Equilibrium and intra-particle diffusion of stabilized landfill leachate onto micro- and meso-porous activated carbon

Stabilized landfill leachate has previously been treated with activated carbon (AC); however, information on the selectivity of AC depending upon the pore size is minimal. Isotherm and kinetic experiments were conducted using three commercially available AC products, one micro-porous and two meso-porous. Equilibrium adsorption and intraparticle diffusion of organic matter from stabilized leachate was studied. Isotherm experimental data were fitted to Langmuir, Freundlich, and Redlich-Peterson isotherm models in non-linear forms. Of the three isotherm models, the Redlich-Peterson model provided the best fit to the experimental data and showed a similar organic matter adsorption capacity (approximately 0.2 g total organic carbon (TOG) g(-1) AC) for both microporous and meso-porous AC. The organic matter effective intra-particle diffusion coefficients (D-e) in both AC types were on the order of 10(-10) m(2) s(-1) for AC particle sizes greater than 0.5 mm. Mesa-porous ACs showed slightly higher D-e compared to micro-porous AC. Rapid small-scale tests showed a maximum of 80% TOG removal from leachate by each AC investigated. Fluorescence spectroscopy showed a preferential adsorption of fulvic-type organic matter with an increase in empty bed contact time by each AC. (C) 2011 Elsevier Ltd. All rights reserved.