Nickel sorption capacity of ground xylem of Quercus ilex trees and effects of selected ligands present in the xylem sap.

TitleNickel sorption capacity of ground xylem of Quercus ilex trees and effects of selected ligands present in the xylem sap.
Publication TypeJournal Article
Year of Publication2009
AuthorsAraújo, G. C. L., Lemos S. G., & Nabais C.
JournalJournal of plant physiology
Volume166
Pagination270-277
Accession Number18707798
KeywordsAdsorption isotherms, Nickel, Organic ligands, Xylem
Abstract

In this work the influence of four different ligands present in the xylem sap of Quercus ilex (histidine, citric, oxalic and aspartic acids) on Ni(II) adsorption by xylem was investigated. Grinded xylem was trapped in acrylic columns and solutions of Ni(II), in the absence and presence of the four ligands prepared in KNO(3) 0.1molL(-1) at pH 5.5, were percolated through the column. Aliquots of solutions were recovered in the column end for Ni determination by graphite furnace atomic absorption spectrometry (GFAAS). The experimental data to describe Ni sorption by xylem in both the presence and absence of ligands was better explained by the Freundlich isotherm model. The decreasing affinity order of ligands for Ni was: oxalic acid>citric acid>histidine>aspartic acid. On the other hand, the Ni(II) adsorption by xylem increased following the inverse sequence of ligands. Potentiometric titrations of acidic groups were carried out to elucidate the sorption site groups available in Q. ilex xylem. The potentiometric titration has shown three sorption sites: pK(a) 2.6 (57.7% of the sorption sites), related to monobasic aliphatic carboxylic acids or nitrogen aromatic bases, pK(a) 8.1 (9.6%) and pK(a) 9.9 (32.7%), related to phenolic groups.