Cesium removal from wastewater: High-efficient and reusable adsorbent K1.93Ti0.22Sn3S6.43

Decontaminating liquid-containing Cs-137 by natural Pumice stone

Radionuclides, emanating as consequential by-products of nuclear operations, are recognized as a potent source of environmentally deleterious contamination. In light of these concerns, the present investigation has employed unmodified natural pumice within a batch process to effectuate the removal of Cs-137 radionuclides from real liquid radioactive wastes (RLRWs). The discernment of optimal adsorption parameters encompassed a pH level of 5, a pumice dosage of 3.33 g/L, a mixing duration of 5 min, a mixing speed of 100 revolutions per minute, all maintained at room temperature. The attainment of a peak removal efficiency of 91.75% for Cs-137 substantiates the efficacy of the chosen conditions. Moreover, the determination of regression coefficients (R2) arising from the application of Freundlich and Langmuir isotherm analyses yielded values of 0.91 and 0.96, respectively, thus validating the appropriateness of both models in depicting the adsorption mechanism. Evidently, the pseudo-second-order kinetic model exhibited a high correlation coefficient of 0.99, attesting to its aptitude in characterizing the adsorption dynamics. A thermodynamic appraisal of the process indicated an endothermic nature, offering insights into the fundamental energetics governing the interaction. Consequently, the adsorption phenomenon unfolded predominantly on monolayer, heterogeneous surfaces, with chemical interactions taking precedence on the active pumice sites.

Zein-enhanced sodium alginate/thiostannate microsphere adsorbent Zein@SA/KBS for efficient removal of cesium from wastewater

Although efficient removal of Cs from wastewater is of great importance because of the nuclear energy sustainable development and public health, removing cesium is challenging for the high concentrations of sodium and potassium ions coexist. In this work, we synthesized the first novel bismuth-doped layered tin sulfide (KBS) and applied it to the efficient green adsorption of liquid cesium resources. KBS could reach the adsorption equilibrium for Cs+ within only 2 min with a theoretical adsorption capacity of 425.55 mg/g. Furthermore, the adsorption performance remained reliable after 10 cycles of use. The structure and properties of KBS were explained at the molecular level by DFT calculations, and the calculated results were in sound agreement with the experimental data. Meanwhile, in this study, the material was reinforced and shaped by the electrostatic interaction of Zein and sodium alginate hydrogel, and finally, Zein@SA/KBS spherical composite adsorbent was obtained. The problem of the difficult recovery of adsorbent and the secondary contamination was solved. The adsorption performance of Zein@SA/KBS on Cs+ was better than most composite adsorbents and showed reliable stability. Therefore, the new microspherical adsorbent (Zein@SA/KBS) has great potential for industrial application in removing radioactive cesium from wastewater.

Metal Sulfide Ion Exchangers: High Acid Stability of Na2xMg2y-xSn4-yS8 (NMS) and Topotactic Conversion to 2D Solid Acids with Semiconducting Character

Metal sulfide ion exchange materials (MSIEs) are of interest for nuclear waste remediation applications. We report the high stability of two structurally related metal sulfide ion exchange materials, Na2xMg2y-xSn4-yS8 (Mg-NMS) and Na2SnS3 (Na-NMS), in strongly acid media, in addition to the preparation of Na2xNi2y-xSn4-yS8 (Ni-NMS). Their formation progress during synthesis is studied with in-situ methods, with the target phases appearing in <15 min, reaction completion in <12 h, and high yields (75-80%). Upon contact with nitric or hydrochloric acid, these materials topotactically exchange Na+ for H+, proceeding in a stepwise protonation pathway for Na5.33Sn2.67S8. Na-NMS is stable in 2 M HNO3 and Mg-NMS is stable in 4 M HNO3 for up to 4 h, while both NMS materials are stable in 6 M HCl for up to 4 days. However, the treatment of Mg-NMS and Na-NMS with 2-6 M H2SO4 reveals a much slower protonation process since after 4 h of contact both NMS and HMS are present in the solution. The resultant protonated materials, H2xMg2y-xSn4-yS8 and H4x[(HyNay-1)1.33xSn4--1.33x]S8, are themselves solid acids and readily react with and intercalate a variety of organic amines, where the band gap of the resultant adduct is influenced by amine choice and can be tuned within the range of 1.88(5)-2.27(5) eV. The work function energy values for all materials were extracted from photoemission yield spectroscopy in air (PYSA) measurements and range from 5.47 (2) to 5.76 (2) eV, and the relative band alignments of the materials are discussed. DFT calculations suggest that the electronic structure of Na2MgSn3S8 and H2MgSn3S8 makes them indirect gap semiconductors with multi-valley band edges, with carriers confined to the [MgSn3S8]2- layers. Light electron effective masses indicate high electron mobilities.

