The amorphous titanium dioxide nanoparticulate sorbent is prepared by treating the titanyl sulfate mixture in its crystalline form with a concentrated aqueous solution of an alkaline agent in the presence of crushed ice so that its initial temperature is 0 °C. after stirring, the pH of the mixture will be at least 9 and its temperature will reach ambient temperature. The reaction product consists of nanoparticles of titanium dioxide or amorphous hydrated titanium dioxide, with nanoparticles arranged in needle aggregates that correspond to the original shapes and dimensions of the crystals of the starting titanyl sulfate dihydrate. It can be used as a highly effective sorbent of radionuclides for removing them from contaminated water and their subsequent separation from the aqueous environment.