We studied the mechanism of cellulose esterification by inorganic polyacids and established the parameters for cellulose modification that allow the phosphorylation to primary alcohol groups of polymer upon introducing pyro- and tripolyphosphates into the ester groups. The product obtained is an ionite with an exchange capacity of about 6 mmol/g. We obtained derivatives of cellulose by Introducing the residues of phosphorus-containing heteropolyacids into ester groups by the sorption of ammonium molybdate and sodium tungstate. The materials are effective sorbents for purification of technogene waters containing radionuclides and are active components of sorption membranes for the separation of alkaline metals.