Valorization of biosorbent obtained from a forestry waste: Competitive adsorption, desorption and transport of Cd, Cu, Ni, Pb and Zn

- Valorization of pine bark for multimetal removal was studied in lab-scale experiments.
- Multi-metal batch-type experiments showed the adsorption sequence Pb≈Cu>Cd>Zn>Ni.
- Bi-metal experiments show that Cu and Pb had a high capacity to desorb other metals.
- Column experiments showed the sequence Pb>Cu>Zn>Cd>Ni for retention capacity.
- Pine bark could be useful in the treatment of multi-metal systems.

Bark from Pinus pinaster is one of the most abundant forestry wastes in Europe, and among the proposed technologies for its reutilization, the removal of heavy metals from wastewater has been gaining increasing attention. In this work, we have studied the performance of pine bark for heavy metal biosorption on competitive systems. Pb, Cu, Ni, Zn and Cd sorption and desorption at equilibrium were studied in batch experiments, whereas transport was studied in column experiments. Batch experiments were performed adding simultaneously different concentrations (0.08-3.15 mM) of two or more metals in solution to pine bark samples. Column experiments were performed with 10 mM solutions of two metals or a 5 mM solution of the five metals. In general, the results under competitive conditions were different to those obtained in monoelemental experiments. The multi-metal batch experiments showed the adsorption sequence Pb≈Cu>Cd>Zn>Ni for lower metal doses, Pb>Cu>Cd>Zn>Ni for intermediate doses, and Pb>Cu>Cd≈Zn≈Ni for high metal doses. Desorption followed the sequence PbCu>Zn>Cd>Ni. The presence of a second metal affected the transport of all the elements studied except Pb, and confirmed the strong influence of Pb and Cu on the retention of the other metals. These results can help to appropriately design decontamination systems using this forestry waste.