Xingjie Lu,Zhen Liu,Xin Wang,Yuekun Liu,Hongchao Ma,Meiwen Cao,Wentao Wang,Taihong Yan
Novel MnO 2 @ZIF-8 nanocomposites were synthesized for efficient adsorptive removal of Sr 2+ from aqueous solution. ZIF-8 nanoparticles with controlled morphology and size were first synthesized by using amino acids to modulate the crystal nucleation and growth. Then, a layer of MnO 2 nanoparticles were deposited on ZIF-8 surface by using the adsorbed amino acid molecules as binding sites to mediate MnO 2 mineralization and by adjusting the reactive KMnO 4 concentration to control the size and surface density of the MnO 2 nanoparticles . The as-prepared MnO 2 @ZIF-8 nanocomposites showed a core-shell structure and displayed superior performance in Sr 2+ adsorption and removal from aqueous solution. The adsorption process can be described well by the pseudo-second-order equation. The adsorption isotherm accords well with the Langmuir model and the maximum adsorption capacity can reach 65.7 mg/g. The study paves a new way to develop novel inorganic nanocomposites as highly efficient and potential adsorbents for the treatment of radionuclide-containing wastewater.
Yucheng Hao,Yongjian Chen,Xin Cao,Changlin Chen,Min Xu,Yuan Lin,Haijian Li,Kunhong Hu
Graphical A Remarkable potassium fluoroaluminate possesses an excellent adsorption selectivity ( K d =~6.1×10 4 mL ⋅ g −1 ) and a maximum adsorption capacity of ( q m =~120.32 mg ⋅ g −1 ) for Sr 2+ . Importantly, it still keep a very good selectivity for Sr 2+ ions even in the presence of competing Na + , Mg 2+ and Ca 2+ aqueous solutions. 90 Sr, as a typical artificial radionuclide, poses a serious threat to human health and the ecological environment. The selective removal of this radionuclide from industrial nuclear waste is crucial for our environment. Here we report a novel potassium fluoroaluminate, K 2 [(AlF 5 )H 2 O], which was synthesized by a simple low-temperature one-step method. It adopts a 1D AlF 6 -chain structure, which consists of exchangeable potassium ions in between the infinite chains of octahedral Al centers. As a remarkable inorganic ionic exchanger, K 2 [(AlF 5 )H 2 O] has a high chemical stability (resistance of pH=~3-12) and thermal stability (≥~300 °C). It possesses an excellent adsorption selectivity ( K d =~6.1×10 4 mL ⋅ g −1 ) and a maximum adsorption capacity of q m =~120.32 mg ⋅ g −1 for Sr 2+ . Importantly, it still keep a very good selectivity for Sr 2+ ions even in the presence of competing Na + , Mg 2+ and Ca 2+ aqueous solutions. K 2 [(AlF 5 )H 2 O] is the first example of fluoroaluminate ionic exchange materials that can capture Sr 2+ . This result opens up a new way to design and synthesize inorganic ionic exchangers for the selective removal of Sr 2+ ions from radioactive waste water.
Among the nuclides in radioactive wastewater, strontium (90Sr) is a highly toxic water-soluble fission product, which will be extremely harmful to the ecological environment and consequently bring great risk to human health. Therefore, the removal of the strontium element from the aquatic environment is increasingly attracting the attention of the scientific community. In this paper, using poly(vinyl alcohol) (PVA) and chitosan (CS) as raw materials and glutaraldehyde as a cross-linking agent, a kind of interpenetrating PVA/CS hydrogel microsphere was prepared by a facile reversed-phase emulsion method. On this basis, the mechanical strength and stability of the hydrogel microspheres were further enhanced by a freezing–thawing technique. It was discovered that synthetic hydrogel microspheres can effectively remove Sr2+ ions from radioactive wastewater. The influences of the mass ratio of PVA to CS, initial concentrations of Sr2+, pH value, and adsorption times, along with competitive metal ions and nuclides, on the adsorption performance of the hydrogel microspheres were further systematically investigated. Especially, it was found that the freezing–thawing process significantly improved the adsorption capacity of the hydrogel microspheres for strontium ions, and the maximum adsorption capacity of the PVA/CS hydrogel microspheres for Sr2+ was as high as 205.45 mg/g, which was superior to the results of most similar adsorbents at present. Especially, the PVA/CS hydrogel microspheres still maintained satisfactory adsorption capacity and a high degree of sphericity after seven cycles. Furthermore, through the analysis of kinetics and thermodynamics of the adsorption process, a plausible adsorption mechanism was proposed, which will be helpful for designing and constructing adsorbents to remove radioactive ions from aquatic environments.
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