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An adsorbent for uranium was developed by placing upon the surface of a porous char an organic substance which has a very low aqueous solubility and a strong tendency to form chelate compounds with uranium under the solution conditions at which uranium adsorption is desired. The quantity of uranium adsorbed from a sulfuric acid solution onto char modified with di-2-ethylhexyl pyrophosphate is on the order of ten times that obtained on unmodified char. Activity and capacity of a modified adsorbent are observed to be dependent on the modifier selected, the surface concentration of the modifier, and the nature of the char adsorbent. The experimental behavior of the modified adsorbents supports the assumption that adsorption occurs by formation of a uranyl chelate compound with the modifier at the surface of the adsorbent and that the adsorptive capacity of the modified adsorbent for uranium is limited by steric considerations determined by the size of the chelate molecule being formed and the pore size distribution of the adsorbent.

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Previous studies of the radiation chemistry of tetranitromethane (TNM) in aqueous solution have shown that this substance is an effective radical scavenger when present at concentrations above 10-s mole/1.2 Hydrogen atoms reduce this solute to give nitroform which in aqueous solutions ionizes to form the intensely colored anion | ( 02)3]-(extinction coefficient at 350 µ; 15,000 mole-1 1. cm.-1). Since a colored material is formed from H-+ C(N02)4 ->-H+ + [C(NOa)3]-+ N02 (1)