Research On The Selective Uranium Extraction Performance Of Aminoxime Functionalized Silica And Its Micro/Nanomotor Composite Adsorbent

Under the goal of achieving"carbon peaking and carbon neutrality",the development of new energy industry has accelerated.Nuclear energy as an efficient and low-carbon green energy is an important part of the new energy industry.As the source of living water for the sustainable development of nuclear energy,the stable supply of uranium resources is of great practical significance.The selective separation and enrichment of uranium(UO₂²⁺)in seawater and nuclear industry wastewater is expected to provide an important guarantee for the green and sustainable development of the nuclear power industry.The adsorption method is considered to be one of the most cost-effective implementation options for the complex components and low concentrations of target ions in the actual water environment.In this work,silica（Si O₂）nanoparticles are used as carriers,and the functional group of amidoxime（AO）with specific selectivity for uranium is selected for modification;at the same time,combining with chemical/physical propelled micro/nanomotors to prepare amidoxime（AO）functionalized micro/nanomotor composite adsorbents for efficient enrichment of uranium in water.Through characterization and adsorption experiments,the regulatory laws and conformational relationships of composite adsorbent microstructures were explored,and the adsorbent composition,driving,and recognition mechanisms were elucidated.The main research content is as follows:（1）The preparation of silica nanoparticles（Si O₂）with a particle size of about 100nm was carried out using the St?ber method.The Si O₂ was then modified with 3-aminopropyltriethoxysilane（APTES）to obtain Si O₂-NH₂,which was further modified with diaminomaleonitrile（DAMN）monomer crosslinked with glutaraldehyde（GA）to obtain Si O₂-CN.Finally,hydroxylamine hydrochloride（NH₂OH·HCl）was used to reduce C≡N to amidoxime（AO）functional groups,resulting in Si O₂-AO.In addition,cross-linked monomeric salicylaldoxime was reacted with GA-modified Si O₂ to obtain Si O₂-SA.The performance of the two adsorbents for uranium extraction was investigated.The experimental results show that Si O₂-AO and Si O₂-SA have the highest adsorption capacity at p H 6.0 and 7.0,respectively,and both of them reach adsorption equilibrium at around 30 min.The adsorption process conforms to the pseudo-second-order kinetic equation model.Meanwhile,Si O₂-AO has a higher adsorption capacity for uranium(UO₂²⁺)than Si O₂-SA.According to the Langmuir model equation,the maximum adsorption capacity of Si O₂-AO for UO₂²⁺in the adsorption equilibrium experiment at 25℃is 121.65 mg/g.Furthermore,the removal rate of UO₂²⁺by Si O₂-AO was close to 100%in the simulated seawater solution where multiple metal ions where co-existed.（2）Polystyrene microspheres（PS@PDA）modified with polydopamine were selected as Pickering particles,and oil-in-water（O/W）emulsions were prepared at 75℃with paraffin wax as the dispersed phase and pure water as the continuous phase.After cooling to room temperature,the solid particles were embedded in paraffin and the surface properties of polydopamine（PDA）were utilized to reduce Ag⁺to Ag nano-particles modified in the exposed part of PS@PDA.The solid paraffin was then eluted to obtain Janus motors（PS@PDA@Ag）,and finally the nanosorbent Si O₂-AO was covalently attached to the part without Ag nano-particles by Michael addition reaction to obtain anisotropic micro/nanomotor composite adsorbent（PPA/SA）that avoids overlapping of adsorption sites and the catalytic site.The experimental results show that Janus motors exhibit effective self-propulsion under low concentrations of hydrogen peroxide（H₂O₂）,with a motion speed of 25μm/s under 5%H₂O₂ conditions.The adsorption of PPA/SA for the target in the uranyl test solution containing 1%H₂O₂reached 38.71 mg/g and is higher than that without H₂O₂,indicating that the self-propelling of the motor effectively enhanced the solution mixing and mass transfer efficiency.In addition,XPS analysis shows that the coordination of amidoxime functional groups with UO₂²⁺is the main adsorption mechanism.（3）Polystyrene particles（PS@PDA）modified with polydopamine of about 200nm in diameter were used as a template and Au particles were reduced in situ on the surface of polydopamine（PDA）.Subsequently,a layer of silica was coated and the template was removed by calcination at 500℃to obtain the photo-thermal driving material Si O₂∩Au.Finally,a mesoporous silica layer with cyanogroup（C≡N）was coated on the outside of Si O₂∩Au by co-condensation,and the C≡N was reduced to amidoxime（AO）functional groups using hydroxylamine hydrochloride（NH₂OH·HCl）to obtain hollow mesoporous motor adsorbents（MSSA-AO）for the adsorption of uranium(UO₂²⁺).The research results showed that near-infrared light（NIR）with different output powers would affect the movement speed of the motor.Under 1.2W/cm² infrared light irradiation,the motor movement speed reached a maximum of22.5μm/s.Under the conditions of 1.0 W/cm² and 1.2 W/cm² light irradiation,the adsorption capacity of MMSA-AO for UO₂²⁺reached 38.66 mg/g at 5 minutes,which is approximately 1.17 times that without light irradiation,indicating that the non-thermal equilibrium generated by near-infrared irradiation effectively increased the contact opportunity between the binding site and the target substance.In addition,MSSA-AO has excellent selectivity and regeneration performance,and has great potential for application in seawater uranium extraction.