Enrichment of bromine in sea-bittern with recovery of other marine chemicals

Abstract

The bromide concentration of sea bittern is 2.0-2.5 g L^-1 at 29 °Bé. Evaporation to 34.5-35.0 0Bé increases the bromide concentration to the highest achievable level without significant losses in solid precipitates. Br^- and K⁺ concentrations at this point are ca. 4.0 and 25.0 g L^-1, respectively. It is reported herein that bromide concentration in bittern can be enhanced to 8.4 g L^-1 with 93% recovery. This is achieved by integrating the process of bromide enrichment with recovery of gypsum, carnallite, magnesium hydroxide, and magnesium chloride. The process revolves around desulfatation of bittern with calcium chloride to promote carnallite (KCl.MgCl₂·6H₂O) formation. Calcium chloride is generated from the reaction of MgCl₂ in carnallite decomposed liquor (CDL) with lime. Recycling of the liquor in this manner enables us to recover the bromide that co-precipitates with carnallite and also the K⁺ lost in CDL during decomposition of carnallite, leading to high yields of both.