Sorption behavior of phenanthrene to natural carbonaceous sediments

Natural sediments impacted by previous coal mining activities were collected and separated according to grain size and density. Sorption experiments were performed with original sediments and different sub-fractions. Abundant coal and other coal-derived particles were identified using organic spectrographic analysis. Both Freundlich and partitioning and pore-filling model were applied to fit the experimental data. All sorption isotherms showed non-linear sorption properties, with n in the range of 0.72-0.76. The light fraction had the highest sorption capacity (lgK_Fr= 4.03), which is comparable to that of raw coal. In addition, partitioning and pore-filling model yields the better fitting than Freundlich model, indicating that at low c_w, "pore-filling" dominants the whole sorption; while with the increase of c_w, partition takes place of adsorption and dominants the sorption. In addition, in spite of the very low mass weight, the light fraction dominated by carbonaceous materials contributed more than 60% of the sorption for the whole sediments.