Extraction of MgCl₂ from Sea Water with Mixed Ionic Extractants

Abstract

The extraction of MgCl₂ was investigated with the mixed ionic extractants consisting of a liquid cationic exchanger and a liquid anionic exchanger diluted with toluene. The extractability, the selectivity for magnesium over sodium and calcium, the efficiency of the recovery process with two-stage extraction and five-stage strip, and the phase separationability were examined for these extractants. On the basis of these results, the most suitable extractant type was selected. The results obtained can be summarised as follows: (1) In the extraction of magnesium from MgCl₂ solution the Aliquat 336 system was superior to the Priment JMT system and above all the mixed ionic extractant consisting of Aliquat 336-Versatic Acid 911 had the highest extractability. (2) In the recovery process utilizing a two-stage extraction and a five-stage strip to recover 90% of MgCl₂ from 10-fold concentrated sea water, the mixed ionic extractant consisting of Priment JMT-Versatic Acid 911 had the highest concentration of the product and the mixed ionic extractant consisting of Priment JMT-D2EHPA had the smallest volume of organic flow required to produce a given amount of MgCl₂. (3) The impurities such as sodium and calcium co-extracted with magnesium into the organic phase could be sufficiently eliminated by scrubbing the extracted organic phase with MgCl₂ solution. (4) The Aliquat 336 system had good phase separationability in contact with concentrated sea water, but was emulsified in contact with water. On the other hand, the mixed ionic extractant consisting of Priment JMT-Versatic Acid 911 had good phase separationability in contact with either concentrated sea water or water.