The Bureau of Mines is investigating a dewatering technique that facilitates disposal of phosphatic clay wastes. The technique involves flocculation by high-molecular-weight polyethylene oxide (peo) and mechanical deformation of the flocs in a trommel to release water. Field tests in central Florida determined that the ion-exchange form of the clay wastes affect their dewaterability. For this reason, the effect of sodium, potassium, calcium, magnesium, and aluminum exchange ions on the dewaterability of attapulgite slurries was investigated for peo of both 5 and 8 million molecular weights. An empirical equation was developed that describes the dewatering of attapulgite with the polymer peo.