A nafion film cover to enhance the analytical performance of the CuO/Cu electrochemical sensor for determination of chemical oxygen demand

We modified and evaluated the performance of a CuO/Cu electrochemical electrode for chemical oxygen demand (COD) determination by covering it with a Nafion (Nf) film. The resulting modified CuONf/Cu electrode sensor was used for the electrochemical determination of COD in river, slaughterhouse and estuarine water samples in order to evaluate its performance for this particular task. It was compared with the CuO/Cu sensor with no Nafion. The main electrochemical characteristics of interest, resistance, sensitivity, accuracy and reproducibility, were assessed by means of Linear Sweep Voltammetry using glucose as a standard. Results of these essays indicate that the procedure used produced smooth and firmly attached Nf films covering the whole copper surface. This sensor was shown to be resistant to interferences and effective in electro-oxidation of a wide range of organic compounds and therefore very useful for COD determination. Using the newly developed CuONf/Cu electrode an analytical linear range of 50 to 1000 mg·L-1 COD, with a detection limit of 2.11 mg·L-1 (n = 6) COD was achieved. The comparison shows that the CuONf/Cu sensor is more appropriate for COD determination than its counterpart with no Nafion.Peer ReviewedPostprint (published version

In vitro wearing away of orthodontic brackets and wires in different conditions: A review

Introduction: The release of metallic ions from orthodontic brackets and wires typically depends on their quality (chemical composition) and the medium to which they are exposed, e.g., acidic, alkaline, substances with a high fluoride concentration, etc. This review examines corrosion and wear of orthodontic brackets, wires, and arches exposed to different media, including: beverages (juices), mouthwashes and artificial saliva among others, and the possible health effects resulting from the release of metallic ions under various conditions. Objective: This review aims to determine the exposure conditions that cause the most wear on orthodontic devices, as well as the possible health effects that can be caused by the release of metallic ions under various conditions. Sources: A search was carried out in the Scopus database, for articles related to oral media that can corrode brackets and wires. The initial research resulted in 8,127 documents, after applying inclusion and exclusion criteria, 76 articles remained. Conclusion: Stainless steel, which is commonly used in orthodontic devices, is the material that suffers the most wear. It was also found that acidic pH, alcohols, fluorides, and chlorides worsen orthodontic material corrosion. Further, nickel released from brackets and wires can cause allergic reactions and gingival overgrowth into patients.Fil: Espinoza Montero, Patricio J.. Pontificia Universidad Católica del Ecuador; EcuadorFil: Montero Jiménez, Marjorie Elizabeth. Pontificia Universidad Católica del Ecuador; Ecuador. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Fernández, Lenys. Pontificia Universidad Católica del Ecuador; EcuadorFil: Paz, Jose Luis. Universidad Nacional Mayor de San Marcos; PerúFil: Piñeiros, José Luis. Pontificia Universidad Católica del Ecuador; EcuadorFil: Ceballos, Sandra Macías. Universidad Central del Ecuador; Ecuado

Electrochemical degradation of surfactants in domestic wastewater using a DiaClean® cell equipped with a boron-doped diamond electrode

Treating domestic wastewater has become more and more complicated due to the high content of different types of detergents. In this context, advanced electro-oxidation (AEO) has become a powerful tool for complex wastewater remediation. The electrochemical degradation of surfactants present in domestic wastewater was carried out using a DiaClean® cell in a recirculation system equipped with boron-doped diamond (BDD) as the anode and stainless steel as the cathode. The effect of recirculation flow (1.5, 4.0 and 7.0 L min−1) and the applied current density (j = 7, 14, 20, 30, 40, and 50 mA cm−2) was studied. The degradation was followed by the concentration of surfactants, chemical oxygen demand (COD), and turbidity. pH value, conductivity, temperature, sulfates, nitrates, phosphates, and chlorides were also evaluated. Toxicity assays were studied through evaluating Chlorella sp. performance at 0, 3, and 7 h of treatment. Finally, the mineralization was followed by total organic carbon (TOC) under optimal operating conditions. The results showed that applying j = 14 mA cm−2 and a flow rate of 1.5 L min−1 during 7 h of electrolysis were the best conditions for the efficient mineralization of wastewater, achieving the removal of 64.7% of surfactants, 48.7% of COD, 24.9% of turbidity, and 44.9% of mineralization analyzed by the removal of TOC. The toxicity assays showed that Chlorella microalgae were unable to grow in AEO-treated wastewater (cellular density: 0 × 104 cells ml−1 after 3- and 7-h treatments). Finally, the energy consumption was analyzed, and the operating cost of 1.40 USD m−3 was calculated. Therefore, this technology allows for the degradation of complex and stable molecules such as surfactants in real and complex wastewater, if toxicity is not taken into account