Novel Zr-Doped Thiostannate Spinning Fiber (Fiber-KZrTS) for Highly Efficient and Renewable Recovery of Cesium and Strontium from Geothermal Water

The efficient and renewable recovery of cesium and strontium by absorption from a new type of geothermal water liquid mineral resource is highly desirable but still challenging. In this work, a new Zr-doped layered potassium thiostannate adsorbent (KZrTS) was first synthesized and used for Cs⁺ and Sr²⁺ green and efficient adsorption. It was found that KZrTS had very fast adsorption kinetics toward both Cs⁺ and Sr²⁺ with an equilibrium reached within 1 min, and the theoretical maximum adsorption capacities for Cs⁺ and Sr²⁺ were 402.84 and 84.88 mg/g, respectively. Moreover, to solve the loss problem of the engineering application of the powdered adsorbent KZrTS, KZrTS was uniformly coated with polysulfone by wet spinning technology to form micrometer-level filament-like absorbents (Fiber-KZrTS), whose adsorption equilibrium rates and capacities toward Cs⁺ and Sr²⁺ are almost the same as that of powder. Furthermore, Fiber-KZrTS showed excellent reusability, and the adsorption performance remained virtually unchanged after 20 cycles. Therefore, Fiber-KZrTS has potential application for green and efficient cesium and strontium recovery from geothermal water.

Separation and Removal of Radionuclide Cesium from Water by Biodegradable Magnetic Prussian Blue Nanospheres

As the main component of radioactive wastewater, the cesium ion has seriously endangered the environment and human health. Prussian blue nanoparticles (PB NPs) are used as adsorbents for the purification of cesium-containing wastewater because of their ability to selectively adsorb cesium ions. In this work, novel magnetic Prussian blue nanospheres (MPBNs) were developed from polylactic acid nanospheres as a carrier, loaded with Fe3O4 nanoparticles (Fe3O4 NPs) inside and PB NPs outside for the removal of cesium ions with the help of magnetic separation. Meanwhile, the effects on the adsorption efficiency of MPBNs, such as pH, time, temperature and initial concentration of cesium ion solution, were studied. The adsorption isotherms, kinetic models and adsorption thermodynamics were investigated to research the absorption mechanism. The results showed that MPBNs were spherical with a rough surface, and their particle size, iron content and saturation magnetization were 268.2 ± 1.4 nm, 40.01% and 41.71 emu/g, which can be recovered by magnetic separation. At 293 K, MPBNs could reduce the cesium ion solution from 40 mg/L to 4.8 mg/L, and its cesium ion removal rate and adsorption capacity were 82.46% and 16.49 mg/g, respectively. The optimum pH of MPBNs for cesium ion adsorption was 5~9, the adsorption equilibrium time was 60 min, and the maximum adsorption capacity was 17.03 mg/g. In addition, MPBNs were separated rapidly by an external magnetic field, and the adsorption process was an endothermic reaction. The adsorption isotherm and kinetics of MPBNs were in accordance with the Freundlich model and quasi-second-order fitting model, respectively, and the adsorption process of MPBNs was controlled by the diffusion step in particles. Notably, these MPBNs could be effectively separated from water by a magnetic field, facilitating engineering applications in cesium-containing wastewater.