SORPTION OF ALPHA-NAPHTHOL ONTO ORGANIC SORBENTS VARYING IN POLARITY AND AROMATICITY

Relation of alpha-naphthol uptake with polarity and aromaticity of selected organic matter surrogates was investigated using batch equilibration. The organic sorbents used were: lignin (organosolv), lignin (alkali), collagen, chitin, cellulose, and a collagen-tannic acid mixture (CTM). These materials represent model input sources for soil organic matter. Aromaticity of the sorbents was calculated from CPMAS C-13 NMR spectrum data. Concentration of alpha-naphthol in solution was measured using liquid scintillation counting and elemental composition of the sorbents was determined with an elemental analyzer. Hysteresis between adsorption and desorption was not observed. We infer that uptake of alpha-naphthol is through partitioning as indicated by linear isotherms. K(d) values for lignins were 12 to 24 fold higher than that for chitin and 130 to 260 fold higher than that for cellulose. The carbon referenced sorption coefficient (K(OC)) decreased from approximately 436 to approximately 3 mLg with increasing polarity index [(O+N)/C] and decreasing aromaticity of organic sorbents. We concluded that the quality of organic sorbents significantly influences partitioning of hydrophobic organic chemicals in aqueous systems. If this conclusion holds for all hydrophobic organic pollutants, then K(OC) of such xenobiotics cannot be accurately predicted from its K(OW) or solubility without some description of organic sorbent quality such as polarity and degree of aromaticity.