Evaluación de la acumulación de cadmio en células de tomate de árbol a través de detección electroquímica indirecta de péptidos ricos en cisteína

The accumulation of Cd(II) by tamarillo (Solanum Betaceum) cells was evaluated through the detection of cysteine-rich peptides. It was used the method of electrochemical generation of iodine. These compounds are synthesized in the plant when it is contaminated by metals. The calibration curve obtained indicates a linear range from 0 to 250 µmol L-1, with a detection limit of 4.82 µmol L-1 (3.3s/m). The concentration of peptides in cell suspensions increases with the CdSO4 concentration and the exposure time. The results indicate that tamarillo cells accumulate cadmium. During 5 days of exposure and 100 µmol L-1 CdSO4, the cells of the suspension still do not suffer from apoptosis. The proposed method shows useful characteristics for monitoring heavy metals in growing plants.Mediante la generación electroquímica de yodo se evalúa la acumulación de Cd(II) por células de tomate de árbol (Solanum Betaceum) a través de la detección de péptidos ricos en cisteína, compuestos sintetizados por la planta cuando está contaminada con metales. La curva de calibración obtenida indica un intervalo lineal de 0 a 250 µmol L-1, con un límite de detección de 4,82 µmol L-1 (3,3 s/m). La concentración de péptidos en las suspensiones celulares incrementa conforme aumenta la concentración de CdSO4 y el tiempo de exposición. Los resultados indican que las células de tomate de árbol acumulan cadmio. Durante 5 días de exposición a 100 µmol L-1 CdSO4 las células en suspensión aún no sufren la apoptosis. El método propuesto muestra características útiles para su implementación en el monitoreo de contaminación por metales pesados en plantas en crecimiento

Natural Gums to Improve the Physicochemical Stability of Cake Creams

The physicochemical properties of pastry and confectionery products greatly influence the aesthetic design of a cake topping, since they can be susceptible to physicochemical changes in a very short time, so maintaining a good appearance and texture of the topping becomes a challenge. Generally, cake creams deteriorate over time. The evaluation of the physicochemical properties of natural gums (arabic gum, tara gum, carrageenan, and pectin) is proposed in this work as a way to improve the physicochemical stability of butter-based cake creams (coverage creams) to maintain the initial appearance of the cream and to lengthen the separation time of their phases. For this purpose, some parameters related to the physicochemical stability of the cream, such as viscosity, density, bubble size, syneresis, volume and rheological behavior were measured. The result of the ANOVA and Tukey’s tests displayed significant differences for the measured parameters, which shows that natural gums substantially improve the stability of butter cream. The best natural gum found was the tara gum (TG) which improved viscosity 5.6 times with respect to that of the cream without gums (η¯ without gums = 15.49 Pa·s, η¯ with TG = 87.09 Pa·s), while the bubble size remained small, 1.6 times smaller compared to that of the cream without gum (BS¯) without gums = 57 μm, (BS¯) with TG = 35 μm), and the volume loss decreased two times when compared to that of the cream without gums ((ΔV¯) without gums = 1.57 cm3, (ΔV¯) with TG = 0.80 cm3). The cream with TG showed better rheology compared to that of the cream without gums (the cream without gums exhibited a plastic and thixotropic behavior, with permanent elastic deformation, while cream with TG exhibited thixotropic behavior without permanent elastic deformation). Finally, it was found that the cream with TG acquired a higher thixotropic index (TI) compared to that of the cream without gums (TI max. without gums = 17.40 y 71.78 q.u., TI max. with TG = 74.67 and 1559.90 q.u., at 4 °C and 25 °C, respectively) which demonstrates the effective contribution of cream with TG in 66.67% of the measured parameters

Development and Evaluation of Copper Electrodes, Modified with Bimetallic Nanoparticles, to be Used as Sensors of Cysteine-Rich Peptides Synthesized by Tobacco Cells Exposed to Cytotoxic Levels of Cadmium

