Published online by Cambridge University Press: 27 October 2009
Vertical freezing of clayey suspensions contaminated by heavy metals was conducted. A small unidirectional thermal gradient applied to a sample placed in a parallelopipedic cell led to the low-rate propagation of an upward freezing front. During this propagation, segregation of salts occurred and the non-solidified phase ahead of the freezing front became enriched with metallic salts. Moreover, some of the non-miscible particles in suspension were repelled by the freezing front. Therefore, the solidified phase became poorer with metallic pollutants bound to such nonmiscible particles as clayey colloids or complexes. Thus, artificial cooling was able to purify a suspension contaminated by heavy metals that exist in various chemical forms. This paper presents results for different experimental conditions and physico-chemical parameters such as the pH and the ratio between the concentrations of metallic cations and clay particles. The influence of these physico-chemical parameters on the speciations of lead and on the efficiency of this method is discussed. These freezing tests carried out on polluted soils should succeed in their remediation. This new method is called ‘cryoremediation’.