DEGRADACIÓN SELECTIVA DE FENOL UTILIZANDO CATALIZADORES DE TiO2 DOPADO CON METALES

Los métodos convencionales de tratamiento de efluentes industriales no pueden remover eficazmente muchos contaminantes, con efectos negativos en el medio ambiente y la salud humana. Una alternativa es la utilización de procesos avanzados de oxidación (PAO). En los últimos años se han evaluado en una amplia variedad de condiciones para la remediación y detoxificación de aguas especiales, generalmente en pequeña o mediana escala, con buenos resultados. La irradiación con luz UV o visible conduce a varios métodos oxidativos, en los que generalmente la eficiencia de degradación es muy buena. En particular, el TiO2, se encuentra dentro de los materiales con propiedades idóneas para llevar a cabo reacciones fotosensibilizadas. Por otro lado, entre los contaminantes biorecalcitrantes, los fenoles y sus derivados son de relevancia ambiental por su toxicidad ya que presentan capacidad peroxidativa, son hematotóxicos y hepatotóxicos y pueden provocar mutagénesis y carcinogénesis en los humanos y otros organismos vivos. De acuerdo a la legislación y reglamentación de la República Argentina se categoriza a los fenoles y compuestos fenólicos, como residuos especiales o peligrosos que deben ser controlados (Ley Nacional Nº 24051). El objetivo general de este trabajo es encontrar nuevos catalizadores y/o fotocatalizadores para la destrucción selectiva de contaminantes en efluentes acuosos. Se plantea modificar las propiedades del TiO2 para aumentar la eficiencia y especificidad en la degradación de compuestos fenólicos, en presencia de la materia orgánica natural. Se espera que estos estudios permitan la optimización del proceso, para su potencial aplicación en descontaminación. Los objetivos específicos son: 1. Síntesis y caracterización de catalizadores de TiO2 dopados con metales. 2. Evaluación de la eficiencia y la selectividad de los materiales para la degradación de fenol. 3. Estudio de estrategias de inmovilización de los catalizadores. 4. Optimización de las condiciones de reacción para la degradación de fenol con los catalizadores inmovilizado

Diversidad catabólica de un suelo crónicamente contaminado con hidrocarburos policíclicos aromáticos (PAHs) post estrés acido

El conocimiento del rol de los organismos indígenas en suelos contaminados es esencial para el desarrollo y aplicación de tecnologías de biorremediación exitosas. Las zonas petroquímicas de la provincia de Buenos Aires son un buen ejemplo de suelos expuestos crónicamente a hidrocarburos. Existen diferentes opiniones sobre si la contaminación con hidrocarburos reduce la diversidad microbiana conllevando a la perdida de resiliencia de las comunidades microbianas del suelo. Muchos microorganismos del suelo presentan tasas de respiración bajas, que pueden incrementarse al ser estimulados con sustratos fácilmente asimilables. Algunos autores sostienen que la respiración inducida por sustrato (SIR) es proporcional al tamaño original de la biomasa microbiana del suelo. SIR permite evaluar la diversidad catabólica del suelo estableciendo un perfil fisiológico de la comunidad. La diferencia con la técnica de Biolog radica en que en la primera el sustrato es adicionado directamente en el suelo evitando así los problemas que representan la inoculación de microorganismos de suelo en un medio semi-solido

Composting and biostimulation as strategies for chronically hydrocarbon contaminated soil recovering

