Application of a dealginated seaweed derivative for the simultaneous metal ions removal from real and synthetic effluents

Abstract

In this study, the alginate extraction residue (RES) from Sargassum filipendula was employed as biosorbent for the simultaneous removal of Cr3+, Ni2+ and Zn2+ from ternary synthetic solutions and for the decontamination of industrial (leather industry) and urban real effluents that were collected from different areas of Strasbourg (France). For this purpose, biosorption experiments in batch mode, multimetals equilibrium isotherms fitting and biosorbent characterization were carried out. In synthetic effluents, RES exhibited a greater affinity for Cr3+ ions, while a still unknown affinity for Al3+ and Pb2+ was verified for real conditions, reaching up to 80 % removal in some cases. At equilibrium, the higher sorption capacities were found at 50 °C as 0.864, 0.302 and 0.347 mmol/g for Cr3+, Zn2+ and Ni2+, respectively. Regarding the equilibrium models fitting, just the Extended Langmuir equation was able to describe the experimental data, showing an increase in qmax as the temperature rose, besides a decay in KL,1, KL,2 and KL,3 at the higher temperatures that indicates a weakening of adsorbent-adsorbate interactions. The characterization analyzes revealed a complex biosorption with a depth participation of carboxylic and hydroxyl groups was revealed by the characterization analyses, whereas the ion exchange mechanism played a really important role. The cation exchange capacity of RES was quantified as 34.12 mg/gRES with main exchangeable position of Ca2+ and Na+ ions. Based on these results, RES could be used as a novel and efficient biosorbent for toxic metals removal even from quite diluted real effluents, contributing to its valorization.