Removal of selenium and iodine radionuclides from waste solutions using synthetic inorganic ion exchanger

Enhanced sorption of strontium radionuclides onto a modified molybdenum titanate composite

A study was conducted to investigate the sorption of 85Sr from aqueous solutions using a fabricated magnesium molybdenum titanate (MgMoTi) composite. The MgMoTi composites were synthesized through the co-precipitation technique and characterized using different analytical tools, including FT-IR, XRD, SEM, and EDX. The sorption studies focused on 85Sr and examined factors such as shaking time, pH, ionic strength, temperature, initial ion concentration, and saturation capacity. The results obtained from the study indicated that, under optimum sorption conditions, the saturation capacity for 85Sr onto S-4 and S-5 was determined to be 23.31 and 37.72 mg g-1, respectively. The sorption of 85Sr exhibited dependence on pH and ionic strength. The kinetics of the sorption process followed the pseudo-2nd-order model, while the thermodynamics revealed an endothermic and spontaneous nature. Desorption studies revealed that 0.1 M HCl was the most effective eluent for the complete recovery of 85Sr. Furthermore, the recycling results demonstrated the excellent recyclability of MgMoTi, suggesting its potential application as a sorbent for the removal of 85Sr from aqueous solutions. Overall, the study highlights MgMoTi as a promising composite with practical utility in the sorption of 85Sr from aqueous solutions.

Adsorption Behavior of Co2+, Ni2+, Sr2+, Cs+, and I- by Corrosion Products α-FeOOH from Typical Metal Tanks

Throughout the nuclear power production process, the disposal of radioactive waste has consistently raised concerns about environmental safety. When the metal tanks used for waste disposal are corroded, radionuclides seep into the groundwater environment and eventually into the biosphere, causing significant damage to the environment. Hence, investigating the adsorption behavior of radionuclides on the corrosion products of metal tanks used for waste disposal is an essential component of safety and evaluation protocols at disposal sites. In order to understand the adsorption behavior of important radionuclides 60Co, 59Ni, 90Sr, 135Cs and 129I on α-FeOOH, the influences of different pH values, contact time, temperature and ion concentration on the adsorption rate were studied. The adsorption mechanism was also discussed. It was revealed that the adsorption of key nuclides onto α-FeOOH is significantly influenced by both pH and temperature. This change in surface charge corresponds to alterations in the morphology of nuclide ions within the system, subsequently impacting the adsorption efficiency. Sodium ions (Na+) and chlorate ions (ClO3-) compete for coordination with nuclide ions, thereby exerting an additional influence on the adsorption process. The XPS analysis results demonstrate the formation of an internal coordination bond (Ni-O bond) between Ni2+ and iron oxide, which is adsorbed onto α-FeOOH.

Efficient uptake of 85Sr and 60Co using fabricated inorganic sorbent for reducing radiation doses of simulated low-level waste

The present study investigated the sorption behavior of 85Sr and 60Co radionuclides from aqueous solutions onto tin molybdate (SnMo) sorbent. SnMo has been synthesized using the precipitation method and was characterized using four analytical techniques including FT-IR, XRD, SEM, and XRF. The sorption studies applied on 85Sr and 60Co include the effect of shaking time, pH, concentration, and saturation capacity. The experimental data revealed that the sorption process was carried out after equilibrium time (180 min). The saturation capacity for 85Sr and 60Co is measured to be 58.1 and 52.2 mg g-1, respectively. The sorption behavior of studied radionuclides is dependent on pH values. Sorption kinetic better fit with the pseudo-second-order model. Furthermore, the sorption isotherm is better represented by the model proposed by Langmuir. The results of the desorption investigations indicated that the most effective eluents for achieving full recovery of investigated radionuclides were identified. Finally, the recycling results demonstrate the suitability of SnMo for affected sorbing of 85Sr and 60Co from aqueous solutions. All the obtained data clarify that the SnMo sorbent is an effective means of removing 85Sr and 60Co from liquid waste.

Selenium volatilization in plants, microalgae, and microorganisms

The augmented prevalence of Se (Se) pollution can be attributed to various human activities, such as mining, coal combustion, oil extraction and refining, and agricultural irrigation. Although Se is vital for animals, humans, and microorganisms, excessive concentrations of this element can give rise to potential hazards. Consequently, numerous approaches have been devised to mitigate Se pollution, encompassing physicochemical techniques and bioremediation. The recognition of Se volatilization as a potential strategy for mitigating Se pollution in contaminated environments is underscored in this review. This study delves into the volatilization mechanisms in various organisms, including plants, microalgae, and microorganisms. By assessing the efficacy of Se removal and identifying the rate-limiting steps associated with volatilization, this paper provides insightful recommendations for Se mitigation. Constructed wetlands are a cost-effective and environmentally friendly alternative in the treatment of Se volatilization. The fate, behavior, bioavailability, and toxicity of Se within complex environmental systems are comprehensively reviewed. This knowledge forms the basis for developing management plans that aimed at mitigating Se contamination in wetlands and protecting the associated ecosystems.

