Study On Preparation Of Phosphorus-containing Melamine Resin And Its Adsorption To Uranium

With the rapid development of the social economy and the in-depth implementation of the concept of environmental protection development,the urgent need for high-efficiency and clean energy of humanity has also become an urgent problem for all countries to solve.Nuclear energy,as an efficient and clean energy source,is constantly meeting human needs.However,the uranium mining,fuel production,reactor operation,and post-processing stages in developing nuclear energy will produce much radioactive waste liquid.Furthermore,uranium is the main nuclide in the nuclear fuel cycle,and it will be produced a large amount of uranium-containing radioactive waste liquid in the cycle.Because uranium has radioactive hazards,metal toxicity,and proliferation characteristics,uranium poses a severe threat to human health and environmental safety.Therefore,it is essential to develop materials for U（Ⅵ）high-efficiency capture in the radioactive waste liquid.In this paper,based on Melamine resin（MF）,a compound containing many primary amines,secondary amine,and hydroxymethyl active functional groups was synthesized by Melamine and formaldehyde polymerization.Then two kinds of phosphate-containing melamine resin materials were prepared by phosphoric acid modification.The adsorption efficiency and adsorption mechanism of materials for U（Ⅵ）in the solution were studied by batch static adsorption experiments and material microstructure characterization.The research content and conclusions of this article are as follows:1.A strip-shaped melamine resin MF12 was prepared by hydrothermal method,and a phosphorous-containing melamine resin MF12-POA was further prepared by grafting with phosphorous acid,which was used as an adsorbent for trapping U（Ⅵ）in the solution.The MF12-POA material was characterized by scanning electron microscopy（SEM）,X-ray diffraction（XRD）,Fourier transform infrared spectroscopy（FT-IR）,thermogravimetric analysis（TGA）,and specific surface area test（BET）,which proved the successful synthesis of the material and its ability to capture U（Ⅵ）.The microstructure of the material was consistent with that of MF12 and improved its thermal stability.We studied the effects of solution pH,contact time,U（Ⅵ）concentration,ionic strength,and the participation of multi-metal ions on the adsorption efficiency for the U（Ⅵ）adsorption experiment.The experimental results showed that the adsorption capacity of MF12-POA for U（Ⅵ）reached 294.5 mg/g at pH=4.0 and T=298 K,which has significant improvement compared with the unmodified melamine resin（7.6 mg/g）.After adsorption,the material and solution could be separated by simple filtration.Besides,the high ionic strength solution had no apparent effect on the adsorption capacity of the material.The material showed the best selectivity to U（Ⅵ）under the condition of multi-metal ions.After adsorption of U（Ⅵ）,the material could be desorbed by 0.5 mol/L Na₂CO₃ solution,and the desorption rate reached the maximum.2.Based on the research content of phosphite grafted melamine resin（MF12-POA）,considering that phytic acid（PTA）contains six phosphoric acid functional groups and has excellent complexation with U（Ⅵ）,PTA was further used as an active group.Similarly,MF12 was used as the substrate material to prepare MF12-PTA by grafting PTA onto the surface of MF12 using Epichlorohydrin（ECH）.The composition and structure of the material were obtained by SEM,XRD,FT-IR,TGA,and BET,which also verified the successful synthesis of the material and the effective capture of U（Ⅵ）.In the adsorption experiment of U（Ⅵ）,we also studied the adsorption properties of U（Ⅵ）on materials with different pH,contact time,U（Ⅵ）concentration,ionic strength,and multi-metal ions.The results showed that it reached the adsorption equilibrium after 20 minutes of contact.The adsorption capacity of the material went 343.1 mg/g at pH=4.0 and T=298 K.The separation of the material from the solution after adsorption was very simple.Also,the adsorption capacity of the material in the solution with high ionic strength was not significantly affected.In the adsorption of multiple metal ions,the selectivity of the material to U（Ⅵ）was higher than that of other metal ions.After adsorption of U（Ⅵ）,the material could be separated by 0.5mol/L Na₂CO₃,and the desorption rate reached 93.62%.The material was applied to the removal of U（Ⅵ）from real radioactive wastewater containing U（Ⅵ）,and the adsorption capacity reached 327.60 mg/g.The SEM results,FT-IR,and other characterizations and adsorption experiments show that MF12-PTA and U（Ⅵ）are mainly through an internal complexation,and the adsorption is primarily carried out on the surface of the material.P=O,-OH,and other groups play a positive role in U（Ⅵ）adsorption.In summary,the successful preparation and application of MF12-PTA material is a positive promotion for the development of melamine resin containing phosphorus and an excellent supplement to the adsorbent for radioactive waste liquid containing U（Ⅵ）.In this paper,we successfully developed two kinds of melamine resins containing phosphorus,and a series of characterization methods clarified the composition and structural characteristics of the materials.By studying the adsorption effect of pH,contact time,U（Ⅵ）concentration,ionic strength,and various metal ions,we obtained U（Ⅵ）adsorption characteristics.We conducted the adsorption experiments of actual radioactive waste containing U（Ⅵ）for both materials.The results also confirmed the potential application value of the developed material in U（Ⅵ）treatment-containing radioactive waste.It provided a theoretical basis for subsequent related adsorption,which also provided a theoretical basis for developing and applying subsequent related adsorbents.