Abstract: Palygorskite is a chain-layered silicate, with a a perture pass of 3.8 ×6.3A.It is gene?rally regarded that because this mineral has microapertur e pass and relatively larger specific surface area, the palygorskite clay is capable o f adsorbing the pollutants in wastewater. Based on the crystal structure of paly gorskite,its adsorption selectivity and our adsorption experiments, the present author holds the following opinion: because most molecules and hydrated ions hav e the diameters larger than that for the aperture pass of palygorskite, they u sually can not get into the aperture pass of palygorskite. Moreover, the inner ape rture pass of palygorskite preferentially adsorbs the water molecules. Terefore, in most cases during wastewater disposal processing the adsorption of palygorsk ite to pollutants is not an inner-surface adsorption, but an outer-surface ad sorption. This outer-surface adsorption is a kind of colloidal and ion exchange ad s orption. Besides the acidity of the solutions, the interaction of coexisting col loidal montmorillonite and palygorskite may play an important role in adsorption ability of palygorskite clay.