Effect of Kaolin concentration on distribution coefficient of copper

Varying amounts of H⁺-Kaolin were equilibrated with spiked (high activity radioactive⁶⁴Cu) water and kept overnight in a constant temperature water bath shaker. After proper filtration, through 0.45 µm Millipore memberane, the amount of radioactivity on the filter paper and the filtrate was measured separately using a Gamma ray well counter. Adsorption of Cu (expressed as distribution coefficient ? K_d) was plotted against the final clay concentration. Kd values decrease initially with increasing clay concentration and then seem to reach an equilibrium condition at higher clay concentrations. At low clay concentration higher particle aggregation (nucleation) of the metal with clay in suspension is a possible explanation for this behavior.