Strontium (Sr) is a valuable metal that is increasingly utilized in many industries. Due to the numerous problems associated with land-based mining, extracting Sr from seawater and seawater desalination brine has become an alternative option. Among the various methods for recovering Sr from seawater and seawater brines, the adsorption process is particularly attractive. Because seawater contains other metal ions (Na+, K+, Ca2+, and Mg2+) at much higher concentrations than Sr2+, adsorbents that can selectively remove Sr2+ are required. This paper presents a comprehensive and critical review of advanced adsorbents used and their mechanisms for selectively adsorbing Sr2+ from seawater and brines. Although these adsorbents remove a higher proportion of Sr2+ than other metal ions from seawater, other metals are also adsorbed—some in much larger quantities than Sr2+. Therefore, it has not been possible to recover only Sr2+ through desorption to produce a high-purity Sr product. Because of its similar valence and chemical hardness, Ca2+ competes most strongly with Sr2+ adsorption. In this review, an improved method is proposed in which Ca2+ and Mg2+ are first removed by hydroxide precipitation, followed by repeated adsorption/desorption cycles to progressively increase the proportion of Sr2+ relative to other ions in the selective adsorbent until only Sr2+ remains adsorbed. At this stage, the adsorbed Sr2+ can be desorbed to produce a solution containing only Sr2+, from which a high-purity Sr salt can be manufactured.
Loganathan et al. (Tue,) studied this question.