SPECTROSCOPIC STUDY OF THE INTERACTION BETWEEN A HUMIC ACID AND AN OXAZINE DYE

GRACIELA P. ZANINI; MARCELO J. AVENA; SARAH FIOL; FLORENCIO ARCE; RAMON A. ROSELL

Sao Pedro

Congreso; XII International Meeting of IHSS; 2004

IHSS

Humic substances play an important role in controlling the transport and fate of both organic and inorganic pollutants (metals, pesticides, dyes, etc) in natural waters. This control is carried out by binding contaminants molecules, modifying their solubility, their capacity to attach mineral surfaces and eventually their mobility and bioavailability. The aim of this work is to study the interaction between a humic acid (HA) and an oxazine dye (OX) by UV-Vis spectrophotometry. The binding capacity of HA is evaluated by measuring binding isotherms as a function of pH and electrolyte concentration. The results show that the presence of HA modifies the spectrum of OX and thus binding isotherms can be constructed from UV-Vis data. These isotherms reveal that the affinity of HA for OX does not depend on the pH and electrolyte concentration. However, the number of binding sites for OX in the studied HA changes significantly by changing pH and ionic strength. Oxazine dye is an appropriate compound to be used to as a probe to determine properties of humic substances. The technique seems to be adequate to study the interaction between humic substances and other UV or Vis absorbing contaminant.