Chemical effects of goethite colloid on the transport of radionuclides through a quartz-packed column

Laboratory experiments were carried out to investigate the effects of inorganic colloids on the transport of radionuclides through quartz sand packed columns. Submicrometre size particles, goethite (α-FeOOH), were used to represent the colloids. The radionuclides were 137Cs, 22Na and 131I (as iodate). It was found that pH is a controlling parameter affecting goethite transport. At low pH, goethite is strongly retained by the quartz. At high pH, the breakthrough of goethite followed predictions based on the electrostatic repulsion between the colloids and the quartz. In addition, the flow rate and the initial goethite colloid concentration influenced the colloid breakthrough from the quartz column. There is not any similarity between either sodium and goethites or cesium and goethites breakthrough curves. The transport of iodate, however, is greatly altered in the presence of goethite at low pH. No such similarity was found at high pH.