Chromophoric compounds from an Eucalyptus bleached Kraft pulp mill effluent: new insights from comprehensive two-dimensional liquid chromatography

摘要

Macromolecular organic compounds, essentially lignin derived, are the main waste products in pulp mill effluents [1,2]. They are responsible for the notorious colour of those effluents, which is one of the environmental problems associated to this type of industry. The knowledge of the molecular structure of those chromophoric compounds in pulp mill effluents has become, therefore, important to predict changes of the bulk properties of the dissolved organic matter in receiving waters and it can also be useful for choice of effluent treatment procedures. However, the task of characterizing these complex organic mixtures is a true analytical challenge, since no single technique provides adequate information regarding all their different distributions (e.g. molar mass, chemical composition, functionality). In this work, a comprehensive two-dimensional liquid chromatography (2D-LC) method was established for the separation and further characterization of molecular structures in chromophoric dissolved organic matter from a bleached Kraft pulp mill effluent. Such methodology comprised the use of a reversed-phase (RP) column in the first dimension and a size-exclusion (SEC) column in the second dimension, coupled to three on-line detectors (ultraviolet, molecular fluorescence, and evaporative light scattering). By applying two different separation mechanisms in a single run it was possible to draw insights into how the molecular weight profile of the chromophoric compounds relate to their hydrophobic features. The 2D-LC simplified fractions were further characterized in order to understand how the structural information varies with polarity and molecular weight profile.