Modeling of the effect of EDTA on copper(II) biosorption onto Posidonia oceanica waste in batch and fixed-bed systems

• Significant influence of EDTA in the copper(II) uptake of P. oceanica was observed.
• Copper(II)–EDTA complexes were not sorbed by P. oceanica.
• Mass transport and copper(II)–EDTA chemical equilibrium were coupled for modeling.
• Breakthrough curves of copper(II) sorption in the presence of EDTA were simulated.
• Serial system of P. oceanica and activated carbon columns reduced copper(II)–EDTA leaks.

The performance of Posidonia oceanica for copper(II) biosorption in the presence of EDTA was investigated in batch and column experiments. In batch mode, copper(II) uptake in the presence of EDTA was lower than in its absence for the pH range 1.5–6.0. The decrease in the copper(II) uptake, attributed to the change in the chemical speciation of copper(II) with EDTA in solution, was from 71.7 to 58.8 mg/g in the absence and presence of EDTA respectively at pH 6. Column experiments were carried out at 5 and 20 mg Cu(II)/dm3 and different doses of EDTA. Constant copper(II) leaks were detected in the effluent of the columns. Leak concentrations matched the copper(II)-EDTA complexes’ concentration in the feed solution. Copper(II)-EDTA complexes were retained in neither batch nor continuous mode. A technological approach to solve this limitation was adopted: a dual biosorption system with P. oceanica and Scharlau AC in serial column configuration was investigated with promising results. Final effluent free of copper(II) was obtained since the copper(II)-EDTA leak was removed by the Scharlau AC. Copper(II) biosorption dynamics in fixed-bed column in the presence of EDTA were modeled by coupling the mass transport process with the chemical equilibrium between copper(II) and EDTA.