. Moreover, the overall PCT degradation rate does not change when Qr is increased, thus allowing the system to be operated with a recirculation flow three times lower than that the one used in the experiments. Thereby, the developed model allows identifying the reaction conditions that maximize the overall PCT conversion, making efficient use of H 2 O 2 (main chemical reagent) and reducing the electrical energy consumption (recirculation flow) by operating the system under conditions present in large-scale photochemical reactors.
Photonic efficiency of the photodegradation of paracetamol in water by the photo-Fenton process
Environmental Science and Pollution Research, 2014
An experimental study of the homogeneous Fenton and photo-Fenton degradation of 4-amidophenol (Paracetamol, PCT) is presented. For all the operation conditions evaluated, PCT degradation is efficiently attained by both Fenton and photo-Fenton processes. Also, photonic efficiencies of PCT degradation and mineralization are determined under different experimental conditions, characterizing the influence of hydrogen peroxide (H 2 O 2) and Fe(II) on both contaminant degradation and sample mineralization. The maximum photonic degradation efficiencies for 5 and 10 mg L-1 Fe(II) were 3.9 (H 2 O 2 = 189 mg L-1) and 5 (H 2 O 2 = 378 mg L-1), respectively. For higher concentrations of oxidant, H 2 O 2 acts as a "scavenger" radical, competing in pollutant degradation and reducing the reaction rate. Moreover, in order to quantify the consumption of the oxidizing agent, the Specific Consumption of the Hydrogen Peroxide was also evaluated. For all operating conditions of both hydrogen peroxide and Fe(II) concentration, the consumption values obtained for Fenton process were always higher than the corresponding values observed for photo-Fenton. This implies a less efficient use of the oxidizing agent for dark conditions.
Photo-Fenton degradation of wastewater containing organic compounds in solar reactors
Separation and Purification Technology, 2004
In this work, the photo-Fenton oxidation of phenol in aqueous solutions has been investigated using Fe 2+ , H 2 O 2 and UV-visible light (sunlight). Laboratory-scale experiments were carried out using solar reactors of two different configurations: (1) a concentrating parabolic trough reactor (PTR) and (2) a non-concentrating thin-film reactor. Global solar irradiance was measured during the experiments. Additional laboratory experiments were carried out in an annular photochemical reactor using an artificial light source, at the same experimental conditions. The results indicate that the photo-Fenton process using solar irradiation is an effective treatment for industrial wastewater containing phenol. At low contaminant concentration (TOC 0 = 100 ppm), more than 90% of the total organic carbon content of the initial phenol solution could be converted to inorganic carbon within about 3 h of irradiation, using artificial light or sunlight (even on cloudy days), in reactors of different geometry. At moderate or higher phenol concentrations (TOC 0 = 550 or 1000 ppm), the results indicate satisfactory TOC removal (45-55%) at reasonable degradation rates. Experiments under different insolation conditions suggest a direct linear dependence of the organic carbon removal on the accumulated sunlight energy reaching the system. Solar light can be used either as a complementary or alternative source of photons to the process.
Kinetic study of the photo-Fenton degradation of formic acid
Catalysis Today, 2009
This study is focused on the kinetic modelling of the Fenton and photo-Fenton degradation of a model pollutant (formic acid) in aqueous solution, for relatively low iron concentrations (1–9 ppm). The reaction rate expressions are derived from an accepted reaction mechanism and explicitly having into account the local volumetric rate of photon absorption. The experimental work was performed in a well-stirred tank laboratory reactor irradiated from the bottom. Afterward, the proposed kinetic model and the experimental data were used to estimate the Arrhenius parameters between 20 and 55 °C, applying a non-linear regression procedure. To avoid the precipitation of iron compounds during the experimental runs, simultaneous high reaction temperatures (55 °C) and iron concentrations (9 ppm) were prevented. To achieve this goal, an experimental design based on the D-optimality criterion was adopted. The proposed kinetic model was able to reproduce the combined effects of changing the ferric iron concentrations, reaction temperatures, and formic acid to hydrogen peroxide molar ratios on the pollutant degradation rate. Kinetic model predictions are compared with experimental data of the organic compound conversion, and a good agreement is obtained. For the whole set of Fenton and photo-Fenton experimental runs, the maximum root mean square error is 7.64%.
