Photocatalytic activation of peroxymonosulfate using ilmenite (FeTiO3) for Enterococcus faecalis inactivation

In this work, a raw and low cost mineral, ilmenite (FeTiO3), has been tested for the first time as a photocatalyst paired with peroxymonosulfate (HSO5-; PMS) for the inactivation of Enterococcus faecalis as an alternative to conventional treatments to disinfect wastewater for reuse. The influence of some operational parameters such as reagent dosage, catalyst concentration, initial pH, or flow rate was also studied and optimized. After several tests, the scarce pure photoactivity under UV-A was remarked by ilmenite because of its high iron content, which favors photogenerated charge recombination. However, ilmenite activity was highly promoted when combined with low concentrations of PMS and UV-A light, reaching total inactivation of Enterococcus faecalis in 120 min. Quenching tests were performed using methanol, tert-butyl alcohol, furfuryl alcohol, and Cu(II) to assess the main reactive species involved in the disinfection process determining the critical role of both HO·and SO4·- radicals in the process. Finally, the influence of the water matrix was also evaluated by studying the effect of water hardness and the presence of nutrients on the system. Overall, the PMS/Ilmenite/UV-A system yielded promising results with a total removal of Enterococcus faecalis in 120 min. However, it also showed the need for further study and understanding of the disinfection mechanism to achieve the same level of performance in real wastewaterPGM acknowledges Escuela Técnica Superior de Ingenieros Industriales (UPM) for the project ETSII-UPM20–03. SGR acknowledges UPM for the predoctoral contract granted within the ’Programa Propio’. JRC acknowledges Comunidad de Madrid for funding the research project IN_REUSE (APOYO-JOVENES-X5PKL6–88-KZ46KU), and also by the pluriannual agreement with the Polytechnic University of Madrid in the line of action Programme of Excellence for University Teaching Staf

Nitrate removal in saline water by photo-reduction using natural FeTiO as catalyst

As climate change progresses, there is an increasing interest on the use of non-conventional water sources such as brackish or saline waters. Nowadays, the main threat in Europe detected in these waterbodies is nitrate contamination. Within the multiple available methods studied for nitrate reduction, photocatalysis presents promising results, but this technology has not yet been tested in saline water. This work tackles the elimination of nitrate ([NO3−] =50 mg/L) in brackish and saline water ([sea salt] = 5–33 g/L) using ilmenite as photocatalyst and oxalic acid as an environmental-friendly reducing agent. The main challenge when working in saline water is to overcome oxalic acid scavenging by Ca2+ present in the water matrix. This can be solved either working at over stoichiometric concentrations of oxalic acid (≈300% stoich. dose) or acidifying the reaction media. The addition of hydrochloric acid ensures the protonation of oxalic acid, reducing drastically its precipitation as CaC2O4. Working at [C2O42−] = 180 mg/L, [FeTiO3] = 450 mg/L and [HCl 37%] = 13 mM, 73% total nitrogen (TN) elimination was reached after 420 min. Reaction temperature was also evaluated in the range of 20–80 °C, which allowed to calculate the Ea=9.8 kJ/mol. Finally, the effect of dissolved O2 on the TN reduction was assessed. Overall, photocatalytic nitrate reduction presents itself as a feasible technology regardless of the water salinit

Practicando Ingeniería Química: Prácticas colaborativas de bajo coste para grupos numerosos

Elaboración de un catálogo de prácticas de laboratorio de bajo coste para trabajar los fundamentos de ingeniería química con grupos numerosos, usando metodologías activas de aprendizaje para incrementar la motivación de los estudiantes.Depto. de Ingeniería Química y de MaterialesFac. de Ciencias QuímicasFALSEsubmitte

Aplicación de la fotocatálisis solar a la degradación de contaminantes orgánicos en fase acuosa con catalizadores nanoestructurados de TiO2

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Aplicación de la fotocatálisis solar a la degradación de contaminantes orgánicos con catalizadores nanoestructurados de TiO2

Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Química Física Aplicada. Fecha de lectura: 09-07-201

Influence of water matrix on the photocatalytic degradation of pesticides

Trabajo presentado en el ANQUE.ICCE.BIOTEC - Congress on Chemistry, Chemical Engineering and Biotechnology, celebrado en Madrid del 01 al 04 de julio de 2014.In the beginning of the 21st century, mankind must face the problem of the availability water as an important threat given that demand of water has increased with population growth, industrialization, and expansion of irrigated agriculture in recent years. Therefore, the increasingly stringent wastewater regulations and the growing demand for water recycling have generated a need for more efficient technologies to remove pollutants from aqueous effluents. So, there is a growing interest in developing cheaper and improved technologies that make industrial development and environmental protection compatible, such as AOPs which are emerging as promising solutions. Among them, one of the most frequently investigated in recent years is the photocatalytic heterogeneous technology which is especially attractive when polluted effluents are characterized by low or moderate organic charges and when solar irradiation can be used as the primary source of energy. Heterogeneous photocatalytic oxidation process, employing semiconductors such as TiO2 and UV light, has proved to be a promising technology for the degradation of persistent organic pollutants such as pesticides, producing more biodegradable by-products. Actually, in the last decades the exponential increase of intensive agriculture in the Mediterranean area has caused an important pollution of water resources with pesticides. Therefore, the present work analyses the photocatalytic activity of some commercial TiO2 catalysts in the photodegradation of four pesticides classified by the EU as priority pollutants: Diuron, Alachlor, Isoproturon and Atrazine, and the effect of two water matrix compositions on the final photoefficiency.Peer Reviewe

