Radiation Induced Modification Of Polymeric Materials And Their Applications In Uranyl Ion Adsorption And Photothermal Conversion

Currently,the global demand for energy consumption is increasing continuously.Among them,fossil energy and fresh water crisis are the two most representative common problems.As a great treasure trove of resources,the ocean’s safe utilization and exploitation are an effective way to solve this human dilemma.Uranium（U）,as a pivotal survival resource of nuclear industry,its extraction and utilization are the strategic premise to guarantee the development of clean nuclear energy.And the oceans are unquestionably the source of a massive supply of fresh water.The U reserves in marine environments are richer than those on land,but its concentration is very low as well as many competing ions coexist.Over half a century of research has showed that the adsorption extraction of uranyl ions by the amidoxime（AO）based polymer fiber（AOPF）is an effective way.As for access to fresh water,recently,solar-driven interfacial evaporation（SDIE）with photothermal conversion cotton fabric（PCCF）materials has been considered as an ideal way to implement seawater desalination because of its cost efficiency,sustainability and environmental friendliness.In addition,further realization of SDIE synergistic uranium extraction from seawater through the composite device of the two materials is also a current research hotspot.Obviously,the primary core is to solve the preparation and application evaluation of low-cost,efficient and suitable for large-scale AOPF and PCCF materials.In general,physical modification（such as coating,blending,etc.）and chemical modification（such as surface grafting,block polymerization,crosslinking,etc.）are common techniques to functionalize polymer fibers and fabrics.Among them,physical modification is mainly carried out by Van der Waals force or hydrogen bonding,which inevitably has the defects that functional units are difficult to disperse and easy to exuviate between substrates,thus limiting its durability and large-scale application.As one of the important means of chemical modification,radiation modification can fundamentally solve the above problems because functional groups are connected with the substrate in the form of covalent bond,which can not only maintain the excellent mechanical properties of the polymer main chains,but also give the material special function.Radiation grafting modification（RGM）,as its technical representative,recently has been widely and maturely used in polymer functionalization due to its advantages of simple energy saving,mild implementation conditions,no additional initiation and batch processing.Herein,this thesis devotes to prepare low-cost,high-performance uranium adsorption AOPF and PCCF by mainly utilizing the advantages of RGM,study the process and mechanism of material synthesis,and evaluate their application performance.The specific two parts in this thesis:Preparation and application of the Uranyl ion AOPF adsorption material by RGM:In this paper,commercialized ultra-high molecular weight polyethylene（UHMWPE）fibers were used as substrate materials.Polyacrylic acid（PAA）and polyacrylonitrile（PAN）were grafted onto UHMWPE substrates successively by pre-radiation induced graft polymerization（PIGP）combined with vapor-phase graft polymerization（VPGP）,and the AO-HPE fibrous adsorbent with functional polymer particles was prepared by following amidoximation.The effects of reaction temperature,monomer concentration and reaction time on the degree of grafting（DG）were investigated in detail.And the chemical structure,element composition,micromorphology,thermal properties and pore-size distribution of fibers were carefully characterized and analyzed by Fourier transform infrared spectrometer（FT-IR）,X-ray photoelectron spectroscopy（XPS）,scanning electron microscopy（SEM）,thermogravimetric analysis（TGA）and Brunauer-Emmett-Teller（BET）.The results indicate that the functional groups were successfully covalently introduced onto the fiber substrates,and the AO-HPE fiber maintains good thermal stability and mechanical property.In the VPGP process,the utilization ratio of AN monomer is nearly 100%.The adsorption capacity of the uranyl ion for AO-HPE fiber reaches 14.11 mg/g in simulated seawater,and is nearly 5 times that of vanadium（V）for the adsorption selectivity.Further screening shows that the optimum p H condition was neutral.The adsorption kinetic experiments show that the adsorption process of pure uranyl ion system with different initial concentrations accords with pseudo second-order model.The adsorption isotherm shows that the maximum adsorption capacity of AO-HPE fiber for U can reach 1144.94 mg/g.The adsorption behavior of AO-HPE fibrous adsorbent follow both Langmuir and Freundlich models and are more consistent with the Freundlich model.Preparation and application of the PANI-based PCCF by RGM:Commercialized cotton fabrics were used as substrate materials.γ-ray co-irradiation induced graft polymerization（γ-CIGP）poly（4-aminostyrene）（PASt）was carried out to introduce aniline groups onto the surface of cotton fabrics as active sites.Further,polyaniline（PANI）was covalently grafted onto the modified fabric via in situ redox graft polymerization and obtained the PANI-based（AS-g-PANI）fabric with stable functional groups loading and excellent photothermal conversion performances.Compared with traditional preparation,this technical route successfully introduced PANI functional units that cannot be grafted in one step onto the surface of fabric through stable covalent graft,which cleverly improved the weak combination,practical application,and realizability in large-scale production.The effect of monomer concentration on DG was investigated in detail.Physical and chemical properties of samples were carefully characterized by FT-IR,XPS,SEM,TGA,conductivity test and contact angle test,etc.The results show that the stable PANI-based PCCF can be successfully prepared byγ-CIGP technology,and DG and morphology of the AS-g-PANI fabric are highly controllable.The UV-vis-NIR analysis shows that the absorbance of the AS-g-PANI fabric in wide-brimmed absorption reaches over 92%.One-hour SDIE test under 1 sun irradiation for the two-dimensional（2D）evaporator shows the pure water photothermal evaporation rate（E.R.）of 1.39 kg·m^-2·h^-1 and photothermal evaporation efficiency（η）of 92%,respectively.During 60-day outdoor natural placement,the performance of 2D evaporator in 3.5 wt.%brine with SDIE has always maintained an excellent level,which is far higher than the existing reports.One-hour same SDIE tests for designing three-dimensional（3D）evaporators show the pure water E.R.(1.50 kg·m^-2·h^-1)and 26wt.%saturated brine E.R.(1.38 kg·m^-2·h^-1).Further continuous and cyclic SDIE tests in brine systems（3.5 wt.%simulated seawater and 26 wt.%saturated brine）for the AS-g-PANI fabric show excellent photothermal conversion performance,intrinsic antibacterial and anti-fouling performance,self-regulation,and evaporation crystallization property of brine.