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The radionuclides 60Co and 54Mn are the main activation products produced in the operation of nuclear power facilities. Wastewater with these radionuclides must be treated to meet standards before being discharged. A variety of zeolite imidazole frameworks (ZIFs) materials were synthesized at room temperature, and the adsorption effect of ZIF-67 was found to be the best through adsorption experiments on Co(II) and Mn(II). The thermal stability test and structural characterization of ZIF-67 were carried out. At the same time, the influence of the initial pH value, adsorption time, and initial concentration of the solution on the adsorption of Co(II) and Mn(II) by ZIF-67 was investigated. The results show that: ZIF-67 has a microporous structure with a BET surface area of 1,035.72 m2/g. In addition, ZIF-67 has good thermal stability, under the condition of pH = 6, a temperature of 303 K and the initial concentration of 500 mg/L. The saturated adsorption capacity for Co(II) and Mn(II) reached 230.25 mg/g and 338.75 mg/g, respectively. ZIF-67 exhibits good selective adsorption performance for Co(II) and Mn (II) in high concentration interfering ion solutions and multi-ion solutions. The adsorption process of ZIF-67 was analyzed by kinetics, thermodynamics, isotherms, and adsorption diffusion models. The analysis of thermodynamic parameters shows that the adsorption process of ZIF-67 to Co(II) and Mn(II) is spontaneous and endothermic. The pseudo-second-order kinetic model, Langmuir isotherm model, and Boyd model are more in line with the adsorption process of Co(II) and Mn(II) by ZIF-67. It shows that the active sites on the surface of ZIF-67 are evenly distributed, and the adsorption process is single-molecule chemical layer adsorption. In addition, the liquid film diffusion dominates the adsorption rate during the adsorption process of Co(II) and Mn(II) by ZIF-67. [ABSTRACT FROM AUTHOR]

In order to effectively remove Co2+ from radioactive wastewater, β-cyclodextrin/graphene oxide (β-CD/GO) was synthesized. The factors affecting the adsorption of Co2+in water were determined by static adsorption experiments, and the synthesis and adsorption mechanism of the materials were discussed by using Density Functional Theory (DFT). The results show that β-CD and GO are mainly bonded by ester group and hydrogen bond, the adsorption of Co2+ by β-CD/GO belongs to single molecular layer chemisorption, and the intramolecular diffusion is the main factor of affecting the adsorption rate. The adsorption capacity of Co2+ can reach 95.83 mg/g under appropriate conditions, but it will be affected by interference ions. [ABSTRACT FROM AUTHOR]

Aiming at the removal of radioactive cobalt ions from water by graphene oxide (GO), the adsorption mechanism of Co2+ on graphene oxide was analyzed using the quantum chemical calculation software Gaussian 16 based on density functional theory. The influence of material structure factors such as carboxyl groups, hydroxyl groups, epoxy groups and graphene sheets as well as external environmental factors such as pH, temperature and interfering ions on the adsorption effect was determined, and the influence of external environment was verified through experiments. Through calculation and experiment, it was found that the existence of oxygen-containing functional groups on graphene oxide can improve the adsorption efficiency of the material appropriately, and increasing the pH under acidic conditions was also helpful to improve the adsorption effect. The material had certain selectivity for Co2+, and the adsorption capacity and selectivity could be further improved when it was modified by increasing hydroxyl groups. [ABSTRACT FROM AUTHOR]

The efficient segregation of radioactive nuclides from low-level radioactive liquid waste (LLRW) is paramount for nuclear emergency protocols and waste minimization. Here, we synthesized Na3FePO4CO3 (NFPC) via a one-pot hydrothermal method and applied it for the first time to the selective separation of Sr2+ from simulated LLRW. Static adsorption experimental results indicated that the distribution coefficient Kd remained above 5000 mL·g−1, even when the concentration of interfering ions was more than 40 times that of Sr2+. Furthermore, the removal efficiency of Sr2+ showed no significant change within the pH range of 4 to 9. The adsorption of Sr2+ fitted the pseudo-second-order kinetic model and the Langmuir isotherm model, with an equilibrium time of 36 min and a maximum adsorption capacity of 99.6 mg·g−1. Notably, the adsorption capacity was observed to increment marginally with an elevation in temperature. Characterization analyses and density functional theory (DFT) calculations elucidated the adsorption mechanism, demonstrating that Sr2+ initially engaged in an ion exchange reaction with Na+. Subsequently, Sr2+ coordinated with four oxygen atoms on the NFPC (100) facet, establishing a robust Sr-O bond via orbital hybridization. [ABSTRACT FROM AUTHOR]

