As a model of chemical soil contamination, adsorption of aniline and p-nitrophenol onto Ca-bentonite at different pH has been studied. At pH around the value corresponding to pK(s) aniline is adsorbed to the maximal extent of almost-equal-to 15%. So we may conclude that this contaminant is mainly adsorbed by ion exchange as aniline cation. Desorption or soil decontamination may be achieved by HCl or NaOH to almost-equal-to 30% under clay destruction; however, through ion re-exchange with an excess amount of CaCl2, 100% of aniline is desorbed. Alternatively, aniline may be removed from bentonite by oxidation in air at 250 to 400-degrees-C. Nitrophenol is only very weakly adsorbed at any measured pH.