| 摘要 |
<p>The dialkylphosphoric acid mentioned in the organic extract phase is at least partly saturated with cations, in particular calcium cations, magnesium cations and iron cations. At least one extraction stage is carried out at a temperature below 75 DEG C using an aqueous reextraction agent which contains hydrochloric acid, possibly together with soluble salts, in particular with magnesium chloride and calcium chloride. The concentration of the hydrochloric acid in the reextraction agent and the phase ratio in the reextraction are selected in such a manner that the resulting reextract contains at least 1 g/l of free hydrochloric acid and at most 300 g/l of calcium chloride. The resulting reextract is contacted with a substance containing active magnesium oxide or magnesium hydroxide and with carbon-dioxide-containing gases, whereupon, following the conversion into magnesium chloride and calcium carbonate, the liquid phase is separated off, which is used for the preparation of magnesium oxide or magnesium hydroxide, the organic phase being returned into the extraction process.</p> |
