Highly efficient removal of strontium from contaminated wastewater by a porous zirconium phosphate material

Alginate-collagen fibers composite biomass material for ultra-rapid recovery of strontium from contaminated water with excellent reusability

Recovering 90Sr from nuclear wastewater and nuclide-contaminated water not only avoids its potential environmental and health risks, but it can also be used for cancer treatment, manufacturing isotope batteries and environmental monitoring. A novel adsorbent material (OSA@CF/Zr) for ultra-fast recovery of Sr2+ was obtained by grafting oxidized sodium alginate on zirconium cross-linked collagen fibers. The OSA@CF/Zr demonstrated rapid adsorption of Sr²⁺, achieving a maximum capacity of 0.415 mmol g-¹ within 6 min. Even after 17 recycling cycles, it retained an adsorption capacity of approximately 0.26 mmol g-¹ , highlighting its superior reusability. The OSA@CF/Zr could be applied at pH of 4-10, were hardly affected by co-existing K+, Na+, and Cs+ ions, and the effects of Mg2+ and Ca2+ were easily masked by CDTA, exhibiting high selectivity for Sr2+. The OSA@CF/Zr was well suited for continuous column adsorption operation, and the amount of treated wastewater and the removal rate was almost independent of the flow rate. The adsorption column, containing 1 g of OSA@CF/Zr, successfully removed over 95 % of Sr2+ from 1.737 L of simulated surface water with an initial Sr2+ concentration of 7.886 mg L-1. OSA@CF/Zr is a very promising material for strontium recovery.

Insights into the Structural Transformation of Amorphous ZrP, α-ZrP, and γ-ZrP: Sr2+ Sorption Behavior and Mechanism

This study investigates the synthesis and Sr2+ sorption properties of three different crystal types of zirconium phosphate (ZrP)─amorphous ZrP (am-ZrP), α-ZrP, and γ-ZrP─prepared via a one-pot reflux method. The materials were characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, thermogravimetry (TG), solid-state 31P magic angle spinning nuclear magnetic resonance (NMR) spectroscopy, and sodium hydroxide titration. Sorption experiments revealed that Sr2+ uptake by all three ZrPs increased with pH. Sorption isotherms were evaluated across a range of Sr2+ concentrations, with maximum sorption capacities at pH 9 of 2.48 mmol g-1 for am-ZrP, 2.71 mmol g-1 for α-ZrP, and 2.04 mmol g-1 for γ-ZrP. Sorption kinetics and the influence of competing ions on Sr2+ uptake were also examined. Notably, all three ZrP materials demonstrated excellent reusability in sorption-desorption cycles. Finally, the structural transformation and Sr2+ sorption mechanism were elucidated through 31P NMR, XPS, FTIR and TEM analyses.

Phosphination of amino-modified mesoporous silica for the selective separation of strontium

Radioactive strontium (90Sr) is considered as one of the most dangerous radionuclides due to its high biochemical toxicity. For the efficient and selective separation of Sr from acidic environments, a novel functional adsorbent CEPA@SBA-15-APTES was prepared in this work through the phosphorylation of amino-modified mesoporous silica with organic content of approximately 20 wt%. CEPA@SBA-15-APTES was characterized by TEM, SEM, EDS, TG-DSC, BET, FTIR, and XPS techniques, revealing its characteristics of an ordered hexagonal lattice-like structure and rich functional groups. The experimental results demonstrated that the adsorbent exhibited good adsorption capacity for Sr over a wide acidity range (i.e., from 10-10 M to 4 M HNO3). The adsorption equilibriums of Sr by CEPA@SBA-15-APTES in 10-6 M and 3 M HNO3 solutions were reached within 30 and 5 min, respectively, and the adsorption capacities at 318 K were 112.6 and 71.8 mg/g, respectively. Furthermore, by combining the experimental and characterization results, we found that the adsorption mechanism consisted of ion exchange between Sr(II) and H+ (in P-OH) in the 10-6 M HNO3 solution and coordination between the Sr(II) and oxygen-containing (CO and P = O) functional groups in the 3 M HNO3 solution.

Three-dimension titanium phosphate aerogel for selective removal of radioactive strontium(II) from contaminated waters

The effective removal of radioactive strontium (especially ⁹⁰Sr) from nuclear wastewater is crucial to environmental safety. Nevertheless, materials with excellent selectivity in Sr removal remain a challenge since the similarity with alkaline earth metal ions in the liquid phase. In this work, a novel titanium phosphate (TiP) aerogel was investigated for Sr(II) removal from the radioactive wastewater based on the sol-gel method and supercritical drying technique. The TiP aerogel has amorphous, three-dimensional and mesoporous structures with abundant phosphate groups, which was confirmed by X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), atomic force microscope (AFM) and Fourier transform infrared spectroscopy (FT-IR). The adsorbent exhibited high efficiency and selectivity for the removal of Sr(II) with an extensive distribution coefficient up to 4740.03 mL/g. The adsorption equilibrium reached within 10 min and the maximum adsorption capacity was 373.6 mg/g at pH 5. And the kinetics and thermodynamics data fitted well with the pseudo-second-order model and Langmuir model respectively. It can be attributed to the rapid trapping and slow intraparticle diffusion of Sr(II) inside the mesoporous channels of the TiP aerogel. Furthermore, TiP aerogel exhibited over 80% removal for 50 mg/L Sr²⁺ in real water systems (seawater, lake water and tap water). X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy revealed that strong ionic bonding formed during Sr(II) adsorption with the phosphate group on TiP aerogel. These results indicated that TiP aerogel is a promising high-capacity adsorbent for the effective and selective capture of Sr(II) from radioactive wastewater.