Calidad de agua de vertientes protegidas en la zona centro de la provincia de Misiones

Tesis para optar al título de Magister Scientiae en Tecnología de los Alimentos, de la Universidad Nacional de Misiones, en 2018Proyectos tecnológicos como las vertientes protegidas, son opciones no convencionales que permiten el acceso al agua en cantidad y calidad a comunidades rurales reducidas. El objetivo del trabajo fue evaluar la calidad de agua de vertientes protegidas de la zona centro de la provincia de Misiones y proporcionar soluciones con tecnologías apropiadas para su mejora. Se realizó un monitoreo anual de parámetros físicos, químicos y microbiológicos en 6 vertientes protegidas y se compararon vertientes antes y después de la protección, utilizando métodos normalizados, el Código Alimentario Argentino y el Manual de la FAO, para consumo humano y riego respectivamente. Se estudió la influencia de tres factores que influyen en la calidad de agua de las vertientes: tipos de suelo, estaciones del año y precipitaciones; además se encontraron correlaciones entre las variables analizadas. Se aplicaron 4 alternativas de tratamiento a utilizar en los puntos de uso del agua. Los resultados de los parámetros físicos y químicos fueron normales, a excepción de pH y turbiedad. El 67% de las vertientes presentó un pH ligeramente menor de lo especificado en el CAA (6,5-8,5), debido a la sobresaturación de CO2 en el agua y 2 vertientes presentaron valores de turbiedad mayores a 3 UNT. Los bajos contenidos de Coliformes Totales (298 NMP/100mL) y Coliformes Fecales (94 NMP/100mL) se solucionarían con el método de filtración simple y desinfección. Los análisis realizados antes y después de la protección evidenciaron la mejora en la calidad de agua, al evitar la contaminación externa. Los tratamientos propuestos con uso de pastillas de disolución rápida, hipoclorito de sodio y ebullición fueron efectivos. Se cuestionan los elevados niveles de cloro libre residual encontrados al aplicar las pastillas de disolución rápida que podrían formar sustancias tóxicas. El método UV se recomienda para los casos en que puedan cumplirse las condiciones de radiación, tiempo y temperatura requeridas.Technological projects such as protected watersheds are unconventional options that allow access to water in quantity and quality to small rural communities. The objective of this work was to evaluate the water quality of protected watersheds in the central area of the province of Misiones and to provide solutions with appropriate technologies for its improvement. Annual monitoring of physical, chemical and microbiological parameters was carried out on 6 protected slopes and comparing slopes before and after protection, using standardized methods, the Argentine Food Code and the FAO Manual, for human consumption and irrigation, respectively. The influence of three factors influencing the water quality of the slopes was studied: types of soils, seasons of the year and rainfall; in addition, correlations were found between the variables analyzed. Four treatment alternatives were applied to the water use points. The results of the physical and chemical parameters were normal, with the exception of pH and turbidity. 67% of the watersheds presented a pH slightly lower than the one specified in the CAA (6,5-8,5), due to the CO2 supersaturation in the water and 2 slopes presented turbidity values greater than 3 UNT. The low content of Total Coliforms (298 NMP / 100mL) and Fecal Coliforms (94 NMP / 100mL) would be solved with the simple filtration and disinfection method. The analyzes performed before and after the protection evidenced the improvement in water quality, by avoiding external contamination. The treatments proposed with the use of slow dissolving tablets, sodium hypochlorite and boiling were effective. The high levels of residual free chlorine found when applying slow-release tablets that could form toxic substances are questioned. The UV method is recommended for cases where the required radiation, time and temperature conditions can be met.EEA Cerro AzulFil: Iwasita, Bárbara Eloisa. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Cerro Azul; Argentin

Understanding the CO Preoxidation and the Intrinsic Catalytic Activity of Step Sites in Stepped Pt Surfaces in Acidic Medium

