Walter Ruggeri Waldman

Ion exchange kinetics of magnetic alginate ferrogel beads produced by external gelation

This paper reports on a study of the influence of sodium alginate concentration and iron addition on the ion exchange kinetics of calcium alginate ferrogel beads produced by external gelation. The calcium absorption and sodium release of the beads were fitted to Ficks second law for unsteady state diffusion in order to obtain the effective diffusion coefficients of Na(+) and Ca(2+). The dried beads were characterized concerning their thermal stability, particle size distribution and morphology. The gelation kinetics showed that an increase in alginate concentration from 1% to 2% increased the Ca(2+) equilibrium concentration, but presented no effect on Ca(2+) effective diffusion coefficient. Alginate concentration higher than 2% promoted saturation of binding sites at the bead surfaces. The addition of iron promoted faster diffusion of Ca(2+) inside the gel beads and reduced the Ca(2+) equilibrium concentration. Also, iron particles entrapped in the alginate gel beads promoted greater absorption of water compared to pure alginate gel and lower thermal stability of the beads. The main diffusion of Ca(2+) into and Na(+) out from the bead took place during the first 60 min, during which almost 85-90% of the Ca(2+) equilibrium concentration is achieved, indicating that this period is sufficient to produce a Ca-alginate bead with high crosslinking of the polymer network.

Mechanical properties, morphology and thermal degradation of a biocomposite of polypropylene and curaua fibers: coupling agent effect

Biocomposites of polymers with vegetal fibers have a broad spectrum of applications due to their high specific properties in comparison to their counterparts made with fiberglass. Polypropylene, PP, composites with curaua fiber compatibilized with different concentrations of maleic anhydride grafted polypropylene, PP-g-MA, were characterized according to their mechanical properties, morphologies and thermal stabilities in oxidative and inert atmospheres. The composites were prepared by single screw extrusion and injection molded specimens were used for testing. The composite with 20 wt % of curaua fiber with and without compatibilizer presented improved mechanical properties compared to pure PP. The use of PP-g-MA as a compatibilizer significantly increased fiber/matrix adhesion, however, the mechanical properties were only slightly improved in comparison with composites without compatibilizer. We observed an improvement in thermal stability of the composites, compared to that expected from the weighted average of the individual components, both under inert and oxidative atmospheres. Furthermore, the thermal stability improved under inert atmosphere as a function of the concentration of compatibilizer. In this situation, indeed, there was a different shift of the weight loss processes owing to the presence of the compatibilizer.

Influence of Compatibilizer on Blends Degradation During Processing

The thermomechanical degradation of blends made from polypropylene and polystyrene, with or without compatibilizer, was studied using an internal mixer coupled to a torque rheometer. The blends processed without compatibilizer presented regular and expected results regarding torque reduction, with evidence of chain scission. The blends processed with the block copolymer of styrene and butadiene, SBS, as a compatibilizer presented unchanged or less reduced variation on torque values during processing. The extraction of stabilizers from the compatibilizer before processing did not affect the results. The compatibilizer concentration in the blends was varied, with its influence still being observed in concentrations as low as 0.03 parts per hundred. Similar results were obtained in an experiment comparing the performance of a primary commercial anti-oxidant, Irganox 1076, and the compatibilizer SBS. Therefore, the compatibilizer can be considered as a processing aid agent with positive influence on avoiding thermomechanical degradation.

Natural organic matter residue as a low cost adsorbent for aluminum

The contamination of aquatic and terrestrial environments by potentially toxic metals is highlighted by the possible impacts that their high availability can have on the environment. Thus, the development of alternative absorbents that can be used in the remediation of contaminated areas is of great environmental interest. Humin, one of the fractions of natural organic matter, is a promising alternative in studies on the retention of different metals that are environmentally toxic. In this study, the influence of the organic and inorganic humin constituents that are involved in the retention of aluminum species was evaluated. After extraction and calcination to obtain the ashes (inorganic constituents), humin and ash samples were structurally characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. Interaction studies between aluminum-humin and ash-humin were performed in the pH range of 4.0-8.0 and with various contact times. The results of the characterization of humin and ash showed different functional groups present in the structures of these materials. Based on the results of the interaction between humin-aluminum and ash-aluminum, it can be inferred that both the organic and inorganic components of humin are efficient at absorbing aluminum. However, the adsorption isotherms showed that humin and the ashes have different adsorption behaviors. Humin is the only fraction of natural organic matter with a significant inorganic constituent content; it is the fraction least used by researchers in this field and is often discarded as waste. In light of this, the results obtained in this work highlight the importance of humin as a natural adsorbent material. Humin may be promising for the removal of aluminum species in contaminated environments due to the presence of organic and inorganic constituents.

