engleski

Examination of B_2O_3 in magnesium oxide obtained from seawater

The study has examined the possibility of repeated application of the agent used to rinse the precipitate of magnesium hydroxide obtained from seawater by substoichiometrical precipitation with addition of 80 percentage of the stoichiometrical quantity of dolomite lime as the precipitation agent. The purpose of the study has been to ensure high purity product i.e. magnesium oxide, particularly as regards the B_2O_3 content, because the hot-strength properties of certain magnesia refractory products are markedly affected by their boron content. The rinsing agent was alkalized distilled water with pH=12.5, which was alkalized by addition of concentrated NaOH prior to each use. The aim of the study has been to save the magnesium hydroxide rinsing agent, provided the purity of the magnesium oxide product remains satisfactory. The product quality was established by determination of MgO, CaO and B_2O_3 content in calcined magnesium oxide. Examinations were carried out with magnesium oxide samples prepared by rinsing of the precipitate by fresh alkalized distilled water or by recycled alkalized distilled water, and with magnesium oxide samples prepared by rinsing with non-alkalized distilled water and without previous rinsing of the magnesium hydroxide precipitate. The results indicate that when recycled alkalized distilled water with pH=12.5 is used, the B_2O_3 content in MgO samples (80 percentage precipitation) amounts to 0.0807 mass percentage, which is less by 58 percentage compared to the B_2O_3 content in samples prepared without rinsing of the magnesium hydroxide precipitate (B_2O_3 = 0.1937 mass percentage).

magnesium oxide from seawater; substoichiometric precipitation; rinsing agent; B_2O_3 content

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