Studies On Preparation And Adsorption Performance For Uranium Of Carbon Materials From Glucose

There are abundant of uranium resources in the waste water coming from the ore-processing of uranium deposit,the previous stage o f nuclear fuel and the spent fuel reprocessing.The treatment and recycling of the uranium from the radioactive waste water is to make full use of uranium resources,and effectively avoid the harm to human and damage to the ecological environment from it.Adsorption with the advantages of economy,high efficiency and simple operation has become the preferred method of the treatment of wastewater containing uranium and the extraction of uranium.According to the properties of the uranium wastewater,it is key for the treatment of radioactive wastewater to research and develop a new adsorbent which possesses the characteristics of radiation resistance,acid-proof performance,efficiency and large adsorption capacity of uranium.In this study the carbonaceous microspheres and porous carbon adsorbent have been prepared with glucose as the main raw material through the hydrothermal carbonization,KOH activation and acidification.The hydrothermal carbonization of glucose at low temperature and the influence of catalyst(e.g.,Al Cl3)on the yield and surface morphology of carbonaceous microspheres were studied systematically.The formation mechanism of carbonaceous microspheres was studied simultaneously.More research is also carried out,for example,the influences of KOH dosage and acid treatment method on the morphology and performance of porous carbon were studied.The adsorption characteristics of U(VI)by carbonaceous microspheres and porous carbon were studied.Finally the adsorption mechanism of U(VI)on c arbon materials,and their characteristics of recycling were discussed.Results were as follows.1.The preparation of carbonaceous microspheres by hydrothermal method in the range of the temperature of 120-150 oC was studied using glucose as raw material and Al Cl3 as catalyst.The obtained carbonaceous microspheres possess single spherical microspheres and smooth surface when the dosage of Al Cl3 is 20 mol %,the temperature of hydrothermal carbonization is 130 oC,and the reaction time is 20 h.However,the size distribution of the microspheres is 0.5-5.5 ?m,and their surfaces have a lot of reactive oxygen species groups.It is confirmed that the chemical structure of carbonaceous microspheres possess es abundant furan ring,but the proportion of furan rin g decreases as the temperature rises.The quantity of carboxyl groups on the surface of the carbonaceous microspheres increased when the microspheres were calcinated in the air,which is advantageous to the adsorption of uranium.2.The adsorption behavior of U(VI)on the calcinated carbonaceous microspheres(HTC-COOH)is studied,the results show that the maximum adsorption capacity of the microspheres for U(VI)is 163 mg·g-1 when the medium temperature is 25 oC,p H value of the solution is 4.5,initial concentration is 140 mg·L-1,and adsorption time is 22 h.In addition,the adsorption isotherm can be described using the Langmuir model,and the dynamics results conform to pseudo-second-order equation.The adsorption behavior of uranium mainly occurs on the outer surface of carbonaceous microsphere,with an ion exchange between carboxyl group and U(VI)and an interaction between the hydroxyl and U(VI),actually.3.The porous carbon(m-a-4-NC)was prepared using glucose and urea as raw material through the synthetise of glucose-urea resin synthesized firstly,and then the KOH activation and acid treatment.The results of adsorption show that the maximum adsorption capacity of the m-a-4-NC adsorbent is 397 mg·g-1,when the p H value of the solution is 4.5,the reaction time is 120 min.Adsorption kinetics results conform to pseudo-second-order equation,and the adsorption isotherm can be described using the Langmuir model.There is an ion exchange between carboxyl group of m-a-4-NC adsorbent and U(VI)in the solution during the adsorption.4.The surface morphology and chemical structure of porous carbon were detected by a series of advanced measure method such as FTIR,XPS,SEM and N2 adsorption-desorption isotherm model.The results show that the unmodif ied material(a-4-NC)contains rich open pore structure.Most of the mesoporous and macroporous structure of porous carbon still exists after acidification treatment,but its outer surface become rough according to SEM picture.The above structure of adsorbent is beneficial to the flow of the liquid when the adsorption occurs.