In order to deepen the knowledge about the origin of the CO preoxidation process and the intrinsic catalytic activity of Pt superficial steps toward CO oxidation, a series of CO stripping experiments were performed on stepped Pt electrodes in acidic medium. For the occurrence of CO preoxidation, it was found that it arises (reproducibly) whenever four interconnected conditions are simultaneously fulfilled: (1) CO adsorption at potentials lower than about 0.2 V; (2) on surfaces saturated with COads; (3) in the presence of traces of CO in solution; (4) in the presence of surface steps. If any of these four conditions is not satisfied, the CO preoxidation pathway does not appear, even though the steps on the electrode surface are completely covered by CO. By controlling the removal of the CO adlayer (voltammetrically), we show that once the CO adlayer has been partially oxidized, the (111) terrace sites of stepped surfaces are released earlier than the (110) step sites. Moreover, if (110) steps are selectively decorated with CO, its oxidation occurs only at potentials ∼150 mV higher than the CO preoxidation peak. Our results systematically demonstrate that step sites are less active to oxidize CO than those ones responsible for the CO preoxidation process. Once the sites responsible for the CO preoxidation are made free, there is no apparent motion of the remaining adsorbed CO layer, suggesting that the activation of the surface controls the whole process, rather than the diffusion of COads toward hypothetically “most active sites”. Voltammetric and chronoamperometric experiments performed on partially covered CO adlayers suggest that adsorbed CO behave as a motionless species during its oxidation, in which the CO adlayer is removed piece by piece. By means of in situ FTIR experiments, the stretching frequency of CO selectively adsorbed on (110) step sites was examined. Band frequency results confirm that those molecules adsorbed on steps are fully coupled with the adsorbed CO on (111) terraces when the surface reaches full coverage.M.J.S. Farias is grateful to the CNPq (Brazil) (grants 200390/2011-2 and 313402/2013-2) for the financial support. G. A. Camara acknowledges financial assistance from CNPq (grants 305494/2012-0 and 405695/2013-6) and FUNDECT (grant 23/200.583/2012). J. M. Feliu thanks the MINECO (Spain) project CTQ2013-44083-P

Electrochemical behaviour of gamma hydroxybutyric acid at a platinum electrode in acidic medium

The electrooxidation of Gamma Hydroxybutyric Acid (GHB) on a polycrystalline platinum electrode is studied by cyclic voltammetry in acidic medium. Two oxidation peaks, A and B, are obtained in the positive scan within the potential range of the double layer region and of the platinum oxide region, respectively. In the negative going potential sweep an inverted oxidation peak with an onset partially overlapping with the tail of the cathodic peak for the reduction of the platinum oxide formed during the anodic scan is obtained (peak C). This inverted peak can be observed at a potential close to +0.2 V (vs Ag/AgCl at pH 2) and separated 0.4 and 0.8 V from the two other oxidation peaks obtained during the anodic scan and in such conditions that the surface is particularly activated to favour this electrochemical process. The response obtained in the electronic current for the different peaks when GHB concentration and scan rate were changed to allows inferring that these are the result of a potential dependent mechanism. The behaviour observed is according with the oxidation of the alcohol group to the corresponding aldehyde and carboxylic acid (succinic acid) as main products

Combined voltammetry and in situ infrared spectroscopy of tetramethylthiourea on gold in aqueous acid solutions

The voltammetric behaviour of tetramethylthiourea (TMTU) dissolved in aqueous perchloric and sulphuric acid solutions on polycrystalline gold combined with in situ Fourier transform infrared reflection absorption spectroscopy (FTIRRAS) was investigated. Conventional and triangular modulated voltammetry and rotating disc electrode data demonstrate the occurrence of two redox surface processes in the potential ranges −0.1 ≤ E ≤ −0.3 V and 0.7 ≤ E ≤ 0.8 V (versus SHE), respectively. These processes would involve the participation of TMTU adsorbates. The redox surface process observed in the range −0.1 to −0.3 V can be related to the electrosorption of TMTU. The absence of infrared absorption bands from these adsorbates agrees with a flat, almost parallel adsorption of TMTU molecules on gold that has been already reported. In the range 0.4 V ≤ E ≤ 0.8 V both electrochemical and spectroscopic data indicate the anodic formation of soluble gold–TMTU complex and tetramethylformamidine disulphide (TMFDS2+) ions presumably via Au(TMTU)+ adsorbates. The kinetics of soluble gold– TMTU complex ion formation is under diffusion control, whereas the formation of TMFDS2+ ions behaves as a rather irreversible process with the anodic slope, derived from current–potential curves, ∂E/∂ log I = 0.120 V decade−1 at 298 K. At E > 1.2 V, the global electro-oxidation of both TMTU and TMFDS2+ species yields carbon dioxide, sulphate ions and carbonyl-containing compounds, as indicated by IR spectra. These reactions involve the participation of oxygen-containing adsorbates produced from water electro-oxidation on gold.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