TRATAMENTO COM CLORETO DE CÁLCIO NA PÓS-COLHEITA RETARDA O DESVERDECIMENTO E A PERDA DE FIRMEZA DO MAMÃO UENF/CALIMAN01

In order to prolong the shelf life and maintain the quality of Papaya/UENF/Caliman01, different concentrations of CaCl2 applied by vacuum infiltration were tested. The fruit were separated into six groups: control (no treatment) and treatments with CaCl2 at 0%, 2%, 4%, 6%, and 8% CaCl2 (w/v), applied by immersion under vacuum during 3 min at 50kPa tension. Further analysis was then performed with respect to weight loss, fruit firmness, mesocarp firmness, hue angle color, soluble solids (SS), titratable acidity (TA), ascorbic acid, total sugars, and the SS/TA ratio. The calcium treatment did not affect the weight loss, which generally increased over time. However, the fruit remained green and firm longer when treated with CaCl2 at 6% and 8% (w/v). The use of CaCl2 did not affect chemical fruit characteristics such as soluble solids, titratable acidity, and SS/TA ratio, but did decrease the synthesis of ascorbic acid and the degradation of soluble sugars.

Potencial Energético da Casca de Coco (Cocos nucifera L.) para Uso na Produção de Carvão Vegetal por Pirólise

A falta de um destino correto para o descarte dos residuos de coco verde e seu potencial como biomassa estimula sua utilizacao para fins energeticos. Este trabalho teve como objetivo investigar o potencial energetico da casca de coco verde (Cocos nucifera L.) para producao de carvao vegetal atraves de estudo pirolitico. Para a obtencao do carvao vegetal, as amostras foram submetidas a pirolise, nas temperaturas de 300 °C (CP300), 350 °C (CP350), 400 °C (CP400), 450 °C (CP450) e 500 °C (CP500). A casca de coco e os carvoes produzidos foram caracterizados mediante: analise imediata, poder calorifico superior (PCS) e analise termogravimetrica (TG). Para os carvoes vegetais produzidos, foram tambem determinados seus rendimentos gravimetricos, energeticos e em carbono fixo. Observou-se que, com o aumento da temperatura de pirolise, houve a diminuicao do teor de volateis (CP300=37,95% e CP500=14,94%) e, consequentemente, aumento do carbono fixo (CP300=56,42% e CP500=79,39%) e PCS (CP300=28,84 MJ/kg e CP500=29,59 MJ/kg). O aumento da temperatura tambem provocou a diminuicao do rendimento gravimetrico (CP300=48,05% e CP500=33,29%) e energetico (CP300=66,50% e CP500=52,76%) e um aumento na estabilidade termica. Pode-se concluir que o carvao vegetal da casca de coco verde e uma alternativa para o reaproveitamento energetico desse residuo e tem condicoes para ser utilizado como carvao vegetal comercial.

Fly-Ash from Biomass Burning: Applications and Potentialities

Brazil is one of the largest agricultural producers in the world and the disposal of its waste is an economic and environmental concern. With the emergence of newer opportunities in bioenergy, this article discusses some of the various lines of research on characterization and utilization of ashes, the final residue after burning the bagasse sugarcane and several kinds of biomass in thermoelectric. Ashes are a complex material, chemical and morphologically heterogeneous, composed of particles as cenospheres, silicates and unburned carbons. Some of the uses addressed in this paper are its use as adsorbents for industrial wastewater treatment, the use of cenospheres in composites, the use of the ash in construction as inert or pozzolanic materials and their use in agriculture as a source of nutrients and correction soil pH. We hope this article help to foster the interface of the chemistry community in Brazil and the research lines disclosed herein.