Magnetic recovery of radium, lead and polonium from seawater samples after preconcentration on a magnetic adsorbent of manganese dioxide coated magnetite

Ra, Pb and Po were preconcentrated from seawater samples by addition of a magnetic adsorbent followed by mixing and collection of the adsorbent using a magnet. The magnetic adsorbent is prepared by coating micron sized magnetite particles with manganese dioxide. When yield tracers (133Ba for 226Ra, 208Po for 210Po and stable lead for 210Pb) were added to small seawater samples, recoveries of the tracers were better than 90% with quantitative recovery of the manganese dioxide adsorbent. For large (401) samples of ocean water, processed on board ship, recovery of the manganese dioxide adsorbent was 70–100%. Recovery of 133Ba (35%) and stable lead (80%) was adequate for measurement of 226Ra and 210Pb in the water. Recovery of 208Po was not satisfactory under the conditions used. The magnetic adsorbent of MnO2 on magnetite is easy to prepare and allows simple and rapid processing of large water samples at sea.