Design And Synthesis Of Cobalt-based Prussian Blue Nanoparticles And Their Cesium Removal Performance And Mechanism

In recent decades,with the increasing depletion of fossil fuel resources and the serious environmental pollution caused by their massive use,safe,economical and clean nuclear energy has been favored worldwide and has become an important part of the energy structure.Under the strategic deployment of the country to actively develop nuclear power,the vigorous development of nuclear energy is bound to produce a large amount of radioactive wastewater.Uranium,strontium,cesium,plutonium and transuranic elements are the main nuclides in radioactive wastewater,and they pose a great threat to human living environment and biosphere.Among these nuclides,cesium,with its long half-life（30 years）and high solubility,is a particularly harmful radionuclide.Therefore,the capture and removal of cesium ions from radioactive wastewater can not only reduce its radioactive hazards and solve environmental problems,but also alleviate the problem of resource shortage.In this study,a class of inexpensive and green cobalt-based framework-like Prussian blue materials（Cu-Co PBA,Ni-Co PBA）was designed to explore its adsorption performance and stability performance for the removal of cesium ions,and to reveal the interaction mechanism with cesium.（1）Prussian blue-like materials（Cu-Co PBA）with Cu-Co as a framework were designed and synthesized by a simple low-temperature co-precipitation process.The obtained adsorbents were analyzed for crystal structure,surface functional groups,morphological features,specific surface area and pore size structure with the help of material characterization analysis methods such as XRD,FTIR,SEM,TEM,BET,etc.Cu-Co PBA nanoparticles are porous materials with an average pore size of 6.53 nm and a large amount of potassium ions are intercalated in the lattice interstices,therefore,Cu-Co PBA nanoparticles particles can provide abundant atom-occupying sites for the capture and mineralization of cesium.The quasi-second-order kinetic model and the Langmuir model fit well with the adsorption of Cu-Co PBA on Cs⁺with a maximum capture capacity of 95.75mg/g within 5 min,confirming that Cu-Co PBA nanoparticles can rapidly capture Cs⁺.Cu-Co PBA nanoparticles exhibit excellent adsorption selectivity even though Na⁺,NH₄⁺,Ca²⁺and Mg²⁺and other interferents are 50 times higher than Cs⁺,Cu-Co PBA nanoparticles interact strongly and selectively with Cs⁺.Cu-Co PBA nanoparticles also exhibit excellent stability,and after five reuses their removal efficiency of cesium is still80%,and the leaching rate of Cu-Co PBA nanoparticles after adsorption of Cs⁺is only 5.7%.Cu-Co PBA nanomaterials adsorption of Cs⁺involves the entry of Cs⁺into the crystals of Cu-Co PBA nanoparticles,replacing K⁺and finally achieving the lattice doping of cesium.（2）A novel nickel-cobalt Prussian blue analogue（Ni-Co PBA）nanoparticle was fabricated by the same method as Cu-Co PBA.Ni-Co PBA nanoparticles exhibited higher adsorption performance and better stability performance.The quasi-second-order kinetic model and Langmuir model can well describe the adsorption of Cs⁺on Ni-Co PBA nanoparticles;the maximum adsorption amount of Cs⁺on Ni-Co PBA nanoparticles was201.09 mg/g calculated by Langmuir model,and the removal rate of Cs⁺was still as high as92.40%after 6 h ofγ-radiation at 30 k Gy.It can be seen that Ni-Co PBA nanoparticles can resist the influence of high-energyγ-rays and have excellent stability performance,which is its potential for application in practical radioactive wastewater treatment.The adsorption mechanism of Cs⁺was revealed by XRD,FT-IR,XPS and EDS techniques.In the process of cesium capture,Cs⁺undergoes ion exchange with K⁺in the cubic skeleton.（3）This thesis also simulated and estimated the economic cost of Cu-Co PBA and Ni-Co PBA nanoparticles in treating real industrial wastewater.The cost of treating a batch of experiments with Cu-Co PBA and Ni-Co PBA were about 0.60 and 0.66 USD,respectively,and about 3 L of wastewater containing cesium could be treated in each experiment.Compared with the conventional hazardous wastewater treatment,the treatment cost per ton can be saved by 21.8 and 23.3 USD,respectively.In addition,Cu-Co PBA and Ni-Co PBA can be synthesized at room temperature and reach adsorption equilibrium within 15 min,indicating their potential for cost savings in industrial-scale applications.Therefore,Cu-Co PBA and Ni-Co PBA nanoparticles have promising applications as cesium adsorbents.