Interaction between Humic Acids and Anthraquinone Dyes

Abstract

Interactions between humic acids and anthraquinone disperse-dyes were studied. A humic acid extracted from a marine sediment and a commercial one were used to solubilize dyes sparingly soluble in water. The solubility of dyes in humic acid solution was measured by the shake-flask method. The dye solubility in humic acid solution increases with humic acid concentration and enhancement was marked for solution of Aldrich humic acid. The addition of salts decreased the solubility of the dye but the effects were complicated. Differences in salts appeared to affect the solubility of dye little in both marine and commercial humic acids. Dye solubility increased with temperature, especially in the case of a 0.1% solution of marine humic acid at high temperature. The spectrum of the dye solubilized in humic acid solution changed and a twin peak characteristic of 1, 4-isomers of polyaminoanthraquinone disappeared and a broad peak appeared. The dye solubilized by humic acid may thus possibly exist as a solid state as a deposit on quartz. From the effects of temperature and change in the spectrum, it is suggested that interactions of the dye and humic acids may be attributable to a partition like process but structural and compositional factors of humic acid should also be considered.