Spectroscopic characteristics of ultrafiltration fractions of fulvic and humic acids isolated from an eucalyptus bleached Kraft pulp mill effluent

In order to investigate the chemical heterogeneity of fulvic and humic acids previously isolated from a bleached Kraft pulp mill effluent, a sequential ultrafiltration (UF) scheme through four polyethersulphone membranes was applied. The unfractionated fulvic and humic acids and their fractions were characterized by UV-VIS, synchronous fluorescence (with (delta)(pi)-bonds in the fractions of highest molecular sizes. In what concerns the humic acids size fractions, the FTIR spectra did not exhibit major differences but, as observed for the fulvic acids’ fractions, UV-VIS and synchronous fluorescence spectra also suggest a higher degree of conjugation of (pi)-bonds in the fractions with the highest molecular sizes. It was also observed that the fulvic and humic acids fractions of the same molecular size, operationally defined by the UF process, exhibit major differences in their spectroscopic features.