Transport of acridine in saturated porous media.

The effects of the aqueous solution pH, temperature, initial solute concentration and non-equilibrium processes on the transport of acridine in saturated porous media (silica) were investigated in a series of continuous-flow column experiments. The enthalpy of the adsorption reaction was more exothermic when the solution pH was above acridine's pKa (5.6) than when it was below. The extent of adsorption was greater when the solution pH was below the pKa of acridine than when it was above. Non-equilibrium effects on the adsorption reaction were found to be unimportant at groundwater velocities. The results from this study suggest that the mobility of acridine in aquifers, in which adsorption to silica edge sites is significant, would increase as the temperature of the groundwater increased and the acridine mobility would be greatest when the pH of the groundwater is above the pKa of acridine. The transport of acridine in such aquifers can be effectively modeled using the local equilibrium assumption.