Study On Preparation Of KH550@NaH₂PO₄/Illite And Its Adsorption Properties For Radioactive Uranium In Water

The development and utilization of uranium resources will produce a large amount of uranium-containing wastewater.If uranium-containing wastewater is discharged directly into the environment,it will cause potential harm to the ecological environment and human health,and it is necessary to treat uranium-containing wastewater effectively.In this work,the modified Illite material（KH550@NaH₂PO₄/Illite）was prepared by modifying calcined sodium dihydrogen phosphate/Illite withγ-aminopropyltriethoxysilane（KH550）.We characterized the surface morphology,physicochemical properties of the prepared samples by means of SEM-SDS,XRD,FT-IR,BET and other characterization methods.We examined the effect of KH550@NaH₂PO₄/Illite under different preparation conditions on the adsorption performance of U（Ⅵ）by conditonal optimization experiments to obtain the optimal adsorption conditions.Discussed the selective adsorption and stability of uranium in wasterwater by KH550@NaH₂PO₄/Illite materials.The adsorption mechanism of KH550@NaH₂PO₄/Illite before and after uranium adsorption was analyzed by SEM-EDS,FT-IR,XPS and other characterization methods.We systematically studied the adsorption properties and adsorption mechanism of KH550@NaH₂PO₄/Illite on uranium.The main findings was as follows:（1）SEM-EDS,XRD,FT-IR,BET and other characterization results showed that sodium dihydrogen phosphate and KH550 were successfully modified on the surface of Illite.Compared with Illite and calcined NaH₂PO₄/Illite,KH550@NaH₂PO₄/Illite has larger specific surface areas.The increased phosphate functional groups and amino functional groups on the surface of Illite provided a large number of adsorption sites for uranyl ions in water environment.The results of adsorption experiment showed that the uranium adsorption properties of modified KH550@NaH₂PO₄/Illite materials is better than that of Illite and calcination NaH₂PO₄/Illite,and the low concentration uranium-containing wastewater can be treated efficiently.Under the condition that the initial uranium concentration was 11.927 mg/L,the solution pH was 5.03,the solid-liquid ratio was 0.4 g/L and the reaction temperature was 30℃,the removal rate of uranium reached 97.52%and the residual uranium concentration was 0.296 mg/L when absorbed for 5 min.When absorbed for 240 min,compared with Illite,the removal rate of KH550@NaH₂PO₄/Illite uranium increased by 86.02%and the adsorption capacity of uranium was 29.81 mg/g.（2）Changing the ratio of dihydrogen phosphate/Illite,calcination time,calcination temperature,volume ratio of KH550 could improve the adsorption properties of uranium.The optimized preparation conditions of KH550@NaH₂PO₄/Illite was as follows:the ratio of sodium dihydrogen phosphate to Illite was 2:1,the calcination time was 1 h,the calcination temperature was 400℃,and the volume ratio of KH550 was 2%.The uranium removal rate reached 95.09%at the initial uranium concentration of 4.870 mg/L.（3）The adsorption experimental results of KH550@NaH₂PO₄/Illite under the optimized preparation conditions was carried out by single factor method and showed that under the condition that the initial uranium concentration was 5.172 mg/L,pH was 6.09,the solid-liquid ratio was 0.4 g/L,the reaction temperature was 30℃,the removal rate of uranium by KH550@NaH₂PO₄/Illite could reach 95.84%when adsorbed for 10 min.When absorbed for 120 min,the material removal rate reached 99.67%,and the residual uranium concentration is 0.017 mg/L,which was up to the discharge standard of uranium in waste water specified in GB23727-2009“Ragulations for Radiation and Environment Protection in Uranium Ming and Milling”（<0.05mg/L）.The results of different initial uranium concentration adsorption tests showed that the KH550@NaH₂PO₄/Illite is suitable for the removal of low concentration uranium-containing wastewater,and the maximum adsorption capacity was 100.31 mg/g.（4）With the coexistence of multiple metal ions,the KH550@NaH₂PO₄/Illite showed good selectivity for uranium,and other metal ions did not change significantly.We use 0.25mol/L of NaHCO₃ solution for elution,the uranium removal rate of KH550@NaH₂PO₄/Illite after five adsorption-desorption cycles was 48.66%,and it still showed favorable stability.（5）Under the optimized preparation conditions and adsorption conditions,the removal rate of uranium by KH550@NaH₂PO₄/Illite reached 99.22%at the initial uranium concentration of 4.878 mg/L,and the residual uranium concentration was 0.038 mg/L.The adsorption process of KH550@NaH₂PO₄/Illite for U（Ⅵ）is more in line with the second-order kinetic model,the adsorption process is mainly chemical adsorption.Langmuir model can better describe the adsorption law of KH550@NaH₂PO₄/Illite,mainly monolayer adsorption.The FT-IR analysis before and after adsorption showed that amino groups on KH550@NaH₂PO₄/Illite surface interacted with U（Ⅵ）.The XPS characterization results showed that amino groups（-NH₂）,phosphate roots(PO₄^3-)on the KH550@NaH₂PO₄/Illite surface were involved in the process of U（Ⅵ）adsorption,while the complexation of uranium by hydroxyl group（OH-）on the surface of the material could not be ignored.