A hybrid photoelectrocatalytic/photoelectro-Fenton treatment of Indigo Carmine in acidic aqueous solution using TiO2 nanotube arrays as photoanode

This article reports the synthesis of TiO2 nanotube arrays (TiO2 NTs), grown by Ti anodization, and their use as photoanode in a hybrid photelectrocatalytic (PEC)/photoelectro-Fenton (PEF) treatment of Indigo Carmine solutions in sulfate medium at pH 3.0. The anode was combined with an air-diffusion cathode that ensured continuous H2O2 electrogeneration. Comparative trials by electrochemical oxidation with electrogenerated H2O2 (EO-H2O2), electro-Fenton (EF) and PEF with Pt anode were made. The photoanode was stable operating up to 3 mA cm−2 with irradiation from a 36-W UV LED lamp, showing photoelectroactivity from an anodic potential (Ean) of +0.20 V, as determined by cyclic voltammetry. At 3 mA cm−2, color removal by EO-H2O2 with Pt and PEC with TiO2 NTs was very slow, being much faster in EF, PEF and PEC/PEF due to main role of OH formed from Fenton's reaction upon addition of Fe2+. The absorbance and dye concentration decays agreed with a pseudo-first-order kinetics, yielding a slightly lower rate constant for decolorization because of the formation of colored products. The mineralization ability increased as: EO-H2O2 ≪ EF ≪ PEF < PEC/PEF. The holes photogenerated at the TiO2 NTs surface had higher oxidation ability than OH formed at the Pt surface from water discharge. In PEC/PEF, a slower mineralization was found at 2 mA cm−2, although the final mineralization percentage was similar to that attained at 3 mA cm−2. Both, SO42− and NH4+ ions were released during the treatments, along with isatin-5-sulfonic and formic acids as main products

Treatment of waste dye by electroflocculation: an experiment for undergraduate in chemistry

This paper describes the use of a simple experiment of electroflocculation for classroom in Chemistry. Parameters such as electrode material, current density and temperature direct influence the process efficiency. Due to the process low cost and efficient color removal, the methodology proposed has shown good potential for use in wastewater treatment. In addition, the proposed experiment allows discussion about environmental electrochemistry, introduction to concepts of water contamination by industry and university, and also about different alternatives in wastewater treatment used nowadays. Finally, the very easy operation make possible to easy adapt this experiment for high school and elementary school.CNPqCoordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES

The kinetic behavior of dehydrogenase enzymes in solution and immobilized onto nanostructured carbon platforms

This paper describes the kinetic behavior of alcohol (ADH) and aldehyde (AldDH) dehydrogenases in solution and immobilized onto carbon platform via polyamidoamine (PAMAM) dendrimers. All the kinetic constants achieved for soluble ADH and AldDH are in agreement with literature data. The influence of pH and temperature was evaluated. Results showed that physiological conditions and ambient temperature can satisfactorily be applied to systems containing dehydrogenase enzymes, so as to ensure an environment where both ADH and AldDH display good activity. It is noteworthy that the affinity between both ADH and AldDH and their substrates and coenzyme is retained after the immobilization process. Investigation of the influence of the storage time demonstrated that there was no appreciable reduction in enzymatic activity for 50 days. Results showed that the PAMAM dendrimers provide a good environment for immobilization of dehydrogenase enzymes and that the affinity observed between the enzymes and their substrates and coenzymes seems to be retained, despite the considerable loss of enzymatic activity after immobilization. Furthermore, the anchoring methodology employed herein, namely layer-by-layer (LbL), required very low catalyst consumption.FAPESPCNPqCAPE

Degradação De Corantes Reativos Por Meio De Processo Fotocatalìtico Eletroquimicamente Assistido.

A presente invenção se refere a elaboração de eletrodos de titânio, modificados com oxido de rutênio, e a sua utilização num processo de degradação fotoquímica eletroquimicamente assistida para degradação de corantes reativos. O processo permite completa descoloração de soluções aquosas do corante e mineralização da ordem de 50%, para tempos de reação de 120 min. Trata-se de um procedimento bastante simples, que permite a obtenção de resultados bastante significativos em tempos relativamente baixos, quando aplicado a este tipo de espécies químicas, de reconhecido caráter recalcitrante e toxico.BR9804165 (A); BR9804165 (B1)C02F1/30C02F1/46C02F103/30C02F1/30C02F1/46C02F103/30BR19989804165C02F1/30C02F1/46C02F103/30C02F1/30C02F1/46C02F103/3

Chemical and physical factors influencing lead and copper contamination in drinking water: approach for a case study in analytical chemistry

