Electron Paramagnetic Resonance and Atomic Absorption Spectrometry as tools for the investigation of Cu(II) biosorption by Sargassum filipendula

A basic investigation into the removal of copper ions from aqueous solutions by Sargassum filipendula was conducted in batch conditions. The influence of different experimental parameters such as initial pH, sorption time, equilibrium conditions, and initial concentrations of copper ions on copper uptake was evaluated. Results indicated that copper uptake capacity increased from pH 2.0 to 3.0, being constant at pH values 4.0 and 5.0. Electron Paramagnetic Resonance proved to be a useful tool for studying the mechanism involved in copper biosorption by S. filipendula. For initial copper concentrations smaller than 250 μg mL− 1 axial type spectra were obtained, typical of isolated immobilized copper ions, and a hyperfine structure was observed (A|| = 150(2)G, g|| = 2.31(1)). For initial copper concentrations greater than 250 μg mL− 1, (qe = 53.3 mg g− 1), a distorted line, typical of aggregates, was observed, due to dipole–dipole magnetic interactions.The Langmuir model better represented the sorption process, as compared to the model of Freundlich. The process followed a second-order kinetics, and equilibrium was reached after 10 min of contact between the biomass and the metal solution. Due to its outstanding copper uptake capacity (1.30 mmol g− 1 biomass), S. filipendula proved to be an excellent biomaterial for accumulating and recovering copper from industrial solutions. The results show that the biomass has sorption capacities comparable to other biomasses and conventional ion-exchange materials.