“…Even more general have been studies of the way in which radioisotopes, usually of heavy metals, behave in tank waste sludges, 275 in peat, 276 in different soils 277 and in alluvial sediments. 278,279 Organic materials from plants, such as chitin 280 (Pu & Np), hydrolised wood lignin 281 (Th, Ra & U), and cotton stalks 282 (rare earths, Th & U) have also been shown to be very effective at adsorbing radio-isotopes. Studies have also been reported of the adsorption of technetium 283 onto stibnite (Sb 2 S 3 ), of americium onto silica 284 impregnated with g-irradiated thiacalix [4]arene, of neptunium 285 on hydroxy-apatite, of many radioisotopes on zirconium molybdate 286 and of caesium and americium 287 on ion-exchange resins in the presence of liquid carbon dioxide.…”