Performance Of Zirconium-based Phosphonate Hybrid Material In Adsorption Of U(?) In Aqueous Solution

In order to cope with the greenhouse effect and climate change caused by fossil fuels,and meet people's growing energy needs,the development of efficient and clean nuclear energy has become the first choice.At present,uranium is the most important raw material for nuclear energy development and utilization.However,the uranium-containing wastewater generated during the extraction and application of uranium causes environmental pollution to varying degrees.How to deal with these uranium-containing wastewater and recover the uranium resources has become a current research hotspot.At present,the adsorption method has attracted increasing attention in the field of waste water containing uranium.The phosphonate organic hybrid adsorbent has the advantages of simple preparation process,mild synthesis conditions,rich surface functional groups,and environmental friendliness.Therefore,it is of great theoretical and practical significance to use zirconium phosphonate organic hybrid materials to remove and recover uranium in wastewater.In this paper,ZrOCl2_·8H2O is used as the source of inorganic zirconium,with aminotrimethylenephosphonic acid(ATMPA),2-phosphonobutane-1,2,4-tricarboxylic acid(PBTCA),and hydroxyethyldiphosphine acid(HEDP)using as the organic phosphine source,and a series of zirconium phosphonate materials(Zr-ATMPA,Zr-PBTCA,and Zr-HEDP)were synthesized by a hydrothermal method,and the preparation process was optimized using the adsorption amount as an index.Scanning electron microscopy and energy dispersive spectroscopy(SEM&EDS),Fourier transform infrared spectroscopy(FT-IR),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),Zeta potential analyzer,etc.were used to characterize the above Phosphonate organic hybrid materials.The above characterization shows that three kinds of zirconium phosphonate organic hybrid adsorbents were successfully prepared.At the same time,the effects of phosphine-zirconium ratio,preparation temperature and preparation time on adsorption were studied,and the optimum preparation conditions were determined.The effects of pH,temperature,contact time,initial uranium concentration,and ionic strength on adsorption were determined by batch static adsorption experiments.The results showed that the optimum pH values for the adsorption of uranium by zirconium phosphonate Zr-ATMPA,Zr-PBTCA and Zr-HEDP were both 5.0,and the adsorption was basically independent of the ionic strength,and the adsorption equilibrium time was120 min,90 min,90 min,respectively.The uranium(VI)uptake increased with increasing temperature.Based on the above studies,the kinetics of uranium adsorption on zirconium phosphonate Zr-ATMPA,Zr-PBTCA and Zr-HEDP were studied using pseduo-first and pseduo–second adsorption kinetic model and particle diffusion model.The adsorption of uranium(VI)on the material meets the pseudo-second-order kinetics model,and the adsorption is controlled mainly by chemical action.The adsorption of U(VI)can be carried out in three stages:rapid adsorption on the outer surface,and ion entry into the inner surface from the outer surface.The adsorption rate slows down and eventually reaches equilibrium.Adsorption mechanism of uranium(VI)by Zr-ATMPA,Zr-PBTCA and Zr-HEDP zirconium phosphonate adsorbents was studied using Langmuir,Freundlich and D-R adsorption isotherms models.The results showed that the adsorption of uranium by the three adsorbents conformed to the Langmuir adsorption isotherm model.The adsorption of monolayers was monolayer,and the saturated adsorption capacity of Zr-ATMPA reached 238.10 mg/g.Zr-PBTCA was monolayer saturated with zirconium phosphonate.The adsorption capacity was 203.25 mg/g,and the saturated adsorption capacity of Zr-HEDP was 198.41 mg/g.Adsorption thermodynamic studies show that the temperature increase is conducive to the adsorption.From the three adsorption zirconium phosphate thermodynamic parameters?H>0,?G<0 and?S>0,we know that Zr-ATMPA,Zr-PBTCA and Zr-HEDP The adsorption of uranium is a spontaneous endothermic chemical process.The reusability studies of the three adsorbents showed that the uranium(VI)adsorbed on Zr-ATMPA,Zr-PBTCA and Zr-HEDP can be efficiently eluted in a 1 mol/L HCl solution.After 5 repeated experiments,the three materials were used.The uranium adsorption capacity still reaches more than 90%.The above studies show that the zirconium-based phosphonate hybrid material can effectively remove uranium(VI)in aqueous solution,and it is expected to be used to remove and recover uranium in low-level radioactive waste water,thereby reducing the uranium harm to the environment and humans.