PREDICTABILITY OF THE HOMOGENEOUS SURFACE-DIFFUSION MODEL FOR ACTIVATED CARBON ADSORPTION-KINETICS - FORMULATION OF A NEW MATHEMATICAL-MODEL

The predictive capability of the Homogeneous Surface Diffusion Model ( HSDM) for activated carbon adsorption kinetics under different environ mental conditions is investigated in this study. Experimental studies conducted at room temperature, neutral pH, with DO concentrations of 0 , 4, 9, and 30 mg/l indicate that the HSDM model describes the anoxic adsorption much more accurately than the oxic uptake. This pattern is rationalized as due to the simultaneous adsorption and surface reactio n in the oxic batches which is unaccounted for in the HSDM model. Furt hermore, the data reveals that divergence from the model fit increased with DO concentration with the HSDM model overpredicting the initial data and underpredicting the latter part of the curve. Kinetic experim ents performed for phenol and o-cresol at pH values of 3, 7, and 11 sh ow that HSDM model describes the anoxic data very well, while underpre dicting the latter part of the curve. Kinetic experiments performed fo r phenol and o-cresol at pH values of the largest divergence of the ox ic data from the HSDM model was at neutral pH. On the other hand, when the aforementioned kinetic experiments were conducted at temperature values of 8 degrees C, 21 degrees C, and 35 degrees C, the HSDM model was found to describe the anoxic data very well with the fit improving with temperature. The fit of the surface reaction-controlled part of the kinetic curve improved substantially with temperature. A simultane ous adsorption reaction model is formulated to account for the relativ ely slow telomerization reactions that impact sorbate uptake kinetics and equilibria.