The adsorption of Zn(II) from both synthetic solution and kaolin industry wastewater by cattle manure vermicompost was studied. The adsorption process was dependent on the various operating variables, viz., solution pH, particle size of the vermicompost, mass of vermicompost/volume of the Zn(II) solution ratio, contact time and temperature. The optimum conditions for Zn adsorption were pH 6.0, particle size of < or = 250 microm, 1 g per 10 mL adsorbent dose, contact time of 4h and temperature of 25 degrees C. Langmuir and Freundlich adsorption isotherms fit well in the experimental data and their constants were evaluated, with R(2) values from 0.95 to 0.99. In synthetic solution, the maximum adsorption capacity of the vermicompost for Zn(2+) ions was 20.48 mg g(-1) at 25 degrees C when the vermicompost dose was 1 g 10 mL(-1) and the initial adjusted pH was 2. The batch adsorption studies of Zn(II) on vermicompost using kaolin wastewater have shown the maximum adsorption capacity was 2.49 mg g(-1) at pH 2 (natural pH of the wastewater). The small values of the constant related to the energy of adsorption (from 0.07 to 0.163 L mg(-1)) indicated that Zn(2+) ions were binded strongly to vermicompost. The values of the separation factor, R(L), which has been used to predict affinity between adsorbate and adsorbent were between 0 and 1, indicating that sorption was very favorable for Zn(II) in synthetic solution and kaolin wastewater. The thermodynamic parameter, the Gibbs free energy, was calculated for each system and the negative values obtained confirm that the adsorption processes are spontaneous. The DeltaG degrees values were -19.656 kJ mol(-1) and -16.849 kJ mol(-1) for Zn(II) adsorption on vermicompost in synthetic solution at pH 6 and 2, respectively, and -13.275 kJ mol(-1) in kaolin wastewater at pH 2.
The chemical composition of pastes is one of the factors responsible for the behaviour of the paste during the drying process in spouted bed. Therefore, the aim of this study was to analyse the drying process of paste in spouted bed for four types of milk: whole, skimmed, semi‐skimmed and low lactose content milk, which have different concentrations of sugar and fat. A neuronal model was proposed in order to describe the influence of the presence of pastes on the spouted bed fluid dynamics. The change of moisture content of the powder during the drying process and of the heat and mass transfer phenomena were estimated using a hybrid model based on the global balance of mass and energy and a phase‐coupling term given by a neural network.
The mucilage of Pereskia aculeata Miller is a hydrocolloid with the potential to be used as a food additive. Thus, data on its physical, chemical and microbiological stability are necessary to evaluate the storage stability of the product. This study aimed to determine the thermodynamic properties of water vapor adsorption onto freeze-dried ora-pro-nobis mucilage (OPNM) and to interpret the mechanisms that govern water adsorption onto powder particles through the study of enthalpy-entropy compensation. In addition, OPNM was characterized in terms of moisture, ash, ether extract, protein, fiber and carbohydrates beyond the functional chemical groups by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Thermodynamic analysis showed that water adsorption onto OPNM powder was characterized as a spontaneous process with strong attractive forces in the water and OPNM mixture. The water sorption mechanism for OPNM at the studied adsorption range was regulated by energy interactions related to the chemical composition of the product.
Elaborado por Maurício Amormino Júnior-CRB6/2422 O conteúdo dos artigos e seus dados em sua forma, correção e confiabilidade são de responsabilidade exclusiva dos autores. 2019 Permitido o download da obra e o compartilhamento desde que sejam atribuídos créditos aos autores, mas sem a possibilidade de alterá-la de nenhuma forma ou utilizá-la para fins comerciais.
Scientists are developing new technologies for biodegradable active packaging made from natural polymers and antioxidant agents as a more sustainable alternative to conventional packaging made from fossil fuels. In this study, the biodegradation of the films was evaluated using techniques such as Fourier transform infrared spectroscopy (FTIR), thermogravimetry (TG), visual and morphological analysis using scanning electron microscopy (SEM). Water sorption isotherms and thermodynamic parameters were analyzed at different temperatures (5 °C, 15 °C, and 25 °C) and relative humidities until the samples reached a constant weight. The results showed changes in the morphology, color, and mass of the cassava starch films with tomato peel due to biodegradation. FTIR revealed structural changes in the films, while TG/DTG curves did not show significant differences over time. The addition of tomato peel to the polymer matrix resulted in lower water solubility. The Guggenheim-Anderson-de Boer (GAB) model provided the best fit for the water sorption isotherms. The monolayer moisture content (Xm) increased with temperature, indicating the availability of active sites for water sorption in the material. Thermodynamic analyses indicated that lower moisture content corresponded to more active sorption sites, and the sorbed water molecules exhibited greater order. In conclusion, biodegradable active packaging offers an environmentally friendly alternative as it decomposes more rapidly than conventional packaging made from fossil-derived materials. The sorption isotherms demonstrated that the adsorption in the packaging materials is controlled by entropy, emphasizing the importance of the number of available active sites for binding rather than the chemical composition of the film.
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