The concept of treating PAH-contaminated soil by means of co-composting with organic materials or by mixing soil with mature compost has proved to be effective in the degradation of PAHs at the laboratory and/or field-scales. A contaminated soil was collected from a petrochemical area, near La Plata. It was characterized by a very low biological activity, probably due to the hydrocarbon content (4000ppm of aliphatic and 300ppm of PAH). The microbial populations were similar to those determined in pristine soils near of the area. The goals of our study were to investigate the potential of composting related practices in the biological recovery of the contaminated soil. Composting treatment (CT). A sample of soil was treated with amendment in ratio 0,7:0,3 (w/w) and the resulting material was mixed with bulking agent. It was incubated at room temperature in reactors of 34L during 4 months. The moisture was adjusted to 45%. Biostimulation treatment (BT). A sample of soil was mixed with compost (prepared 30 days before use) in ratio 0,7:0,3 (w/w) and it was incubated during 1 month at 25°C. This experiment was carried out in triplicate trays. The moisture was adjusted to 45%. Control reactors (S). Contaminated soil microcosm with any additive was used as control system. Microbial population densities. Viable heterotrophic bacterial count was performed using R2-Agar. The value for CT was higher than for S whereas the BT did not show differences with S. Fungi were enumerated on Rose Bengal Agar. For both treatments the counts were higher than for S. Phosphorus solubilising bacteria was enumerated on PIM media: the count in CT was higher than in S while BT did not show any difference. The most probable number of aromatic hydrocarbon-degrading bacteria was determined using mineral salts medium with the addition of a mix of PAHs. No differences were detected after both treatments in the hydrocarbon degrading bacteria counts. Biological Activity. Dehydrogenase assays were performed using soluble tetrazolium salt as an artificial acceptor. Both treatments produced significant increase in the dehydrogenase activity that was higher than those determined in S, during all the incubation time. Toxicity assays. Seed germination test using Lactuca Sativa was performed on water extracts. Only the CT increased significantly the germination. Hydrocarbons concentrations. The extracts were analyzed by GC-FID. No significant decrease was detected after 1 and 4 months respectively. Molecular analysis. PCR-DGGE analysis was performed. Both treatments produced a significant diversity increase of the populations. A successful composting treatment was evidenced by the visible changes in the matrix aspect in the CT treatment, in agreement with the higher bacterial counts, biological activity and percentage of seed germination. Although this treatment did not reduce significantly the hydrocarbon concentration, it was able to improve the soil quality in the experiment time

Chloride anion effect on the advanced oxidation processes of methidathion and dimethoate: role of Cl2(center dot-) radical

NOTICE: this is the author’s version of a work that was accepted for publication in Water Research. Changes resulting from the publishing process, such as peer review, editing, corrections,structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in WATER RESEARCH [VOL 47, ISSUE 1, (January 2013)] DOI 10.1016/j.watres.2012.10.018¨ IWA Publishing : Set statement to accompany deposit, "©IWA Publishing 2013. The definitive peer-reviewed and edited version of this article is published in Water Research 47 1 351-362 2013 DOI 10.1016/j.watres.2012.10.018 and is available at www.iwapublishing.com."The reaction of phosphor-containing pesticides such as methidathion (MT) and dimethoate (DM) with dichloride radical anions (Cl-2(center dot-)) was investigated. The second order rate constants (1.3 +/- 0.4) x 10(8) and (1.1 0.4) x 10(8) M-1 s(-1) were determined for the reaction of Cl-2(center dot-) with MT and DM, respectively. A reaction mechanism involving an initial charge transfer from the sulfide groups of the insecticides to Cl-2(center dot-) is proposed and supported by the identified transient intermediates and reaction products. The formation of chlorinated byproducts was determined. The unexpected consequences of an efficient Cl-2(center dot-) activity towards MT and DM on the degradation capacity by Advanced Oxidation Procedures applied to polluted waters containing the insecticides and Cl- anions is discussed. (C) 2012 Elsevier Ltd. All rights reserved.This research was financially supported by Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET), Agencia Nacional de Promocion Cientifica y Tecnologica (Argentina, project PICT 2007 number 00308), and Agencia Espanola de Cooperacion Internacional (project A/8199/07). MCG, JAR and PC are research members of Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET), Argentina. D.O.M. is a research member of CICPBA, Argentina. This research was supported by the grant PIP 112-200801-00356 from CONICET.Caregnato, P.; Rosso, JA.; Soler Escoda, JM.; Arques Sanz, A.; Martire, DO.; González, MC. (2013). Chloride anion effect on the advanced oxidation processes of methidathion and dimethoate: role of Cl2(center dot-) radical. Water Research. 47(1):351-362. https://doi.org/10.1016/j.watres.2012.10.018S35136247

