Rates of dissolved oxygen-induced polymerization reactions of phenol and o-cresol on activated carbon

The effect of different dissolved oxygen (DO) levels on the kinetics of phenol and o-cresol uptake by granular activated carbon (GAC) was investigated in batch reactors. The equilibrium batch capacities matched the corresponding isotherm capacities within a maximum deviation of 6 percent. Equilibrium was attained in the anoxic batches only after 2 days while taking about 14 days for the oxic batches. The homogeneous surface diffusion model (HSDM) accurately predicted the uptake in the anoxic batches but deviated substantially from that of the oxic batches. The diffusivity coefficients for phenol and o-cresol on GAC were highly affected by the DO concentration. The higher the DO content in the sorbate solution the lower the diffusivity coefficient. Three distinct stages were observed in the kinetics of the polymerization reactions; the lag time stage, followed by a stage in which DO was not limiting reactions, and finally, the limiting DO stage. A kinetic model was developed for the polymerization reactions relating the rate constant to the DO levels using a nonlinear relationship.