Uses of cyclic amine monoamides for extracting uranium(VI) and/or plutonium(IV) from an acidic aqueous solution, as well as for totally or partially separating uranium(VI) from plutonium(IV) from an acidic aqueous solution. A method for treating an aqueous solution resulting from the dissolution of spent nuclear fuel in nitric acid to extract, separate and decontaminate uranium(VI) and plutonium(IV) in a single cycle and without resorting to any operation of reducing plutonium(IV), and wherein a cyclic amine monoamide or a mixture of cyclic amine monoamides is used as extractant. The cyclic amine monoamides have formula (I):

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The invention relates to a separation and recovery method for radioactive waste slag and specifically relates to a separation and recovery method for monazite slag. The separation and recovery method comprises the following steps: acid leaching, pressure filtration, water washing, extraction of valuable components and treatment of filtration slag. The separation and recovery method provided by the invention performs low-acid and low-temperature leaching on monazite slag, so that a liquid phase and a solid phase are easy to separate; after an ore dressing process is adopted for performing ore dressing and alkali decomposition on secondary slag, closed-loop circulation and recovery of uranium, thorium and rare earth is realized; and simultaneously, extraction raffinate waste acid is recycled, so that the emission of waste water is reduced, the consumption of sulfuric acid and fresh water and the treatment cost of the waste water are reduced, the production cost is reduced, the recovery rate of the valuable elements, namely the uranium, the thorium and the rare earth is more than 97%, and the whole process has no emission of the radioactive waste water and waste slag.