Adsorption Characteristics of Oxide Coated Buoyant Media $\left({\rho }_s<1.0\right)$ for Storm Water Treatment. II: Equilibria and Kinetic Models

Divalent metal species adsorption onto a manganese oxide coated polymeric medium (MOPM) was evaluated through batch adsorption experiments using a flow-through batch reactor. In this paper, Part II, the batch equilibrium and kinetic data examined in Part I are modeled using a triple layer surface complexation model and a potential driving second order kinetic model. Surface complexation modeling using FITEQL-TLM generated intrinsic surface acidity constants for the MOPM of $\log K{ }_{\mathrm{a1}}^{\mathrm{int}}=3.196$ and $\log K{ }_{\mathrm{a2}}^{\mathrm{int}}=-5.802\text{.}$ The intrinsic surface reaction constants for Pb(II), Cu(II), and Zn(II) were $\log K{ }_{\mathrm{Pb}}^{\mathrm{int}}=-1.91\text{,}$ $\log K{ }_{\mathrm{Cu}}^{\mathrm{int}}=-2.53\text{,}$ and $\log K{ }_{\mathrm{Zn}}^{\mathrm{int}}=-4.45\text{,}$ respectively. A potential driving second order kinetic model was developed to predict sorption of the divalent metal ions onto the MOPM. The general adsorption kinetics for MOPM can be described as a fast reaction occurring within 30 min and a slower reaction continuing from 5 to 15 h. Kinetic results can be interpreted using assumptions of the potential driving second order model that the dominant control forces are the chemical potential of the MOPM activated surface sites and chemical potential of sorbate in the solution.