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  • Author or Editor: Dong Wenming x
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Abstract  

The adsorption-exchange equilibrium time and the adsorption isotherms of UO2 2+,137Cs,169Yb and HPO4 2− on modified peat have been investigated by batch experiments. The effect of pH on the adsorption-exchange percentage (E) and the distribution coefficients (K d) was also examined. It was found that the adsorption-exchange of UO2 2+ and169Yb on the modified peat was described well by Freundlich isotherm, whereas the adsorption-exchange of137Cs and HPO4 2− on modified peat corresponded to a Langmuir isotherm and the maximum adsorption capacities of the modified peat for137Cs and HPO4 2− ions were 4.4 and 4.1 μg/g respectively. The optimum pH for the adsorption-exchange of UO2 2+,137Cs,169Yb and HPO4 2− on the modified peat was 7.0 at 25°C.

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Abstract  

The factors affecting the sorption of radioeuropium(III) by bentonite and kaolinite were studied with the aim to assess the important factors which should be included in modeling of radioeuropium(III) migration in soils and sediments. Europium(III) is an analogue of trivalent actinides. The distribution coefficients of radioeuropium for sorption on bentonite and kaolinite from aqueous solutions were determined by using the batch method, and it was found that they were sensitive to the loading, the pH, the humic substance and the sorption direction. Thus, these sorption characteristics of radioeuropium on bentonite and kaolinite were found to be different from those of radiocobalt1, and the mathematical modeling of trivalent lanthanides and actinides migration will be more complicated than that of radiocobalt. It is improbable that the migration modeling with a constant distribution coefficient will be successful in the case of trivalent lanthanides and actinides.

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Abstract  

The effect of different solid components of calcareous soil on the retention of I was investigated by a batch technique and selective extraction method, and the effect of -irradiation was also investigated. The sorption and desorption isotherms of I on the one untreated, three treated soils and the calcareous soil irradiated with -rays were determined at 30 °C, pH 8.1±0.2 and in the presence of 1.0×10–4M or 0.67×10–5M CaCl2. It was found that the sorption-desorption hysteresis on the calcareous soil actually occurs on the same time scale, that iodine can be easily transported in the calcareous soil and that the exceptionally high contribution of organic matter to the iodine sorption is demonstrated.

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Abstract  

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.

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Abstract  

The factors affecting the sorption of radiocobalt by bentonite and kaolinite were studied with the aim to assess important factors which should be included in modelling radiocobalt migration in soils and waters. The distribution coefficients of radiocobalt sorption on bentonite and kaolinite from aqueous solutions were determined by using the batch method, and it was found that they were insensitive to the loading, the initial pH, the ionic strength, the humic substance and the sorption direction. Thus, the sorption characteristics of radiocobalt on bentonite and kaolinite facilitated the mathematical modelling of radiocobalt migration. In addition, the sorption kinetics and the sorption mechanism of radiocobalt on bentonite and kaolinite were also examined.

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Abstract  

The effect of different solid soil components of calcareous soils 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 calcareous soil and the three treated soils were determined at 20°C, pH 7.8±0.2 and in the presence of 0.001M CaCl2. It was found that all isotherms are linear, the sorption-desorption hysteresis for untreated soil and treated soils is obvious and the retention of SeO3 in calcareous soil is mainly attributed to the oxides.

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Abstract  

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.

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Abstract  

This paper is an extension of previous papers1–3. The breakthrough curves and the displacement curves of125I and75SeO3 on the calcareous soil, the treated soil to remove CaCO3 and the treated soil to remove organic matter were determined at pH 7.8, at 20°C and in the presence of 1·10−3 or 1·10−4 mol/l CaCl2. These results from column experiments and from batch experiments in the previous papers1,2 were mutually complementary. It can be definitely concluded that iodide is retained to a very small degree and tetravalent-selenium is retained to a small degree by calcareous soil and that organic matter in calcareous soil acts as a significant trap of iodide and CaCO3 acts as a trap of tetravalent selenium. Iodide and tetravalent-selenium would be expected to have relatively high dissemination in calcareous soil.

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Abstract  

The effect of different solid components of calcareous soil on the retention of Sr was investigated by using batch technique and selective extraction method. The sorption and desorption isotherms of Sr on the untreated calcareous soil and the three treated soils were determined at 20°C, pH 7.8±0.2 and in the presence of 0.001 M CaCl2. It was found that all isotherms are linear and that the sorption of Sr on the calcareous soil can be described by a reversible sorption process and the sorption mechanism is mainly ion exchange.

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Abstract  

The effect of various solid soil components on the retention of Cs was investigated by using batch technique and selective extraction method. The sorption and desorption isotherms of Cs on the untreated, calcareous soil and the three treated soils were determined at 20°C, pH 7.8±0.2 and in the presence of 0.001M CaCl2. It was found that all isotherms are nonlinear, and that the sorption-desorption hysteresis on the calcareous soil actually occurs on the same time scale.

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