Microbiological diversity and functionality of a chronically hydrocarbon Contaminated soil post chemistry oxidation

In situ chemical oxidation (ISCO) is increasingly used for the remediation of soil containing organic contaminants such as polycyclic aromatic hydrocarbons (PAH). However, the impact on the soil microbial community has not been thoroughly elucidated. The aim of the study was to analyze the effect of the ammonium persulfate application followed by a bioremediation process on the matrix, microbial community and the PAH removal of the soil. Chronically contaminated soil (S) was collected from a petrochemical area (214 ppm PAH). Ammonium persulfate (PS) was sprayed as aqueous solution on contaminated soil by three additions (1% wt/wt) every two days and incubated at 30°C ( SOx). S and SOxwere further incubated at 25°C, 25% moisture content, mixed and monitored for 28 days. These microcosms were named SB and SOxB respectively. The PAH concentrations were determined by GC-FID. No PAH elimination was detected in SB. A significant elimination (35%) was observed in SOx while no additional decrease was detected SOxB. Alkaline extraction was performed to obtain an aqueous solution of natural organic matter of the soil. The Total Organic Carbon contents (TOC, TOC-5000 Shimadzu) and the Fluorescence Excitation Emission Matrixes (FEEM, Perkin-Elmer LS-50B) were determined for Sand SOx. FEEM of Spresents two zones of emission. The zone on lexc ~ 320 nm and lem ~ 440 nm could be assigned to the presence of PAH. These emissions were absent in SOx in line with the PAH elimination, and a significant increment on TOC values was also detected. A significant decrease in the microbial counts was observed in SOx. The subsequent bioremediation only increased the heterotrophic bacterial population which suggested that the available organic carbon allowed the growth of this population. To evaluate the microbial activity, four enzymes lipase, aril sulphatase, urease and protease were analyzed. All of them were slightly expressed in S microcosms and only lipase activity was significantly increased in SOx. Seed germination test using Lactuca Sativa on water extracts was performed to evaluate the soil toxicity. The toxicity detected in S was exacerbated in SOx and it was not reversed in SOxB. The dynamics of the bacterial community structure, analyzed by 16S rRNA PCR DGGE, evidenced a great change due to the oxidation. The clustering among the S and SOxB profile bands suggested the tendency of SOxB to recover the original structure. The pyrosequence analysis showed that members of actinobacteria, bacilli and acidimicrobiia classes were the predominant populations in SOx. Members of the actinobacteria became the dominant population in SOxB. This group was considered as k-strategist microorganisms and a major component in the later stages of successions in bioremediated soils. The initial PAH elimination provoked by PS was not followed by an additional elimination under bioremediation condition. However, a microbial succession of generalist populations was observe

Kinetic study of the oxidation of phenolic derivatives of α,α,α-trifluorotoluene by singlet molecular oxygen [O₂(¹Δg)] and hydrogen phosphate radicals

The oxidation kinetics and mechanism of the phenolic derivatives of α,α,α-trifluorotoluene, 2-trifluoromethylphenol, 3-trifluoromethylphenol (3-TFMP), 4-trifluoromethylphenol and 3,5-bis(trifluoromethyl)phenol, mediated by singlet molecular oxygen, O2(¹Δg), and hydrogen phosphate radicals were studied, employing time-resolved O2(¹Δg) phosphorescence detection, polarographic determination of dissolved oxygen and flash photolysis. All the substrates are highly photo-oxidizable through a O2(¹Δg)-mediated mechanism. The phenols show overall quenching constants for O2(¹Δg) of the order of 106 M⁻¹ s⁻¹ in D2O, while the values for the phenoxide ions in water range from 1.2 × 10⁸ to 3.6 × 10⁸ M⁻¹ s⁻¹. The effects of the pH and polarity of the medium on the kinetics of the photo-oxidative process suggest a charge-transfer mechanism. 2-Trifluoromethyl-1,4-benzoquinone is suspected to be the main photo-oxidation product for the substrate 3-TFMP. The absolute rate constants for the reactions of HPO4•− with the substrates range from 4 × 10⁸ to 1 × 10⁹ M⁻¹ s⁻¹. The 3-trifluoromethylphenoxyl radical was observed as the organic intermediate formed after reaction of 3-TFMP with HPO₄•⁻, yielding 2,2’-bis(fluorohydroxymethyl)biphenyl-4,4’-diol as the end product. The observed results indicate that singlet molecular oxygen and hydrogen phosphate radicals not only react at different rates with the phenols of α,α,α-trifluorotoluene, but the reactions also proceed through different reaction channels.Instituto de Investigaciones Fisicoquímicas Teóricas y AplicadasLaboratorio de Estudio de Compuestos Orgánico

