Demonstration of Seawater Strontium (Sr(II)) Extraction and Enrichment by a Biosorption Technique through Continuous Column Operation

Abstract

Alginate beads are promising strontium (Sr (II)) adsorbents because of their high Sr(II) adsorption capacity and cost-effectiveness. This study analyzed the selective adsorption by alginate beads in the column operation mode to recover and enrich Sr(II) from seawater. Alginate beads of 2-8 wt % were prepared and bead size was varied to optimize the column module. All beads expanded 10-20% in seawater because of its high ion content, but decreased slightly in 0.1 M HCl, which was used in the eluent but did not cause bead destruction after reaction for 14 days. In the batch adsorption experiment, 8 wt % alginate beads showed a maximum Sr(II) uptake from seawater of 147.3 mg/dm(3), a concentration 25 -fold higher than the Sr(II) concentration (approximate to 6.1 mg/L) in seawater. Using a continuous Sr(II) adsorption column system, Sr(II) adsorption equilibrium was achieved at 12 h with a 50-100 mL/min flow rate. Elution from this column yielded an eluent containing 24.3 mg/L of Sr(II). Three consecutive elutions with pH control yielded an eluent containing SO mg/L of Sr(II), demonstrating that this selective Sr(II) adsorption system can be used to recover Sr(II) from seawater.