Removal of strontium by physicochemical adsorptions and ion exchange methods

Abstract

Strontium, a relatively abundant alkaline element in the earth’s crust, occurs in four stable isotopes, 84Sr, 86Sr, 87Sr and 88Sr. The separation of soluble Sr2+ ion from water, mainly seawater, can be achieved through one or a combination of methods such as adsorption, chemical precipitation, ion exchange, membrane technology and solvent extraction, amongst which adsorption and membrane processes are popular solutions. The regeneration of spent adsorbents along with Sr recovery is the inherent advantage of the adsorption process. Natural adsorbents such as alginate microspheres, attapulgite, bentonite, dolomite, goethite, hematite and natural zeolites and inorganic ion-exchange materials, viz. activated carbon, antimony oxide, artificial zeolites, carbon and titanate nanotubes, gel and macroporous resins, titanium oxide and synthetic birnessite, have been used for immobilization of Sr. Industrial wastes (coal fly ash and industrial sludges) and agricultural byproducts (almond green hull, eggplant hull, moss and waste rice straw) are also potential Sr adsorbents. The adsorption process is greatly influenced by pH, initial concentration of contaminant, temperature and textural characteristics of the adsorbents. Membranes from polymeric and ceramic materials have also been used for Sr attenuation, and hybrid membrane technologies using multiple membranes have been found to be effective. © Springer Nature Switzerland AG 2020.