Effect of different synthesis methodologies on the adsorption of iodine

Radioactive nuclides such as cesium, ruthenium, and iodine are difficult to remove in radioactive wastewater, which could be removed by coprecipitation of special chemical precipitants. In this study, dynamic Cu/Ag-mordenite (Cu/Ag-MOR) material was synthesized to be treated as the precipitant to selectively adsorb the iodine ion (I^-) through controlled chemisorption combined with physical adsorption. XRD, XPS, and FTIR characterization demonstrated the successful modification of the MOR carrier surface by Cu/Ag particles and the high selectivity of the active component Cu (I) on the dynamic Cu/Ag-MOR material. SEM, TEM, and BET methods were used to characterize the Cu/Ag-MOR material, demonstrating these results: the MOR carried a stable porous structure, which allowed the silver to be well dispersed on its surface. The silver improved the copper distribution by being well-coated by the copper species. Furthermore, the analysis of the factors influencing the chemical plating of copper showed that the pH, the concentration of EDTA-2Na and the temperature all influenced the deposition rate of Cu₂O. The activation energy for Cu₂O deposition in dynamic Cu/Ag-MOR was 20.31 kJ/mol. The highest removal of I^- in the presence of dynamic Cu/Ag-MOR could reach 99.1% in the adsorption tests. The adsorption kinetics was under a proposed second-order model, with chemisorption being the controlling step of the reaction. The adsorption/desorption experiments demonstrated the reusability of the nano-sorbent. It was also demonstrated that dynamic Cu/Ag-MOR materials showed good applicability in complex situations where multiple pollutants co-exist.

Impact of microbial processes on the safety of deep geological repositories for radioactive waste

To date, the increasing production of radioactive waste due to the extensive use of nuclear power is becoming a global environmental concern for society. For this reason, many countries have been considering the use of deep geological repositories (DGRs) for the safe disposal of this waste in the near future. Several DGR designs have been chemically, physically, and geologically well characterized. However, less is known about the influence of microbial processes for the safety of these disposal systems. The existence of microorganisms in many materials selected for their use as barriers for DGRs, including clay, cementitious materials, or crystalline rocks (e.g., granites), has previously been reported. The role that microbial processes could play in the metal corrosion of canisters containing radioactive waste, the transformation of clay minerals, gas production, and the mobility of the radionuclides characteristic of such residues is well known. Among the radionuclides present in radioactive waste, selenium (Se), uranium (U), and curium (Cm) are of great interest. Se and Cm are common components of the spent nuclear fuel residues, mainly as 79Se isotope (half-life 3.27 × 105 years), 247Cm (half-life: 1.6 × 107 years) and 248Cm (half-life: 3.5 × 106 years) isotopes, respectively. This review presents an up-to-date overview about how microbes occurring in the surroundings of a DGR may influence their safety, with a particular focus on the radionuclide-microbial interactions. Consequently, this paper will provide an exhaustive understanding about the influence of microorganisms in the safety of planned radioactive waste repositories, which in turn might improve their implementation and efficiency.

A Bibliometric Analysis of Research on Selenium in Drinking Water during the 1990-2021 Period: Treatment Options for Selenium Removal

A bibliometric analysis based on the Scopus database was carried out to summarize the global research related to selenium in drinking water from 1990 to 2021 and identify the quantitative characteristics of the research in this period. The results from the analysis revealed that the number of accumulated publications followed a quadratic growth, which confirmed the relevance this research topic is gaining during the last years. High research efforts have been invested to define safe selenium content in drinking water, since the insufficient or excessive intake of selenium and the corresponding effects on human health are only separated by a narrow margin. Some important research features of the four main technologies most frequently used to remove selenium from drinking water (coagulation, flocculation and precipitation followed by filtration; adsorption and ion exchange; membrane-based processes and biological treatments) were compiled in this work. Although the search of technological options to remove selenium from drinking water is less intensive than the search of solutions to reduce and eliminate the presence of other pollutants, adsorption was the alternative that has received the most attention according to the research trends during the studied period, followed by membrane technologies, while biological methods require further research efforts to promote their implementation.

