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Cadmium uptake by algal biomass in batch and continuous (CSTR and packed bed column) adsorbers

Publication . Vilar, Vítor J.P.; Santos, Sílvia; Martins, Ramiro; Botelho, Cidália; Boaventura, Rui

In this work, the properties of marine algae Gelidium, algal waste from agar extraction industry and a composite material were investigated for cadmium(II) biosorption. Equilibrium experiments were performed at three pH values (4, 5.3 and 6.5). Equilibrium data were well described by the Langmuir and Langmuir–Freundlich isotherms. Two models predicting the pH influence in the cadmium biosorption (discrete and continuous models) have been developed in order to better describe the equilibrium. The continuous model also considers a heterogeneous distribution of carboxylic groups, determined by potentiometric titration. The results of batch kinetic experiments performed at different pH values were well fitted by two mass transfer models and the homogeneous diffusion coefficients for the cadmium ions inside the biosorbentwere obtained. Continuous stirred tank reactor (CSTR) and packed bed column configurationswere also examined for the biosorption of cadmium ions. A strong acid (0.1MHNO3)was used as eluant to regenerate the biosorbents in the column. Several mass transfer models were applied with success to describe the biosorption process in batch mode, CSTR and fixed bed column.

2008Journal article

Open access

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

Publication . Vilar, Vítor J.P.; Freitas, Olga; Costa, Pedro; Botelho, Cidália; Martins, Ramiro; Boaventura, Rui

In this work, biosorption of trivalent chromium by the marine brown algae Sargassum muticum was 37 studied in a batch system. The effect of the solution pH on Cr(III) uptake by Sargassum was 38 investigated. Kinetics and equilibrium experiments were conducted at different pH values (3.0, 4.0 and 39 5.0). Equilibrium data are well described by the Langmuir and Langmuir-Freundlich isotherms and 40 kinetics follows the pseudo-second-order model, at different pH values. The two mass transfer models 41 give comparable results, but they did not provide a perfect representation of the sorption data. The 42 homogeneous diffusivity, Dh, was found to be around 1.6´10-8 cm2 s-1 for 100 mg l-1 Cr(III) 43 concentration. 44 Sargassum muticum was compared with the brown algae Laminaria hyperborean and the red algae 45 Gelidium sesquipedale in terms of uptake capacity. The maximum uptake capacities for Sargassum, 46 Laminaria and Gelidium were, respectively, 56 ± 3, 70 ± 4 and 18 ± 1 mg Cr(III) g-1, at pH = 5.

2011Journal article

Open access