Fig. 6 shows the XPS oxygen signal. It is possible to note that there are two deconvolutions corresponding to the covalent union of C–OH and the ether C–O–C. As expected the hydroxyl group signal is more intense. After the contact of the biosorbent with the lead ions, the XPS oxygen signal is modified as depicted in Fig. 7. The signal now is deconvoluted in four peaks. These peaks indicate that the lead is forming a complex with the oxygen, since the displacements do not correspond to a covalent union. This evidences that the oxygen is interacting with the lead and that the oxygen has two plausible sources: hydroxyl group and ether group.