Preparation Of Amidoxime-based TMP-g-AO Materialand Its Adsorption Of Uranium

Uranium,as an important nuclear energy,is of great significance to industry,agriculture,national defense,science and technology.Terrestrial uranium reserves are very limited which are less than one thousandth of the total uranium reserves in seawater.Therefore,uranium resources in seawater can provide significant energy for the development of the nuclear industry.The amidoxime group is considered as one of the most efficient ligand for uranium adsorption,which have high selectivity and affinity for uranium ions.And for this reason,amidoxime-containing adsorbents are used widely in the extraction of uranium from seawater.In this work,a novel amidoxime based adsorbent Titanium-molybdopyrophosphate-g-amidoxime?TMP-g-AO?was prepared by chemical coprecipitation and subsequent chemical modifications,which were characterized by scanning electron microscopy/energy dispersive spectroscopy,Fourier transform infrared spectroscopy,X-ray photoelectron spectroscopy,N₂-BET,and thermal gravity analysis.The influences of different factors,such as adsorbent dosage,coexisting ions,initial uranium concentration,contact time and temperature,on uranium?VI?adsorption were investigated by batch experiment at fixed p H 8.2±0.1.The kinetic,isotherm models and thermodynamic were used to explore sorption behavior and mechanism.The adsorption and regeneration were performed to evaluate the stability,reusability and economy efficiency of TMP-g-AO material.In order to predict the potential application of TMP-g-AO for uranium extraction from seawater,the adsorption of uranium?VI?from natural seawater and the uranium-doped seawater was conducted.The SEM/EDS images showed that TMP was nanoscale spherical particles whose surfaces became rough and dense during chemical modification processes,and the surface of TMP-g-AO changed obviously after uranium adsorption and the content of uranium ions reached to 1.75%.The FT-IR and XPS analysis indicated that the grafted acrylonitrile was converted successfully to amidoxime groups andthe amidoxime groups on the surface of TMP-g-AO complexed with uranium ions.The values of BET surface area,pore volume,and average pore diameter from N₂-BET analysis were 48.183m³/g,0.116 cm³/g and 3.911 nm,respectively.Moreover,the results of TGA analysis showed that the thermal stability of TMP-g-AO was good,and the mass ratio of the polymerized amidoxime group to TMP-g and the weight percent of polymerized amidoxime group in dry TMP-g-AO were 0.353:1 and26.07%,respectively.The results of experiments showed that the selectivity for the coexisting ions by the TMP-g-AO adsorbent was in the order of U⁶⁺>Fe³⁺>Co²⁺>Pb²⁺>Ni²⁺>Zn²⁺>V⁵⁺>Cu²⁺,and the adsorbent exhibited high selectivity and affinity for uranium ions.The kinetic data followed the pseudo-second-order model better which indicated that the adsorption of uranium was mainly chemical adsorption on the surface of TMP-g-AO.The adsorption equilibrium data fitted the Langmuir isotherm model well which indicated that the adsorption of uranium on TMP-g-AO was a single layer of chemical adsorption,and the maximum adsorption capacity was 35.37 mg/g.The thermodynamics parameters??H,?S and?G?demonstrated that the adsorption process were feasible,spontaneous and endothermic.Furthermore,desorption was performed by 0.1 M HCl solution,and the adsorption rate of uranium on TMP-g-AO only had a 1.42%decrease after five consecutive adsorption-desorption cycles.The TMP-g-AO adsorbent also had high adsorption rate of 81.92%for uranium in seawater.As a result,TMP-g-AO has potential application prospect in the field of uranium extraction from seawater.