We report on two new electrochemical sensors which, coupled to differential pulse voltammetry, constitutes a useful tool for diagnosis of heavy metal pollution. The electrochemical sensors AgHgNf/Cu and the AgBiNf/Cu were obtained by deposition of bimetallic particles of AgHg or AgBi on copper electrodes covered with a Nafion (Nf) film, respectively. Micrographs of the electrode’s surface showed evenly scattered bimetallic particles, with an approximate diameter of 150 nm, embedded in the Nafion (Nf) film. In order to test the electrodes, the hydrogen evolution signal according to the Brdička reaction was measured for the determination of cysteine-rich peptides (CRp) produced by plants. To check the accuracy of the electrodes, real samples of Nicotiana tabacum cells exposed to cytotoxic levels of cadmium were tested. The AgHgNf/Cu electrode produced detection limits (DLs) of 0.088 µmol L−1 for Cysteine and 0.139µmol L−1 for Glutathione, while for the AgBiNf/Cu electrode DLs were 0.41 µmol L−1 for cysteine and 0.244 µmol L−1 for glutathione. Thus, the new electrodes could be a useful analytical electrochemical system very convenient for fieldwork. The electrodes were capable of direct, accurate, and sensitive detection of synthesized peptides, despite the complex matrix where the Nicotiana tabacum cells were grown

Humedales artificiales y celdas de combustibles microbianas como sistemas individuales y combinados para el tratamiento de aguas residuales: una revisión

The population increases and the technological development has caused a great energy demand, which has given way to several research groups venturing into the search for solutions in the short and medium term. The use of technologies to treat contaminated water and the generation of electrical energy simultaneously emerge as viable alternatives to solve the problem. This work reviews the mechanism for the treatment of wastewater and the generation of electrical energy simultaneously through combined systems of wetlands coupled to microbial fuel cells (CW-MFC). The objective of this review is to describe the components and operation of the individual CW and MFC systems, as well as the CW-MFC system, which have been used in recent research. The main studies were explored, studies related to the material that electrodes are built, which generate more energy efficiency and filtering materials that benefit the wastewater treatment. In addition, the challenges in this field of research are presented. The CW and the MFC are systems that, combined, improve the efficiency in the wastewater treatment and at the same time they allow to take advantage of the electrical energy that the microorganisms generate during the oxidation process of the organic matter.El aumento poblacional y el desarrollo tecnológico ha ocasionado una gran demanda energética, lo que ha dado paso a que varios grupos de investigación incursionen en la búsqueda de soluciones a corto y mediano plazo. El uso de tecnologías que permitan tratar aguas contaminadas y la generación simultánea de energía eléctrica surge como una alternativa viable para dar solución a este problema. En este documento se revisa el mecanismo para el tratamiento de agua residual y la generación de energía eléctrica simultánea, a través de sistemas combinados de humedales acoplados a celdas de combustible microbianas (CW-MFC, por sus siglas en inglés). El objetivo de esta revisión es describir los componentes y funcionamiento de los sistemas individuales CW y MFC, así como también del sistema combinado CW-MFC, los cuales han sido empleados en investigaciones recientes. Se exploran los principales estudios, relacionados con el material con el cual se construyen los electrodos, que generen mayor eficiencia energética y materiales filtrantes que beneficien el tratamiento del agua residual. Además, se presentan los desafíos en este ámbito de investigación. Los CW y las MFC son sistemas que combinados mejoran la eficiencia en el tratamiento de agua residual y a la vez permiten aprovechar la energía eléctrica que los microorganismos generan durante el proceso de oxidación de la materia orgánica

Degradación fotocatalítica de Aroclor 1254 utilizando dióxido de titanio irradiado con haz de electrones acelerados

