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 (Ba-133 for Ra-226, Po-208 for Po-210 and stable lead for Pb-210) 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 Ba-133 (35%) and stable lead (80%) was adequate for measurement of Ra-226 and Pb-210 in the water. Recovery of Po-208 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.