Extraction of free magnesia from steelmaking slags using iodine-ethanol solutions

Abstract

The optimum composition of mixtures of iodine, ethanol, and ethylene glycol as selective extraction media for free magnesia in steelmaking slags was explored. Hydration of free magnesia in steelmaking slags increases its volume to expand the slags, resulting in deteriorate pavement of roads when the steelmaking slags were used as a road-constructing material. Therefore, accurate analytical methods to determine free magnesia in the steelmaking slags have been sought in steel industries. Ethanolic solutions of iodine without ethylene glycol afforded higher selectivity for the extraction of magnesia than ternary mixtures of iodine, ethanol, and ethylene glycol. Although the addition of up to 5 wt% of ethylene glycol to the ethanolic iodine solution increased the amount of magnesia extracted, it also increased the extraction of other magnesium species present in the steelmaking slags, resulting in decreased selectivity toward magnesia. The dissolution of magnesia in ethanolic iodine solution was promoted by the alkalinity of the magnesia. Meanwhile, the dissolution of magnesia promoted the redox reaction between ethanol and iodine in the extraction medium.