Remoção dos corantes azul brilhante, amarelo crepúsculo e amarelo tartrazina de soluções aquosas utilizando carvão ativado, terra ativada, terra diatomácea, quitina e quitosana: estudos de equilíbrio e termodinâmica

This work compared activated carbon, activated earth, diatomaceous earth, chitin and chitosan to removal acid blue 9, food yellow 3 and FD&C yellow nº 5 dyes from aqueous solutions with different pH values (2-10). In the best process condition for each dye, equilibrium studies were carried out at different temperatures (from 298 to 328 K) and Langmuir, Freundlich, Redlich-Peterson, Temkin and Dubinin-Radushkevich models were fitted with experimental data. In addition, entropy change, Gibbs free energy change and enthalpy change were obtained in order to verify the thermodynamic adsorption behavior.

Descoloração e degradação do azo corante Vermelho GRLX-220 por ozonização

The discoloration and degradation of the textile dye RED GRLX-220 using the electrochemically generated ozone was investigated. Total discoloration was rapidly achieved in both acid and basic conditions. A pseudo-first order kinetics was observed for discoloration, influenced by pH and ozonation time. A considerable degree of mineralization (60%) was obtained after 30 min of ozonation in alkaline medium. The feasibility of organic matter oxidation during the ozonation process increased in both acidic and alkaline media. The toxicity decreased after the ozonation process, suggesting that the byproducts are less toxic than the parental compound.

Materiais SiO2-TiO2 para a degradação fotocatalítica de diuron

SiO2-TiO2 materials prepared by sol-gel method were evaluated in the photocatalytic degradation of diuron. The materials were prepared with and without surfactant cetyltrimethylammonium chloride at different temperatures (25, 50 and 100 ºC). The samples were characterized by N2 adsorption-desorption measurements, scanning electron microscopy, X-ray diffraction, ultraviolet-visible diffuse reflectance spectroscopy and infrared diffuse reflectance spectroscopy. The results showed that the materials synthesized with the surfactant had higher surface areas and band-gap values similar to anatase. All materials were more active than the commercial catalyst P-25 and better performance was achieved using the surfactant in the material synthesis.

Degradação eletroquímica da vinhaça usando eletrodo de diamante dopado com boro

The degradation of vinasses in aqueous solution from ethanol industry has been investigated by electrochemical oxidation using a boron doped diamond electrode (BDD). Samples of vinasses were electrolyzed in medium of (0.1 mol L-1) Na2SO4 solutions at controlled potentials of +2.4, +3.0 and +4.0 V (vs. Ag/AgCl) and exhibited considerable reduction of total organic carbon. The cyclic voltammetry studies indicate that the vinasses are oxidized irreversibly over the BDD at 2.0 V (vs. Ag/AgCl) in diffusion controlled process. From the experimental results it is clear that the BDD electrode can be a valuable tool to the electrochemical degradation of vinasses in practical applications

Degradação fotoeletroquímica do herbicida bentazona sobre eletrodos de carbono modificados por TiO2

This work involved the study of degradation of the herbicide bentazone in aqueous solution by different routes, in order to search a method that generates safe products to the environment. It was tested electrochemical polarization methods involving positive and negative potential, irradiation with UV light and deposition of TiO2 on the electrode surface, seeking a catalytic effect. After different times of degradation, aliquots were removed and the scan of molecular absorption spectrum of UV-Vis was performed. From the spectra decay of bentazone, the kinetics of different processes was accompanied and the rate constants were determined.

Degradação fotoeletroquímica do corante azul QR 19 em solução aquosa

In this work the degradation capacity of a photo-electrocatalytic system was evaluated, mainly regarding the effect of the electrolyte solution on the degradation capacity toward a reactive textile dye. In the presence of NaCl the photo-electrochemical process shows high degradation efficiency, permitting almost total color removal in treatment of about 5 min. In view of the low degradation efficiency observed for the photocatalytic process it is possible to assume that the high degradation efficiency of the process is a function of electrochemical generation of oxidant active chlorine species, which are subsequently transformed to higher oxidant radical forms.

Degradação de corantes têxteis e remediação de resíduos de tingimento por processos Fenton, foto-Fenton e eletro-Fenton

In this work the degradation of textile dyes were evaluated, using Fenton, photo-Fenton and electro-Fenton processes. Under optimized conditions Fenton and photo-Fenton processes showed high decolorization capacity of the model dyes. The electro-Fenton process was carried out in an undivided electrochemical reactor (1000 mL) equipped with a carbon-felt cathode (253 cm²) and a platinum gauze anode (6 cm²). Under optimal conditions (J: 1.6 mA cm-2, Na2SO4: 0.075 mol L-1, pH: 3) H2O2 concentration of about 60 mg L-1 was observed. The addition of Fe2+ (15 mg L-1) induces Fenton reactions that permit almost total decolorization of textile dyes.

Degradação de poluentes emergentes por processos Fenton e foto-Fenton

A continuous photochemical treatment system was developed for aiming the treatment of aqueous solutions containing relevant micro-pollutants (microcystin-LR, sulfamethoxazole and 17-b estradiol). The continuous photo-Fenton process provided high degradation efficiency. However, contact time between samples and the irradiated region is short relative to total treatment time, indicating that observed changes are predominantly due to the Fenton process. Higher degradation efficiency was observed in systems operated using two treatment cycles, the first involving a batch Fenton process and the second a continuous photo-Fenton treatment.

