Sulfur-modified zeolite A as a low-cost strontium remover with improved selectivity for radioactive strontium
Hee‐Man Yang, Hyungmin Jeon, Yeonsoo Lee, Minkee Choi
Abstract
Selective removal of radioactive strontium (90Sr) from the environment is important, and selective adsorption/ion exchange is appropriate for removal of trace amounts of 90Sr from large volumes of 90Sr-contaminated water. Although various inorganic ion-exchange materials, including zeolites, have been investigated intensively for removal of Sr2+ due to their excellent resistance to radiation and high ion-exchange capacity, their ion-exchange selectivity for Sr2+ is poor in the presence of competing ions such as Ca2+ and Mg2+. Here, sulfur-modified NaA zeolite (S-NaA) was prepared for low-cost, selective 90Sr removal because the elemental sulfur encapsulated in micropores provides additional Lewis acid-base interactions with Sr2+ during the Sr2+ ion-exchange. Our ion-exchange experiments revealed that S-NaA with 3 wt% sulfur (3 S-NaA) showed the highest Sr2+ selectivity among various S–NaAs containing up to 10 wt% sulfur because ion exchange involving bulky hydrated Sr2+ depends on the reduced micropore volume of S-NaA after sulfur loading. Most importantly, 3 S-NaA effectively and efficiently (>99.4%) removed 90Sr from groundwater containing 8.4 ppt 90Sr, demonstrating its excellent potential for practical application in the treatment of 90Sr-contaminated water.