Design And Application Of On-line Adsorption Test Platform For Radionuclides (Eu、U) And Organic Pollutants(Methyl Orange)

In the 2035 long-term plan,it is mentioned to vigorously develop green energy,and nuclear power is a typical representative.However,many radioactive waste gas,waste water,and waste solids have been generated in the process of nuclear energy utilization.Therefore,the study on the adsorption,migration,and recycling of radionuclides is very important.In the previous research on nuclide adsorption,static batch processing and dynamic solid phase extraction were often used,but the experiments were delayed,unable to reflect the real-time adsorption process,and unable to finely present the regularity of nuclide adsorption with time.In this thesis,an online adsorption performance test platform was successfully built through the transformation of the ordinary spectrophotometer,the selection of the filter membrane that separates the adsorbent and the adsorbate,and the transformation of the data processing automation of the adsorption device.It solves the delay of the static batch method and dynamic solid phase extraction method that are often used in the adsorption research of the nuclides in the inorganic adsorbent.The online adsorption-color development system was constructed through the online adsorption performance test platform.Using the online adsorption method to replace the off-line static and dynamic method research can realize the online adsorption-migration kinetics research.The online adsorption performance test platform is used to realize the economical,cost-effective,and common and easily available mineral soil adsorbents:bentonite and hydrotalcite as adsorbent materials,which are used to replace the radioactive transuranium element Am,which is a low-toxic rare earth element Eu（Ⅲ）The radioactive nuclide U（Ⅵ）and the water-soluble azo organic dye methyl orange have been studied for a long time on-line adsorption,which provides a scientific basis for waste water treatment and the safe disposal of radioactive waste water.The experimental results show that the adsorption shows a fluctuating upward trend in the initial stage.The automatic programming record realized on the computer side and the online determination of p H and conductivity in the adsorption system are used.Through the SEM,XRD,FT-IR characterization tests of the adsorbent samples bentonite and hydrotalcite,and the reaction mechanism of the adsorbent sample to the adsorbate is discussed under the guidance of the kinetic and thermodynamic model framework.The conclusions are as follows:（1）Under the best experimental conditions,the removal rate of Eu（Ⅲ）adsorbed by bentonite reaches 73.21%,and the adsorption capacity is 14.56 mg/g.The removal rate of U（Ⅵ）adsorbed by bentonite reaches 59.67%,and the adsorption capacity is 24.3 mg/g.The removal rate of methyl orange adsorbed by hydrotalcite reaches 87.39%,and the adsorption capacity is 58.25 mg/g.（2）The characterization results show that the morphology of bentonite after successfully adsorbing Eu（Ⅲ）and U（Ⅵ）has changed from a rough lamellar structure to a relatively flat and smooth block hierarchical structure.Hydrotalcite successfully adsorbed methyl orange,and its morphology changed from a cluster spherical morphology with clear particles before adsorption to an agglomerated irregular floc.From the FT-IR spectrum diagram,it can be seen that the groups on the surface of the material participated in the adsorption reaction.（3）The adsorption kinetics shows that the adsorption of Eu（Ⅲ）and U（Ⅵ）by bentonite is more in line with the quasi-first-order kinetic equation.The process is dominated by physical adsorption and supplemented by ion exchange.The adsorption of Eu（Ⅲ）and U（Ⅵ）on bentonite is a spontaneous exothermic reaction.The fitting results of the quasi-second-order kinetic model are more in line with the experimental results of the adsorption of methyl orange on hydrotalcite.The adsorption process is mainly dominated by chemical adsorption,and the process conforms to the Langmuir isotherm model.The adsorption of methyl orange on hydrotalcite is a spontaneous endothermic reaction.（4）Combined with the tidal adsorption model,the adsorption process of radionuclides on the adsorbent can be divided into three layers in sequence,namely the diffusion layer,the adsorption layer and the inner diffusion layer.Under the action of physical mechanism,hydrated ions enter the diffusion layer and carry out physical adsorption in the diffusion layer;when hydrated ions are to further interact with the adsorbent,external energy is needed to realize the peeling of the outer sheath of hydration,and the hydroxyl-OH on the surface of the adsorbent forms a complex with the uranyl ions entering the adsorption layer.This process is ion exchange or outer layer complexation reaction,and is usually an endothermic reaction;finally,uranyl ions enter the adsorbent,internal mesopores,gaps,etc.,for inner surface complexation.In each adsorption process,a large amount of adsorption-a small amount of desorption occurs,resulting in adsorption fluctuations,showing a tidal adsorption state.According to the experimental results,the fluctuating adsorption formula of Eu（Ⅲ）on bentonite is:Y=1.014+0.938x+0.015x²-9.574×10^-4x³+1.666×10^-5x⁴-9.705×10^-8x⁵;The wave adsorption formula of U（Ⅵ）on bentonite is:Y=1.298+0.887x-5.718×10^-4x²+4.241×10^-4x³-1.588×10^-5x⁴+1.351×10^-7x⁵;The wave adsorption formula of methyl orange on hydrotalcite is:Y=1.293+0.670x+0.062x²-0.003x³+6.672×10^-5x⁴-4.081×10^-7x⁵.