The rise of nuclear power plants to meet escalating global energy needs has made environmental pollution including the contamination of uranium due to improper disposal of radioactive wastewater during uranium milling and mining processes. Adsorption, a water purification method known for its fast kinetics, high selectivity, and ease of use, has emerged as a popular choice for the treatment of radioactive wastewater. In response to the critical need for the purification of radioactive wastewater contaminated with U(VI), this review provides a comprehensive summary of the various types of materials, synthetic methods, and adsorption mechanisms used for the purification process. The materials are categorized into four main groups: organic, inorganic, composite/nanomaterials, and framework materials. To enhance the adsorption capacity for U(VI), researchers have explored physical and chemical modifications as well as the development of organic-inorganic hybrids. The improved adsorption performance resulting from these modifications is mostly attributed to electrostatic interaction, surface complexation, and ion exchange mechanisms. However, despite the present understanding of the processes involved, further research is still needed to fully determine the optimal approach for purifying contaminated radioactive wastewater.

To raise the physical strength of alginate beads, this study manufactured alginate-cellulose bead by adding cellulose to alginate, and wanted to identify whether falginate-cellulose beads were sufficiently efficient in removing heavy metals. To find out optimal amounts of alginate and cellulose injection, this study conducted a pilot study, and repeated experiments proved that alginate 2 w/v% + cellulose 1 w/v% were the optimal amounts in manufacturing beads. Using micro materials tester, this study compared strengths of alginate beads and alginate-cellulose beads. Choosing Cd2+, Pb2+, and Ni2+ as materials to be removed, this study analyzed concentrations of them before and after the treatment. Experiments showed that, compared with alginate beads, the strength of alginate-cellulose beads was 2.26 times stronger, and that the latter could remove 98.22%, 99.99%, and 92.57% of Cd2+, Pb2+, Ni2+, respectively. While addition of cellulose to alginate made the absorption rate drop by about 1%, the beads were still highly efficient in removing heavy metals. Accordingly, it seems that alginate-cellulose beads can be used in removing heavy metals.

Removing CO2 gas to address the global climate crisis is one of the most urgent agendas. To improve the CO2 adsorption ability of activated carbon, nitrogen plasma surface treatment was conducted. The effect of nitrogen plasma treatment on the surface chemistry and pore geometry of activated carbon was extensively analyzed. The porosity and surface groups of the activated carbon varied with the plasma treatment time. By plasma treatment for a few minutes, the microporosity and surface functionality could be simultaneously controlled. The changed microporosity and nitrogen groups affected the CO2 adsorption capacity and CO2 adsorption selectivity over N2. This simultaneous surface etching and functionalization effect could be achieved with a short operating time and low energy consumption.

Benzene, toluene, ethylbenzene, and xylenes are commonly known as (BTEX) and include volatile organic compounds (VOCs) in ambient air. Exposure to some BTEX has been associated with health risks. This study aimed to reduce BTEX on the environment and human health dramatically. This research targeted decreasing the BTEX in an air environment by producing high surface area activated carbon (KA-AC) under optimized synthesis conditions from Ricinus communis as lignocellulosic waste using ZnCl2 solution, respectively. The influence of several activation parameters was investigated on the surface area, such as impregnation ratio, carbonization time, and carbonization temperature. The KA5-AC prepared under optimized conditions showed BET surface area and total pore volume of 1225 m2/ g, and 0.72 cm3/ g, respectively. The optimized synthesis conditions were as follows: 0.1, 0.5, 1, 2, and 5 M impregnation ratio, 450–950 °C carbonization temperature, and 100 min carbonization time. The characteristics of the optimized KA-AC were analyzed using nitrogen adsorption–desorption isotherm, scanning electron microscopy, and pore structural analysis. The results confirmed that the VOCs adsorption on KA-AC followed a monolayer adsorption isotherm over a homogeneous adsorbent surface. It showed the removal efficiency of benzene, toluene, ethylbenzene, and m, p-xylene (R2 = from 0.991 to 0.997). Moreover, the KA-AC exhibited good performance without considerable loss of efficacy throughout the experiments. Accordingly, it is concluded that developing low-cost activated carbon to use BTEX vapor adsorption research could be practical and developments to overcome for utilization in air pollution control.

