Juliana de C. Izidoro

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.

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.

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.

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.

Aplicação de material zeolítico sintetizado de cinzas de carvão como adsorvente de poluentes em água

Coal fly ashes treated by hydrothermal method were used as low-cost adsorbent for the removal of metals ions and dye from aqueous solution. The adsorption isotherms of the treated fly ashes were studied and results were fitted using Langmuir and Freundlich models. It shows that the Freundlich isotherm is better in describing the adsorption process for methylene blue. The equilibrium data for zinc and cadmium ions adsorption well fitted to the Langmuir equation. The maximum adsorption capacity value obtained was 0.78 (mg g-1)(L mg)1/n for methylene blue, 38.05 mg g-1 for Zn2+ and 67.48 mg g-1 for Cd2+. The synthesized materials exhibit much higher adsorption capacities than raw fly ashes. The study showed that the zeolitic material can effectively adsorb methylene blue and metals ions with removal efficiencies ranging from 82-99%.