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 o f a magnetic adsorbent followed by mixing and collection of the adsorb ent using a magnet. The magnetic adsorbent is prepared by coating micr on sized magnetite particles with manganese dioxide. When yield tracer s (Ba-133 for Ra-226, Po-208 for Po-210 and stable lead for Pb-210) we re added to small seawater samples, recoveries of the tracers were bet ter than 90% with quantitative recovery of the manganese dioxide adsor bent. 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 u nder the conditions used. The magnetic adsorbent of MnO2 on magnetite is easy to prepare and allows simple and rapid processing of large wat er samples at sea.