Du Jinzhou

Effect of fulvic acids on sorption of U(VI), Zn, Yb, I and Se(IV) onto oxides of aluminum, iron and silicon

The sorption of Yb3+, UO22+, Zn2+, I- and SeO32- onto Al2O3, Fe2O and SiO2 were determined by a batch technique in the presence and absence of fulvic acids. The effects of fulvic acid on sorption were compared. The existing general consensus, that humic substances tend to enhance metal cation sorption at low pH, reduce metal cation sorption at high pH and reduce inorganic anion sorption between pH values 3 to 10, was generally shown to be true. However, in this work many exceptions to the general consensus were found. The study indicated that the effect of humic substances on sorption of inorganic cations or anions depends not only on pH, but also on the nature of the oxide, the nature of humic substance, fractionation of the humic substance by sorption, the relative strength of complexes of both soluble and sorbed humic substances, the extent of surface coverage by humic substance, the initial concentration of humic substance and the inorganic electrolyte composition

Sorption and desorption of Eu and Yb on alumina: mechanisms and effect of fulvic acid.

The effects of pH, ionic strength and FA (fulvic acid) on the sorption and desorption of Eu(III) and Yb(III) on alumina were respectively investigated by using batch technique and radiotracers 152 + 154Eu and 169Yb. The distribution coefficients for sorption and desorption of Eu on alumina at pH 4.4, 4.6 and 5.7 in 1 mol/l NaCl solutions as a function of solid phase concentration were determined in the presence or absence of FA. The effects of pH, FA and ionic strength on the distribution coefficients for sorption and desorption of Yb on alumina were determined in 0.01-2.0 mol/l NaNO3. It was found that pH and FA influenced the sorption of Eu(III) and Yb(III) on alumina greatly. A surface hydrolysis model can satisfactorily and qualitatively explain the observations on bare alumina. The competition among the complexations of surface free hydroxyl groups, soluble and sorbed fulvic acids can satisfactorily and qualitatively explain the observations on the coated alumina.

Sorption characteristics of zinc(II) by calcareous soil–radiotracer study

65Zn was used as a radiotracer to study the sorption characteristics of zinc by two calcareous soils from Gansu Province (China). The sorption and desorption isotherms of Zn on two untreated calcareous soils and on two soils treated to remove CaCO3 were determined at 20 +/- 2 degrees C, pH 7.8 +/- 0.2 in the presence of 0.001 mol/l CaCl2. The contribution of CaCO3 to the Zn sorption by the two calcareous soils was approximately 70% of the total amount sorbed and the sorption-desorption hysteresis was definitely demonstrated, thus the CaCO3 in calcareous soil is undoubtedly the most significant sink for zinc at high pH range.

ADSORPTION AND DESORPTION STUDIES OF RADIOCESIUM ON AL2O3 FROM AQUEOUS SOLUTIONS

The adsorption and the desorption of radiocesium from aqueous solutions containing NaNO3 or CaCl2 on Al2O3 were studied over a wide range of background electrolyte concentration and solution pH by using batch techniques in polyethylene and glass test tubes. It was found that the wall of the glass test tubes has a great effect on the adsorption and desorption data, and the adsorption-desorption hysteresis on the same time scale is negligible by using the same aqueous solutions for both adsorption and desorption in the polyethylene test tubes. The dependences of the distribution coefficient on the pH and background electrolyte concentration and the adsorption mechanism were discussed.

Sorption and desorption of radiocesium on calcareous soil: Results from batch and column investigations

The sorption and desorption of radiocesium on a calcareous soil from Jiuqian County of Gansu Province (China) were studied by using batch and column experiments. The sorption-desorption isotherms and the breakthrough curves, displacement curves on the whole soil and two treated soils were determined. Based on these results, it was found that the sorption and retention of cesium are mainly determined by the clay minerals, that the sorption-desorption hysteresis of cesium on the calcareous soil is obvious and that the organic matter has a little positive contribution and the calcium carbonate has a little negative contribution to the sorption of cesium on the whole soil. The results from batch experiments were consistent with the results from column experiments.

Use of the Ion Exchange Method for Determination of Stability Constants of Uranyl Ions with Three Soil Fulvic Acids

The stability constants of uranyl ion complexes with three soil fulvic acids were determined by using the modified Ardakani-Stevensons method at pH = 6, ionic strength 0.1 mol/l and 25 degrees C. It was found that 1:1 and 1:2 type complexes, respectively, are formed at different concentration ratios of UO22+ to the fulvic acid.

SORPTION AND DESORPTION OF RADIOSELENIUM ON RED EARTH AND ITS SOLID COMPONENTS

The effect of organic matter and iron oxides as solid components of the red earth on the retention of SeO3 has been investigated by a batch technique and selective extraction method. The sorption and desorption isotherms of SeO3 on the untreated red earth and the three treated soils were determined at 20°C, pH 6.8 or 7.2 and in the presence of 0.01M CaCl2. It was found that the sorption-desorption hysteresis for untreated an treated soils is obvious and the clays play an important role in the sorption-desorption hysteresis, and that the retention of SeO3 on red earth is attributed to the iron oxides to a great extent.

Adsorption of H+, OH− and Background Electrolyte Ions on Alumina — Point of Zero Charge, Triple Layer Model (TLM) Parameters and Thermodynamic Parameters

The surface charge σ0 on aqueous suspensions of alumina was measured as a function of pH in various NaNO3 concentrations and at different temperatures. The values of the point of zero charge (p.z.c.), pK1(int), pK2(int), pKNa+(int) and pKNO3–(int) for alumina suspended in NaNO3 solutions were obtained in the temperature range 17–45°C from potentiometrie titration data. The values of ΔS0 and ΔH0 of the dissociation equilibria and complexation equilibria were calculated from these equilibrium constants. Standard Gibbs energies, enthalpies and entropies for proton adsorption on alumina were also obtained. The surface charge σ0 on aqueous suspensions of alumina was measured as a function of pH and concentration of Ca(NO3)2 or Na2SO4 solution.

Static and kinetic studies of the adsorption/desorption of H+ and OH- ions on alumina in aqueous NaNO3 solution

The adsorption/desorption of H+ and OH− ions under static conditions on to alumina in aqueous NaNO3 solution was studied at 30°C by potentiometric titration and calculations undertaken using the triple layer model (TLM). Intrinsic dissociation constants and intrinsic complexation constants at 30°C were used to calculate surface charge density, surface potential and surface species as a function of pH and ionic strength (I). Related adsorption/desorption studies of H+ and OH− ions under dynamic conditions on to alumina in aqueous NaNO3 solution were studied by means of the concentration-jump technique. Mechanistic information regarding H+ and OH− ion adsorption/desorption on to alumina was discussed using the experimental data in conjunction with the TLM.

(EC+

Abstract: The (EC+β+) decay of 128Ce was reinvestigated in the 116Sn (16O, 4n) reaction by using a helium-jet tape transport system. The close half-lives of 128Ce and 129Ce made it difficult to separate the decay γ rays of both nuclei apart. Instead of the excitation-function measurements, both reactions of 16O+116Sn and 16O+117Sn were carried out, and from their comparisons, the decay γ rays of 128Ce were clearly told from those of 129Ce. Based on X-γ and γ-γ coincidence measurements, a detailed (EC +β+) decay scheme of 128Ce has been proposed, which revises the previous one.