The purpose of this study is the development and experimental testing on simulation solutions of a precipitation-membrane method for fractionation of liquid radioactive waste and sorption post-treatment of the filtrate. The choice of processing method is based on the analysis of factors affecting the efficiency of ion-exchange purification of solutions; properties of complex compounds of polyvalent metals; characteristics of commercially available membrane elements and economic aspects of the preparation and disposal of radioactive waste. The basic idea is to use the internal properties of solutions to isolate polyvalent cations and acidoligands in the form of poorly soluble compounds in the volume of an inert polypropylene element, which will increase the efficiency of ion-exchange post-treatment and reduce the amount of waste. The architecture and operating parameters of the experimental setup are designed to provide favorable conditions for the formation in solution of complexes (ion pairs) of polycharged cations with acid ligands of various nature.