Dual reactive domain model for sorption of aqueous organics by wood fiber

An experimental study of 2,4,5-trichlorophenol (2,4,5-TCP) sorption to kraf t papermaking fiber demonstrates that the dual reactive domain model (DRDM) effectively characterizes the process over a broad concentration region. I sotherm data were deconvoluted into linear partitioning and nonlinear adsor ption contributions in accordance with the model demonstrating the importan ce of both mechanisms to the overall process. DRDM accurately fit concentra tion-dependent distribution coefficient, Kd(C), data that could not be char acterized with the Freundlich or Langmuir equations, and the model predicts the asymptotic movement toward a limiting Kd(C) value at high solute or co solute concentrations observed in experiments. Competitive effects were acc ounted for by modifying the adsorption portion of the model. With its limit ations understood, the extended Langmuir equation was utilized and provided an effective fit of data. Langmuir fitting parameters for competitive data with five different n-alcohol homologs allowed estimates of free energy va lues per methylene linkage, which were in agreement with previously reporte d values. Also obtained from competitive data were relative sorption values for various benzene analogs, indicating that interactions in addition to t hose stemming from solute hydrophobicity often contribute in driving the ov erall sorption process. These results have implications for papermaking giv en the ubiquitous nature and importance of sorption in the process, (C) 200 1 Academic Press.