Selective removal of Sr2+ by cation exchange using silica-based titanate adsorbents

Titanate is regarded as a highly selective inorganic adsorbent for removing 90Sr. A sol-gel method was developed to prepare the K2Ti6O13/SiO2 adsorbent using optimized annealing temperatures. A well-crystallized structure of the K2Ti6O13/SiO2 phase has been identified after the annealing temperature from 500 to 600 ​°C. The crystallized structure shows uniform ion sites for Sr2+ replacement, and the K2Ti6O13/SiO2 adsorbent shows high adsorbability and selectivity for metal ions at neutral pH in radioactive wastewater with the following selectivity orders: Sr2+ ​> ​Ca2+ ​> ​Mg2+ ​> ​Na+. The breakthrough curve of Sr2+ showed that 0.78 ​g of K2Ti6O13/SiO2 was able to decontaminate 152 ​cm3 of blended solution containing 100 ​ppm of Sr2+. In addition, the adsorption mechanism of high selectivity for Sr2+ was also further proposed and proved by Density functional theory (DFT) calculations. A highly selective removal of Sr2+ among some competitive ions (Sr2+ ​> ​Ca2+ ​> ​Mg2+ ​> ​Na+) were highlighted in this paper using the K2Ti6O13/SiO2 adsorbent prepared by a sol-gel method for potential use in radioactive wastewater. The experimental glass column packed with K2Ti6O13/SiO2 shows high capacity to decontaminate Sr2+ from high salinity wastewater. The mechanism of high selectivity was also further proved by Density functional theory (DFT) calculations, which was in good agreement with the experimental values. [Display omitted] •A highly selective removal of Sr2+ using K2Ti6O13/SiO2 adsorbent.•High capacity to decontaminate Sr2+ from high salinity wastewater.•The mechanism of high selectivity proved by DFT calculations and experimental.