Avaliação do tratamento eletroquímico (direto e indireto) como alternativa de degradação do corante azul de metileno

Textile industry has been a cause of environmental pollution, mainly due to the generation of large volumes of waste containing high organic loading and intense color. In this context, this study evaluated the electrochemical degradation of synthetic effluents from textile industry containing Methylene Blue (AM) dye, using Ti/IrO2-Ta2O5 and Ti/Pt anodes, by direct and indirect (active chlorine) electrooxidation. We evaluated the influence of applied current density (20, 40 and 60 mA/cm2 ), and the presence of different concentrations of electrolyte (NaCl and Na2SO4), as well as the neutral and alkaline pH media. The electrochemical treatment was conducted in a continuous flow reactor, in which the electrolysis time of the AM 100 ppm was 6 hours. The performance of electrochemical process was evaluated by UV-vis spectrophotometry, chemical oxygen demand (COD) and total organic carbon (TOC). The results showed that with increasing current density, it was possible to obtain 100 % of color removal at Ti/IrO2-Ta2O5 and Ti/Pt electrodes. Regarding the color removal efficiency, increasing the concentration of electrolyte promotes a higher percentage of removal using 0,02 M Na2SO4 and 0,017 M NaCl. Concerning to the aqueous medium, the best color removal results were obtained in alkaline medium using Ti/Pt. In terms of organic matter, 86 % was achieved in neutral pH medium for Ti/Pt; while a 30 % in an alkaline medium. To understand the electrochemical behavior due to the oxygen evolution reaction, polarization curves were registered, determining that the presence of NaCl in the solution favored the production of active chlorine species. The best results in energy consumption and cost were obtained by applying lower current density (20 mA/cm2 ) in 6 hours of electrolysis.

Avaliação das condições de precipitação do azul da Prússia sobre pó de grafite visando o desenvolvimento de eletrodos de pasta de carbono para a quantificação de nitrito

An amperometric FIA method for nitrite quantification based on nitrite electroreduction and employing a carbon paste electrode (CPE) chemically modified with iron hexacyanoferrate (HCF) as an amperometric detector was developed. The influence of experimental conditions on the preparation of the electrode materials was evaluated and the materials obtained in each study were used for the development of modified electrodes. The electrochemical sensors were prepared by a fast, simple, and inexpensive procedure, and the long-term performance of the electrodes were quite satisfactory as the stability was maintained over one year. HCF was an effective redox mediator for nitrite electroreduction in acidic media, allowing nitrite detection at +0.2 V vs. Ag/AgClsat, which is a potential free of possible interfering species that are normally present in food and water samples. The electrochemical cell used in the FIA system was similar to a batch injection analysis cell, enabling recirculation of the carrier solution. This is an attractive feature because it allows the use of a high flow rate (6 mL min-1) leading to high sensitivity and analysis speed, while keeping reagent consumption low. The proposed method had a detection limit of 9 μmol L-1 and was successfully employed for nitrite quantification in spiked water and sausage samples. The obtained results were in good agreement with those provided by the spectrophotometric official method. At a 95 % confidence level it was not observed statistical differences neither in nitrite content nor in the precision provided by both methods. The experimental conditions for the synthesis of HCF were optimized and the best electrode material was prepared by mixing FeCl3, K4[Fe(CN)6] and carbon powder subjected to an acid and thermal treatment (400 ºC), followed by ultrasonic agitation at 4 °C. This material was used to construct an electrode with improved analytical performance to reduce nitrite, which presented greater stability compared to HCF film electrodeposited on the EPC, showing that the preparation procedure of the electrode material is an effective strategy for the development of HCF modified electrodes.

En memoria de la arquitectura : Túnel Azul (ca.1975-2007)

Este artículo hace parte de la revista Papel de colgadura de la Facultad de Derecho y Ciencias Sociales de la Universidad Icesi de Cali, es una publicación de difusión y agitación cultural. La revista nace de la pasión por la música, los libros, las ilustraciones, el graffiti, los cómics, la web, la fiesta, el cine, la cafeína y de las tardes de tertulia con empanadas y cerveza, que circula en versión impresa dos veces al año, pero su versión digital se actualiza con mayor frecuencia.

Mujeres en situaci?n de desplazamiento forzado por la violencia frente al ejercicio de sus derechos sector Charco Azul Comuna 13 Santiago de Cali

En este trabajo se evidencia que comenzando el siglo XXI, el desplazamiento forzado por la violencia a ra?z del conflicto armado interno sigue siendo el fen?meno que evidencia una tragedia humanitaria y que se manifiesta en ?xodo continuo de poblaciones enteras desarraigadas de sus lugares de origen, familias enteras se ven forzadas a establecerse en nuevos lugares de refugio para salvar sus vidas. Tratan de construir sus vidas lejos de los enfrentamientos, masacres y amenazas propias del conflicto armado interno. Los motivos principales que causan el desplazamiento masivo en el pa?s son lo econ?mico y la violencia, lo cual tiene como antecedente los a?os cincuenta del siglo XX, sin embargo entre los a?os ochenta y noventa esta tragedia social alcanza proporciones inocultables a ra?z de las violaciones de los derechos humanos. Para las v?ctimas del conflicto armado la violaci?n de sus derechos por parte de algunas instituciones del Estado, o las infracciones de estos por otros actores, es un evento que altera la cotidianidad diaria y el hecho de no poder hacer valer sus derechos por desconocimiento o por su mecanismo de protecci?n lo cual constituye la poblaci?n m?s vulnerable. A ra?z de la magnitud de este fen?meno dentro del territorio nacional el Estado crea la ley 387 de 1987 mediante la que establece medidas para la prevenci?n de desplazamiento forzado. Sin embargo, el problema de vulneraci?n de derechos a la poblaci?n desplazada en Colombia no tiene que ver con la falta de mecanismo de protecci?n en el ordenamiento jur?dico, sino porque este, no ha sido aplicado efectivamente. En este trabajo se escogi? como grupo poblacional a mujeres cabeza de hogar del sector Charco Azul comuna 13 de Santiago de Cali. Porque evidencia la feminizaci?n de la pobreza en cabeza de las jefas de hogar de conformidad con el art?culo 2do de la Ley 82 de 1993 que luego fue modificada por la ley 1232 de 2008, tema que ha generado debate y pol?mica, ya que son ellas las...