The CDI (Capacitive deionization) is one of the desalination technologies that use a carbon material electrode with large surface area and excellent electrical conductivity. Recently, research on a MCDI (Membrane Capacitive deionization) process, which is a combination of an ion-exchange membrane, has been actively conducted. In this study, we tried to find out the water quality of treated water and the concentration characteristics of concentrated water through TDS analysis by MCDI conventional and circulation process. In producing treated water, there was no significant difference in adsorption efficiency between MCDI conventional and circulation process. It was confirmed that both processes adsobed more than 96 %. However, the MCDI conventional process showed a low yield of 50 %, whereas the MCDI circulation process showed a high yield of 97.6 %. It's because, the wasted water was reused at desorption. In the case of the TDS concentration using MCDI circulation process, as the cycle progressed, the TDS concentration was concentrated up to 1,300 mg/L, but the rate gradually decreased. It is believed that this is because the volume of the concentrated water tank is limited, and the amount of soluble ions gradually decreases. As a result of analyzing the wasted water at MCDI circulation process through Ion Chromatography, it was confirmed that the concentration of all ions were concentrated. However, there was no significant difference in the types and proportions of analyzed ions. It is judged that the types and concentration of ions do not have a significant effect on adsorption and desorption in the MCDI circulation process.

Quality standards of activated carbon for gas-phase applications have been deleted from the Korean national standard list since 2007, and the iodine adsorption test is the only measure currently used for quality assurance. This study was performed to propose a suitable test method and a quality standard for gas-phase activated carbon. The "1/2 saturated vapor adsorption" test has been developed as a simple and convenient method to determine the adsorption capacity of activated carbon. In this study, the developed test method was evaluated using model VOCs including toluene, methyl ethyl ketone (MEK), and ethyl acetate (EA). A virgin activated carbon revealed adsorption capacities of 344mg/g, 322mg/g, and 328mg/g for toluene, EA, and MEK, respectively, and the adsorption capacity for a mixture of the three VOCs was 334 mg/g. When a regenerated activated carbon was applied, the adsorption capacities dramatically decreased to 62 mg/g, 52 mg/g, and 61 mg/ g for toluene, EA, and MEK, respectively. In addition, the 1/2 solvent vapor adsorption tests using 13 different specimens of activated carbon showed that their capacities were closely related to the iodine adsorption numbers, and this study suggested the adsorption capacity of 300 mg/g as a new quality standard. The novel test method and its standard may help to guarantee the quality of gas-phase activated carbon used for VOCs abatement processes.

Though many treatment technologies of contaminated water have been developed for a long time, it is still difficult to find a suitable method for large volumes of low radioactivity tritium-contaminated water. For this reason, most of the tritium-contaminated water been discharged to the biosphere or been stored in a special control area as radioactive waste. Activated carbon is a common material, but since there are few data on the treatment of tritium-contaminated water, its adsorption behavior to HTO is worth studied. In our study, for the tritium-contaminated water having a low radioactivity concentration (350-480 Bq/g), adsorption experiments were performed with activated carbon. The effects on the selective adsorption of HTO were investigated for temperature (5-55°C), hydrogen peroxide (1-10wt%) and activated carbon reuse (1-6 times) under non-equilibrium conditions. The treatment of activated carbon significantly reduced the radioactivity of tritium-contaminated water around 60 minutes of adsorption time. In order to clearly analyze the experimental results, positive factors and negative factors on the HTO selectivity were separately evaluated according to the adsorption time. Temperature and the reuse of activated carbon were evaluated as negative factors for HTO selectivity of activated carbon, whereas hydrogen peroxide (> 5wt%) was evaluated as a positive factor. By the evaluation method of separating the influencing factors into two types, the adsorption experimental results of HTO could be understood more clearly.

