Denise Alves Fungaro

Coal fly ash supported Co3O4 catalysts for phenol degradation using peroxymonosulfate

Several fly ash (FA) samples derived from Australian (FA-WA) and Brazilian coals (FA-JL and FA-CH) were used as supports to prepare Co oxide (Co)-based catalysts. These Co/FA catalysts were tested in peroxymonosulfate activation for sulphate radical generation and phenol degradation in aqueous solution. The physicochemical properties of FA supports and Co/FA catalysts were characterised by N2 adsorption, X-ray diffraction (XRD), scanning electron microscopy coupling with energy dispersive spectroscopy (SEM-EDS), elemental mapping, and UV-vis diffuse reflectance spectroscopy. It was found that the FA supports did not show adsorption of phenol and could not activate peroxymonosulfate for sulphate radical generation. However, fly ash supported Co oxide catalysts (Co/FA) presented higher activities in the activation of peroxymonosulfate for phenol degradation than bulk Co oxide and their activities varied depending on the properties of the fly ash supports. Co/FA-JL showed the highest activity while Co/FA-WA showed the lowest. Activation energies of phenol degradation on three Co/FA catalysts were obtained to be 47.0, 56.5, 56.0 kJ mol−1 for Co/FA-WA, Co/FA-JL and Co/FA-CH, respectively.

Novel polymer-modified electrodes for batch injection sensors and application to environmental analysis

Various polymer coatings have been investigated for the protection of mercury thin-film electrodes in the square wave anodic stripping voltammetry of environmental samples using batch injection analysis, with injection of untreated samples of volume 50 μl directly over the sensing electrode. Polymer coatings studied include those with controlled porosity, and cation-exchange polymers based on sulphonated polymers. Of the polymers tested, films of ca. 1 μm thickness made from Nafion® mixed with 5% poly(vinyl sulphonic acid) were found to give the best results in tests with the model surfactants Triton-X-100 detergent, sodium dodecyl sulphate and protein standard. The validity of the approach is demonstrated by application to real samples.

Poly(ester sulphonic acid) coated mercury thin film electrodes: characterization and application in batch injection analysis stripping voltammetry of heavy metal ions.

Mercury-thin film electrodes coated with a thin film of poly(ester sulphonic acid) (PESA) have been investigated for application in the analysis of trace heavy metals by square wave anodic stripping voltammetry using the batch injection analysis (BIA) technique. Different polymer dispersion concentrations in water/acetone mixed solvent are investigated and are characterised by electrochemical impedance measurements on glassy carbon and on mercury film electrodes. The influence of electrolyte anion, acetate or nitrate, on polymer film properties is demonstrated, acetate buffer being shown to be preferable for stripping voltammetry applications. Although stripping currents are between 30 and 70% less at the coated than at bare mercury thin film electrodes, the influence of model surfactants on stripping response is shown to be very small. The effect of the composition of the modifier film dispersion on calibration plots is shown; however, detection limits of around 5 nM are found for all modified electrodes tested. This coated electrode is an alternative to Nafion-coated mercury thin film electrodes for the analysis of trace metals in complex matrices, particularly useful when there is a high concentration of non-ionic detergents.

Remediação de drenagem ácida de mina usando zeólitas sintetizadas a partir de cinzas leves de carvão

Zeolitic material was synthesized from coal fly ashes (baghouse filter fly ash and cyclone filter fly ash) by hydrothermal alkaline activation. The potential application of the zeolitic product for decontamination of waters from acid mine drainage was evaluated. The results showed that a dose of 30 g L-1 of zeolitic material allowed the water to reach acceptable quality levels after treatment. Both precipitation and cation-exchange processes accounted for the reduction in the pollutant concentration in the treated waters.

Utilização de zeólita preparada a partir de cinza residuária de carvão como adsorvedor de metais em água

Coal ashes produced in coal-fired power plant could be converted into zeolites and can be used as low-cost adsorbents for the treatment of effluents contaminated with high levels of toxic metals. The capacity of synthetic zeolites for the removal of cadmium, zinc and copper ions from aqueous solutions has been investigated under different operating conditions. Zeolite from bottom chimney showed higher removal efficiency for metals ions than zeolite from feed hopper and mixing mill. The results indicated that the treated bottom ash could be applied in environmental technology as an immobilizer of pollutants.

