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Effect of solution conditions (such as contact time, solution pH, ionic strength, reaction temperature, solid-liquid ratio and humic acid (HA)) on U(VI) immobilization on montmorillonite from Huangshan, China in environment was investigated by batch technique. U(VI) adsorption on montmorillonite is fairly affected by the solution pH and the ionic strength. Thermodynamic parameters (ΔH°, ΔS°, and ΔG°) suggest that U(VI) adsorption on montmorillonite shows a spontaneous and endothermic process. The coexisted HA in solution could promote the U(VI) adsorption on montmorillonite. Notably, Huangshan montmorillonite has the potential in enrichment and solidification of U(VI) ions under environmental conditions. [ABSTRACT FROM PUBLISHER]

The bentonite derived from Huangshan County was used as adsorbent for the adsorption of uranium (U(VI)). The effect of environmental factors, such as contact time, pH, ionic strength, HA and reaction temperature, on U(VI) adsorption on bentonite surface was investigated in detail. The adsorption capability of bentonite for U(VI) is obviously rest with pH value and ionic strength. The presence of HA in solution strongly enhance and reduce the adsorption of U(VI) on bentonite at low and high pH, respectively. The Langmuir and Freundlich models were applied to simulate the adsorption isotherms of U(VI) at three different temperatures of 298 ± 1, 318 ± 1 and 338 ± 1 K, respectively. The thermodynamic parameters (ΔH 0 , ΔG 0 and ΔS 0 ) calculated from the temperature-dependence adsorption isotherms indicates that U(VI) adsorption on bentonite is an endothermic and spontaneous process. At pH < 7, the adsorption of U(VI) was dominated by the outer-sphere surface complexation and ion exchange with H + /Na + on bentonite surfaces; At pH > 7, the inner-sphere surface complexation was the main adsorption mechanism. Based on the experimental analysis results, bentonite is an appropriate material for the enrichment and solidification of U(VI) ions. The results are important for the radioactive waste management. [ABSTRACT FROM AUTHOR]

Polyaniline (PANI) modified bentonite (PANI/bentonie) was synthesized by plasma induced polymerization of aniline on bentonite surface, and applied to uptake of uranium(VI) ions from aqueous solution. The as-synthesized PANI/bentonie was characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), thermal gravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). Batch adsorption technique was utilized to investigate the adsorption of U(VI) on bentonite and PANI/bentonite. The adsorption of U(VI) (10 mg/L) on PANI/bentonite surface is fairly depend on solution pH, ionic strength, and temperature in solution. The modified PANI on PANI/bentonite surface significantly enhances its adsorption capability for U(VI). The presence of humic acid (HA) can sound enhance U(VI) adsorption on PANI/bentonite at pH < 6.5 because of the strong complexation, and inhibits U(VI) adsorption at pH > 6.5. According to the thermodynamic parameters, the adsorption of U(VI) on PANI/bentonite surface is a spontaneous and endothermic process. The results highlight the application of PANI/bentonite composites as candidate material for the uptake of trace U(VI) from aqueous solution. [ABSTRACT FROM AUTHOR]