Radionuclides stored in a radioactive waste repository over a long period of time might be leached through the barriers such as engineered rock (cement) and natural rock (granite). Organic complexing agents such as ethylenediaminetetraacetic acid (EDTA) and isosaccharinic acid (ISA) may also influence the mobility of radionuclides. In this study, a continuous fixed-column reactor packed with engineered and natural rocks was designed to investigate the effect of organic complexing agents on cesium mobility through cement and granite under anaerobic conditions. The influent flow rate of the mixed solution (organic complexing agent and cesium) at the column bottom was 0.1 mL/min, while that of groundwater was 0.2 mL/min, which was introduced between cement and granite layers in the middle of the column. The hydraulic properties such as diffusion coefficient and retardation factor were derived by a bromide tracer test. The effects of different operating parameters, such as initial cesium concentrations, initial EDTA or ISA concentrations, and bed size, on the cesium adsorption were investigated. The Thomas, Adams-Bohart, and Yoon-Nelson models were applied to the experimental data to predict the breakthrough curves using non-linear regression. These results suggest that organic complexing agents such as EDTA and ISA significantly influence the mobility of cesium in the barriers, indicating that the presence of complexing agents enhances the migration of cesium to the geosphere.

In the case of decommissioning of a nuclear power plant, it is expected that a significant amount of VLLW and LLW that need to be disposed of are also expected. Conventional reduction technology is a method of extracting or removing radionuclides from waste, but this project is being carried out for the purpose of obtaining a reduction effect through the development of a material that treats another radioactive waste using radioactive waste. In this paper, the technology of impregnating LiOH capable of adsorbing radiocarbon to the gas filter material manufactured from concrete and soil waste as raw materials and the radiocarbon removal performance were reviewed. In this study, a raw material of ceramic filter was prepared by mixing concrete and soil waste with a powder of 40 m or less, and after sintering at 1,250°C, 5wt% to 40wt% of LiOH is impregnated with a filter capable of adsorbing carbon dioxide. was prepared. The prepared filter used ICP-OES and XRD to confirm the LiOH deposition result, and the concentration of carbon dioxide discharged through the carbon dioxide adsorption device was confirmed. It was possible to obtain the result that the amount of adsorption was changed depending on the flow rate of carbon dioxide supplied and the amount of material. Through this, it was possible to confirm the possibility of power generation in the adsorption performance of gas. In this study, after crushing waste concrete and waste soil, powders of 40 m or less were mixed with other additives to prepare raw materials for ceramic filters, and sintered at 1,250°C to manufacture filters. 5wt% to 40wt% of LiOH was impregnated on the prepared filter to give functionality to enable carbon dioxide adsorption. The results of LiOH deposition were confirmed using ICP-OES and XRD, and the change in the concentration of carbon dioxide emitted through a separately prepared adsorption device was confirmed. It was possible to obtain the result that the amount of adsorption was changed according to the flow rate of carbon dioxide supplied and the amount of material, and the possibility of developing a material for radioactive waste treatment using radioactive waste was confirmed when the porosity and specific surface area of the filter material were increased.

