Study On The Adsorption Properties Of Functionalized Hydrothermal Carbon Microspheres For Uranium(VI)

Separation and enrichment of uranium from effluent, not only can improve the utilization of uranium resource, but also can reduce the harm to the environment, which has important scientific and practical significance. As a new member of the carbonaceous material family, hydrothermal carbon spheres(HCSs) not only has the advantages of carbonaceous materials, which are resistant to high temperature, radiation, acid and alkali, but also has following features: mild reaction conditions and simple preparation process. Thus it is an ideal adsorbent material. However, the type and quantity of functional groups on the surface of HCSs was very limited, which restricted its application in the field of adsorption of radionuclides. In this paper, HCSs was grafted with different functional groups, in order to increase its adsorption capacity and selectivity to U(VI). Effects of p H, contact time, initial U(VI) concentration and temperature on U(VI) sorption were investigated in dital through batch experiments. Adsorption kinetics, isotherms and thermodynamics had been studied. Adsorption selectivity of adsorbents to U(VI) had also been researched. Some useful conclusions were obtained as follow:(1) The pristine hydrothermal carbon spheres(HCSs) had been synthesized via one-step hydrothermal carbonization of glucose at 180?. And phosphoethanolamine-grafted hydrothermal carbon spheres(HCSs-PO4),(bis-3,4-dihydroxy benzyl)p-phenylene diamine-grafted hydrothermal carbon spheres(HCS-BDBPD), Salophen-grafted hydrothermal carbon spheres(HCSs-salophen) and oxime-grafted hydrothermal carbon spheres(HCSs-oxime) had been successfully synthesized without changing its surface microstructure.(2) The U(VI) adsorption was of p H dependent, the results showed that the optimum p H of HCSs, HCSs-PO4, HCSs-BDBPD, HCSs-salophen and HCSs-oxime for the adsorption of uranium(VI) is 6.0, and their adsorption equilibrium time respectively was 60, 60, 90, 120 and 60 min.(3) The adsorption kinetic datas of five adsorbents were best described by the pseudo-second-order equation. And all the adsorption processes could be well defined by the Langmuir isotherm, adsorption capacity of HCSs?HCSs-PO4?HCSs-BDBPD?HCSs-salophen and HCSs-oxime respectively was 80.00, 400.00, 357.14, 344.83 and 588.24 mg·g-1. Thermodynamic parameters indicated the adsorption process of all the adsorbents was feasible,endothermic and spontaneous.(4) Selective adsorption studies showed that four functional hydrothermal carbonmicrospheres could selectively remove U(VI) in the presence of co-existing ions, Mg2+, Na+, Zn2+, Mn2+, Co2+, Ni2+, Sr2+, Cs+ and Hg2+.