Biosorption of Cu(II) from aqueous solution by Fucus serratus: surface characterization and sorption mechanisms

In this work, the brown alga Fucus serratus (FS) used as a low cost sorbent has been studied for the biosorption of copper(II) ions in batch reactors. Firstly, the characterization of the surface functional groups was performed with two methods: a qualitatively analysis with the study of FT-IR spectrum and a quantitatively determination with potentiometric titrations. From this latter, a total proton exchange capacity of 3.15 mmolg(-1) was extrapolated from the FS previously protonated. This value was similar to the total acidity of 3.56 mmolg(-1) deduced from the Gran method. Using the single extrapolation method, three kinds of acidic functional groups with three intrinsic pK(a) were determined at 3.5, 8.2 and 9.6. The point of zero net proton charge (PZNPC) was found close to pH 6.3. Secondly, the biosorption of copper ions was studied. The equilibrium time was about 350 min and the adsorption equilibrium data were well described by the Langmuir's equation. The maximum adsorption capacity has been extrapolated to 1.60 mmolg(-1). The release of calcium and magnesium ions was also measured in relation to the copper biosorption. Finally, the efficiency of this biosorbent in natural tap water for the removal of copper was also investigated. All these observations indicate that the copper biosorption on FS is mainly based on ion exchange mechanism and this biomass could be then a suitable sorbent for the removal of heavy metals from wastewaters.