The aim of this study was to evaluate the sorption characteristics of cesium onto freshwater reservoir sediment. For this, batch sorption experiments using sediment collected from a fresh water reservoir were conducted for 27 combinations of water temperature (5, 20 and 35 ºC), pH (5, 7 and 9) and EC (130, 160 and 190 µS/cm). In addition, the distribution of adsorbed Cs was examined using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). The results showed that the equilibrium sorption data of cesium onto reservoir sediment could be fairly-well described by both Langmuir and Freundlich isotherm models. The estimated isotherm parameters indicated that the impacts of water temperature, pH and EC on the sorption capacity of cesium were less obvious within the investigated ranges of these three variables. EDS mapping and elemental analysis of sediment after cesium sorption, together with the analysis by XRD, revealed that sorption of cesium on the reservoir sediment occurs mainly on its surface and the distribution of the adsorbed Cs on sediment was not uniform.
The aim of this study was to evaluate the feasibility of rapid vermicomposting of different fresh fruit and vegetable wastes (FVWs) including banana peels, cabbage, lettuce, potato and watermelon peels using earthworm Eisenia foetida. For this, the changes of physicochemical properties, microbial profiles and earthworm biology were comprehensively evaluated after vermicomposting for 4 weeks. Compared to controls (without earthworms), vermicomposting caused reductions of the total carbon content by 42.7-52.4% and the carbon to nitrogen ratios by 46.5-61.1%, and increases of the electrical conductivity by 6.7-69.4% and the total phosphorous content by 4.0-52.0%. Vermicomposting revealed a higher microbial activity, density and diversity in end products than controls. The vermicomposting treatment for FVWs allowed a high growth rate of earthworms and an increased number of cocoons. Similar microbial community structures were observed in all vermicomposts, indicating a high degree of bio-stabilization and maturity. The results suggest that rapid vermicomposting is a feasible technology for converting fresh FVWs into valuable products and that the quality of vermicomposts is strongly associated with the properties of initial substrates.
To generate information for better understanding of the behavior of cesium in relatively closed water bodies, experiments using four columns consisted of the sediment phase and the overlying water phase, together with batch sorption experiments were conducted, and the kinetics and the binding potential of cesium by sediment were investigated. Through model analysis with both the first order and the pseudo-second order reaction models, the kinetic parameters of cesium within the four columns were determined. In addition, by analyzing batch equilibrium data with both Freundlich and Langmuir isotherm models, associated sorption parameters were also generated. Comparisons of the models’ suitability for description of both kinetics and binding capacity of cesium were thus made, and the effects of pH and EC on the binding capacity were also studied.
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