Abstract Expanding layer silicates have been proposed as sorbents for both organic and inorganic contaminants. With specific surfaces that may exceed 800 m2/g and interlayer distances as large as 30Å, montmorillonite in particular possesses a high capacity to sorb large amounts of pollutants with diverse morphologies. The intercalation of hydrolytic polymers of Al, Cr, Cu, Fe, Mn and Ni by smectite has been widely reported and reduces the bioavailability of these metals in both terrestrial and aquatic ecosystems. Hydroxy-Al interlayers possess the greatest order and, when present with other hydrolysed metals in the interlayer, confer a greater order and stability to the coprecipitated intercalate. Organic contaminants may also be effectively sorbed by expandable layer silicates. Cationic organic molecules may be intercalated through simple exchange reactions. Non-polar organic contaminants may be effectively sorbed only by those clays that have been modified to possess an organophilic character.