Development of Nanoporous Alumino-borosilicate as a Novel Matrix for the Sorption and Stable Immobilization of Cesium Ions

Cesium adsorption from an aqueous medium for environmental remediation: A comprehensive analysis of adsorbents, sources, factors, models, challenges, and opportunities

Considering the widespread and indispensable nature of nuclear energy for future power generation, there is a concurrent increase in the discharge of radioactive Cs into water streams. Recent studies have demonstrated that adsorption is crucial in removing Cs from wastewater for environmental remediation. However, the existing literature lacks comprehensive studies on various adsorption methods, the capacities or efficiencies of adsorbents, influencing factors, isotherm and kinetic models of the Cs adsorption process. A bibliometric and comprehensive analysis was conducted using 1179 publications from the Web of Science Core Collection spanning from 2014 to 2023. It reviews and summarizes current publication trends, active countries, adsorption methods, adsorption capacities or efficiencies of adsorbents, tested water sources, influencing factors, isotherm, and kinetic models of Cs adsorption. The selection of suitable adsorbents and operating parameters is identified as a crucial factor. Over the past decade, due to their notable capacity for Cs adsorption, considerable research has focused on novel adsorbents, such as Prussian blue, graphene oxide, hydrogel, and nanoadsorbents (NA). However, there remains a need for further development of application-oriented laboratory-scale experiments. Future research directions should encompass exploring adsorption mechanisms, developing new adsorbents or their combinations, practical applications of lab-scale studies, and recycling radioactive Cs from wastewater. Drawing upon this literature review, we present the most recent research patterns concerning adsorbents to remove Cs, outline potential avenues for future research, and delineate the obstacles hindering effective adsorption. This comprehensive bibliometric review provides valuable insights into prevalent research focal points and emerging trends, serving as a helpful resource for researchers and policymakers seeking to understand the dynamics of adsorbents for Cs removal from water.

All-in-one treatment: Capture and immobilization of 137Cs by ultra-stable inorganic solid acid materials HMMoO6·nH2O (M = Ta, Nb)

Capture and immobilization of 137Cs is urgent for radioactive contamination remediation and spent fuel treatment. Herein, an effective all-in-one treatment method to simultaneously adsorb and immobilize Cs+ without high-temperature treatment is proposed. According to the strategy of incorporating high-valency metal ions into molybdates to increase the material stability and affinity towards radionuclides, layered HMMoO6·nH2O (M = Ta (1), Nb (2)) are prepared. Both materials exhibit excellent acid resistance (even 15 mol/L HNO3). They maintain remarkable adsorption capacity for Cs+ in 1 mol/L HNO3 solutions and can selectively capture Cs+ under excessive competitive ions. Furthermore, they show successful cleanup for actual 137Cs-liquid-wastes generated during industrial production. In particular, adsorbed Cs+ can be firmly immobilized in interlayer spaces of materials due to the highly stable anionic framework. The removal mechanism is attributed to ion exchange between Cs+ and interlayer H+ by multiple characterizations. Study of the structure-function relationship shows that the occurrence of Cs+ ion exchange is closely related to plate-like layered structure. This work develops an efficient all-in-one treatment method for capturing and immobilizing radiocesium by ultra-stable inorganic solid acid materials with low energy consumption and high safety for radionuclide remediation.

Adsorption and safe immobilization of Sr ions in modified zeolite matrices

In the present study, an Iranian natural zeolite (Sabzevar region) was evaluated as a natural adsorbent for the elimination and immobilization of strontium ions from an aqueous solution. For improving the adsorption efficiency of strontium ion, the zeolite surface was modified by the Schiff base ligand of bis (2-hydroxybenzaldehyde)1,2-diaminoethane (H2L). The natural zeolite and zeolite/H2L were characterized using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), X-ray fluorescence (XRF), BET and scanning electron microscope (SEM). Analysis of the natural zeolite showed that the zeolite is from the type of clinoptilolite and has a crystalline structure with the specific surface area 29.74 m2/g. The results showed that strontium adsorption onto modified zeolite increases compared to unmodified zeolite from 64.5% to 97.2% (at pH = 6). The effective parameters pH, adsorbent dosage, initial concentration of strontium ions, contact time, temperature, and interfering ions, were studied and optimized. The maximum adsorption efficiency was confirmed by modified zeolite and found to be 97.5% after 60 min of equilibrium time at pH 6, 0.05g as adsorbent dosage, and at 25 °C. Adsorption of strontium was confirmed by Langmuir model with maximum adsorption capacity of 10.31 mg/g. Kinetic studies showed that the adsorption of strontium ions on the adsorbent follows pseudo-second-order (PSO) model. Also, the thermodynamics of the adsorption process indicated that the adsorption of strontium on zeolite/H2L is an endothermic and spontaneous process, and the adsorption mechanism is a combination of physical and chemical adsorption. Finally, to manage the secondary waste generated from the adsorption process, strontium ions were immobilized in a zeolite structure. The results showed that the stabilization is well done with the thermal preparation process. After thermal treatment at 25-900 °C, modified zeolite satisfactorily retains strontium during back-exchange tests with NaCl solution. According to the results, the amount of strontium released from the adsorbent phase decreases from 52.6 to 1.6% with increasing heat treatment temperature.

Sorption of Palladium(II) from Aqueous Solution Using Diphenylthiocarbazone Immobilized onto Kieselguhr

Kieselguhr was immobilized with diphenylthiocarbazone (dithizone) and utilized as a new sorbent to extract palladium ions from an aqueous solution. The physicochemical features of the immobilized kieselguhr (K–Dz) were specified by Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and thermogravimetric analysis–differential thermal analysis. The average crystal size of the prepared material was found to be 24.41 nm. The sorption potential of the immobilized kieselguhr for the extraction of Pd(II) and La(III) in a batch mode was studied. The effects of pH, shaking time as well as the initial concentration of metals have been examined. The results demonstrate that the optimum pH was found to be 4.5 and the equilibrium was attained within 15.0 min. The adsorption kinetics and equilibrium data were well described by the pseudo-second-order kinetic model and Sips isothermal model with a maximum sorption capacity of 20.3 (mg/g). Thermodynamic parameters of the studied metal ions show that the process is spontaneous and endothermic in nature. The desorption process of Pd(II) was highly managed using acidified thiourea giving a desorption percent of approximately 80.0%. The separation possibility of Pd(II) from some metal ions such as La(III) was achieved successfully. The developed (K–Dz) composite method was applied for the recovery and separation of Pd(II) and other metal ions from a simulated automotive catalyst leachate solution. The results indicated that the (K–Dz) composite has a good reusability potential.