Abstract <p>Clinoptilolites from the Shivyrtui and Kholinskoe deposits modified with manganese dioxide and with titanium hydroxide and phosphate, as well as manganese dioxide modified bentonite from the 10th Khutor deposit, were prepared. The physicochemical properties of the modified samples and their ability to take up strontium, cesium, uranium, and americium were studied. The cesium, strontium, and uranium adsorption isotherms were obtained over a wide concentration range. The distribution coefficients and the static exchange capacity of the materials were determined. The effect of solution pH on the sorption of ⁹⁰Sr onto natural and modified clinoptilolite and of ²⁴¹Am onto natural and modified bentonite was compared. The modified sorbents show promise for use within sorption barriers to immobilize ¹³⁷Cs, ⁹⁰Sr, uranium, ²⁴¹Am, and other transuranic elements. This would significantly reduce their migration into groundwater and enhance the safety of radioactive waste storage and disposal facilities.</p>