Analysis and modelling of non-equilibrium sorption of aromatic micro-pollutants on GAC with a multi-compartment dynamic model

The optimisation of granular activated carbon (GAC) processes for industrial wastewater treatment requires the development of dynamic model that considers adsorption in multi-compartment porous media. In this work, the adsorption of toluene and naphthalene on GAC is investigated. Sorption equilibrium and kinetic experiments were performed at laboratory scale using low contaminant concentrations. The experimental conditions were chosen so as to simultaneously explore the different ranges of concentrations typically encountered in industrial wastewaters. The sorption behaviour was then explained through modelling taking into account the main equilibrium and transport phenomena and three adsorption compartments: the GAC particle surface, the macro- and meso-pores, and the micro-pores. The pore diffusion and solid diffusion were both considered to be coupled with a linear adsorption isotherm. With one set of four parameters adjusted for an adsorbent/contaminant pair, the model satisfactorily describes the non-equilibrium adsorption/desorption processes in different operating conditions and initial conditions.