DEVELOPMENT OF A SURROGATE SEDIMENT TO STUDY THE MECHANISMS RESPONSIBLE FOR ADSORPTION DESORPTION HYSTERESIS/

A surrogate sediment was developed to reduce some of the complexity in the structural aspects of the adsorbed organic carbon phase. Layers o f an anionic surfactant were sorbed to colloidal anatase to produce an organic carbon phase that had hydrophobic regions and resisted desorp tion. The surrogate is verified as a model sediment by comparing the r esults of contaminant [2,2',5,5'-tetrachlorobiphenyl (PCB) and naphtha lene] adsorption and desorption batch experiments to the results of si milar experiments performed an a well-studied natural sediment. The su rrogate exhibited adsorption of contaminants via a hydrophobic interac tion in the same magnitude as to a natural sediment for the two differ ent hydrophobic organic contaminants in 0.1 or 0.15 M NaCl solution. T he sorption of PCB to the surrogate at varied organic carbon contents was observed to follow a linear adsorption isotherm. Desorption experi ments were conducted by successive dilutions. Both the surrogate and n atural sediment were observed to exhibit similar desorption behavior. The solution concentration during desorption was lower than predicted by the adsorption isotherm and remained unchanged from 4 h to 168 days . The heterogeneous nature of sediments should be greatly reduced in t he surrogate yet desorption still appears to be low.