Aug 19, 2008

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

Journal of Plant Physiology
G C L AraújoCristina Nabais

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 gro...Continue Reading

Mentioned in this Paper

Quercus ilex
Histidine
Natural graphite
Pectins
Citricum acidum, citric acid, homeopathic preparation
Quercus
Amino Acids, I.V. solution additive
Complex (molecular entity)
Nickel
Oxalicum acidum, oxalic acid, sorrel acid, Homeopathic preparation

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