Desenvolvimento e caracterização de micropartículas de amido reticuladas com agente fosfatado e avaliação da adsorção do azul de metileno

Starch has properties that make it one of the most studied biopolymers today. It is biodegradable, biocompatible, stable and non-toxic. This work has synthesis of starch and tapioca microparticles, through chemical modification by crosslinking with sodium tripolyphosphate agent in concentrations 7.5 and 15% (m / m). The amylose content was measured for starch and commercial cassava starch at 21.8% and 28.6%, respectively. According to the solubility index, processing in basic medium does not change the solubility of the material, but the addition of crosslinking agent increases this index, which changed from 12.8% for the control unprocessed, to 22.4% for the A5R15 sample. Soluble starch-based materials had a significant increase in the crosslinking density by increasing the concentration of crosslinker, from 1.4 in A5R7,5 sample, to 1.9 in A5R15. The cassava starch-based materials exhibited an opposite behavior: to increase the concentration of crosslinker crosslinking density decreased significantly in F5R7.5 from 2.9, to 1.9 in F5R15 sample. The point of zero charge (PZC) shows that below pH 4 the surface is positively charged. The surface area data is between 3,04 and 1,15 m2.g-1. The pore volume between 2.94 and 1.33 cm3.g-1 and pore size around 1.5 nm. The SEM indicates uneven distribution of microparticles, which are smooth, with no ridges. The maximum adsorption capacity of the materials were tested at pH 7.7 and for A5R15 and CA sample, at pH 2, 5, 6 and 9. It is noted that the processing in basic medium reduces the adsorption capacity of CA and CF in respect fo A and F. The adsorption in A5R15 sample has great dependency on the pH, reaching a value of 587 μg.g-1 in pH 7.7. The samples A5R15 and F5R7,5 adsorbed similar amounts, according to the statistical analysis, and significantly higher than their respective controls and showed lower desorption, indicating that the modification process was effective to control the release of methylene blue. The infrared spectra not show the characteristic bands of the phosphate bonds to the material formed, however, developments in hydroxyl characteristic band suggest modification in the way this group was linked after the reaction. After adsorption, the infrared spectra show different format in the band of hydroxyl. PCA analysis shows that the greatest changes observed in the IR spectra are observed in the region of 3500 cm-1. Thermal analysis showed three thermal events related to dehydration and material degradation. It is observed that the processing increases the temperature to the first mass loss, fixed at 12%, but not observed increased stability due to the presence of crosslinker or process.

Modulação da expressão da proteína XPA em resposta ao tratamento com azul de metileno fotossensibilizado

Reactive oxygen species (ROS) are produced by aerobic metabolism and react with biomolecules, such as lipids, proteins and DNA. In high concentration, they lead to oxidative stress. Among ROS, singlet oxygen (1O2) is one of the main ROS involved in oxidative stress and is one of the most reactive forms of molecular oxygen. The exposure of some dyes, such as methylene blue (MB) to light (MB+VL), is able to generate 1O2 and it is the principle involved in photodynamic therapy (PDT). 1O2 e other ROS have caused toxic and carcinogenic effects and have been associated with ageing, neurodegenerative diseases and cancer. Oxidative DNA damage is mainly repaired by base excision repair (BER) pathway. However, recent studies have observed the involvement of nucleotide excision repair (NER) factors in the repair of this type of injury. One of these factors is the Xeroderma Pigmentosum Complementation Group A (XPA) protein, which acts with other proteins in DNA damage recognition and in the recruitment of other repair factors. Moreover, oxidative agents such as 1O2 can induce gene expression. In this context, this study aimed at evaluating the response of XPA-deficient cells after treatment with photosensitized MB. For this purpose, we analyzed the cell viability and occurrence of oxidative DNA damage in cells lines proficient and deficient in XPA after treatment with MB+VL, and evaluated the expression of this enzyme in proficient and complemented cells. Our results indicate an increased resistance to treatment of complemented cells and a higher level of oxidative damage in the deficient cell lines. Furthermore, the treatment was able to modulate the XPA expression up to 24 hours later. These results indicate a direct evidence for the involvement of NER enzymes in the repair of oxidative damage. Besides, a better understanding of the effects of PDT on the induction of gene expression could be provided

Para lá do azul: radiações ionizantes para preservar alimentos

A radiação visível representa apenas uma parte do espectro de radiação electromagnética com o qual temos interacção permanente. As radiações com maior energia, para além do azul, como os UV, raios-X ou radiação gama têm diferentes usos tecnológicos. Estas radiações são consideradas ionizantes podendo ser utilizadas na preservação de alimentos, permitindo a inibição da germinação, a eliminação de insectos ou microrganismos patogénicos. O conhecimento destas aplicações tem mais de um século e o seu uso industrial meio século. Propomo-nos apresentar o estado-de-arte relativo ao uso desta tecnologia em Portugal em alimentos, apresentando estudos recentes e perspectivas futuras.