Phenol photodegradation with oxygen and hydrogen peroxide over TiO2 and Fe-doped TiO2

Photodegradation of phenol was investigated with two types of oxidant agents in water, oxygen and hydrogen peroxide, at two different reaction pH with a series of nanosized iron-doped anatase TiO2 catalysts with different iron contents. The catalysts have been prepared by a sol-gel/microemulsion method. Firstly, iron-doped titania catalysts were studied with respect to their activity behavior when oxygen was used as oxidant agent in the photocatalytic degradation of aqueous phenol in comparison with un-doped reference catalysts. Secondly, two catalysts (TiO2 and 0.7 wt.% Fe-doped TiO2) were selected to extend the study for the employment of hydrogen peroxide as oxidant at different concentrations and two initial reaction pHs. An enhancement of the photocatalytic activity is observed only for relatively low doping level (ca. 0.7 wt.%) in catalyst calcined at 450 °C preferably using hydrogen peroxide as oxidant agent which is attributable to the partial introduction of Fe3+ cations into the anatase structure. Nevertheless, it has been demonstrated that catalyst surface properties can play an important role during phenol photodegradation process on the basis of the analysis of differences found in the photoactivity as a function of reaction pH. © 2008.The authors would like to thank the MEC projects CTQ2004-03409/BQU, CTQ2006-15600/BQU and CTM2007-60577/TECNO and CSIC (project PIF 200420F0280) for financial support

Characterization of the gas effluent in the treatment of nitrogen containing pollutants in water by Fenton process

This work evidences for the first time the production of CO and NOx during the removal of nitrogen containing pollutants in water by Fenton Process, the most popular method for Advanced Oxidation Processes. Four representative nitrogen containing pollutants were selected, viz. aniline, 4-nitrophenol, pyridine and monoethanolamine. The gas effluent accumulated after 3 h of reaction at 90 °C and 3 bar was analysed. In all cases, the carbon and nitrogen mass balance was assessed. Also, an on-line off-gas analysis system was set up to monitor the off-gas variation of CO and CO2 from the beginning of the reaction. CO2 was the major component of the gas effluent. It was progressively produced upon oxidation. In contrast, CO was detected in fairly lower amounts and it was immediately produced after H2O2 injection, due to the rupture and opening of the aromatic ring. The CO formation was more favorable upon degradation of aromatic than aliphatic compounds, or when the nitrogen was in the aromatic ring, as in the case of pyridine. The nitrogen functional groups were majorly transformed into NH4+ and NO3−, while NOx was detected in low amounts (<1 mg/m3) and favoured in presence of single bondNO2 group. These results highlight the importance of monitoring the gas phase generated in the treatment of high-loaded wastewater by AOPs in order to guarantee the environmental sustainability of the processes.MINECODepto. de Ingeniería Química y de MaterialesFac. de Ciencias QuímicasTRUEpu

Solar Assisted Photodegradation of Isoproturon: Recovery and Reuse of Titania Catalysts

Trabajo presentado en el 8th European Meeting on Solar Chemistry and Photocatalysis, celebrado en Salónica (Grecia) del 25 al 28 de Junio de 2014.Heterogeneous Photocatalysis, using TiO2 is one of the most successful applications to degrade moderate charges of recalcitrant pollutants, such as pesticides, in ambient conditions. However, catalyst efficiency and recovery after the photocatalytic processes are key challenges that have limited the practical deployment of TiO2 catalysts in wastewater applications. In this context, the present work analyzes the photo-efficiency of two titania catalysts in the solar light assisted photodegradation of isoproturon, and their reuse in two consecutive cycles, where titania catalysts were easily recovery by sedimentation and no catalyst deactivation was observed.This work have been supported by the Spanish Plan Nacional I +D+I throught the projet CTM2010-14883/TECNO.Peer Reviewe

Photocatalytic degradation of phenol and isoproturon: Effect of adding an activated carbon to titania catalyst

An integrated process based on combination of adsorption, with a commercial activated carbon (AC), and heterogeneous photocatalysis, with a home-made titania catalyst (TiEt), has been studied in phenol and isoproturon removal. In this work, different physical mixtures of TiEt and AC catalysts were first studied in phenol photodegradation in order to optimize the TiEt/AC concentration ratio. In this sense, a higher degree of mineralization and an improvement of phenol photodegradation were reached with a 500/100 TiEt/AC mixture (500 mg L−1 TiO2: 100 mg L−1 AC) in the same photoassisted reactor in ambient conditions. The best photo-efficiency found with this TiEt/AC physical mixture can be well explained by means of a synergistic effect between both catalysts, where the activated carbon and titania particles interaction provides the formation of an active common contact interphase between both materials, and part of the adsorbed compounds on AC surface are photo-oxidized by the active species photogenerated in titania particles under irradiation conditions. Nevertheless, the higher photo-efficiency found during isoproturon photo-oxidation, when AC was combined with TiO2 in aqueous suspensions, is better related to an associative phenomena where an important adsorption step with the commercial AC is followed by photo-oxidation with the home-made titania catalyst, leading to a moderate improvement in TOC removal efficiency.This work has been supported by the Spanish Plan Nacional de I+D+i through the project CTM2010-14883/TECNO. Jaime Carbajo thanks to the Spanish Ministerio de Economía y Competitividad (MINECO) for his FPI grants, and Patricia Garcia-Muñoz thanks CSIC and SECAT for her initial research grants.Peer Reviewe