Biosorption of toxic metals using the alginate extraction residue from the brown algae Sargassum filipendula as a natural ion-exchanger

摘要

In order to aggregate extra value to dealginated seaweed waste (RES1 and RES2) and to establish a new usage for the process waste, this study evaluated the use of this biomass in the removal of toxic metals from contaminated wastewater. Both residues showed similar affinity for almost all metallic ions studied, and the comparison revealed that the largest reduction in the percentage removal was found for cadmium. It was identified a behavior typical of ion exchange, where sodium was the most released ion, mainly in the presence of Cr and Cd. The kinetic study also showed a maximum adsorption peak of nickel and zinc and this uncommon behavior may be related to the properties of each metal ion, such as strength of ionic bonds and diffusivity. The Boyd model fits indicated that the removal of chromium and cadmium is predominantly controlled by the internal diffusion, while the External Mass Transfer Resistance model showed that the Ni and Zn uptake are mainly controlled by the external diffusion. In relation to the pseudo-first order and pseudo-second model, the first better describes Ni and Zn experimental data, whereas the last one is more representative to Cd and Cr data. (C) 2017 Elsevier Ltd. All rights reserved.