Remediación de un suelo crónicamente contaminado con Hidrocarburos mediante oxidación química y compost

La biorremediación tiene gran aceptación en la recuperación de suelos contaminados con hidrocarburos a pesar de sus limitaciones cuando se trata de mezclas complejas con policíclicos aromáticos (PAH), como la baja velocidad de biodegradación y baja biodisponibilidad. La bioestimulación con compost maduro, y la oxidación química directa del suelo son estrategias que podrían favorecer la accesibilidad al PAH, promoviendo su degradación. Con el fin de estudiar el efecto combinado de ambas estrategias, fueron preparados microscosmos de suelo crónicamente contaminado con PAHs (270ppm) para evaluar el efecto del agregado de compost (3g:7g); de la oxidación con persulfato de amonio y la acción combinada de oxidación y posterior estimulación con compost. El tratamiento oxidativo consistió en 3 aplicaciones del oxidante (3,5g%), con 24% de humedad a 30°C. Los microcosmos fueron incubados a 25°C durante 30 días. El suelo en estudio evidenció alta densidad de poblaciones bacterianas pero no actividad deshidrogenasa. La estimulación con compost incrementó la actividad deshidrogenasa y redujo parcialmente la toxicidad del sistema, sin disminuir significativamente la concentración total de PAHs. El tratamiento oxidativo redujo significativamente la concentración de PAHs y la densidad de poblaciones microbianas, aumentando la toxicidad. El posterior agregado de compost recuperó las poblaciones microbianas sin reducir los índices de toxicidad respecto del suelo original. La recuperación biológica, aunque parcial, dado que la actividad deshidrogenasa aumentó solo un 10% respecto de la bioestimulación, fue correspondida con un 70% de eliminación de PAH en 30 días

Exploring the effect of composting technologies on the recovery of hydrocarbon contaminated soil post chemical oxidative treatment

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous organic pollutants that contaminate large areas. They are mainly released to environment by anthropogenic activities principally due to the petrochemical industry. The low biodegradation rate characteristic of PAHs in aged contaminated soils could be overcome trough the chemical oxidation. In this study, composting with the soil and stimulation with mature compost were the strategies applied in soil microcosms after chemical oxidation with ammonium persulfate in a PAHs chronically contaminated soil. A 29% of PAHs elimination and an increase of their bioavailability were found after chemical oxidation with ammonium persulfate. Due to the oxidative treatment the total bacterial and the gram-positive population PAH dioxygenase genes were significantly reduced and no gram-negative PAHs degraders were detected. The following application of organic amendments produced a higher increase in total bacteria and recovery of the degrading population of GP PAH after one year of treatment, in comparison with the pre-oxidized soil bioremediation, only promoted by irrigation and aeration. Also a significant increase in the content of bioavailable PAHs was observed. However, from both composting strategies only the stimulation with mature compost led to a net PAHs removal. Taking into account the residual dissolved total carbon and humification degree (E4/E6 ratio), it was attributed to the preferential consumption of more easily degradable compounds than hydrocarbons the low removal efficiency observed after one year of treatment. Due to the high bioavailable content of PAH and the residual sulfate, long-term treatments will require careful monitoring to reduce environmental risk