Alberto Álvarez-Gallegos

Photoelectrocatalytic inactivation of fecal coliform bacteria in urban wastewater using nanoparticulated films of TiO2 and TiO2/Ag

ABSTRACT Photocatalysis has shown the ability to inactivate a wide range of harmful microorganisms with traditional use of chlorination. Photocatalysis combined with applied bias potential (photoelectrocatalysis) increases the efficiency of photocatalysis and decreases the charge recombination. This work examines the inactivation of fecal coliform bacteria present in real urban wastewater by photoelectrocatalysis using nanoparticulated films of TiO2 and TiO2/Ag (4%w/w) under UV light irradiation. The catalysts were prepared with different thicknesses by the sol-gel method and calcined at 400°C and 600°C. The urban wastewater samples were collected from the sedimentation tank effluent of the university sewage treatment facility. The rate of bacteria inactivation increases with increasing the applied potential and film thicknesses; also, the presence of silver on the catalyst surface annealed at 400°C shows better inactivation than that at 600°C. Finally, a structural cell damage of Escherichia coli (DH5α), inoculated in water, is observed during the photoelectrocatalytic process.

Recent Overview of Solar Photocatalysis and Solar Photo-Fenton Processes for Wastewater Treatment

This literature research, although not exhaustive, gives perspective to solar-driven photocatalysis, such as solar photo-Fenton and 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.

Treatment of industrial effluents by electrochemical generation of H2O2 using an RVC cathode in a parallel plate reactor

ABSTRACT Electrochemical techniques have been used for the discolouration of synthetic textile industrial wastewater by Fentons process using a parallel plate reactor with a reticulated vitreous carbon (RVC) cathode. It has been shown that RVC is capable of electro-generating and activating H2O2 in the presence of Fe2+ added as catalyst and using a stainless steel mesh as anode material. A catholyte comprising 0.05 M Na2SO4, 0.001 M FeSO4.7H2O, 0.01 M H2SO4 and fed with oxygen was used to activate H2O2.The anolyte contained only 0.8 M H2SO4. The operating experimental conditions were 170 mA (2.0 V < ΔECell < 3.0 V) to generate 5.3 mM H2O2. Synthetic effluents containing various concentrations (millimolar – mM) of three different dyes, Blue Basic 9 (BB9), Reactive Black 5 (RB5) and Acid Orange 7 (AO7), were evaluated for discolouration using the electro-assisted Fenton reaction. Water discolouration was measured by UV–VIS absorbance reduction. Dye removal by electrolysis was a function of time: 90% discolouration of 0.08, 0.04 and 0.02 mM BB9 was obtained at 14, 10 and 6 min, respectively. In the same way, 90% discolouration of 0.063, 0.031 and 0.016 mM RB5 was achieved at 90, 60 and 30 min, respectively. Finally, 90% discolouration of 0.14, 0.07 and 0.035 mM AO7 was achieved at 70, 40 and 20 min, respectively. The experimental results confirmed the effectiveness of electro-assisted Fenton reaction as a strong oxidizing process in water discolouration and the ability of RVC cathode to electro-generate and activate H2O2 in situ.

Elimination of bio-refractory chlorinated herbicides like atrazine, alachlor, and chlorbromuron from aqueous effluents by Fenton, electro-Fenton, and peroxi-coagulation methods

AbstractAlachlor, atrazine (broad-leaf herbicides), and chlorbromuron (photosynthesis inhibitor) have been used worldwide to control weeds in crops. Their extensive use have led to widespread contamination of soils, and water which has consequently led to increasing concern about the environmental fate of these substances, since these herbicides are persistent in the environment and exhibit relatively slow rate of decomposition. Several advanced oxidation processes have been used to degrade such bio-refractory organic contaminants present in wastewater. The Fenton process is classified among these processes and has been used for the removal of many hazardous organics from wastewater efficiently. This study reports the removal of alachlor, atrazine, and chlorbromuron from aqueous effluents by classical Fenton, electro-Fenton, peroxi-coagulation, and photoperoxi-coagulation processes in slightly acidic aqueous solutions. A UV lamp was used to assist the peroxi-coagulation process. Herbicide concentration de...

Fenton Process Coupled to Ultrasound and UV Light Irradiation for the Oxidation of a Model Pollutant

The Fenton process coupled to photosonolysis (UV light and Us), using Fe2O3 catalyst supported on Al2O3, was used to oxidize a model pollutant like acid green 50 textile dye (AG50). Dye degradation was followed by AG50 concentration decay analyses. It was observed that parameters like iron content on a fixed amount of catalyst supporting material, catalyst annealing temperature, initial dye concentration, and the solution pH influence the overall treatment efficiency. High removal efficiencies of the model pollutant are achieved. The stability and reusability tests of the Fe2O3 catalyst show that the catalyst can be used up to three cycles achieving high discoloration. Thus, this catalyst is highly efficient for the degradation of AG50 in the Fenton process.

Modeling methylene blue oxidation by means of Fenton chemistry enhanced by UV irradiation at mild conditions

AbstractTaking into account that Fenton chemistry can be enhanced under UV radiation, a systematic activation of different H2O2 concentrations (7–50 mM) in 0.05 M Na2SO4 (pH 2 adjusted with H2O4) was carried out, in the presence of UV/Fe2+ in a photochemical reactor. From the experimental results, a simple empirical correlation between the H2O2 activation velocity (AV) and its concentration was derived, as a result, a chemical model for the production was obtained. Considering that the attractiveness of the Fenton chemistry is its near-stoichiometric generation of a strong oxidant, it is possible to model the oxidation of organic matter under mild conditions. In this way, the fraction of H2O2 produced/consumed provides a measure of the efficiency of the oxidation process. The chemical model was tested in the photochemical reactor with several methylene blue (MB) concentrations (0.1–0.3 mM). Experimentally and theoretically, it was found that 0.1, 0.2, and 0.3 mM MB can be oxidized in 85, 90, and 100 min, ...