Adsorção do corante reativo laranja 16 de soluções aquosas por zeólita sintética

Coal fly ash, a waste generated in a coal-fired electric power plant, was used to synthesize zeolite by hydrothermal treatment with NaOH solution. This zeolite was used as adsorbent to investigate the adsorption kinetics and isotherm parameters of the reactive orange 16 (RO16) dye from aqueous solutions at different concentrations (1.3-15.4 mg L-1). Three kinetic models, the pseudo-first-order, second-order, and intraparticle diffusion were used to predict the adsorption rate constants. The kinetics of adsorption of the RO16 dye followed pseudo-second-order kinetics. The adsorption isotherm data were closely fitted to the Langmuir equation. Keywords: coal fly ash; zeolite; reactive dye adsorption.

Microelectrode arrays: application in batch-injection analysis

The application of microelectrode arrays in electrochemical batch-injection analysis, injection volumes100 ml, has been investigated using a random array of microdisks (RAM) electrode made with carbon fibres. Preliminary batch-injection experiments involving hexacyanoferrate(II) oxidation, using fixed-potential amperometry and cyclic voltammetry, showed the expected lesser dependence on injection flow rate and the steady-state current characteristics of the RAM electrode, compared to results from similar experiments at macroelectrodes. After electrodepositing mercury on the carbon fibre disks, square wave anodic stripping voltammetry of the test of heavy metals zinc, cadmium and lead was carried out by batch-injection analysis. It was found that the accumulation time of the metals influenced the response to a greater extent than at macroelectrodes, that the influence on the injected volume was similar to that at macroelectrodes and the influence of injection flow rate was less. Detection limits are improved at the RAM electrode; sensitivity as a function of normalised electrode area is also enhanced. Experiments in which the RAM electrode was covered by a thin Nafion film before carrying out BIA‐SWASV were also performed, and showed similar trends. Although BIA can be performed directly on real samples without added electrolyte, the combination with microelectrodes, which by themselves permit measurements in highly resistive media and fast scan rates, may prove to be very valuable in extreme situations. # 1999 Elsevier Science B.V. All rights reserved.

Remoção de azul de metileno de solução aquosa usando zeólitas sintetizadas com amostras de cinzas de carvão diferentes

Batch sorption experiments were carried out to remove methylene blue from its aqueous solutions using zeolites synthesized from fly ashes as an adsorbent. The adsorbents were characterized by XFR, XRD and SEM. Nearly 90 min of contact time are found to be sufficient for the adsorption of dye to reach equilibrium. Equilibrium data have been analyzed using Langmuir and Freundlich isotherms and the results were found to be well represented by the Freundlich isotherm equation. Adsorption data were fitted to both Lagergren first-order and pseudo-second-order kinetic models and the data were found to follow pseudo-second-order kinetics.

Estabilização de solo contaminado com zinco usando zeólitas sintetizadas a partir de cinzas de carvão

The effect of synthetic zeolites on stabilizing Zn-contaminated soil using 0.01 mol L-1 CaCl2 leaching solution in batch experiments was investigated. The zeolites were synthesized from coal ash by hydrothermal treatment with alkaline solution. The additive enhanced the sorption capacity of the soil and reduced leaching. Zinc leaching was reduced by more than 80% using a minimum of 10% additive. The higher cation exchange capacity of the zeolite/soil mixtures and higher pH were responsible for stabilizing Zn in soil. The poly(2-aminobenzenesulfonic acid)-coated mercury thin-film electrode was used for the determination of zinc.

Zeolite Synthesis from Brazilian Coal Fly Ash for Removal of Zn2+ and Cd2+ from Water

A Brazilian fly ash sample (CM1) was used to synthesize zeolites by hydrothermal treatment. Products and raw materials were characterized in terms of real density (Helium Pycnometry), specific surface area (BET method), morphological analysis (SEM), chemical composition (XRF) and mineralogical composition (XRD). The zeolites (ZM1) from fly ash were used for metal ion removal from water. Results indicated that hydroxy-sodalite zeolite could be synthesized from fly ash sample. The zeolite presented higher specific surface area and lower SiO2/Al2O3 ratio than the ash precursor. The adsorption showed that cadmium is more preferentially adsorbed on ZM1 than zinc. The adsorption equilibrium time for both Zn2+ and Cd2+ was 20 hours in a batch process. The adsorption isotherms were better fitted by the Langmuir model and the highest percentages of removal using ZM1 were obtained at pH 6 and 5 and doses of 15 and 18 g L-1 for Zn 2+ and Cd2+ , respectively. Thermodynamic studies indicated that adsorption of Zn2+ and Cd2+ by ZM1 was a spontaneous, endothermic process and presented an increase of disorder at the interface solid/solution.