Evaluation of the combined solar TiO2/photo-Fenton process using multivariate analysis (original) (raw)
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Journal of Hazardous Materials, 2006
This study reports the photodegradation of 4-chlorophenol (4-CP) in aqueous solution by the photo-Fenton process using solar irradiation. The influence of solution path length, and Fe(NO3)3 and H2O2 concentrations on the degradation of 4-CP is evaluated by response surface methodology. The degradation process was monitored by the removal of total organic carbon (TOC) and the release of chloride ion. The results showed a very important role of iron concentration either for TOC removal or dechlorination. On the other hand, a negative effect of increasing solution path length on mineralization was observed, which can be compensated by increasing the iron concentration. This permits an adjustment of the iron concentration according to the irradiation exposure area and path length (depth of a tank reactor). Under optimum conditions of 1.5 mM Fe(NO3)3, 20.0 mM H2O2 and 4.5 cm solution path length, 17 min irradiation under solar light were sufficient to reduce a 72 mg C L−1 solution of 4-CP by 91%.
Chemosphere, 2002
The photo-Fenton process using potassium ferrioxalate as a mediator was investigated for the photodegradation of dichloracetic acid (DCA) and 2,4-dichlorophenol (DCP) in aqueous medium using solar light as source of irradiation. The influence of the solution depth, the light intensity and the effect of stirring the solution during irradiation process were evaluated using DCA as a model compound. A negligible influence of stirring the solution was observed when the concentration of ferrioxalate (FeOx) was 0.8 mM and solution depth was 4.5 or 14 cm. The optimum FeOx concentration determined for solution depths between 4.5 and 14 cm was 0.8 mM considering total organic carbon (TOC) removal during DCA irradiation. The high efficiency of the photo-Fenton process was demonstrated on summer days, when only 10 min of exposition (around noon) were sufficient to completely destroy the organic carbon of a 1.0 mM DCA solution in the presence of 0.8 mM FeOx and 6.0 mM H2O2 using a solution depth of 4.5 cm. It was observed that the photodegradation efficiency increases linearly with the solar light intensity up to values around 15 W m−2 but this linear relationship does not hold above this value showing a square root dependence. The photodegradation of a solution of DCP/FeOx showed a lower TOC removal rate than that observed for DCA/FeOx, achieving ∼90% after 35 min irradiation under 19 W m−2, while under this light intensity, the same TOC removal of DCA/FeOx was achieved in only 10 min irradiation.
Use of Fe2O3-TiO2 in solar photo-Fenton process for the phenol degradation
2018
In this work a Fe 2 O 3 -TiO 2 catalyst, at the proportion 60:40 (%mass), was produced using a modified Pechini method. The catalyst was characterized and used in the degradation of phenol in aqueous solution through a solar photo-Fenton reaction. Experiments were performed varying the concentration of H 2 O 2 , catalyst, phenol, and pH of the aqueous solution, in order to determine the reaction rate and propose a mechanism. Characterization showed the presence of Fe 2 O 3 and anatase and rutile phases of TiO 2 . Pseudobrookite (Fe 2 TiO 5 ) was also found in the material. The Fe 2 O 3 -TiO 2 catalyst presented higher efficiency (90% of phenol removal) and degradation rate than the two isolated oxides in the process photo-Fenton heterogenous in optimum conditions. The proposed mechanism shows that the union of the two oxides, Fe 2 O 3 and TiO 2 , facilitates the reduction and oxidation reactions of Fe + 2 /Fe + 3 and Ti +4 /Ti +3 , increasing the amount of surface OH groups and co...
Recent Overview of Solar Photocatalysis and Solar Photo-Fenton Processes for Wastewater Treatment
International Journal of Photoenergy, 2017
This literature research, although not exhaustive, gives perspective to solar-driven photocatalysis, such as solar photo-Fenton and TiO2 solar photocatalysis, reported in the literature for the degradation of aqueous organic pollutants. Parameters that influence the degradation and mineralization of organics like catalyst preparation, type and load of catalyst, catalyst phase, pH, applied potential, and type of organic pollutant are addressed. Such parameters may also affect the photoactivity of the catalysts used in the studied solar processes. Solar irradiation is a renewable, abundant, and pollution-free energy source for low-cost commercial applications. Therefore, these solar processes represent an environmentally friendly alternative mainly because the use of electricity can be decreased/avoided.
