Removal of Arsenic, Cadmium and Lead from Synthetic Stormwater by Two Low-Cost Adsorbents: A Kinetic and Equilibrium Study

The adsorption isotherms and kinetics of two low cost adsorbents, Ladybug Sand and Greensand, were determined from multi-solute batch experiments using prepared synthetic stormwater containing arsenic, cadmium and lead. The adsorption equilibrium data were fit to the Langmuir, Freundlich and Henry isotherms using both nonlinear and linear regression techniques. Kinetic data were obtained at two different stormwater concentrations. The kinetic curves were fit to the pseudo-first-order, pseudo-second-order and homogenous surface diffusion model (HSDM). A solution to the HSDM was achieved using the user-oriented numeric solution proposed by Zhang et al. (2009). From the fitted kinetic models the reaction constants, k1 and k2, as well as the surface diffusion coefficient (Ds) were determined. The maximum service lives of adsorbent columns comprised of Ladybug Sand or Greensand were calculated using the equilibrium column model (ECM) to evaluate the feasibility of the adsorbents for use in advanced stormwater treatment.