densation of phenol (P) and formaldehyde (F) using P/F Pure compounds, whose structures model that of phenol-formalratios in excess of unity. Whereas commercial novolacs condehyde resins, were synthesized and their adsorption from ethanol tain a number of phenolic units (typically 8-13) with the solvent on activated carbon examined. Two series of compounds methylene linkages existing in a variety of substitution posiwere studied, (i) those with methylene linkages substituted in only tions, ortho-ortho, ortho-para, or para-para to the hydroxyl the ortho-positions relative to the phenolic hydroxyl group (the group, we have successfully synthesized in our laboratories ortho-series), and (ii) those in which all para-positions together a range of pure, multinuclear compounds which model inwith sufficient ortho-positions were used to synthesize the comdustrial phenolic resins (5). Thus, we have available a range pounds (the para-series). Successive coupling of phenolic units of model compounds varying in molecular weight and in to bis-(2-hydroxyphenyl)-methane and bis-(4-hydroxyphenyl)methane resulted in tetra-, hexa-, and octa-nuclear species, which position of methylene linkages. Other workers ( 6) have deare referred to as tetramer, hexamer, and octamer, respectively, scribed the synthesis of all-ortho methylene linked comwith the appropriate prefix (ortho-or para-). Experimental adpounds.
sorption isotherms could be fitted to the Langmuir equation. From
The adsorption of phenol-formaldehyde resins has rethe maximum amounts adsorbed for each compound, it was shown ceived little attention in the literature. Several reports have that ortho-linked species were adsorbed to a greater extent than been presented in which novolac or phenol-formaldehyde their para-linked analogues. This could be attributed to ethanol resins have been used as the adsorbent itself (7-10). The being a better solvent for the para-linked compounds relative to majority of studies, however, have originated from the pulp the ortho-series. The differences in behavior toward solvent could and paper industry, where the adsorption of resins onto cellube attributed to the presence of strong intramolecular hydrogen lose, pulp, or wood has been investigated (11-14). Adsorpbonding in the ortho-linked compounds, an interaction minimal tion of sulphonated novolac resins on nylon-6 has also been (or absent) in the para-linked series. This conclusion is supported by results from molecular modeling and intrinsic viscosity mea-studied (15). Brown et al. (16) investigated the adsorption surements for the compounds of interest.