Use and treatment of chicken feathers as a natural adsorbent for the removal of copper in aqueous solution.

PURPOSE: Copper is a heavy metal that causes considerable deterioration to human health and ecosystems, so their elimination in water bodies is of great interest. Present investigation shows the efficiency of chicken feather as a natural adsorbent and its subsequent degradation in order to have an integral treatment and avoid the unconscious disposition. METHODS: Optimal conditions of adsorption process were determined using the Response Surface Methodology (RSM)-Box-Behnken design (BBD) with three variables (pH, temperature and adsorbent dose). After that, the optimal conditions were used to analize the adsorption isotherms by Langmuir, Freundlich and Temkin models; also thermodynamics parameters Gibbs free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) were obtained. Finally, the biodegradation of the residue denominated "adsorbent-adsorbate" complex was evaluated through monitoring the soluble protein production, keratinolytic activity, ninhydrin positive products, sulfhydryl groups, and gravimetrically analysis. RESULTS: The optimum conditions for the adsorption were 30°C and pH 3, the Langmuir model was better described the adsorption process at 30°C, while at 40°C was Temkin model. The chicken feather turned out a natural adsorbent competitive with respect to others used in the removal of copper in liquid systems; obtaining qmax of 7.84 and 11.48 mg/g at 30 and 40°C, respectively; it was also a favorable and spontaneous process. Finally the adsorbent used was degraded by a keratinolytic consortium. CONCLUSIONS: In this study, chicken feather was used as a low cost adsorbent for copper efficiently and with the feasibility that the adsorbent can be biodegraded and release the metal.

Physical properties of inulin and inulin-orange juice: physical characterization and technological application.

In this work two systems based on a carbohydrate polymer were studied: inulin as model system and inulin-orange juice as complex system. Both system were stored at different water activity conditions and subsequently characterized. Water adsorption isotherms type II were fitted by the GAB model and the water monolayer content was determined for each system. From thermal analyzes it was found that at low water activities (aw) systems were fully amorphous. As aw increased, crystallinity was developed. This behavior was corroborated by X-ray diffraction. In the inulin-orange juice system, crystallization appears at lower water activity caused by the intensification of the chemical interaction of the low molecular weight species contained in orange juice. Glass transition temperature (Tg), determined by modulated differential scanning calorimeter, decreased with aw. As water is adsorbed, the physical appearance of samples changed which could be observed by optical microscopy and effectively related with the microstructure found by scanning electron microscopy.

Glass transition study in model food systems prepared with mixtures of fructose, glucose, and sucrose.

The glass transition temperature of model food systems prepared with several glucose/fructose/sucrose mass fractions was studied using differential scanning calorimetry (DSC). A distance-based experimental design for mixtures of 3 components was used to establish the proportion of sugars of the model systems. Thus, 32 compositions including individual sugars and sugar mixtures, both binary and ternary were prepared and analyzed. Thermograms showing the complete process of heating-cooling-reheating were used to determine the precise glass transition temperature during cooling (T(g)(c)) or reheating (T(g)(H) in amorphous sugars. The Scheffe cubic model was applied to experimental results to determine the influence of sugar composition on the glass transition temperature (P < 0.05). The final model proved to be appropriate (R(2) > 0.97, CV < 9%, model significance <0.0001) to predict the T(g) values of any dry mixture of amorphous fructose, glucose, and sucrose.