Biosorption of trace elements from aqueous systems in gold mining sites by the filamentous green algae (Oedogonium sp.)

• The potential use of Oedogonium sp. biomass in metal bioremediation.
• Oedogonium sp. biomass is efficient for wastewater treatment.
• The re-use of the algal biomass showed commendable adsorption capacities.
• The biosorption capacity of the algal biomass increased in a multi-ion system.
• The optimum uptake of Cr, Cu and Ni was reached at pH between 2 to 5.

Metal binding by algae has enormous potential for environmental bioremediation of industrial and urban wastewater. Algae have been proven to be cheaper and more effective for the removal of metallic elements in aqueous solutions. The present work reports the use of dried filamentous green algae, Oedogonium sp., for the sorption of Cu, Co, Cr, Fe, Hg, Ni, Zn and U in single and multi-ion solutions. Algal biomass from a gold mining site in Johannesburg was used in the study. The FT-IR analysis of the biomass revealed the presence of amino, carboxyl, phosphate and carbonyl functional groups. The maximum adsorption capacity was observed between pH 2 and 5 for Cr, Cu, Ni and Zn in single-ion solutions, whereas, in multi-ion solutions, the adsorption capacity was constant for the metals studied over the pH regime from 2 to 7, except for Ni and U. The formation of the negatively charged complexes leads to the decrease of the uptake of U beyond pH 4. The equilibrium data demonstrated a good fit with the Freundlich model for both cases.The biosorption of metals on the Oedogonium sp. biomass was exothermic and spontaneous and occurred on heterogeneous surface. The Oedogonium sp. biomasses could be repeatedly used up to 3 cycles with a virtual increase of their initial adsorption capacity. More than 110% of the metals adsorbed were eluted from the biomass. These results indicate that there were metals initially adsorbed on the biomass which were also released during desorption.Thus, this study demonstrated that algal biomass could be used as an efficient biosorbent for the treatment of trace element-bearing wastewater.