Recent Overview of Solar Photocatalysis and Solar Photo-Fenton Processes for Wastewater Treatment (original) (raw)
Related papers
Recent Overview of Solar Photocatalysis and Solar Photo-Fenton.pdf
This literature research, although not exhaustive, gives perspective to solar-driven photocatalysis, such as solar photo-Fenton and TiO 2 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.
Solar photocatalytic degradation of azo-dyes by photo-Fenton process
Dyes and Pigments, 2006
A solar photocatalytic degradation of the azo-dye acid orange 24 was carried out by means of a photo-Fenton reaction promoted by solar energy. The dye degradation was monitored during the experimental runs through UV/Vis absorption as well as COD and TOC concentration determination and toxicity reduction. In most cases, a discoloration higher than 85% was reached using 50 kJ/l of accumulated energy. In the case of the best reaction conditions, a discoloration of up to 95% and a toxicity reduction from 37 to 5 TU were accomplished with 50 kJ/l. In the same experiment, the removal of COD up to 88% and TOC up to 85% was reached after 105 kJ/l. Results consigned in this work are comparable to others reported in literature for different dyes. The reduction on toxicity values obtained by this methodology was most relevant and present dye degradation by the solar photo-Fenton process as an interesting alternative for coupling with biological processes.
Solar photo-Fenton treatment of winery effluents in a pilot photocatalytic reactor
Catalysis Today, 2015
A pilot-scale solar Fenton process has been applied for the treatment of winery wastewater collected during the vinification period. The importance of the experimental variables was investigated at lab-scale experiments through the application of experimental design methodology. The pilot-scale study was conducted on a pilot CPC photocatalytic reactor under natural solar irradiation. The results show that at low catalyst dose (i.e. [Fe 2+ ] = 5 mg L −1 ) mineralization (i.e. ca. 50%) is dependent on the oxidant consumption (i.e. 500 mg L −1 ), irrespective of the excess oxidant present; however, shorter reaction times are required under excess H 2 O 2 , indicating higher reaction rates due to higher availability of oxidant molecules in the bulk liquid. Increasing the catalyst dose enhances the reaction rate due to higher H 2 O 2 decomposition and HO • production. This is corroborated with the lower H 2 O 2 consumption (i.e. 1270 mg L −1 ) occurring at low catalyst, signifying, however, a more effective use of the oxidant (i.e. less oxidant is required to achieve similar mineralization).
Solar heterogeneous and homogeneous photocatalysis as a pre-treatment option for biotreatment
Research on Chemical …, 2007
In this paper, we present pilot-scale solar Photo-Fenton and TiO 2 treatment of a model compound (α-methylphenylglycine) dissolved in 500 mg/l concentration in water. Not only contaminant disappearance and mineralisation were evaluated, but also enhancement of biodegradability. The solar photoreactors, composed of 4.16 m 2 of compound parabolic collectors, had a total volume of 82 l (44.6 l illuminated). Treatment was successful with both Advanced Oxidation Processes (AOPs) tested, but photo-Fenton was shown to be by far more efficient from the kinetic and practical point of view. To find out the conditions for biocompatibility using the AOPs as a pre-treatment, waste water after certain degradation time, unacclimated municipal sludge and mineral nutrients were placed together and evaluated by the Zahn-Wellens (Z-W) test. Biodegradability was enhanced (70% biodegradable) by both AOPs, but photo-Fenton was demonstrated to be more efficient, requiring a treatment time one order of magnitude shorter than TiO 2 . Hydrogen peroxide management for reduced consumption and elimination prior to discharging water to the biotreatment step is also discussed in detail.
The present study is conducted to compare the performance of different oxidation processes such as the solar photo-Fenton, the solar photocatalyst of TiO 2 and solar photocatalyst of TiO 2 /Fenton process for the treatment of petroleum wastewater from Sohar oil refinery (SOR) by a central composite design (CCD) with response surface methodology (RSM). The degradation efficiency is evaluated in terms of chemical oxygen demand (COD) and total organic carbon (TOC) reductions. The solar photocatalyst of TiO 2 /Fenton method improved the performance of photocatalyst TiO 2 in the normal value of pH (7) for petroleum wastewater, therefore no need to adjust pH during this treatment. In acidic conditions pH <7, the solar photo-Fenton process is more efficient than the solar photocatalyst of TiO 2 process, while it is less efficient than the solar photocatalyst of TiO 2 process in alkaline conditions pH >7. The TiO 2 dosage and pH are the two main factors that improved the TOC and COD removal in the solar photocatalyst of TiO 2 /Fenton and the solar photocatalyst of TiO 2 processes while the pH and H 2 O 2 concentration are the two main factors in the solar photo-Fenton process. Keywords: The solar photo-Fenton process; The solar photocatalyst of TiO 2 process; The solar photocatalyst of TiO 2 /Fenton process; The petroleum wastewater; Chemical oxygen demand; Total organic carbon
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.
Evaluation of the combined solar TiO2/photo-Fenton process using multivariate analysis
Water Science and Technology, 2004
The effect of combining the photocatalytic processes using TiO2 and the photo-Fenton reaction with Fe3+ or ferrioxalate as a source of Fe2+ was investigated in the degradation of 4-chlorophenol (4CP) and dichloroacetic acid (DCA) using solar irradiation. Multivariate analysis was used to evaluate the role of three variables: iron, H2O2 and TiO2 concentrations. The results show that TiO2 plays a minor role when compared to iron and H2O2 in the solar degradation of 4CP and DCA in the studied conditions. However, its presence can improve TOC removal when H2O2 is totally consumed. Iron and peroxide play major roles, especially when Fe(NO3)3 is used in the degradation of 4CP. No significant synergistic effect was observed by the addition of TiO2 in this process. On the other hand, synergistic effects were observed between FeOx and TiO2 and between H2O2 and TiO2 in the degradation of DCA.