抄録
An electrokinetic method accompanying with ion exchange reaction has been developed for remediation of soils contaminated with heavy metals, having relatively low hydraulic permeability. Consolidated bentonite cake contaminated with the zinc ion was prepared by using the mechanical expression method, and the removal of the zinc ion from the cake by the electrokinetic method was conducted accompanying with the addition of the sodium ion. From the preliminary adsorption test of the zinc ion onto the bentonite clay, it was found that the adsorption behavior was described by the equation of the Freundlich type. The zinc ion was desorbed from the bentonite due to cation exchange reaction caused by the addition of the sodium ion, and it was removed from the cake having low hydraulic permeability efficiently by the electroosmotic flow. It was found that the permeation rate of the liquid through the cake at the steady state increased with the current density linearly, and that the rejection ratio of the zinc ion was independent of the current density. Consequently, it was appeared that the rejection rate of the zinc ion was proportional to the current density. Moreover, at the steady state, the variation of the rejection ratio with the permeate volume became marked with the increase of the concentration of the added zinc ion, and it was not influenced by the cake thickness.
