Kaolinite carbonate mixture fabric evolution after electrokinetic tests

Abstract

The aim of this study is to characterise the behaviour and fabric of four clayey samples before and after electrokinetic tests. The samples are formed by either kaolinite or a mixture of 70% kaolinite and 30% of carbonate. The samples are mixed with water and a lead solution and then consolidated. The electrokinetic tests show that for the samples prepared with water, a little increase in current intensity and conductivity is observed, which is due to the H+ ions diffusion into the samples. For the lead solution prepared samples, the current intensity and the conductivity decrease. The tests show that the current intensity decrease is due to cation migration. However, the carbonate presence, leading to high pH values, improves the lead precipitation with carbonate. The electroosmotic flow happens towards the cathode for all the samples, but some observed differences can be attributed to the heterogeneity of the net surface charges during the tests. X-ray diffraction analyses and specific surface area measurements show that, after the electrokinetic tests, the fabric of the samples changes as function of the presence of carbonate and lead.