REDISTRIBUTION OF NEPTUNIUM(V) DURING THE ALTERATION OF FERRIHYDRITE

Redistribution of neptunium(V) during an alteration of amorphous ferri hydrite to both goethite and hematite was studied at initial pH 6.0 an d 7.7 at 90 degrees C. Sorption of neptunium(V) during the alteration was obtained as a function of contact time. At an initial pH of 7.7, t he sorption neptunium(V) was nearly to 100% and remained constant duri ng the alteration of amorphous ferrihydrite to hematite and goethite. On the other hand, at an initial pH of 6.0, the amounts of sorbed nept unium(V) decreased drastically when the amorphous ferrihydrite was con verted to a crystalline structure. The sorption of neptunium on the al tered product, a mixture of hematite and goethite, was studied by a se quential extraction technique in which 1 M MgCl2, 1 M HCl and 6 M HCl solutions were used as the extraction reagents. Results of both initia l pHs indicated that neptunium(V) sorbed on the altered products has c hanged during the alteration of amorphous ferrihydrite from a reversib le form, that could extracted by 1 M MgCl2 solution to an incorporated form that could be not extractable by 1 M MgCl2 solution, but was by 6 M HCl solution.