Table2 presents the results of chemical analyses with determination of pH and concentrations of total iron and aluminum in the original acid and basic fluids and after percolation.
The results of the analyses indicate adsorption/precipitation of aluminum in the case of basic percolation and a significant lixiviation of iron during acid percolation. Iron removal during basic percolation was negligible. It is considered that the significant collapse observed during flooding/percolation of acid fluid is due to
destruction of cementation between particles due to lixiviation/solubilization of iron. For the basic fluid, it is not possible to clearly identify the .physicochemical cause of collapse but it is possible that some
dispersion of the structure might have occured, with retention of aluminum existing in the original basic solution.