EVALUATION ON CHEMICAL NEUTRON-ACTIVATION ANALYSIS FOR TRACE-METALS IN SEAWATER USING MAGNESIUM-OXIDE AS THE PRECONCENTRATION AGENT

Attempts have been made to employ magnesium oxide as the preconcentrat ion agent for determination of trace metals in seawater by neutron act ivation analysis. Hydrous magnesium oxide can efficiently adsorb most cationic transition metals and rare earths in a simple water system. T he adsorption behavior is believed to depend mainly from the associati on of the cationic species of the metals with MgO22- adsorbent. In sea water matrix some of the metal ions such as Hg2+, Ni2+ etc. may become inefficiently adsorbed owing to the formation of highly stable metal- chloro complexes with chloride ion. Usually the adsorption efficiencie s of the metals can be recovered to be as high as the case in the simp le water system if an acidified seawater (to pH less than or equal to 1) is subjected to the adsorption experiment. In practice, a large vol ume of seawater (5 1) is stirred with a small amount of hydrous MgO (1 g). Thereafter, the trace metals adsorbed MgO is separated and taken to be neutron activated. The abundant sodium ion and ubiquitous bromid e ion can be obviated by the adsorption process, thereby beneficial to the gamma-spectrometry of the metals enriched on MgO.