In this work, zeolitic imidazolate framework-8 (ZIF-8) with a microporous structure for 60Co and 54Mn adsorption was prepared at room temperature, and the structure and thermal stability of the material were tested. The effects of the initial pH value, contact time, initial concentration and other factors of the solution on the adsorption performance of Co2+ and Mn2+ on ZIF-8 were investigated. The results suggest that the adsorption process of Co2+ and Mn2+ on ZIF-8 were spontaneous and endothermic, and mainly occurs as monolayer chemisorption. The maximum adsorption capacities of Co2+ and Mn2+ for ZIF-8 were 178.75 mg/g and 236.75 mg/g, respectively, at a pH of 7.0 and a temperature of 303 K. [ABSTRACT FROM AUTHOR]

A novel metal sulfide: potassium niobium sulfide (KNbS) was prepared by hydrothermal method. The morphology and composition of KNbS were characterized by scanning electron microscopy and X-ray diffraction. It was confirmed that the adsorption process of KNbS was carried out by exchange reaction of K+ with Co2+ and Sr2+. The effects of pH, contact time, coexisting ions and initial concentration of strontium and cobalt on the adsorption of Sr2+ and Co2+ by KNbS were studied by static adsorption experiments. Thus, the optimal adsorption conditions of KNbS for Co2+ and Sr2+ were determined. The results show that KNbS has a greater affinity for Sr2+ and Co2+ than other coexisting ions. In addition, the adsorption mechanism was analyzed by kinetic, Weber–Morris, Boyd and isothermal models. It was revealed that the adsorption of Co2+ and Sr2+ by KNbS was chemical adsorption of monolayer and the intraparticle diffusion was the main rate-control step. [ABSTRACT FROM AUTHOR]

In this work, zeolitic imidazolate framework-8 (ZIF-8) with a microporous structure for 60Co and 54Mn adsorption was prepared at room temperature, and the structure and thermal stability of the material were tested. The effects of the initial pH value, contact time, initial concentration and other factors of the solution on the adsorption performance of Co2+ and Mn2+ on ZIF-8 were investigated. The results suggest that the adsorption process of Co2+ and Mn2+ on ZIF-8 were spontaneous and endothermic, and mainly occurs as monolayer chemisorption. The maximum adsorption capacities of Co2+ and Mn2+ for ZIF-8 were 178.75 mg/g and 236.75 mg/g, respectively, at a pH of 7.0 and a temperature of 303 K. [ABSTRACT FROM AUTHOR]

A novel metal sulfide: potassium niobium sulfide (KNbS) was prepared by hydrothermal method. The morphology and composition of KNbS were characterized by scanning electron microscopy and X-ray diffraction. It was confirmed that the adsorption process of KNbS was carried out by exchange reaction of K+ with Co2+ and Sr2+. The effects of pH, contact time, coexisting ions and initial concentration of strontium and cobalt on the adsorption of Sr2+ and Co2+ by KNbS were studied by static adsorption experiments. Thus, the optimal adsorption conditions of KNbS for Co2+ and Sr2+ were determined. The results show that KNbS has a greater affinity for Sr2+ and Co2+ than other coexisting ions. In addition, the adsorption mechanism was analyzed by kinetic, Weber–Morris, Boyd and isothermal models. It was revealed that the adsorption of Co2+ and Sr2+ by KNbS was chemical adsorption of monolayer and the intraparticle diffusion was the main rate-control step. [ABSTRACT FROM AUTHOR]