Removal of Cu and Cr from an industrial effluent using a packed-bed column with algae Gelidium-derived material

The purpose of this work was to evaluate the potential of algal waste from the agar extraction industry, immobilized in a polymer, and the algae Gelidium itself, the raw material of agar extraction, to remove Cu(II) and Cr(III) from industrial effluents. The study involved a Cu(II) bearing effluent and the mixture of this effluent with an effluent containing Cr(VI), previously reduced to Cr(III). The two effluents were collected from metal plating plants, and then filtered and diluted before the biosorption studies. Biosorption results were compared with those obtained from pure Cu(II) and Cu(II)/Cr(III) solution adsorption experiments. Three consecutive adsorption (≈ 50 mg Cu(II)/l)-desorption (0.1 M HNO3) cycles were carried out with algae Gelidium and two with the composite material, for the Cu(II) effluent. The biomass uptake capacity remained almost constant and close to the obtained for adsorption from pure Cu(II) solution, suggesting that the biomass lifetime was long enough to be used in a continuous industrial process. In the biosorption from Cu(II)/Cr(III) mixtures it was observed that Cr leave the column after the residence time, suggesting that the reduction of Cr(VI) to Cr(III) was not completely achieved. Cr(VI) speciation in aqueous solution produces negatively charged species, that do not bind to the negatively charged carboxylic groups on the biosorbent surface and a low breakthrough time is obtained. An “overshoot” was observed for the Cu(II) concentration, suggesting that Cr(III) has a higher affinity to the binding sites than Cu(II).