Sorption of some radionuclides from liquid waste solutions using anionic clay hydrotalcite sorbent

¹²⁹I and ⁷⁹Se are potentially important anionic radionuclides in safety assessments due to their high mobility, radiotoxicity, and long half life's (1.7 × 10⁷ and 3.27 × 10⁵ years, respectively). This study is interested in the sorption of ¹³¹I and ⁷⁵Se radionuclides onto magnesium iron hydrotalcite (Mg/Fe HTlc). Mg/Fe HTlc was prepared by co-precipitation technique and characterized using different analytical tools such as FT-IR, XRD, XRF, TGA & DTA, SEM, and BET. Results obtained from this study showed that the adsorption process was a very fast equilibrium time (20 min). The distribution coefficient values as a function of pH have high separation factors for ¹³¹I at all different pHs. Reaction kinetic obeys the pseudo-second-order model. Maximum sorption capacity for ¹³¹I and ⁷⁵Se has the values 21.45, and 9.25 mg/g respectively. Sorption isotherms are more relevant to a Langmuir isotherm. The % removal of ¹³¹I is decreased by increasing the concentration of competing species. The investigation evidenced that the prepared sorbent is suitable for the removal of ¹³¹I and ⁷⁵Se from radioactive waste and could be considered potential material for purification of effluent polluted with these radionuclides.

Rapid synthesis of polyimidazole functionalized MXene via microwave-irradiation assisted multi-component reaction and its iodine adsorption performance

The adsorption applications of MXene-based adsorbents have intensively investigated recently. However, the performance of MXene-based adsorbents has been largely limited owing to their lack of functional groups and adsorptive sites. Therefore, surface functionalization of MXene is an important route to achieve better performance for environmental adsorption. Herein, polyionic liquid functionalized MXene (named as MXene-PIL) was prepared through a multi-component reaction and adsorptive removal of iodine by MXene-PIL was also evaluated. The successful generation of PIL on MXene was confirmed by a series of characterization measurements. Furthermore, the effects of contact time, iodine concentration, environmental temperature and other factors on the adsorption performance of MXene-PIL were investigated. Adsorption kinetic analysis including pseudo-first-order dynamic model, pseudo-second-order dynamic model and Weber-Morris model, adsorption thermodynamic analysis such as Langmuir and Freundlich models and Van't Hoff equation were used for further analysis the adsorption behavior of iodine by MXene-PIL. We demonstrated that the adsorption capacity could be as high as about 170 mg/g, which is obviously larger than the unmodified MXene and most of other reported adsorbents. Taken together, a simple strategy has been developed for in-situ generation of PIL on MXene and the resultant composites show potential application for adsorptive removal of iodine.

Sponge-like Ca-alginate/Lix-84 beads for selective separation of Mo(VI) from some rare earth elements

In this investigation, a novel alginate complex was developed for the selective separation of molybdenum (Mo(VI)) ions from some rare earth elements (REEs). In this regard, alginate as a natural polysaccharide was impregnated and modified with 2-hydroxy-5-nonylacetophenone oxime (Lix-84) and characterized using FT-IR, TGA/DTA and SEM-EDX. The relation between medium acidity, adsorption kinetics, sorbent dose, isotherm models, temperature and Mo(VI) recovery was investigated. It was concluded that the impregnation stage promoted the Mo(VI) separation. The kinetics and isotherm data were well-fitted and matched with the pseudo-first-order model and Langmuir isotherm model; respectively. The Langmuir maximum adsorption capacity of Mo(VI) reached 72.2 mg/g. The developed material showed excellent separation performance towards Mo ions over the investigated REEs. The desorption and recovery of the loaded Mo(VI) ions were achieved using 1.0 M HCl. Reutilization of Alg/Lix-84 was confirmed up to three adsorption-desorption cycles with no damage of the beads as proved with SEM analysis. The adsorption mechanism of molybdenum onto Alg/Lix-84 was elucidated through FTIR and XPS measurements and was found to be governed by both electrostatic interaction and ion exchange. Therefore, the developed material has a promising potential for the selective separation of molybdenum from REEs-containing solution.

Remarkably enhanced ion-exchange capacity of H2O2-intercalated layered titanate

H2O2-intercalated layered titanate H1.07Ti1.73O4 (H2O2-HTO) exhibits a dramatically enhanced ion-exchange capacity and remarkably improved reaction rate with various divalent cations. The intercalation can increase the negative charge density of the TiO6 octahedral layer and the number of ion-exchangeable H+ by forming a Ti(iv)-O-O-H bond that is the driving force to change the ion exchange performance.

