Biosorption optimization of Ni(II) ions on Macauba (Acrocomia aculeata) oil extraction residue using fixed-bed column

Macauba is a palm tree located in Tropical and Subtropical America. The oil extraction process from the pulp and kernel of the Macauba fruit generates two main residues, mesocarp and endocarp. The extraction process produces considerable quantity of residues that can become an environmental issue. The applications of mesocarp as a biosorbent have been reported, but studies involving the endocarp were no longer conducted. The objective of this paper was to study the application of endocarp, without pre-treatment, for Ni(II) biosorption optimization in fixed-bed column employing a factorial experiment. Spectroscopic studies reveled that Ni(II) biosorption can be related to functional hydroxyls and phenols groups on the biosorbent surface. Large particles with irregular surfaces and without defined pores were observed by micrographs. The biosorption optimization showed that the usable capacity of the bed up to the break-point (tu), total time equivalent to the packaging capacity of the column (tt) and total removal (Rt) were affected by both pH and Ni(II) concentration. Mass Transfer Zone (MTZ) was affected only by biosorbent mass. Equilibrium metal uptake (qe) was affected by pH, biosorbent mass and Ni(II) concentration. Thus, it was possible to determine the equations that control the response variables and observe a significant and rapid removal of Ni(II). Kinetics studies exhibited the appropriateness of Pseudo-second-order model to describe the phenomena involved on biosorption kinetics. The results obtained in this paper showed the applicability of Macauba endocarp as a low-cost and environmentally friendly biosorbent for treatment of wastewaters contaminated with Ni(II).