Extraction chromatographic materials based on polysulfone microcapsules for the sorption of strontium from aqueous solution

Highly efficient removal of Sr2+ from aqueous solutions using a polyacrylic acid/crown-ether/graphene oxide hydrogel composite

With the development of nuclear power, efficiently treating nuclear wastes generated during operation has attracted extensive attention. Hydrogels are common adsorbent materials in the treatment of wastewater due to their high swelling rate and easy post-treatment. In this work, a novel polyacrylic acid/crown-ether/graphene oxide (PAA/DB18C6/GO) hydrogel composite was synthesized by a radical cross-linking copolymerization method and characterized using various analytical tools such as SEM, FT-IR, TGA and XPS. The effects of time, pH, initial Sr2+ concentration, and temperature on Sr2+ adsorption onto the PAA/DB18C6/GO were studied. The PAA/DB18C6/GO shows a high adsorption capacity of 379.35 mg g-1 at an initial Sr2+ concentration of 772 mg L-1 due to the unique structure of dibenzo-18-crown-ether-6 and high swelling. The composite has a high selectivity for Sr2+ with a removal rate of 82.4% when concentrations of Na+ and K+ were 10 times higher than that of Sr2+. The pH and temperature have no apparent impact on adsorption performance of the PAA/DB18C6/GO under the experimental conditions. The composite shows excellent reusability with more than 92% removal rate for Sr2+ after five continuous cycles. In addition, the mechanism of Sr2+ adsorption by PAA/DB18C6/GO was analyzed by fitting the adsorption data to the theoretical models and XPS data.

Study on Dynamic Column Behavior and Complexation Mechanism of DBS-Modified Crown Ether-Based Silica to 90Sr

A crown ether-loaded hybrid adsorbent suitable for the separation and enrichment of strontium from high-level liquid waste was synthesized. 4',4'(5″)-di(tert-butylcyclohexano)-18-crown-6 (DtBuCH18C6) and its modifiers dodecyl benzenesulfonic acid (DBS) and 1-dodecanol were impregnated into silica-based polymer support. The hybrid adsorbent exhibited excellent Sr(II) selectivity ability, and effective chromatographic separation and recovery of Sr(II) from simulated high-level liquid waste could be achieved with a (DtBuCH18C6 + DBS + dodec)/SiO2-P packed column. The recovery rate of Sr(II) calculated based on the mass balance was approximately 99% and over 80% for the other coexisting metal ions. An appropriate increase in the concentration of Na-DTPA eluent was favorable to improve the efficiency of the elution process because of the increased complexation capacity of [DTPA]5- to Sr(II). The developed theoretical model can simulate the dynamic breakthrough curves of the material on the basis of short column data, thereby predicting the scale-up column of the practical operation. Density functional theory calculation was used to explore the action mechanism of DBS modifiers on the Sr(II) complexation process of crown ether groups. Two Sr(II) complexation isomeric models of DtBuCH18C6 were established, and the calculation results revealed a similar complexation ability. DtBuCH18C6 could form a stable Sr(II) complexation structure with DBS coordination, which further indicated that DBS could be a ligand to promote the Sr(II) adsorption ability of crown ether materials.

High strontium adsorption performance of layered zirconium phosphate intercalated with a crown ether

Effective removal of strontium isotopes in radioactive waste streams has important implications for the environment and the sustainable development of nuclear energy. In this work, a zirconium phosphate/18-crown-ether-6 (ZrP/18C6) composite was prepared using the intercalation method by loading crown ether into zirconium phosphate. The composite was structurally and morphologically characterized by XRD, FT-IR, XPS, and SEM. The adsorption experiments of Sr²⁺ onto the ZrP/18C6 composite were conducted as a function of temperature, pH, Sr²⁺ concentration and competing ions. The results indicate ZrP/18C6 can adsorb 98.6% of Sr²⁺ within 30 minutes at an Sr²⁺ concentration of 100 mg L^-1 and maintain a high removal rate with a distribution coefficient of 7 × 10⁵ mL g^-1 when Sr²⁺ is at a low level of 4.28 mg L^-1. The ZrP/18C6 composite reached a maximum adsorption capacity of 195.74 mg g^-1 at an Sr²⁺ concentration of 380 mg L^-1, which is significantly higher than the 43.03 mg g^-1 of α-ZrP. The adsorption performance of Sr²⁺ onto ZrP/18C6 is not significantly affected by temperature, pH and competing ions. Furthermore, the adsorption kinetics and thermodynamics were analyzed based on the adsorption data obtained in the present work. It is shown that the adsorption of Sr²⁺ onto ZrP/18C6 follows the pseudo-second-order model and the Langmuir monolayer model, respectively. Additionally, the adsorption mechanism of Sr²⁺ by ZrP/18C6 is discussed.