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.
Separation and Purification Technology, 2007
A combined homogeneous and heterogeneous photocatalytic decolourisation and degradation of a chlorotriazine azo dye reactive orange 4 (RO 4) have been carried out using ferrous sulphate/ferrioxalate with H 2 O 2 and TiO 2-P25 nanoparticles. Enhancement in the photo-Fenton processes has been observed by the addition of TiO 2-P25. UV/ferrous/H 2 O 2 /TiO 2 and UV/ferrioxalate/H 2 O 2 /TiO 2 processes are found to be more efficient than the individual photo-Fenton and UV/TiO 2-P25 processes. The use of ferrioxalate in the combined process is found to be more advantageous. The effects of various experimental parameters such as pH, initial H 2 O 2 , Fe 2+ , Fe 3+ and TiO 2 concentrations on these combined photocatalytic processes have been investigated. All these parameters strongly influenced the removal rate. The optimum operating conditions of these combined processes are reported.
Revista de Chimie, 2008
An experimental study on 4-chlorophenol (4-CP) degradation in aqueous solutions by advanced oxidation process photo-Fenton type is presented. The efficiency of the oxidation process is determined by the very high oxidative potential of the OH. radicals generated by catalytic and photo-catalytic processes. The presence of the inorganic species inside the reaction medium influences the rate of the oxidation process as function of their nature and concentration. The inorganic anionic species reduce drastically the 4-CP oxidation efficiency by Fe2+/3+ complexing processes, HO. radicals scavenging effect or iron precipitate forming. The decrease of the 4-CP oxidation degree is correlated with the nature of the anions as following: Cl- ] PO43- ] SO42- ]] NO3-. The presence of the insoluble inorganic species (bentonite) modifies the oxidation efficiency by additional 4-CP and UV sorption processes, especially at high solution turbidity values.
Applied studies in solar photocatalytic detoxification: an overview
Solar Energy, 2003
The technical feasibility and performance of photocatalytic degradation of four water-soluble pesticides (diuron, imidacloprid, formetanate and methomyl) have been studied at pilot scale in two well-defined systems which are of special interest because natural-solar UV light can be used for them: heterogeneous photocatalysis with titanium dioxide and homogeneous photocatalysis by photo-Fenton. The pilot plant is made up of compound parabolic collectors specially designed for solar photocatalytic applications. The initial concentration tested with imidacloprid, formetanate and methomyl was 50 and 30 mg/l with diuron, and the catalyst concentrations were 200 mg/l and 0.05 mM with TiO 2 and iron, respectively. Total disappearance of the parent compounds, 90% mineralisation and toxicity reduction below the threshold (EC 50 ) have been attained with all pesticides tested. All these results have contributed to an evaluation of photocatalytic treatment capacity and comments on the main parameters of TiO 2 and Fe separation from the treated water.
Applied Clay Science, 2012
Clay pillared with Al-Fe was synthesized as a catalyst for (photo)-Fenton oxidation of 4-chlorophenol. The catalyst was characterized by X-ray diffraction, nitrogen physisorption, diffuse reflectance UV-VIS spectroscopy and temperature-programmed reduction. The chemical composition, indicating the incorporation of Al and Fe within the clay structure, was determined by ICP-OES. The oxidation of 4-chlorophenol was faster in the UV-A assisted process, followed by VIS-light assisted and "dark" processes. All the processes begin with an induction period, followed by a fast oxidation step. Iron leaching is observed for all the systems and was mainly attributed to proton and reductive dissolution processes. Proton dissolution is very slow and could be responsible for the induction period. The reductive dissolution is induced in the presence of 4-chlorocatechol, the main reaction intermediate. The dissolved iron ions are able to catalyze the homogeneous Fenton-like process. All the experimental findings suggest that a combined heterogeneous-homogeneous mechanism could be envisaged for the studied reaction system.