CHEMICAL AND PHYSICAL FACTORS INFLUENCING LEAD AND COPPER CONTAMINATION IN DRINKING WATER: APPROACH FOR A CASE STUDY IN ANALYTICAL CHEMISTRY. Lead and copper concentrations in drinking water increase considerably on going from municipality reservoirs to the households sampled in Ribeirao Preto (SP-Brazil). Flushing of only 3 liters of water reduced metal concentrations by more than 50%. Relatively small changes in water pH rapidly affected corrosion processes in lead pipes, while water hardness appeared to have a long-term effect. This approach aims to encourage University teachers to use its content as a case study in disciplines of Instrumental Analytical Chemistry and consequently increase knowledge about drinking water contamination in locations where no public monitoring of trace metals is in place

Scientia Agricola Energy generation in a Microbial Fuel Cell using anaerobic sludge from a wastewater

ABSTRACT: In microbial fuel cells (MFCs), the oxidation of organic compounds catalyzed by microorganisms (anode) generates electricity via electron transfer to an external circuit that acts as an electron acceptor (cathode). Microbial fuel cells differ in terms of the microorganisms employed and the nature of the oxidized organic compound. In this study, a consortium of anaerobic microorganisms helped to treat the secondary sludge obtained from a sewage treatment plant. The microorganisms were grown in a 250 mL bioreactor containing a carbon cloth. The reactor was fed with media containing acetate (as the carbon source) for 48 days. Concomitantly, the electrochemical data were measured with the aid of a digital multimeter and data acquisition system. At the beginning of the MFC operation, power density was low, probably due to slow microorganism growth and adhesion. The power density increased from the 15 th day of operation, reaching a value of 13.5 μW cm -2 after ca. 24 days of operation, and remained stable until the end of the process. Compared with data in the literature, this power density value is promising; improvements in the MFC design and operation could increase this value even further. The system investigated herein employed excess sludge as a biocatalyst in an MFC. This opens up the possibility of using organic acids and/or carbohydrate-rich effluents to feed MFCs, and thereby provide simultaneous effluent treatment and energy generation

A hybrid photoelectrocatalytic/photoelectro-Fenton treatment of Indigo Carmine in acidic aqueous solution using TiO2 nanotube arrays as photoanode

This article reports the synthesis of TiO2 nanotube arrays (TiO2 NTs), grown by Ti anodization, and their use as photoanode in a hybrid photelectrocatalytic (PEC)/photoelectro-Fenton (PEF) treatment of Indigo Carmine solutions in sulfate medium at pH 3.0. The anode was combined with an air-diffusion cathode that ensured continuous H2O2 electrogeneration. Comparative trials by electrochemical oxidation with electrogenerated H2O2 (EO-H2O2), electro-Fenton (EF) and PEF with Pt anode were made. The photoanode was stable operating up to 3 mA cm−2 with irradiation from a 36-W UV LED lamp, showing photoelectroactivity from an anodic potential (Ean) of +0.20 V, as determined by cyclic voltammetry. At 3 mA cm−2, color removal by EO-H2O2 with Pt and PEC with TiO2 NTs was very slow, being much faster in EF, PEF and PEC/PEF due to main role of OH formed from Fenton's reaction upon addition of Fe2+. The absorbance and dye concentration decays agreed with a pseudo-first-order kinetics, yielding a slightly lower rate constant for decolorization because of the formation of colored products. The mineralization ability increased as: EO-H2O2 ≪ EF ≪ PEF < PEC/PEF. The holes photogenerated at the TiO2 NTs surface had higher oxidation ability than OH formed at the Pt surface from water discharge. In PEC/PEF, a slower mineralization was found at 2 mA cm−2, although the final mineralization percentage was similar to that attained at 3 mA cm−2. Both, SO42− and NH4+ ions were released during the treatments, along with isatin-5-sulfonic and formic acids as main products

Energy generation in a Microbial Fuel Cell using anaerobic sludge from a wastewater treatment plant

In microbial fuel cells (MFCs), the oxidation of organic compounds catalyzed by microorganisms (anode) generates electricity via electron transfer to an external circuit that acts as an electron acceptor (cathode). Microbial fuel cells differ in terms of the microorganisms employed and the nature of the oxidized organic compound. In this study, a consortium of anaerobic microorganisms helped to treat the secondary sludge obtained from a sewage treatment plant. The microorganisms were grown in a 250 mL bioreactor containing a carbon cloth. The reactor was fed with media containing acetate (as the carbon source) for 48 days. Concomitantly, the electrochemical data were measured with the aid of a digital multimeter and data acquisition system. At the beginning of the MFC operation, power density was low, probably due to slow microorganism growth and adhesion. The power density increased from the 15th day of operation, reaching a value of 13.5 μW cm–2 after ca. 24 days of operation, and remained stable until the end of the process. Compared with data in the literature, this power density value is promising; improvements in the MFC design and operation could increase this value even further. The system investigated herein employed excess sludge as a biocatalyst in an MFC. This opens up the possibility of using organic acids and/or carbohydrate-rich effluents to feed MFCs, and thereby provide simultaneous effluent treatment and energy generation