Biphenyl polychlorides (PCB’s) are organic compounds that were used in capacitors and electrical transformers due to their insulating properties and high chemical stability. By banning the manufacture and use of PCBs, a lot of this electrical equipment became obsolete and huge volumes of dielectric oil with PCBs were stored as hazardous waste pending an alternative for their treatment. In this work, the phase transfer of PCB’s (Aroclor 1254) from the dielectric oil to an aqueous phase, for its subsequent photocatalytic degradation is proposed. Two transfer agents were probed, Polyethylene Glycol 400 and Triton X-100. The catalytic process was carried out with no irradiated TiO2 (0 kGy) and ebeam irradiated TiO2 with 20 and 60 kGy; UV-vis was used as a source of energy during photodegradation. The degradation was evaluated by gas chromatography and the mineralization was verified by Total Organic Carbon (COT). The highest phase transfer efficiency was achieved with the Triton X-100, so this agent was used in subsequent studies. The best results of degradation and mineralization of Aroclor 1254, was reached with the TiO2 irradiated at 20 kGy, these were 98.36 % and 58.92 % respectively, after 240 min of photo-oxidation. In this way this technology becomes a viable alternative to solve the problem of contamination by PCBs.Los policloruros de bifenilo (PCB’s) son compuestos orgánicos que fueron usados en condensadores y transformadores eléctricos debido a sus propiedades aislantes y alta estabilidad química. Al prohibirse la fabricación y el uso de PCB’s, gran cantidad de estos equipos eléctricos quedaron obsoletos y enormes volúmenes de aceite dieléctrico con PCB’s se almacenaron como desecho peligroso a la espera de una alternativa para su eliminación. En este trabajo se reporta la transferencia de fase del Aroclor 1254, desde el aceite dieléctrico hacia fase acuosa, para su posterior degradación fotocatalítica. Se probaron dos agentes de transferencia de fase, Polietilenglicol 400 y Tritón X-100. El proceso fotocatalítico se llevó a cabo con TiO2 sin irradiar (0 kGy) e irradiado con haz de electrones a dosis de 20 y 60 kGy, se utilizó radiación ultravioleta como fuente de energía durante la fotodegradación. La degradación se siguió por cromatografía de gases y la mineralización se verificó mediante Carbono Orgánico Total (COT). La mayor eficiencia de transferencia de fase se logró con el Tritón X- 100, por lo que se utilizó este agente en los estudios posteriores. Los mejores resultados de degradación y mineralización del Aroclor 1254, se alcanzó con el TiO2 irradiado a 20 kGy, estos fueron de 98,36 % y 58,92 % respectivamente, luego de 240 min de fotooxidación. De esta manera esta tecnología se convierte en una alternativa viable para solucionar el problema de la contaminación por PCBs

Correlación analítica-técnica entre ensayos de laboratorio de módulo resiliente y California bearing ratio de la mina Copeto

An analytical-technical correlation between laboratory tests of Resilient Module and California Bearing Ratio for an aggregate that comes from the Copeto Mine (Toachi - Santo Domingo de Los Tsáchilas-Ecuador) is reported, which yields real useful values in the optimization of the material used in road projects, through the obtaining of the Resilient Module. The study is based on the qualification of the mine, through physicochemical tests, which allows to know the characteristics of the aggregates that make it up, according to ASTM standards. We report real values in the behavior of the materials that are going to be used in the structure of the road, which results in thicknesses of smaller layers, as in the base (a reduction of 5 cm) that, at the time of construction It reduces the delivery time, the amount of material and therefore the final cost of the construction of the road. Se reporta una correlación analítica-técnica entre ensayos de laboratorio de Módulo Resiliente y California Bearing Ratio, para un agregado que proviene de la mina de Copeto (Toachi – Santo Domingo de Los Tsáchilas-Ecuador), la cual arroja valores reales útiles en la optimización del material utilizado en proyectos viales, a través de la obtención del Módulo Resiliente. El estudio se sustenta en la cualificación de la mina, mediante ensayos fisicoquímicos, que permite conocer las características propias de los agregados, según las normas ASTM. Con el logro de una correlación entre el CBR y el Módulo Resiliente real de la mina en estudio, se tiene valores reales en el comportamiento de los materiales, que se van a usar en la estructura de la vía, lo que genera como resultado espesores de capas menores, que, al momento de la construcción reduce el tiempo de entrega, la cantidad de material y por consiguiente el costo final de la construcción de la vía

A nafion film cover to enhance the analytical performance of the CuO/Cu electrochemical sensor for determination of chemical oxygen demand

We modified and evaluated the performance of a CuO/Cu electrochemical electrode for chemical oxygen demand (COD) determination by covering it with a Nafion (Nf) film. The resulting modified CuONf/Cu electrode sensor was used for the electrochemical determination of COD in river, slaughterhouse and estuarine water samples in order to evaluate its performance for this particular task. It was compared with the CuO/Cu sensor with no Nafion. The main electrochemical characteristics of interest, resistance, sensitivity, accuracy and reproducibility, were assessed by means of Linear Sweep Voltammetry using glucose as a standard. Results of these essays indicate that the procedure used produced smooth and firmly attached Nf films covering the whole copper surface. This sensor was shown to be resistant to interferences and effective in electro-oxidation of a wide range of organic compounds and therefore very useful for COD determination. Using the newly developed CuONf/Cu electrode an analytical linear range of 50 to 1000 mg·L-1 COD, with a detection limit of 2.11 mg·L-1 (n = 6) COD was achieved. The comparison shows that the CuONf/Cu sensor is more appropriate for COD determination than its counterpart with no Nafion.Peer Reviewe