Olga M. Freitas

Optimization of Cu(II) biosorption onto Ascophyllum nodosum by factorial design methodology

A Box-Behnken factorial design coupled with surface response methodology was used to evaluate the effects of temperature, pH and initial concentration in the Cu(II) sorption process onto the marine macro-algae Ascophyllum nodosum. The effect of the operating variables on metal uptake capacity was studied in a batch system and a mathematical model showing the influence of each variable and their interactions was obtained. Study ranges were 10-40 degrees C for temperature, 3.0-5.0 for pH and 50-150 mg L(-1) for initial Cu(II) concentration. Within these ranges, the biosorption capacity is slightly dependent on temperature but markedly increases with pH and initial concentration of Cu(II). The uptake capacities predicted by the model are in good agreement with the experimental values. Maximum biosorption capacity of Cu(II) by A. nodosum is 70 mg g(-1) and corresponds to the following values of those variables: temperature=40 degrees C, pH=5.0 and initial Cu(II) concentration=150 mg L(-1).

ADSORPTION STUDY OF LEAD BY ASCOPHYLLUM NODOSUM USING A FACTORIAL EXPERIMENTAL DESIGN

A factorial design methodology was used to evaluate the effects of temperature, pH and initial concentration of Pb(II) in sorption process onto the marine macro-algae Ascophyllum nodosum. The Box-Behnken factorial design method gives a mathematical model that shows the influence of each variable and their interactions on the process efficiency. Study ranges were 10-40 oC for temperature, 3.00-5.00 for pH and 50-200 mg/L for initial Pb(II) concentration. Within these ranges, the adsorption capacity is slightly dependent on temperature and pH but markedly increases with initial concentration. Maximum adsorption capacity of Pb(II) by Ascophyllum nodosum was 180 mg/g, which corresponds to the following values of those variables: temperature = 40 oC, pH = 5.00 and initial concentration = 200 mg/L.

Cr(III) uptake by marine algal biomass: equilibrium and kinetics

In this work, biosorption of Cr(III) by the marine brown algae Sargassum muticum was studied in a batch system. Kinetics and equilibrium experiments were conducted at different pH. Equilibrium data are well described by the Langmuir and Langmuir-Freundlich isotherms. The two mass transfer models give comparable results, but they did not provide a perfect representation of the sorption data. Sargassum muticum was compared with the brown algae Laminaria hyperborean and the red algae Gelidium sesquipedale, showing maximum uptake capacities of, 56 ± 3, 70 ± 4 and 18 ± 1 mg Cr(III) g −1 , at pH = 5, respectively.

Preparation and characterization of biodegradable films from keratinous wastes of the leather industry

With increasing demand for sustainable materials, keratin wastes have been regarded, in recent years, as renewable resources worthy of exploitation. Each year, the Portuguese leather industry discards a considerable amount of animal hair, which constitutes a troublesome waste product. In this study, in an attempt to find a potential utilization for this waste, the preparation of biodegradable films from bovine hair, by thermo-compression, was tested. Bovine hair formulations with 20, 30 and 40 wt % of plasticizer (glycerol, lactic acid) were pressed into films, at 147 kN and 120oC or 160oC for 4 minutes. The mechanical properties, colour, solubility and water sorption isotherms of the obtained films were assayed. All films were opaque and dark. Solubility was higher for films processed at higher temperature and with lactic acid as plasticizer. The Guggenheim-Anderson-de Boer (GAB) model gave a good fit to the experimental results for the moisture sorption isotherms. The stress at break, , and the Young’s modulus, E, decreased and the strain at break, , increased with the addition of increasing amounts of plasticizer.