Various radionuclides are released and contaminate soils by the nuclear accidents, nuclear tests and disposal of radioactive waste. Among radionuclides, 137Cs is a harmful radioactive element that emits high-energy β particles and γ rays with a half-life of 30.2 years. 137Cs is difficult to extract because it is fixed to soil particles. For the volume reduction technology development of contaminated soil, this study tried to evaluate the irreversible Cs adsorption capacity of granite-originated soil. The soil sample used in the study was collected from C horizon of the soil developed in Mesozoic mica granite. The soil texture, mineralogy, organic content, pH, EC, cation exchange capacity (CEC), water-soluble cation and anion content of the soil samples were determined. A kinetic adsorption experiment and an isotherm adsorption experiment were performed to understand the overall Cs adsorption characteristics using 133Cs. The desorption of Cs by 0.1 mM KCl was also tested for the sample spiked with 133Cs and 137Cs. The soil sample showed a pH of 6.73, EC of 24.50 μS cm-1, and CEC of 1.34 cmolc kg-1, organic matter of 0.53% and sandy loam in texture. Quartz, feldspar and mica were identified as the major mineral components of bulk sample. The clay fraction consists of mica, hydroxyl-interlayer vermiculite (HIV), vermiculite and kaolinite. In the kinetic adsorption experiment, the Cs adsorption showed fast adsorption rates at the initial stage (6 hours) regardless of the 133Cs concentration, and the adsorption equilibrium state was reached after 48 hours. It was the most suitable for the pseudo second-order model. The 133Cs adsorption increased nonlinearly from low to high concentration, which was well match with the dual site Langmuir model. As a result of the desorption experiment, desorption was not performed up to 1.1 mg kg-1 in the presence of competitive ions K+, which is about 0.035% of CEC calculated by the isotherm model. The adsorption of Cs was controlled by frayed edge sites (FES) at a low concentrations and by basal sites or interlayer sites at a high concentration. Irreversible Cs fixation of by FES may be contributed by mainly weathered mica, and when these minerals are separated from the granite origin soil, the possibility of reducing the contamination concentration and volume of radioactive soil waste can be expected.

The presence of dyes in water is the most popular problem recently, so the current study was directed towards the synthesis of an effective material consisting of NiO and MWCNTs. The NiO/F-MWCNTs nanocomposite was synthesized using a simple hydrothermal method after functionalization of MWCNTs using sulfuric acid and nitric acid and utilized as an efficient surface to adsorption of malachite green dye from polluted water. The nanocomposite sample was characterized using several techniques are X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Thermogravimetric analysis (TGA), Field emission scanning electron microscopy (FESEM), High- resolution transmission electron microscopy (HRTEM), Brunauer–Emmett–Teller (BET) surface area analysis, Barrett-Joyner-Halenda (BJH) analysis and Energy dispersive X-ray (EDX). The analytical results showed that the prepared nanocomposite is of good crystalline nature with a particle size of 25.43 nm. A significant specific surface area was 412.08 m2/ g which indicates the effective impact of the nanocomposite in the adsorption of malachite green (MG) dye. On the other hand, the effect of adsorbent dose, temperature, acidic function and contact time on the adsorption efficiency of dye was studied. The kinetics of dye adsorption were also investigated employing two kinetic models, pseudo-first-order model and pseudo-second-order model. Finally, the thermodynamic functions were determined to identify the type of the reaction and the spontaneity of the process.

In this study, the adsorption/desorption performance of toluene was evaluated using zeolite adsorbent to replace activated carbon with one-off and ignition characteristics. For the proper operation of the VOCs adsorption/desorption and condensate recovery steps, the operating range by various adsorption/desorption temperatures was selected. The adsorbent is a bead-type zeolite, which was put into an adsorption tower of 10 LPM scale. As a result, it was demonstrated that 0.079 mg/g was adsorbed at a low temperature (20°C) during adsorption. In the case of desorption, it was found that VOCs adsorbed on the adsorbent were completely recovered after the desorption operation at 220°C for about 160 minutes. However, in the heating rate step for desorption, it was not possible to maintain an appropriate heating rate by filling the tower with zeolite. This was complemented by applying a copper plate with high thermal conductivity, and it was shown that the time was shortened by about 10 minutes or more. When VOCs are emitted at high concentrations during the desorption process, they can be reused as energy resources through low-temperature maintenance, and a condensation method was attempted. The efficiency of condensing chiller (cooler) with temperature control and liquid nitrogen condensing was compared. It was found that the chiller condensing efficiency increased as the temperature decreased. In the case of liquid nitrogen condensation, the liquid nitrogen temperature was maintained at -196°C, showing a stable efficiency of 90%.

