The process of chemical uranium enrichment by light isotopes has been studied. The kinetic parameters of the adsorption of UO2(NO3)2·2TBP molecules in a heterogeneous system at the vertical interface between a polar HNO3 solution and a solid vertical surface of nonpolar polypropylene (C3H6)n during the extraction of uranyl nitrate UO2(NO3)2 with tributylphosphate from an HNO3 solution were measured.