Combined use of tannic acid-type organic composite adsorbents and ozone for simultaneous removal of various kinds of radionuclides in river water

Tannic acid-type organic composite adsorbents (PA316TAS, AR-01TAS, PYRTAS, WA10TAS, WA20TAS, and WA30TAS), combined with hydrolyzed and sulfonated tannic acid (TAS) and porous-type strongly basic anion-exchange resin (PA316), benzimidazole-type anion-exchange resin embedded in high-porous silica beads (AR-01), pyridine-type anion-exchange resin (PYR), acrylic-type weakly basic anion-exchange resin (WA10), or styrene-type weakly basic anion-exchange resins (WA20 and WA30) for simultaneous removal of various kinds of radionuclides in river water were successfully synthesized. The adsorption behavior of twelve kinds of simulated radionuclides (Mn, Co, Sr, Y, Ru, Rh, Sb, Te, Cs, Ba, Eu, and I (I^- and IO₃^-)) on these composite adsorbents has been studied in real river water at room temperature. PA316TAS adsorbents showed much higher distribution coefficients (K_d) for all metal ions. TAS structure has more selective adsorption ability for Mn, Co, Sr, Y, Cs, Ba, Eu, and IO₃^-. On the other hand, Y, Ru, Rh, Sb, Te, Eu, I (I^- and IO₃^-) were adsorbed on both PA316 and TAS structures. To evaluate the validity of these mechanistic expectations, the respective chemical adsorption behaviors of Mn, Co, Sr, etc. and PA316TAS adsorbent were examined in river water ranging in temperature from 278 to 333 K. As was expected, one adsorption mechanism for Mn, Co, Sr, Cs, and Ba systems and two types of adsorption mechanisms for Y, Ru, Rh, Sb, Te, Eu, I (I^- and IO₃^-) systems were observed. On the other hand, the precipitation of Mn, Co, Y, Ru, Rh, Te, and Eu was formed by ozonation for river water, that is, ozone can transform Mn, Co, Y, Ru, Rh, Te, and Eu ions into the insoluble precipitates. Hence, one straight line for Sr, Cs, Ba systems and two types of straight lines for Sb, I (I^- and IO₃^-) systems were obtained in river water treated with ozone. The chromatography experiments of Cs, Sr, I (I^- and IO₃^-) were carried out to calculate their maximum adsorption capacities. The obtained maximum adsorption capacities of Cs, Sr, and I^- mixed with IO₃^- were 1.7 × 10^-4 (Cs), 1.8 × 10^-3 (Cs/O₃), 7.8 × 10^-5 (Sr), 5.6 × 10^-4 (Sr/O₃), 5.4 × 10^-2 (I^- and IO₃^-), 3.1 × 10^-2 (I^- and IO₃^-/O₃) mol/g - PA316TAS. It was discovered that the maximum adsorption capacities of I^- and IO₃^- for the composite adsorbent is unprecedented high and the capacity become much greater than an order of magnitude, compared with those of previous reports. This phenomenon suggests the formation of electron-donor-acceptor (EDA) complexes or pseudo EDA complex. Based on these results, it was concluded that the combined use of tannic acid-type organic composite adsorbents and ozone made it possible to remove simultaneously and effectively various kinds of radionuclides in river water in the wide pH and temperature ranges.

Adsorptive removal of PAR and Arsenazo-III from radioactive waste solutions by modified sugarcane bagasse as eco-friendly sorbent

In this paper, sugarcane bagasse (SCB) was modified using phosphoric acid. The modified sugarcane bagasse (MSCB) has been used to remove 4-(2-pyridylazo)resorcinol (PAR) and Arsenazo-III (Ar-III) from liquid radioactive waste. The surface morphology and functional groups of the MSCB were studied using scanning electron microscopy (SEM), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). Adsorption ability of MSCB has been tested by batch mode through some relevant factors like initial pH, reaction time, initial coloring reagents (PAR and Ar-III) concentrations, and adsorbent weight. At adsorption equilibrium time 180 min and pH values of 3 and 1 for PAR and Ar-III; the maximum removal (%) for both PAR and Ar-III were 93 and 57%, respectively. The adsorption isotherm data are representative well to Freundlich isotherm model. The mean free energy of adsorption, E (kJ/mol), has been estimated as 5.75 and 2.28 kJ/mol for PAR and Ar-III, respectively, which suggests that the adsorption occurred physically. The maximum adsorption capacity of MSCB for PAR and Ar-III is 96.62 and 15.18 mg/g, respectively. The adsorption kinetics are better fitted by the pseudo-second-order model. The partial film along with intra-particle diffusion controlled the diffusion of coloring reagents from the solution bulk to the particle interior pores. Application of MSCB for removing PAR and Ar-III from simulated liquid radioactive waste containing U(VI) and Th(VI) ions has been achieved successfully.

