Particle release and permeability reduction in a natural zeolite (clinoptilolite) and sand porous medium

To evaluate clinoptilolite, a natural zeolite, as a candidate material for a permeable reactive barrier for removal of strontium from groundwater, we investigated particle release and permeability reduction in clinoptilolite and sand porous media. In flow-through column experiments, we tested the ef fects of solution chemistry, grain size, and clinoptilolite pretreatment on particle release and hydraulic conductivity. Permeability reduction occurr ed not in the clinoptilolite itself but only in finer-grained sand down-gra dient of the clinoptilolite. Solutions of high ionic strength inhibited par ticle release and prevented clogging. Clinoptilolite of larger grain size p roduced slightly less particle release and clogging. Two pretreatments of t he clinoptilolite, rinsing to remove fine particles and calcining to improv e strength, reduced particle release and clogging. Calcining, however, sign ificantly reduced the strontium binding strength of the clinoptilolite.