A porous-carbon material UiO-66-C was prepared from metal–organic frameworks UiO-66 by carbonization in inert gas atmosphere. Physicochemical properties of UiO-66-C materials were well characterized by Powder X-ray diffraction (PXRD), Scanning electron microscope (SEM), Fourier-transform infrared spectroscopy (FT-IR), Raman spectrometer, N2 adsorption/ desorption isotherms (BET), and the adsorption properties of the products were studied UiO-66-C has a high specific surface area up to 1974.17 m2/ g. Besides, the adsorption capacity of tetracycline could reach 678.19 mg/g, the adsorption processes agreed well with the pseudo-second-order kinetic model and Langmuir isotherm model.

An elevated temperature is expected at the deep geological repository (DGR) due to the decay heat from spent nuclear fuel and the positive geothermal gradient. The resulting elevated temperature would change the aqueous speciation and surface complexation of uranium, which is the major component in spent nuclear fuel. Since sorption reactions of uranium species on natural minerals determine the extent of uranium retardation, in this work the temperature-dependent adsorption of hexavalent uranium, U(VI), was studied by choosing alumina as the basic component mineral for complex aluminosilicates. Time-resolved laser fluorescence spectroscopy (TRLFS) was used to assess the dissolved and adsorbed U(VI) species on γ-Alumina in the pH range of 6.5–9.0 at temperatures of 25 to 70°C. Initial concentrations of U(VI), carbonate and calcium were 89 μM, 25 mM, and 3.0 mM, respectively. The parallel factor analysis (PARAFAC) was used for chemical speciation by spectrum deconvolution. In addition, a separate solution system with higher U(VI) concentrations (0.1 mM, 1.0 mM) and carbonate concentration of 25 mM was studied with attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy for adsorbed species at 25°C. The electrophoretic mobility measurements were also conducted at 25°C to assess the coordination mechanism of adsorbed species at 25°C. The uranyl hydrolysis species and uranyl tricarbonato species coexist in solution at 25°C. At the same temperature, both species were found to be adsorbed. ATR-FTIR could confirm the adsorption of uranyl tricarbonato species at 25°C, and the electrophoretic mobility measurements suggested that the reaction mechanism is an inner-sphere coordination. However, in comparison with aqueous speciation at 25°C, at elevated temperatures the available pH range of uranyl tricarbonato species was narrow and that for uranyl hydrolysis species was wider. It was evident that two hydrolysis species are adsorbed at elevated temperatures, but no tricarbonato species. The enhanced U(VI) adsorption was observed with temperatures. This could result from the transition of dominance from the concurrent adsorption of uranyl hydrolysis species and uranyl tricarbonato species to two hydrolysis species. It was seen that the trend of enthalpy of adsorption was endothermic. Combining the present results with temperature-dependent adsorption studies on silica and aluminosilicates, a reliable SCM for the subsurface system can be proposed to explain U(VI) migration.

In this study, the removal efficiency of PFCs(perfluorinated compounds) in the GAC(granule activated carbon) process based on the superheated steam automatic regeneration system was investigated in laboratory scale and pilot-scale reactor. Among PFCs, PFHxS(perfluorohexyl sulfonate) was most effectively removed. The removal efficiency of PFCs was found to be closely related to the EBCT, and the removal efficiencies of PFOA(perfluorooctanoic acid), PFOS(perfluorooctyl sulfonate), and PFHxS were 43.7, 75, and 100%, respectively, under the condition of EBCT of 6 min. Afterward, PFOA, PFOS, and PFHxS exhibited the earlier breakthrough time in the order. After that, GAC was regenerated, and the removal efficiency of the PFCs before and after regeneration was compared. As a result, it was shown that the PFCs removal efficiency in the regenerated GAC process were higher, and that of PFOA was improved to 75%. The findings of this study indicate the feasibility of the superheated steam automatic regeneration system for the stable removal of the PFCs, and it was verified that this technology can be applied stably enough even in field conditions.