Synthesis Of Microwave-assisted Hydrothermal Carbon Microsphere And Its Adsorption Properties Of Uranium

With the rapid development of the nuclear industry,the demand for nuclear fuel uranium is also increasing.On the other hand,in the process of ore-processing of uranium depositand the use of nuclear fuel uranium,a large number of uranium from the radioactive waste water with potential threat to human health and ecological environment are produced,therefore,the extraction and separation of uranium fromwastewaterhas become a great problem to researchers.At present,adsorption method is widely accepted because of its advantages of simple operation,wide adaptability and low cost.There are many factors that affect the treatment of uranium in wastewater.Among them,the adsorption material is one of the key problems of adsorption method.As an adsorption material,carbon material is considered as a potential adsorption material for uranium because of its green raw material,simple preparation process,acid and alkali resistance and radiation resistance.However,at present,there are some shortcomings,such as too high preparation temperature,too long reaction time,poor adsorption effect and selectivity,which are urgent problems for researchers.This topic focuses on the key issues of the preparation and application of the new type of uranium adsorption materials with high adsorption capacity in green energy saving and time saving.A new type of carbon material was synthesized by microwave assisted hydrothermal method and grafting modification with glucose as the main raw material.The surface structure and properties of the material were characterized.The adsorption performance and mechanism of the material were studied in detail by batch adsorption experiment.The main contents are as follows:1.Using glucose as the carbon material and aluminum chloride as the catalyst,carbon microspheres were successfully prepared by microwave and hydrothermal methods in a short time at low temperature.The influence of microwave power,reaction time and temperature on the properties of carbon microspheres was studied.SEM,XPS,NMR,FTIR and particle size analysis were used to investigate the surface morphology,group structure and particle size distribution of materials.The results showed that when the glucose was 1.58 g and the amount of aluminum chloride was 20 mol%,the best synthesis process was that the microwave power was 700 W,the temperature was 130?,the reaction time was 8h,the surface morphology was smooth,the average particle size was 3.57?±0.795??m,the yield was 20%,and the specific surface area was 61.11 m²/g;The synthesis mechanism of the material is that glucose is isomerized into fructose under the catalysis of[Al?OH?₂?aq?]⁺and then hydrolyzed and dehydrated under microwave heating to form furfural.The final microwave assisted hydrothermal carbon microspheres are formed by polymerization or condensation.2.The experimental results of microwave-assisted hydrothermal carbon microspheres adsorption of uranium show that when the pH is 4.5,the temperature is 328.15 K,the concentration is 320 mg/L,and the maximum adsorption capacity of microwave-assisted hydrothermal carbon microspheres is 411.45 mg/g,the fitting analysis of isothermal adsorption model and kinetic model shows that the adsorption of uranium by microwave-assisted hydrothermal carbon microspheres is mainly a monolayer chemical adsorption process,which is a endothermic and spontaneous.adsorption process.The main adsorption mechanism of the material is the ion exchange reaction and coordination between hydrogen and hydroxyl on the surface of carbon microspheres and uranium?VI?in solution.3.The modified microwave-assisted hydrothermal carbon materials containing phosphate functional groups were successfully prepared by one-step hydrothermal method at low temperature using phytic acid and sodium tripolyphosphate as functional monomers:phytic acid functionalized microwave-assisted hydrothermal carbon?MHC-PA?and sodium tripolyphosphate functionalized microwave-assisted hydrothermal carbon?MHC-STPP?.The surface morphology,structure and properties of MHC-PA and MHC-STPP were investigated by means of XPS,BET,TGA and FTIR,and the modification mechanism was analyzed.The results show that phytic acid functionalized hydrothermal carbon causes obvious adhesion.The sodium tripolyphosphate functionalization reduces the particle size of the hydrothermal carbon to nanometer level,but the surface morphology has no significant effect.Phytic acid and sodium tripolyphosphate,two functional monomers,only interact with the surface groups of the hydrothermal carbon microspheres,but have no effect on the body structure of the carbon microspheres.MHC-PA has good adsorption performance for uranium.The mechanism of phytic acid functionalized hydrothermal carbon is that the P-OH group of phytic acid structure and the oxygen-containing functional group C=O group on the surface of microwave-assisted hydrothermal carbon microsphere are successfully combined by hydrogen bond,which makes phytic acid evenly distributed on the surface of carbon microsphere,improves the number and type of active functional groups on the surface of carbon microsphere,and improves the adsorption capacity of carbon microsphere.4.The results of mass adsorption of uranium by MHC-PA carbon microspheres show that:The results show that when the pH is 6,the temperature is 328.15 K,the concentration is 140mg/L,and the maximum adsorption capacity of MHC-PA is 966.45 mg/g,the adsorption process of uranium is more in line with Langmuir isothermal model and Pseudo-second-order kinetic model,which shows that the adsorption process is dominated by monolayer chemical adsorption process,and thermodynamic analysis showed that the adsorption process of U?VI?by MHC-PA was endothermic and spontaneous.The main adsorption mechanism of MHC-PA for U?VI?:mainly the chelation of P=O,P-OH functional group and U?VI?,which improves the selective adsorption performance of MHC-PA for U?VI?.