[en] A new, relatively simple method for the recovery and purification of protactinium-231 is described. Efficient separation of protactinium(V) from a wide range of impurities is readily achieved by precipitating the hydrous oxides and, after elimination of fluoride ion, washing with 0.5 - 4.0 M HNO₃ amd/or 0.5 M HNO₃-0.3M H₂0₂ in which protactinium(V) hydrous oxide is virtually insoluble. The final traces of silicon are removed by dissolving the hydroxides in 20 M HF and evaporating the solution to dryness. Single-crystal recoveries from initial samples containing 30 - 75 wt.% ²³¹Pa have ranged from 92 to 96%. The purity of the products is generally greater than 99%; radiochemical purification is also achieved. (Auth.)