Investigation of paracetamol degradation using LED and UV-C photo-reactors
Water Science and Technology, 2020
This work investigates the efficiency of LED and UV-C photo-reactors for paracetamol degradation using advanced oxidative processes. Among the evaluated processes, photo-Fenton was the most efficient for both radiations. Degradations greater than 81% (λ 197 nm) and 91% (λ 243 nm) were obtained in the kinetic study. These degradations were also observed by means of the reduction in the peaks in both spectral scanning and high-performance liquid chromatography analysis. The good fit of the Chan and Chu kinetic model shows that the degradation reaction has pseudo-first order behavior. Toxicity tests did not indicate the inhibition of growth of Lactuca sativa seeds and Escherichia coli bacterium. However, the growth of strains of the Salmonella enteritidis bacterium was inhibited in all the samples, demonstrating that only this bacterium was sensitive to solutions. The proposed empirical models obtained from the 24 factorial designs were able to predict paracetamol degradation. These mo...
Kinetic degradation of the pollutant guaiacol by dark Fenton and solar photo-Fenton processes
Environmental Science and Pollution Research, 2011
This work is first intended to optimize the experimental conditions for the maximum degradation of guaiacol (2-methoxyphenol) by Fenton's reagent, and second, to improve the process efficiency through the use of solar radiation. Guaiacol is considered as a model compound of pulp and paper mill effluent. The experiments were carried out in a laboratory-scale reactor subjected or not to solar radiation. Hydrogen peroxide solution was continuously introduced into the reactor at a constant flow rate. The kinetics of organic matter decay was evaluated by means of the chemical oxygen demand (COD) and the absorbance measurements. The experimental results showed that the Fenton and solar photo-Fenton systems lead successfully to 90% elimination of COD and absorbance at 604 nm from a guaiacol solution under particular experimental conditions. The COD removal always obeyed a pseudo-first-order kinetics. The effect of pH, temperature, H 2 O 2 dosing rate, initial concentration of Fe 2+ , and initial COD was investigated using the Fenton process. The solar photo-Fenton system needed less time and consequently less quantity of H 2 O 2. Under the optimum experimental conditions, the solar photo-Fenton process needs a dose of H 2 O 2 40% lower than that used in the Fenton process to remove 90% of COD.
Applied Catalysis B: Environmental, 2011
The degradation of 10 L of 157 mg L −1 paracetamol solutions in 0.05 M Na 2 SO 4 has been studied by the solar photoelectro-Fenton (SPEF) method. A solar flow plant with a Pt/air-diffusion electrochemical cell and a compound parabolic collector (CPC) photoreactor was used operating under recirculation mode at a liquid flow of 180 L h −1 with an average UV irradiation intensity of about 32 W m −2. A central composite rotatable design coupled with response surface methodology was applied to optimize the experimental variables. Optimum SPEF treatment was achieved by applying a current of 5 A, 0.40 mM Fe 2+ and pH 3.0 at 120 min of electrolysis, being reduced total organic carbon (TOC) by 75%, with an energy cost of 93 kWh kg −1 TOC (7.0 kWh m −3) and a mineralization current efficiency of 71%. Initial N was partially converted into NH 4 + ion. Under these optimized conditions, paracetamol decays followed a pseudo first-order kinetics. HPLC analysis of the electrolyzed solution allowed the detection of hydroquinone, p-benzoquinone, 1,2,4-trihydroxybenzene, 2,5-dihydroxy-p-benzoquinone and tetrahydroxy-p-benzoquinone. All aromatics were destroyed by the attack of • OH. Maleic, fumaric, succinic, lactic, oxalic, formic and oxamic acids were identified as generated carboxylic acids, which form Fe(III) complexes that are quickly photodecarboxylated under UV irradiation of sunlight. A reaction sequence involving all the detected byproducts was proposed for the SPEF degradation of paracetamol.
Degradation of four pharmaceuticals by solar photo-Fenton process: Kinetics and costs estimation
Journal of Environmental Chemical Engineering, 2015
Solar photo-Fenton process for degradation of four types of pharmaceuticals namely amoxicillin, ampicillin, diclofenac, and paracetamol was studied. Experiments were carried out by solar compound parabolic collectors (CPCs) reactor with borosilicate tubes and capacity of 4.0 L. Oxidation of each pharmaceutical was investigated individually using 100 mg/L synthetic solution. The influence of irradiation time, initial pH value, and dosage of Fenton reagent were investigated. Paracetamol, and amoxicillin were completely removed after 60 and 90 min of irradiation respectively. Complete degradation of ampicillin and diclofenac was occurred after 120 min. The removal of pharmaceuticals was significantly affected by changing pH values from 3 to 10. Complete removal of all pharmaceuticals was achieved under acidic conditions (pH 3). The optimum H 2 O 2 and FeSO 4 .7H 2 O dosage were 1.5 and 0.5 g/L, respectively. The results of photo-Fenton experiments fitted the pseudo-first order kinetic equation with high correlation. Costs estimation of 30 m 3 /d full scale solar photo-oxidation plant was assessed.