Study of the acid-base properties of fulvic acid-like substances extracted from senescent leaves of eucalyptus and oak.
The acid-base properties of two fulvic acids (FA) extracted from senescent leaves of eucalyptus and oak were characterized by carrying out potentiometric titrations at two FA concentrations and four ionic strengths (0.005 M <[KNO(3)] <1.0 M). Experimental data were analyzed by means of the master curve approach, which includes an electrostatic spherical double layer model, and the Langmuir-Freundlich isotherm was used to fit the data. The contribution of the electrostatic effect to the proton binding reaction was lower than that observed for soil fulvic acids. The chemical heterogeneity of both samples was described by two acid sites with p Ks of about 4 and 7.5, the most abundant being the carboxylic site of p K = 4.
Antelo
Juan
J
Departamento de Química Física, Facultad de Química, Universidad de Santiago de Compostela, 15782, Santiago de Compostela, Spain.
López
Rocio
R
Fiol
Sarah
S
Antelo
Juan M
JM
Arce
Florencio
F
D000136:Acid-Base Equilibrium / Q000502:physiology; D001578:Benzopyrans / Q000032:analysis*; D018515:Plant Leaves / Q000737:chemistry* / Q000254:growth & development
D001578:Benzopyrans; C005023:fulvic acid