Calcium alginate beads entrapping a mixture of Fe(0) and nanosized magnetite (NMT) were prepared and evaluated for their capability to reduce nitrate in groundwater. Microscopic and spectroscopic analyses of the beads revealed that clusters of Fe(0)/NMT were entirely embedded in alginate polymer matrix containing a large number of carboxylic and hydroxyl functional groups. The extent of nitrate reduction increased with increasing content of Fe(0) and NMT in the beads, but there was a critical NMT mass limit relative to Fe(0) mass where no further increase in nitrate reduction occurred. The beads showed slower nitrate reduction kinetics than bare Fe(0)/NMT but had comparable capacity in overall nitrate removal. Nitrate reduction increased proportionally with an increase in bead dosage to give a maximum removal of 94.5 % at 37.5 g L −1 in 48 h. Nitrate reduction with 50 g L −1 beads achieved completion of two reduction cycles in 72 h to reduce 2.19 mM nitrate to less than 0.71 mM (10 mg-N L −1 ) in each cycle. The overall results demonstrated that the beads developed in this study have a potential utility in remediation of nitrate in groundwater.
In this study, a hydrogel impregnated with powder activated carbon (PAC), MAA-PAC, was synthesized through the polymerization of acrylic acid (AA) and PB was immobilized using the carboxyl group of AA. In this process, an adsorbent with an enhancement of PB content and stability of immobilization was developed through the additional supply of Fe3+ ions by the layer by layer (LBL) assembly. XRD, FT-IR, SEM (EDS), TEM (EDS, mapping), and TG analyzes of the LBL and non-LBL groups were performed to confirm the change of PB content in the adsorbent as the LBL assembly was applied. The stability of PB immobilization was confirmed during the washing process after the synthesis of the adsorbent. When the LBL assembly process was applied as a PB immobilization strategy, the PB content in the adsorbent was improved and PB leakage was not observed during the washing process. The maximum adsorption (qm) for cesium in the MAA-PAC-PB LBL group that showed high PB content was 40.03 mg/g, and the adsorption isotherm was more suitable for the Langmuir model than the Freundlich model. The LBL group showed a high removal efficiency of 99.81% and a high DF value (525.88) for radioactive cesium (120 Bq/g). These results demonstrate the potential efficiency of the MAA-PAC-PB LBL group for the decontamination of radioactive cesium-contaminated water systems. Furthermore, it was verified that the LBL group of MAA-PAC-PB could be used as an adsorbent without an additional design of the existing water treatment facility. This can an economical decontamination method for removing radioactive cesium.
In the event of nuclear accident in neighboring countries, radioactive materials may enter the country due to the effect of wind. In order to analyze the impact of nuclear accident in neighboring countries, we simulate model about Tianwan nuclear power plant accident in China. The 137 Cs was selected as the target radionuclides and The HYSPLIT 4 model of the NOAA and meteorological data which provided by NOAA/ARL were used to analyze the diffusion effect of 137 Cs and the effect of radionuclide fallout. 6 scenarios were developed to examine the effect of emission time of 137 Cs at a nuclear power plant accident and the effect of rainfall. As the simulation results showed that the higher the emission time, the higher was the concentration of 137 Cs present in the atmosphere and on the ground. Based on the calculation of the 137 Cs deposition rate (%) from Scenario I and Scenario II, it was found that the rainy season during the simulation period was deposited at a higher rate than during the dry season.
The purpose of this study was to develop a process that can be applied to the diffusion of radioactive pollutants in the water due to radioactive fallout. We designed and fabricated an underwater radial impeller with various characteristics and measured the oxygen transfer efficiency and the mixing / diffusion efficiency of the adsorbent. The aim of this study was to develop a treatment technology that can be operated not only for emergency conditions due to diffusion of radioactive pollutants but also for normal water pollution. Experiments were carried out in a water tank for the measurement of oxygen transfer efficiency. The adsorbents used in the adsorption experiments were carried out using natural illite. We tried to derive normal and emergency operating conditions through the analysis of standard oxygen delivery and the results of the mixed diffusion efficiency of the impeller when the adsorbent is introduced.
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