Inter-relationship between adsorption and pH in peat biofilters in the context of a cation-exchange mechanism.

A mathematical model of biofiltration McNevin and Barford (1998) has been augmented to include speciation, acid/base equilibria and pH dependence of adsorptive equilibria. It accurately predicts qualitative aspects of dynamic transients observed in an experimental perfusion column and supported a mechanism of adsorption by cation exchange with acidic functional groups on the surface of peat. It mirrored the buffering capacity of peat when solutions of high and low pH flow over the peat surface. This is a direct result of cation exchange where adsorption of cations increases with pH. This buffering capacity makes peat an attractive medium for engineered biological systems which must often operate within narrow pH bands to optimise biological activity.