Filtration properties of two Tunisian clays suspensions: effect of the nature of clay

The knowledge of the filtration properties are very important and can ascertain if a clay is suitable or not for use as a lining material for waste disposal. The general objective of our work is to determine a relation between structure and microtexture of two Tunisian clays (C1 and C2) and macroscopic properties of cakes formed by filtration. The result of permeability by water and waste solution (pH = 3) shows that the clay C2 is more impermeable than C1. In addition, the cake obtained after filtration test by filter-press for both clays present many interesting observations. However, for a ratio of (40%) of clay-water, the thickness of cake (e) in the case of C2 is more important (e = 10mm) than for C1 (e = 7mm). Similarly, the water retention (WR) is of order 34% for C2 and 26% for C1. This is due to the mineralogical composition of sample C2 which is essentially the smectite (swelling clay). Although, (WR) and (e) are slightly changed using the waste solution, it exist a lowering of plasticity of clay filter cake. This is illustrated by the SEM images that showed an interconnected micro-crack for the cake of sample C2, due to the degradation by acidic attack.