Sulfur-modified zeolite A as a low-cost strontium remover with improved selectivity for radioactive strontium. (July 2022)

• Record Type: Journal Article
• Authors: Yang, Hee-Man; Jeon, Hyungmin; Lee, Yeonsoo; Choi, Minkee
• Is Part Of: Chemosphere. Volume 299(2022)
• Publication Date: 2022-07
• Subjects: Sulfur-modified NaA zeolite -- Radioactive strontium -- Low-cost Sr remover -- Selective ion-exchange; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2022.134309
• Languages: English
• ISSNs: 0045-6535

Abstract

Abstract: Selective removal of radioactive strontium ( 90 Sr) from the environment is important, and selective adsorption/ion exchange is appropriate for removal of trace amounts of 90 Sr from large volumes of 90 Sr-contaminated water. Although various inorganic ion-exchange materials, including zeolites, have been investigated intensively for removal of Sr 2+ due to their excellent resistance to radiation and high ion-exchange capacity, their ion-exchange selectivity for Sr 2+ is poor in the presence of competing ions such as Ca 2+ and Mg 2+ . Here, sulfur-modified NaA zeolite (S-NaA) was prepared for low-cost, selective 90 Sr removal because the elemental sulfur encapsulated in micropores provides additional Lewis acid-base interactions with Sr 2+ during the Sr 2+ ion-exchange. Our ion-exchange experiments revealed that S-NaA with 3 wt% sulfur (3 S-NaA) showed the highest Sr 2+ selectivity among various S–NaAs containing up to 10 wt% sulfur because ion exchange involving bulky hydrated Sr 2+ depends on the reduced micropore volume of S-NaA after sulfur loading. Most importantly, 3 S-NaA effectively and efficiently (>99.4%) removed 90 Sr from groundwater containing 8.4 ppt 90 Sr, demonstrating its excellent potential for practical application in the treatment of 90 Sr-contaminated water. Graphical abstract: A low-cost sulfur-modified NaA zeolite exhibits improved 90 Sr selectivity due to additional Lewis acid-base interactions between sulfur and Sr 2+ under high salt conditions. Image 1 Highlights: Sulfur-modified NaA zeolites were synthesized for selective removal of Sr 2+ . The Sr 2+ selectivity of NaA increased after sulfur encapsulation in NaA micropores. Sr 2+ selectivity increased with up to 3 wt% sulfur added and decreased thereafter. NaA zeolite with 3 wt% sulfur shows an exceptional Kd value of 319, 000 mL/g. Very efficient removal of 90 Sr was obtained with simulated groundwater and seawater.