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  • Author or Editor: Cai Linsen x
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Abstract  

The sorption of Co(II) on Na-montmorillonite was conducted under various conditions, i.e., contact time, adsorbent dosage, pH, ionic strength, foreign ions, fulvic acid (FA), humic acid (HA) and temperature. Results of sorption data analysis indicated the sorption of cobalt on Na-montmorillonite was strongly dependent on pH and ionic strength. At low pH, the sorption of Co(II) was dominated by outer-sphere surface complexation and ion exchange with Na+/H+ on Na-montmorillonite, whereas inner-sphere surface complexation was the main sorption mechanism at high pH. The presence of different cations influenced Co(II) sorption, while the presence of different anions had no differentiable influences on Co(II) sorption. The presence of HA and FA decreased the sorption of Co(II) on montmorillonite. The sorption isotherms are simulated well with the Langmuir model. The thermodynamic parameters (ΔH°, ΔS° and ΔG°) calculated from the temperature dependent isotherms indicated that the sorption reaction of Co(II) on montmorillonite was an endothermic and spontaneous process. The sorption test revealed that the low cost material was a suitable material in the preconcentration of Co(II) from large volumes of aqueous solutions.

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Abstract  

The sorption of UO2 2+ 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 UO2 2+ was strongly dependent on pH and ionic strength. The sorption of UO2 2+ 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 UO2 2+ on attapulgite obviously at low pH because of the strong complexation of surface adsorbed HA/FA with UO2 2+ on attapulgite surface. Sorption of UO2 2+ 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 UO2 2+ from large volumes of aqueous solutions because of its negative surface charge and large surface areas.

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Abstract  

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.

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