Removal of strontium radionuclides from liquid scintillation waste and environmental water samples

Strontium-90 (t_1/2 = 29 y) is one of the most concerned isotopes in both nuclear accidents and reprocessing of nuclear fuel. In this study, the removal of strontium using low cost and valuable Dowex-HCR-S/S (DHS) resin was achieved. The kinetic and equilibrium sorption studies have been investigated using batch technique. The results of kinetic studies showed that the pseudo-second-order kinetic model was found to correlate well with the experimental data. Equilibrium data were also analyzed by sorption isotherm models indicating that the monolayer capacity of Sr(II) at equilibrium is 400.0 mg/g. It was concluded that resin has an efficient sorption capacity compared to many sorbents. The thermodynamic parameters of the removal (ΔH^o, ΔS^o, and ΔG^o) were also determined. The removal process was endothermic and spontaneous. The resin has been successfully applied for the removal of ⁸⁵Sr from organic liquid scintillator waste and some environmental waters such as tap water, river water, sea water and ground water samples. The present work concludes that the low-cost and commercial DHS resin used under these conditions has a major possibility as an efficacious material for the removal of ⁹⁰Sr from environmental and real radioactive wastewaters. It can therefore have a site in the treatment of radioactive liquid waste because it is of an affordable and commercially available retention material.

Synthesis of Fe-impregnated biochar from food waste for Selenium(Ⅵ) removal from aqueous solution through adsorption: Process optimization and assessment

Iron-impregnated food waste biochar (Fe-FWB) was synthesized for Se(Ⅵ) removal from aqueous solution. The effect and interactive effects of different parameters including pyrolysis time, temperature, and Fe concentration were explored using response surface methodology (RSM) to enhance conditions to achieve the highest Se(Ⅵ) removal using Fe-FWB. Pyrolysis time was not significant for Se(Ⅵ) adsorption capacity of Fe-FWB, but temperature and Fe concentration were found to be significant. The highest adsorption was achieved at 3.47 h and 495.0 °C with an Fe concentration of 0.44 M. Fe-FWB synthesized under optimum conditions were used to investigate the kinetic, equilibrium, and thermodynamic adsorption of Se(Ⅵ). Se(Ⅵ) adsorption reached equilibrium within 6 h, and both pseudo-second order and pseudo-first order models were suitable for describing kinetic Se(Ⅵ) adsorption. The Freundlich model was found to suitably fit the equilibrium adsorption data than the Langmuir model. The highest adsorption capacity of Fe-FWB for Se(Ⅵ) was 11.7 mg g^-1. Se(Ⅵ) adsorption on Fe-FWB was endothermic and spontaneous. The enthalpy change for Se(Ⅵ) adsorption was 54.4 kJ mol^-1, and the entropy change was negative at 15-35 °C. The increment of solution pH from 3 to 11 decreased the Se(Ⅵ) adsorption from 19.2 to 7.4 mg g^-1. The impact of interfering anions on Se(Ⅵ) adsorption followed the lineup: HCO₃^- > HPO₄^2- > SO₄^2- > NO₃^-. When compared to some adsorbents, the adsorption capacity of Se(Ⅵ) onto Fe-FWB was comparable even at neutral pH and the Fe-FWB was granular. These results indicate that Fe-FWB has prospective application in the removal of Se(Ⅵ) from aqueous solutions.

Influence of sorption parameters on cesium-137 removal using modified activated carbon obtained from corchorus olitorius stalks

Removal of 137Cs radionuclides from the environment has engrossed the concern of researchers after Fukushima accident. The leakage of radioactive cesium ions can lead up to surface and groundwater contamination, and this leads to pollution of drinking water sources. In this work, corchorus olitorius stalks has been used as a novel precursor for production of low-cost meso porous a ctivated c arbon ( Meso-AC ) and HNO3/H2O2- m odified Meso-AC ( m-Meso-AC ). The physicochemical properties of all adsorbents were evaluated. The influences of sorption parameters and presence of some ligands (humic acid, fulvic acid, and EDTA) on the sorption of 137Cs were studied. The maximum 137Cs capacity of m-Meso-AC was found to be 58.74 mg/g. Efficiency of the new adsorbent to remove 137Cs radionuclides from natural waters (tap, river, and groundwater) was investigated. The studies showed that new adsorbent could be used as promising material for the retention of 137Cs from real radioactive waste and natural water samples.

