Sorption Kinetics of Non-Ionic Organic Pollutants Onto Suspended Sediments

The results of controlled batch experimental studies of the adsorption and desorption kinetics of dichlorobenzene to 1) size fractionated, washed sediments, 2) aggregate, washed sediment, 3) dissolved/colloidal sediment materials, and 4) bulk sediments,are used to determine the effect of inhomogeneous mixtures on the overall sorption rates. The size-segregated sediments are modeled as spherical particles with a porous outer shell of organic matter for sorption and an inert, inorganic core. The characteristic times of intraparticle diffusive transport are found to vary with particle size by about two orders of magnitude. The distribution of natural organic matter content with particle size results in sorption rates which differ greatly from that predicted by the monodisperse, homogeneous particle model. Coupled, reversible reactions between the solute and each solid size fraction are presented as a conceptual model for the interpretation of the empirical results of batch experiments.