Preparation And Uranium Adsorption Performance Of Functionalized Carbon Nanotubes

The development of nuclear industry has made amount of U-wastewater which contribute considerable harm to ecosystem and mankind health.Due to many advantages such as low cost,high stable,easily made etc.,adsorption method is used widely to handle U-containing wastewater.The adsorption performance of the adsorbent is mainly reflected in the adsorption capacity and adsorption rate,so increasing the adsorption capacity and adsorption rate of the adsorbent for extracting uranium ion is a key issue to be studied urgently.In this paper,as the U-contaminated water that was prepared by self-made in laboratory as the object of study,adsorbents were designed and synthesized from the aspect of improving adsorption capacity and rate.The effect of pH,contact time,different initial concentration and temperature for adsorbent were studied.The adsorption dates were fitted by corresponding adsorption model.The adsorption mechanism was studied etc.The main study contents and results are as follows:（1）The adsorbent of carbon nanotubes that was functionalized by Ni-Al layered double hydroxides（CNT-P/LDH）was prepared by chemical precipitation method.The micrograph,microstructure,elements distribution,surface groups etc.were analyzed by SEM-EDS,XRD,FT-IR,XPS etc.The batch adsorption results shown that the optimal adsorption pH was 6,and equilibrium time was 90 min.The adsorption process was consistent with person-second-order model and Sips adsorption isotherm model,and is spontaneous and endothermic.As 0.1 mol/L Na₂EDTA as desorption solution,the removal rate of CNT-P/LDH for uranium still approaches 80%after 5 times cycle adsorption-desorption test.The adsorption mechanism was that uranyl ions were adsorbed,for which complex with-OH,-NH₂ on CNT-P/LDH surface and ions exchange with-NO₃^-from interlayer.（2）The adsorbent of carbon nanotubes that was functionalized by hydroxylapatite（CNT-P/HAP）was synthesized by hydrothermal method.FT-IR,XRD,SEM-EDS were used to analyze the morphology,microstructure,distribution of elements,and surface group etc.The batch adsorption results shown that the optimal adsorption pH was 3,and equilibrium time was 40 min.The adsorption process was consistent with person-second-order model and Sips adsorption isotherm model,and was spontaneous and endothermic.The adsorption mechanism was the formation of autunite（Ca（UO₂）₂（PO₄）₂）where CNT-P/HAP release ample Ca²⁺and PO₄^3-,and re-coordinate with uranyl ions on-NH₂,-NH-of CNT-PEI surface in acid solution.（3）The CNT-MS was prepared by molten salt electrolysis method reduction CO₂.FT-IR,XRD,SEM-EDS,TEM,and XPS were used to analyze the morphology,microstructure,distribution of elements,and surface group etc.The electrolysis product was carbon nanotube with C-C-O.The batch adsorption results shown that the optimal adsorption pH was 5,and equilibrium time was 160 min.The adsorption process was consistent with person-second-order model and Langmuir adsorption isotherm model,and is spontaneous and endothermic.The adsorption mechanism was that uranyl ions were adsorbed and formatting（UO₂）₄O（OH）₆ on CNT-MS surface.