Surface modification of polypropylene membrane for the removal of iodine using polydopamine chemistry

The development of stable and effective iodine removal systems would be highly desirable in addressing environmental issues relevant to water contamination. In the present research, a novel iodine adsorbent was synthesized by self-polymerization of dopamine (PDA) onto inert polypropylene (PP) membrane. This PP/PDA membrane was thoroughly characterized and its susrface propeties was analyzed by various analytical techniques indcluding field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH), contact angle, and surface free energy measurement. The PP/PDA membranes were subsequently used for batchwise removal of iodine at different temperatures (25-70 °C), pH (2-7), and surface areas (1-10 cm²) to understand the underlying adsorption phenomena and to estimate the membrane capacity for iodine uptake. The increase in temperature and pH both led to higher adsorption of iodine. The present approach showed a removal efficiency of over 75% for iodine using 10 cm² PP/PDA membrane (18.87 m² g^-1) within 2 h at moderate temperatures (∼50 °C) and pH > 4, about 15 fold compared to the PP control membrane. The adsorption kinetics and isotherms were well fitted to the pseudo-second-order kinetic and Langmuir isotherm models (R² > 0.99). This adsorbent can be recycled and reused at least six times with stable iodine adsorption. These findings were attributed to the homogenous monolayer adsorption of the iodide on the surface due to the presence of catechol and amine groups in the PP/PDA membrane. This study proposes an efficient adsorbent for iodine removal.

Retention behavior of anionic radionuclides using metal hydroxide sludge

With the speedy growth of nuclear power production, the removal and disposal of radioactive nuclides such as 129I, 99Tc, 79Se, 36Cl, 93Mo, and 137Cs become major environmental security issues. Retention of these radionuclides, especially anionic species such as 129I (t1/2 1.7 × 107 years), 93Mo (t1/2 4 × 103 years) and 79Se (t1/2 3.27 × 105 years) has been challenging. 129I, 93Mo and 79Se bind very weakly to most sorbents and deposits. This study has examined the sorption potential of Metal hydroxide sludge (MHS) for 125I (t1/2 60.2 days), 99Mo (t1/2 2.75 days) and 75Se (t1/2 120 days) as a surrogate for 129I, 93Mo and 79Se, respectively. MHS has been characterized by different techniques and the factors affecting the sorption processes were investigated. The experimental data were analyzed using kinetic models and thermodynamic parameters. The results showed that the kinetics of sorption of 125I and 99Mo on MHS proceeds according to the pseudo-first-order, on the contrary of 75Se sorption follows pseudo second-order kinetic model. The maximum sorption capacity of MHS was found to be 51.2 mg/g, 46.5 mg/g and 40.2 mg/g for 125I, 99Mo and 75Se, respectively. It can be concluded that, in the case of release of anionic radionuclide species to the surroundings the MHS could act as a succeeded and economical sorbent material for retention of different anionic radionuclides such as 133, 129I, 79Se, 36Cl, 93, 99Mo, and 99Tc. To avoid the release of such anionic species from the stored nuclear wastes to the environment.

Decontamination of radioactive wastewater: State of the art and challenges forward

Radioactive substances have been widely used in many industrial sectors, e.g. nuclear power station, biomedical engineering, etc. With increasing applications of nuclear technology, more and more radioactive wastewater is being generated via different channels, which indeed is posing an emerging challenge and threat to the environment and human health. Given such a situation, this review attempts to offer a holistic view with regard to the state of the art of technology for decontamination of radioactive wastewater as well as shed lights on the challenges forward. Different from reclamation of other types of wastewaters, the most challenging issue in decontamination of radioactive wastewater is the effective stabilization and solidification of soluble radioactive nuclides present in wastewater, which are critical for final disposal. Moreover, the potential risk of human exposure to wastewater radiation needs to be carefully assessed, and this issue should also be taken into consideration in the selection, design and operation of the radioactive wastewater treatment process. These clearly differentiate the treatment principle of radioactive wastewater from those of traditional industrial and municipal wastewaters. Lastly, the challenges from the perspectives of technology development, environmental and human health impacts and possible solutions forward are also elucidated.