Study On The Preparation Of High-efficiency Iodine Adsorption Materials And Their Adsorption Performance And Mechanism

With the rapid development of nuclear industry,a large amount of industry wastewater has been inevitably produced.It usually contains some fission products,lanthanides and actinides,which should be reasonably eliminated for great scientific and practical significance.In this paper,3D flower-like Cu-Bi LDHs@ZIF-67,Ag₂O/Ag₂CO₃,and Ag-Ag₂O-CSs were successfully synthesized,respectively.The surface morphology and micro-structure of the composites were characterized by scanning electron microscope?SEM?,energy dispersive spectrometer?EDS?,X-ray diffraction?XRD?,Fourier Transform infrared spectroscopy?FT-IR?and X-ray photoelectron spectroscopy?XPS?.The adsorption performance of composite materials for iodide in aqueous solution were investigated,some parameters that determined adsorption capacity including contact time,pH,co-existing anions and the solution temperature were evaluated.?1?The flower-like microsphere CuBi-CO₃-LDHs was prepared by urea hydrothermal without controlling pH value by the moderate rate of reaction process.The CuBi-CO₃-LDHs was synthesized by co-precipitation method,and its structure was characterized by XRD,FT-IR,SEM and EDS.The results showed that ZIF-67was successfully immobilized on CuBi-CO₃-LDHs,and doped ZIF-67 did not change the structure of CuBi-CO₃-LDHs crystal.The adsorption activities of the ZIF-67@CuBi-CO₃-LDHs were evaluated by using isotherm models,the kinetics and adsorption-desorption-adsorption experiments.The experimental results indicated that ZIF-67@CuBi-CO₃-LDHs possessed excellent adsorption properties for iodine and its maximum adsorption capacity was 285.55 mg/g.The adsorption process accorded with the Freundlich isotherm and pseudo-second-order kinetics,which revealed that the adsorption of iodine was multimolecular layer adsorption and chemical adsorption,the adsorption-desorption process for iodine was reversible.?2?The cubic Ag₂O/Ag₂CO₃ was successfully synthesized via co-precipitation method,and the adsorption abilities and mechanism of Ag₂O/Ag₂CO₃ to for the iodide anions were studied.The results suggested that Ag₂O/Ag₂CO₃ has strong adsorption ability and high selectivity for iodide anions,and no obvious influence of pH on iodide anions adsorption by absorbents was observed.As the concentration of adsorbent was 0.2 g/L,the theoretical maximum adsorption capacity reached 1406.02mg/g at pH 7.0 and 25?.The adsorption process of iodide anions using Ag₂O/Ag₂CO₃was a multilayer-based chemical adsorption process,combined with pore diffusion.?3?The Ag-Ag₂O coated on carbon spheres was prepared by impregnation method.The micro structure of the composites before and after modification was characterized by means of SEM,EDS,XRD and XPS.The adsorption performance and mechanism of Ag-Ag₂O-CSs on iodine were studied.The results confirmed that Ag-Ag2O-CSs suffered little from the effect of co-existing anions and had high selectivity.The equilibrium isotherms data for iodine adsorption onto Ag-Ag₂O-CSs was better fitted with Freundlich isotherm and the monolayer adsorption capability was 374.91 mg/g.The adsorption of iodine is favorable at high temperature.The kinetics study followed the pseudo-second-order kinetics,which implied the adsorption process was accompanied by chemical adsorption and the adsorption rate was not uniquely controlled by the intra-particle diffusion.