Preparation Of Functionalized Magnetic Zeolites And Their Removal Properties To Uranyl Ions

As an efficient,clean and stable supply of energy,nuclear energy is developing rapidly.As the main component of nuclear fuel,uranium element inevitably produces radioactive waste water in the process of development and utilization.Due to the high toxicity and radioactivity of uranium,the excrete of radioactive industrial wastewater beyond the standard would pose a serious threat to human health and the ecological environment.Therefore,how to efficiently treat uranium-containing wastewater has become a major energy and environmental problem that needs to be solved urgently.Because of the adsorption method has the advantages of low operating cost,high treatment efficiency and low secondary pollution,the adsorption method has become an important method of wastewater treatment,and the choice of adsorbent is the key to the adsorption method.Among the adsorbents,zeolite materials with good stability,mechanical properties,suitable pore structure and larger ion exchange capacity have become a class of adsorbents with excellent performance.However,the high cost of synthetic zeolite currently limits its application to a large extent.Based on this problem,two composite materials(NH₂-CTS/MZ and MZ-SH),were prepared in this paper and applied to the removal of uranyl ions in aqueous solutions.First of all,NH₂-CTS/MZ composites based on magnetic zeolite were prepared from waste basalt and CTS by hydrothermal synthesis,co-precipitation,crosslinking and grafting to improve the removal capacity and separation efficiency of U(?)and reduce the cost efficiency.The effects of different factors such as p H,temperature and initial concentration on the ability of NH₂-CTS/MZ to remove U(?)were explored,and the removal process was analyzed by thermodynamics and kinetic rate equation fitting.The reaction mechanism that may exist in the process of the removal of U(?)on NH₂-CTS/MZ was studied.The multifunctional synergistic effect,excellent removal performance and magnetic separation effect exhibited by the composite material indicate its potential practical application value in the actual radioactive wastewater treatment.Secondly,using the non-burning brick powder as the raw material,the sulfhydryl modified magnetic zeolite(MZ-SH)composite material with the magnetic zeolite as the base material was prepared by the alkali fusion-hydrothermal synthesis method,the cross-linking method and the grafting method,and the MZ-SH composite material's remove performance for U(?)was investigated.The single factor experiment method was utilized to evaluate the removal performance of the composite under different conditions.By combining the characterization results of different technical means with the thermodynamics and kinetics of the removal process,the removal mechanism was discussed from the macroscopic and microscopic levels.Experimental results shown that:(1)The remanence(Mr)and specific saturation magnetization(Ms)of the prepared NH₂-CTS/MZ composite are 0.336emu/g and 6.69emu/g,respectively,the specific surface area is 240.67 m²/g,and the pore density is 3.84PPI,which shows that the composite material of NH₂-CTS/MZ have good magnetic separation performance and large specific surface area.Secondly,under the optimal conditions,the equilibrium removal capacity of NH₂-CTS/MZ for U(?)is 749.5 mg/g.The thermodynamic parameters indicate that the removal of U(?)is a spontaneous and endothermic process.The isotherm model and kinetic analysis results prove that the removal process fits better with the Langmuir isotherm model and the quasi-secondary kinetic model.FTIR and XPS analysis showed that the removal of U(?)by NH₂-CTS/MZ is mainly through the complexation of-NH₂,-OH and-COOH with the U(?)surface,and there is also redox reactions of U(?)and Fe₃O₄.Interfering ion experiments show that NH₂-CTS/MZ can still have larger removal capacity and higher removal rate under different ion environments.(2)The prepared MZ-SH composite material under the optimal conditions:t is 180min,T is 308K,C₀is 35mg/L,p H is 6.0,m is0.025g/L,the equilibrium removal capacity of MZ-SH for U(?)is1285.86 mg/g.The removal process of MZ-SH to U(?)better accord with the pseudo-second-order kinetic equation and Langmuir adsorption isotherm model.Interference ion experiments shown that MZ-SH have good application potential for industrial wastewater treatment.