Soil and sediment organic matter plays a major role in the sorption and desorption of polyaromatic hydrocarbons. Such organic matter may coat mineral surfaces and may be adsorbed in nanometer-sized pore spaces. The role of such confinement on sorption and desorption equilibrium is not well understood. This is a problem that has broad application; examples include developing advanced materials such as functional adsorbents and catalyst substrates. In this research, we have adsorbed poly(styrene) (PS) having a range of molecular weights (6-300 kDa) into porous silica having a range of fairly uniform pore sizes (5-100nm) to achieve various Rg-PS/Rp-silica ratios as a way to study the role of organic matter nano-confinement in a model system. We explore how the sorption and desorption characteristics of phenanthrene depend on the Rg-PS/Rp-silica ratio of PS-loaded silica particles and the molecular weights of nano-confined PS. Sorption and desorption characteristics of phenanthrene were related to physical characteristics of PS-loaded silica particles including the pore size distribution after PS loading (by gas phase nitrogen (N2 adsorption) and PS glass transition temperature (Tg) measured by differential scanning calorimetry (DSC).

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