Determination of Partition Coefficient Kp

OMWW contains a number of phenols in quantities determined largely by their partition coefficients. The partition coefficient is defined as: Kp = Co;l/Cwater, where Coil and Cwater are the equilibrium concentrations of a phenolic compound in the oil and water phase, respectively. The Kp of the phenolic compound between the oil and water phases can be determined experimentally according to the methodology described by Archer et al. (1994)9.

Prediction of partitioning coefficients (Kp) between phases, though, may be feasible by using a general group contribution method for prediction of activity coefficients in a liquid-phase, such as the UNIFAC method. This method has enabled the prediction of vapor/liquid or liquid/liquid equilibrium, or the solubility of several substances, in aqueous or non-aqueous phases. The group contribution method is based on the concept of the solution of groups instead of molecules. Each molecule is considered as a mixture of simple groups (-CH2-, -COOH, -OH, etc.), whose thermo-dynamic property parameters are known in the literature, and the various properties are found by the summation of the contributions of the various groups. Thus, the group contribution method has the advantage of predicting various thermodynamic properties through estimation of the effects of the various groups. The UNIFAC method was based on the universal quasi chemical activity coefficient (UNIQUAC) method, which is another method derived from an extension of Guggenheims's quasi-chemical theory of liquid mixture (reported by Rodis P.S. et al., 2002).

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