In situ FTIRRAS study of the electro-oxidation reactions of thiourea and gold in aqueous acid solutions

The electro-oxidation of gold and thiourea (TU) in aqueous acid solutions is investigated by means of in situ FTIRRAS measurements complemented by voltammetry. The formation of soluble species related to the gold(I)-TU complex and TU electrooxidation products is monitored by following the changes in the IR spectra with the applied potential in the range -0.1 -1.5 V. Experimental data show that gold electrodissolution produces soluble [Au(CS(NH2)2)2]2SO4 species. The IR spectrum of solid samples of this complex is reported. The electrodissolution reaction begins at approximately 0.15 V (SHE), concomitantly with the early stages of TU electro-oxidation. The electro-oxidation of TU on gold in acid solutions produces formamidine disulphide (FDS) at potentials below 1.2 V (SHE). The formation of the gold complex and that of FDS are quasi-reversible processes, as revealed by FTIRRAS data. Once the formation of the oxygen-containing layer on gold sets in, the electro-oxidation of TU and FDS yields carbon dioxide, sulphate ions and CN-containing products. Adsorbed sulphate species, which are also detected from 1.2 V upwards, exhibit a band shift of 27 cm-1 V-1.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Extracción de N-P-K de especies aromáticas en suelos rojos

DiapositivasLa demanda de plantas aromáticas se ha incrementado a través de los años. Casi todos estos recursos son explotados de forma extractiva, lo cual pone en riesgo su conservación. Ante esta problemática surge la necesitad de llevarlas a cultivo. Objetivo: Determinar las curvas de absorcion de macronutrientes (N, P, K) y acumulación de biomasa en función de la edad de las plantas. Se trabajó con las siguientes especies: Burrito (Aloysia polystachya), Cedrón (Aloysia citriodora), Salvia blanca (Lippia alba), Melisa (Melissa officinales), Menta (Mentha sp), Peperina (Minthostachys verticillata) y Poleo (Lippia turbinata), en condiciones de campo, en un suelo correspondiente al complejo de series identificada como JNL situado en la EEA INTA Cerro Azul, Misiones.EEA Cerro AzulFil: Bálsamo, Maricel. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Cerro Azul; ArgentinaFil: Iwasita, Bárbara Eloisa. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Cerro Azul; ArgentinaFil: Mazzoni, Ariel Omar. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Bariloche; Argentin

A combined "electrochemical-frustrated Lewis pair" approach to hydrogen activation: surface catalytic effects at platinum electrodes

Herein, we extend our “combined electrochemical–frustrated Lewis pair” approach to include Pt electrode surfaces for the first time. We found that the voltammetric response of an electrochemical–frustrated Lewis pair (FLP) system involving the B(C6F5)3/[HB(C6F5)3]− redox couple exhibits a strong surface electrocatalytic effect at Pt electrodes. Using a combination of kinetic competition studies in the presence of a H atom scavenger, 6-bromohexene, and by changing the steric bulk of the Lewis acid borane catalyst from B(C6F5)3 to B(C6Cl5)3, the mechanism of electrochemical–FLP reactions on Pt surfaces was shown to be dominated by hydrogen-atom transfer (HAT) between Pt, [Pt[BOND]H] adatoms and transient [HB(C6F5)3]⋅ electrooxidation intermediates. These findings provide further insight into this new area of combining electrochemical and FLP reactions, and proffers additional avenues for exploration beyond energy generation, such as in electrosynthesis