| The development of nuclear power and the occurrence of nuclear safety accidents will cause leakage of radioactive cesium.At the same time,due to the high solubility of cesium ions,it can rapidly migrate in the environment,causing pollution of water and soil.In addition,radioactive cesium will enter the human body via food chain,causing a variety of diseases that threaten human health.On the other hand,cesium is an important resource as well.Therefore,it is of great strategic significance to adsorb and separate cesium effectively.At present,relevant researches on the removal of cesium ions in the environment(soil and water)have made some progress.However,there are still certain problems and challenges,such as:rapid adsorption of cesium ions from aqueous solution with large capacity,high-efficiency adsorption and separation of cesium ions from clay,and practical operability of materials.The removal of cesium ions from the human body needs direct and efficient method with low side effects.Therefore,it is of great important to study new materials techniques for the adsorption and separation of cesium ions from environment and human body.It is well-known that Prussian blue and its analogues have strong affinity for cesium ions with non-toxic,environmentally friendly,and low-cost properties.This thesis intends to develop new materials and technologies to solve the related problems in the fields of cesium removal from soil,water and human body.Based on the properties of Prussian blue and its analogues,we designed and synthesized a series of Prussian blue functional composites to meet different demands in different adsorption conditions.The effects of structure of materials on cesium adsorption properties,optimization of adsorption conditions and adsorption mechanism of materials were systematically investigated.The specific research contents are as follows:(1)Thermo-sensitive polymer network crosslinked by Prussian blue nanocrystals for cesium adsorption from aqueous aolution with large capacityPoly(pentacyano(4-vinylpyridine)ferrate-co-sulfobetaine methacrylate)was synthesized by free radical copolymerization.And then the copolymer was crosslinked by Fe3+ to obtain Prussian blue nanocrystal crosslinked poly(sulfobetaine methacrylate)network.FT-IR,EDX,SEM,TEM,XRD,DLS and other characterizations demonstrate the successful synthesis of temperature-sensitive polymer networks.When the temperature is higher than UCST,the adsorption efficiency is enhanced.The polymer network can prevent the aggregation of Prussian blue nanocrystals and maintain the effective specific surface area of the material,which is beneficial to promote and realize the adsorption of cesium with large capacity.A similar concept can be applicable to the other system:synergistic effect of thermo-sensitive property and thermodynamic behavior can enhance the adsorption.According to the adsorption isotherm data,the maximum adsorption capacity obtained by the Langnnuir model can reach 465.1 mg/g,which is the largest adsorption capacity reported so far.The results of adsorption kinetics experiments show that the adsorption process of cesium ions follows the second-order kinetics process,which is dominated by the chemical adsorption.The adsorption equilibrium can be achieved within 2 h.Due to the lattice size and negative potential of Prussian blue in the materials,the adsorbent exhibits high selectivity for cesium ions.The material can be regenerated by 0.5 mol/L hydrochloric acid,and has high adsorption efficiency after five adsorption-desorption cycles.Through XRD and XPS characterization and analysis,it is found that the mechanism of cesium adsorption by materials can be described as follows:there is an interaction between cesium ions and cyano groups to trap cesium ions in the crystal lattice of Prussian blue.(2)Poly(pentacyano(4-vinylpyridine)ferrate)-functionalized polypropylene nonwoven fabric for effective cesium separation from aqueous solutionsPoly(4-vinylpyridine)was grafted onto a polypropylene nonwoven fabric by gamma irradiation.And then,poly(pentacyanoferrate)-functionalized nonwoven fabric was obtained by ligand exchange with sodium p entacyano ami no ferrate.Characterizations of SEM,FT-IR,XPS and contact angle demonstrated the successful preparation of nonwoven materials.The cesium adsorption by materials follows the second-order kinetics process,which is dominated by the chemical adsorption.The adsorption can achieve equilibrium within 24 min with high selectivity at pH 7.0 and 298.15 K.Based on the adsorption isotherm data,the maximum adsorption capacity calculated by the Langmuir equation is 47.4 mg/g.And the adsorption rate and adsorption capacity are closely related to the the graft content:the larger graft content,the higher adsorption kinetics and capacity.XPS analysis indicated that the adsorption mechanism involved the formation of coordination and covalent bonds between cesium and cyano group.In addition,0.1 mol/L NaOH solution can be used to regenerate adsorbent effectively.It is noticed that the covalent combination of functional ligands with nonwoven fabric may improve the practical operability in comparison with nano-adsorbents,and can avoid the elution of ligands during adsorption process.(3)Cesium removal from human blood by poly(ethylene glycol)-decorated Prussian blue magnetic nanoparticlesPolyethylene glycol,sodium acetate,sodium dodecyl sulfate and hydrochloric acid were added to the ethylene glycol solution of ferric chloride.And then,poly(ethylene glycol)-decorated Prussian blue magnetic nanoparticles were prepared by a one-pot hydrothermal reaction.SEM,TEM,FT-IR,XRD and other characterizations confirmed the successful preparation of nanoparticles.The adsorption kinetics of cesium ions in aqueous solution follows the second-order kinetic model.At pH 7.0,adsorbent dose 0.167 g/L,298.15 K,the adsorption reached equilibrium within 1 hour.The maximum adsorption capacity calculated by Langmuir adsorption model is 274.7 mg/g.Nanoparticles show high adsorption selectivity for cesium ions in the presence of competitive and coexisting ions.The adsorbent can be regenerated by 0.5 mol/L hydrochloric acid,and has high adsorption efficiency after five adsorption-desorption cycles.Studies have shown that the adsorption of cesium ions by nanoparticles contains approximately 40%of chemical adsorption and 60%of physical adsorption.At the same time,the material exhibits good chemical stability and adsorption stability in physiological environment.Polyethylene glycol can improve the biocompatibility of materials,reduce toxic side effects,and improve the dispersion of materials.When the initial cesium concentration is 168.4 ppb,the removal efficiency in blood can reach 64.8%,which is more effective than decorporation drugs.This work provides a new approach to directly remove cesium ions from human body utilizing biocompatible Prussian blue magnetic nanoparticles.(4)Prussian blue analogues magnetic microgel for cesium removal from clayIonized chitosan was prepared by using hydrogen peroxide and hydrochloric acid.Prussian blue analogue-functionalized magnetic microgel was synthesized by surface polymerization and ligand exchange reaction.Prussian blue analogues magnetic microgel and ionized chitosan were used for synergistically cleaning of cesium contaminated clay.SEM,TEM,FT-IR,DLS and other characterizations demonstrated the successful preparation of Prussian blue analogues-functionalized magnetic microgel and ionized chitosan.Ionized chitosan with a dose of 200 mg/g clay can be used to achieve 88%of cesium desorption from clay within 2 h.The adsorption process of magnetic microgels in aqueous solution follows the second-order kinetics process,which is dominated by the chemical adsorption.At pH 7.0,adsorbent dose 2.0 g/L and 1.0 ppm of cesium concentration,Prussian blue analogues magnetic microgel can reach the adsorption equilibrium within 20 min.Based on adsorption isotherm data,the maximum adsorption capacity was calculated to be 149.70 mg/g by Langmuir adsorption model.Magnetic microgels combined with chitosan can achieve 83.7%of purification efficiency from cesium-contaminated clay.At the same time,the microgel can adsorb about 90%of the residual chitosan in the solution by electrostatic interaction.This work provides a new material system for cesium removal from clay. |
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