Authors:Yaling Chi, Yuantao Chen, Xia Liu, Zhijun Guo and Linsen Cai
The sorption of UO22+ from aqueous solution on attapulgite was investigated as a function of contact time, solid content, pH, ionic strength, foreign
ions, humic acid (HA), and fulvic acid (FA) under ambient conditions by using batch technique. The attapulgite sample was
characterized by XRD and FTIR in detail. The results indicated that the sorption of UO22+ was strongly dependent on pH and ionic strength. The sorption of UO22+ on attapulgite increased quickly with rising pH at pH < 6.5, and decreased with increasing pH at pH > 6.5. The presence of
HA or FA enhanced the sorption of UO22+ on attapulgite obviously at low pH because of the strong complexation of surface adsorbed HA/FA with UO22+ on attapulgite surface. Sorption of UO22+ on attapulgite was mainly dominated by ion-exchange or outer-sphere surface complexation at low pH values, but by inner-sphere
surface complexation at high pH values. The results indicate that attapulgite is a very suitable adsorbent for the preconcentration
and solidification of UO22+ from large volumes of aqueous solutions because of its negative surface charge and large surface areas.
Authors:Liu Xia, Chen Yuantao, Chi Yaling, Guo Zhijun and Cai Linsen
In this article, a series of batch experiments were carried out to investigate the effect of various environmental factors
such as contact time, solid content, pH, ionic strength, foreign ions, temperature and coexisting humic acid on the sorption
behavior radionuclide 60Co(II) on illite. The results indicated that the sorption of Co(II) was strongly dependent on pH, ionic strength and temperature.
At low pH, the sorption was dominated by outer-sphere surface complexation and ion exchange on illite surfaces, whereas inner-sphere
surface complexation was the main sorption mechanism at high pH. The Langmuir, Freundlich and Dubinin-Radushkevich (D-R) models
were used to simulate the sorption isotherms at three different temperatures of 303.15, 323.15 and 343.15 K. The thermodynamic
data (∆G0, ∆S0, ∆H0) were calculated from the temperature dependent sorption isotherms and the results suggested that the sorption process of
Co(II) on illite was an endothermic and spontaneous process. The sorption test revealed that the illite can be as a cost-effective
adsorbent suitable for pre-concentration of Co(II) from large volumes of aqueous solutions.