Heterogeneity analysis based on liquid-phase adsorption of chlorophenols on activated carbon and polymer resins

Energy distribution function is the fundamental information that describes heterogeneous characteristics of porous solid adsorbents. This study focuses on the analysis of surface energy heterogeneity from the liquid-phase adsorption of chlorophenols (2-CP and 2,4-DCP) on three different adsorbents (F-400, XAD-1600, and XAD-7). The Langmuir-Freundlich isotherm equation was used to estimate the monolayer adsorption capacity of adsorbents studied. The adsorption energy distribution functions were calculated by using the generalized nonlinear regularization method (GENEREG) which is a linear Fredhohn integral equation of first kind. Analysis of energy distribution functions of porous sorbents provided significant comparative information of their heterogeneity. Compared to polymeric sorbents, F-400 with relative large surface area and small pore size showed a wide range of adsorption energy. It was also found that the surface energy heterogeneity highly depends on the heterogeneity parameter of isotherm and the structural differences of adsorbates.