Selective recovery of strontium from oilfield water by ion-imprinted alginate microspheres modified with thioglycollic acid

The efficient recovery of Sr2+ from brine is a great challenge due to the interference of a large number of coexisting ions. Herein, a new-type spherical Sr2+ adsorbent with a diameter of about 2–3 mm was developed by the ion-imprinting method using low-cost and high hydrophilic sodium alginate (SA). It was found that although SA could be granulated in HCl solution, it showed no adsorption ability for Sr2+. However, when SA was ion-imprinted with Sr2+ and then eluted with HCl, the material exhibited excellent adsorption performance. Especially, after modification with thioglycollic acid, the maximum adsorption capacity reached approximately 177 mg·g−1, which was far higher than that of the spherical materials reported at present. The Sr2+ in the material could be eluted easily with 0.05 mol·L−1 HCl at an eluent dosage of only 0.02 L·g−1, and the Sr2+ concentration in the eluate was nearly 25 times higher than that in the original solution. Because of the ion-sieve effect, the developed adsorbent presented high stability and selectivity when used for Sr2+ recovery from oilfield water. The attenuation of adsorption capacity was only 0.42% after five adsorption-desorption. The separation factors between Sr2+ and other ions were all higher than 54, indicating that the selective recovery of Sr2+ is almost unaffected by coexisting Na+, K+, Mg2+, and Ca2+. All these properties suggest that the proposed material has excellent properties and can be used as a candidate for selective recovery of Sr2+ from oilfield water or other liquid strontium resources.