Desenvolvimento e avaliação de eletrodos de difusão gasosa (EDG) para geração de H2O2 in situ e sua aplicação na degradação do corante reativo azul 19

This work reports the development of GDE for electrogeneration of H2O2 and their application in the degradation process of Reactive Blue 19 dye. GDE produced by carbon black with 20% polytetrafluoroethylene generated up to 500 mg L-1 of H2O2 through the electrolysis of acidic medium at -0.8 V vs Ag/AgCl. Reactive Blue 19 dye was degraded most efficiently with H2O2 electrogenerated in the presence of Fe(II) ions, leading to removal of 95% of the original color and 39% of TOC at -0.8 V vs Ag/AgCl.

Avaliação da lixiviação do cádmio e níquel provenientes da degradação de baterias níquel-cádmio em uma coluna de solo

Spent nickel-cadmium (Ni-Cd) batteries and salts of nickel and cadmium were placed in two different columns of soil for a period of two years. A leaching solution was passed through them at ambient temperature in this period. The behavior of metals in each column was then evaluated. Under the conditions of the experiment, cadmium and nickel demonstrated the potential to contaminate and affect the natural cycles of soil. The disposal of Ni-Cd batteries directly to the soil also increased the concentration of nickel (349 mg kg-1) and cadmium (2890 mg kg-1), sometimes exceeding the intervention values defined in CONAMA resolution 420/09.

Análise dos produtos de degradação do esfenvalerato por SBSE/CLAE-UV/DAD utilizando planejamento fatorial fracionário

A simple procedure based on stir bar sorptive extraction and high-performance liquid chromatography-ultraviolet/photodiode array detection (SBSE/LC-UV/PAD) to determine intermediates and by-products of esfenvalerate is described. The influence of organic modifier, ionic strength, extraction time, temperature and pH were simultaneously evaluated by using a factorial experimental design. The utilization of different organic solvents and desorption times were also investigated to establish the optimal conditions for SBSE liquid desorption. Among the ten different peaks (intermediates and by-products) detected after degradation of esfenvalerate, eight (including 3-phenoxybenzoic acid and 3-phenoxybenzaldehyde) were successfully extracted by SBSE under the optimized conditions.

Ocorrência e degradação de quinolonas por processos oxidativos avançados

In this review, the presence of quinolones in the environment, their risks and the available processes for water decontamination were addressed. Their occurrence in surface waters and also in soil raises concerns about the risk of the development of resistant bacteria and other potential chronic effects. AOPs (UV/H2O2, Fenton, photo-Fenton, and UV/TiO2) and ozonation proved effective for degrading these emerging contaminants due to hydroxyl radical formation, surpassing the efficacy of conventional methods. In addition, the main degradation mechanisms of these drugs as well as data on residual biological activity were analyzed.

Solo contaminado com cádmio: extratibilidade do metal e cinética química de degradação da matéria orgânica de torta de filtro

The chemical kinetics of sugarcane filter cake (FC) organic matter degradation at rates (0, 40, 80, and 120 t ha-1) in non-contaminated and different degrees of cadmium-contaminated Oxisol (0.19, 28, 56, 112 and 200 mg Cd kg-1) and DTPA-extractable Cd was studied. FC degradation was determined by quantifying CO2 emitted from soil samples during 72 days of incubation. DTPA-extractable Cd was performed after the incubation period. FC degradation was described by a two-stage equation of chemical kinetics. FC degradation rates were between 15 and 33%. Total CO2 emitted from FC declined with increasing degree in Cd-contamination and the DTPA-extractable Cd declined with FC rates.

Avaliação da eficiência de degradação de hidrocarbonetos aromáticos por bactérias provinientes de estação de tratamento de efluente de refinaria de petróleo

Three bacterial strains were isolated from the activated sludge system of petroleum refinery wastewater, identified by partial sequencing of 16S rDNA, and classified as Acinetobacter genomospecies 3, Bacillus pumilus, and Bacillus flexus. The degradation efficiency of aromatic hydrocarbons was evaluated by gas chromatography with a flame ionization detector. In a mineral medium containing anthracene and phenanthrene and the consortium of microorganisms, the removal efficiency was 96% and 99%, respectively, after 30 days. The good rate of hydrocarbon degradation proves the operational efficiency of the microbial consortium in treating effluents containing these compounds.

DEGRADAÇÃO MICROBIOLÓGICA E ENZIMÁTICA DE POLÍMEROS: UMA REVISÃO

Polymer recycling has been one of the most important trend in the petrochemical area. Among different technologies, biotechnological (enzymatic and/or microbial) degradation of polymers for the recovery of monomers and oligomers is environmentally-friendly and meet some green chemistry principles. In this work, conditions for the biotechnological degradation of some industrially-relevant polymers (e.g. poly(ethylene terephthalate) and polyethylene) were revised, and the main biocatalysts were identified. In most cases, biodegradation mechanisms are still unclear, thus being necessary more studies to unravel these promising bioprocesses. Polymer biodegradation studies also present considerable importance for other fields, including biomedical and agricultural.