Preparation Of Functionalized Hydrothermal Carbon Derived From Glucose And Its Adsorption Properties Of Uranium

With the rapid development and application of nuclear energy and power,the contradiction of demand for uranium becomes serious.Meanwhile the pollution of radioactive wastewater must be solved,which is important to the ecological security.Therefore,it is vital to research the materials and technologies of extraction and separation for uranium from wastewater,which is beneficial to the utilization of uranium resource,optimization of energy structure and purification of eco-environment.Hydrothermal carbon is a potential adsorbent for separation of uranium owing to its advantages including the excellent thermal stability,radiation resistance and chemical stability.However,the poor adsorption capacity and selectivity become the major defects of hydrothermal carbon,caused by the limit of functional groups on the surface.In this paper,aiming to solve the key problems of development and application of hydrothermal carbon materials with high adsorption capacity,the novel functionalized hydrothermal carbon materials were prepared using glucose as raw material via hydrothermal carbonization combined with chemical grafting and functionalization technology.Their adsorption properties and adsorption mechanism were studied.The main contents are as follows: 1.The collagen peptide grafted hydrothermal carbon material(HTC-COP)was successfully prepared using glucose as raw material and collagen peptide as functional ligand,which was then applied to the research of adsorption for uranium(Ⅵ)from aqueous solution.The results showed that the maximum adsorption capacity of HTC-COP for uranium(Ⅵ)was 494.02 mg/g when the p H was 6,the temperature was 328.15 K,and the initial concentration was 160 mg/L.The adsorption process of uranium(Ⅵ)on HTC-COP was well described by the pseudo-second-order kinetics model and the Langmuir isothermal model,which reflected that the adsorption of HTC-COP for uranium(Ⅵ)was dominated by the monolayer chemisorption and was endothermic and spontaneous.The coexisting ions had little effect on the adsorption of uranium(Ⅵ).The high uranium-selectivity(80 %)demonstrated the high selectivity of HTC-COP for uranium.The adsorbent was analyzed by many characterization methods and the suppose mechanism was proposed.Many amino groups and carboxyl groups were introduced to the surface of HTC-COP via chemical grafting,so that the uranium would chelate or coordinate with the carboxyl and amino groups of the ligand,and carboxyl and hydroxyl groups of the matrix.2.The phenolic hydroxyl-functionalized hydrothermal carbon material(BT-HTC)was successfully synthesized via one-step hydrothermal carbonization in the presence of glucose and tannin used as raw source and functional monomer.The adsorption performance of uranium(Ⅵ)was investigated by batch experimental studies.The results showed that the maximum adsorption capacity of BT-HTC for uranium(Ⅵ)was 316.77 mg/g when the p H was 6,the temperature was 328.15 K,and the initial concentration was 140 mg/L.The adsorption process of BT-HTC for uranium(Ⅵ)was well described by the Langmuir isothermal model and the pseudo-second-order kinetics model.The adsorption was feasible,endothermic and spontaneous reflected by analysis of thermodynamic parameters.The coexisting ions showed no effect on the adsorption of uranium.The optimal uranium-selectivity was up to 87 %,which indicated the high selectivity of BT-HTC for uranium(Ⅵ)adsorption.After adsorption-desorption cycle,BT-HTC showed high adsorption efficiency,illustrating that BT-HTC can be recycled many times.The adsorbent was analyzed by many characterization methods,which indicated that there were many phenolic hydroxyl groups on the surface of BT-HTC.The suppose mechanism would be the coordination of uranium and the phenolic hydroxyl groups.3.The carboxylic-functionalized hydrothermal carbon material(CA-HTC)was successfully synthesized via one-step hydrothermal carbonization in the presence of glucose and citric acid,which showed excellent performance for uranium adsorption and separation.The results showed that the optimal p H value was 5,and the maximum adsorption capacity of CA-HTC for uranium(Ⅵ)was 322.0 mg/g when the temperature was 328.15 K and the initial concentration was 160 mg/L.It was found that the pseudo-second-order kinetics model and the Freundlich isothermal model could better describe the adsorption process of CA-HTC for uranium(Ⅵ).The parameters calculated from the thermodynamic model showed that the adsorption was a spontaneous and endothermic process with randomness increase.The high distribution coefficient and uranium-selectivity reflected the excellent affinity and selectivity of CA-HTC towards uranium.The adsorbent was characterized by FTIR,EDX and XPS which proposed the suppose mechanism was the cooperation of uranium and the carboxyl groups on the surface of CA-HTC.