Adsorption of copper(II) on Shirasu

The adsorption of copper(II)to Shirasu, a pyroclastic flow deposit, was examined by a batch-and-column method. The effect of the grain size was investigated in the range < 74 similar to 250 mu m. The amount of copper(II) adsorbed on Shirasu increased with decrease of the grain size. A highest value was observed for grain size of < 74 mu m. This tendency was remarkably observed at a higher copper(II) concentration. The effect of the pH was investigated at pH 1.0, 3.0 and 5.0. At pH 1.0, no adsorption of copper(II) on Shirasu was observed. As the pH increased, the adsorbed amount of copper also increased. The adsorption data for copper(II) was also analysed using logarithmic form of the Freundlich isotherm, logW = logK + 1/nlogC(e). When logW is plotted against logC(e), a straight line with a slope of 1/n and an intercept of logK is obtained. This reflects satisfaction of the Freundlich isotherm model for the adsorption of copper(II). The increase in the adsorption amount of copper(II) with a decrease of the grain size can be explained by the increase in the K value. The increase of the pH can be explained by the increase in both of the K and 1/n values.