Interaction of radium with freshwater sediments and their mineral components

Radiotracer method has been used for investigation of the adsorption and desorption of traces of radium on kaolinite and montmorillonite under conditions similar to those prevailing in waste and surface waters. It has been found that adsorption depends on the pH and ionic strength of the solution, and the character of these dependences is different for kaolinite and montmorillonite. Sulfates at concentration 60 mg·l^–1 have negligible effect on the adsorption. Montmorillonite represents better adsorbent for radium than kaolinite, but both minerals may significantly affect the form and migration of radium in surface waters, if present as (major) components of freshwater sediments. Radium can be quantitatively desorbed by 1M HCl from kaolinite but not from montmorillonite. The desorption by 0.1M NaCl is generally lower and depends on the pH during the preliminary adsorption. Mechanisms of radium adsorption on both minerals and the character of the adsorption sites are discussed.     

Mobilization of radionuclides from uranium mill tailings and related waste materials in anaerobic environments

Specific extraction studies in our laboratory have shown that iron and manganese oxide- and alkaline earth sulfate minerals are important hosts of radium in uranium mill tailings. Iron- and sulfate-reducing bacteria may enhance the release of radium (and its analog barium) from uranium mill tailings, oil field pipe scale [a major technologically enhanced naturally occurring radioactive material (TENORM) waste], and jarosite (a common mineral in sulfuric acid processed-tailings). These research findings are reviewed and discussed in the context of nuclear waste forms (such as barium sulfate matrices), radioactive waste management practices, and geochemical environments in the Earth's surficial and shallow subsurface regions.     

Europium removal with a mineral mixtre

Natural mixture containing mostly minerals of iron, sillicon, magnesium, aluminium and calcium was exploited for the decontamination study of europium radionuclides from aqueous radioactive waste solutions. The physicochemical conditions, such as shaking and equilibration time, nature of hydrogen ions, pH, temperature, concentrations of adsorbate and adsorbent were experimentally determined. This study showed quantitative adsorption beyond pH 7 and under optimized conditions, up to 33 g of the adsorbate can be rapidly removed from radioactive effluents using only 1 kg of the mineral mixture (MM). Desorption study of the solidified radioactive waste product reveals no significant loss (< 0.01% month), indicating MM as an effective material for removal of radioactive europium and storing it in solid form over a long period of time.     

Interaction of radium with freshwater sediments and their mineral components

Radiotracer method has been used for investigation of the adsorption and desorption of traces of radium on muscovite and feldspar (albite) under conditions similar to those prevailing in waste and surface waters. The effects of pH, liquid to solid ratio, time, ionic strength (Na⁺) and presence of Ca²⁺ or SO ₄ ^2? ions have been studied. It has been concluded that both minerals can significantly affect the fate and migration of radium in surface waters if present as major components of bottom sediments or as suspended solids in concentrations of several milligrams per liter or higher. Muscovite can absorb radium even from moderately acidic waters. Radium adsorbed on muscovite and albite cannot be easily released upon an increase of the salinity of ambient water. However, almost complete desorption can be achieved with 1M HCl. Mechanisms of radium adsorption on both minerals and character of the adsorption sites are discussed.     

Fe（Ⅱ）-矿物对亚硒酸的还原作用

79Se是核反应过程中产生的长半衰期（T1/2=2.95×105年）裂片产物核素,具有化学和辐射双重毒性,是高放废物地质处置中重点关注的几个放射性核素之一.硒的溶液化学性质比较特殊,以高价态形式存在的硒酸和亚硒酸,几乎不受溶解度控制,并难以被黏土或花岗岩等处置库围岩介质所吸附,迁移性极强,而当其以低价态（0、–I、–II）形式存在时,易形成固体沉淀.因此将高价态的硒还原生成沉淀是阻滞79Se迁移的最主要方式.从另一方面讲,Fe（II）-矿物是自然界中普遍存在的具有还原性的物质.本文对近年来国内外在Fe（II）-矿物还原亚硒酸方面开展的研究工作进行了一个回顾,并从热力学的角度,对这些矿物还原亚硒酸的可行性及控制产物生成的因素进行了分析.     

Interaction of radium with freshwater sediments and their mineral components. I.

The radiotracer method has been used for investigation of the adsorption and desorption of traces of radium on ferric hydroxide and quartz under conditions similar to those prevailing in waste and surface waters. The effects of pH, liquid to solid ratio, ionic strength and presence of Ca²⁺ or SO ₄ ^2- ions have been studied. It has been concluded that at pH less than 7 and at concentration of suspended sediments (of common composition) less than 100 mg·1^–1 ferric hydroxide and quartz have negligible effect on the state and migration of radium in surface waters. Radium adsorbed on quartz can be easily desorbed with dilute solutions of hydrochloric acid or sodium chloride.     

Cesium sorption on bentonites and montmorillonite K10

The physical and chemical properties of illitic clay minerals from Slovak deposit suitable for application in engineering barriers for high level radioactive waste repositories and spent nuclear fuels were studied. The isolation of spent nuclear fuels and high level radioactive wastes from the outer environment in a deep repository is gained by means of a system of multiple engineering and natural sealing barriers. Vital segments in a multiple barrier system are clay rocks, of which bentonites represent the most suitable clay material. Cs-adsorption on fine fractions of adsorbents (bentonites from three Slovak deposits: Jelšovy potok J15, Kopernica K15, Lieskovec L15 and montmorillonite K10) has been studied with using batch of radiometric techniques. Adsorption parameters have been determined for adsorbent-cesium solution system as a function of contact time and adsorbate concentration. The influences of pH change, the effect of competitive cations, complex-forming organic chelating agents on the adsorption of Cs have also been studied.     

Determination of retardation factors of137Cs in migration process in concrete

Determination of retardation factors and coefficients of distribution using a simplified mathematical model for analyzing the migration of leachate and radioactive material contained in radioactive waste burial concrete trench systems has been developed. Results show that concrete for engineered trench systems secures radionuclide preservation in solidified medium for longer than 300 years. These results will be used for constructing future radioactive waste storing centers in Yugoslavia.     

Adsorption characteristics of traces of radium on membrane filters,glass and polyethylene

Adsorption of radium was studied on glass and polyethylene from aqueous solutions containing 8–40 pg·dm^{–3 224}Ra and on membrane filters, glass and polyethylene bottles from waste and river waters containing 2–170 pg·dm^{–3 226}Ra. The adsorption from aqueous solutions was determined as a function of pH and composition of the solutions and interpreted as due to ion exchange of Ra²⁺ ions for counter ions in the electric double layer on glass and polyethylene or due to chemisorption of RaSO₄ (RaCO₃) ion pairs on glass. Borosilicate glass adsorbed radium substantially more than polyethylene. The adsorption of dissolved forms of radium from the waste and river waters during storage and membrane filtration of the waters was negligible, but a significant loss of particulate forms of radium was sometimes observed during the storage. It has been recommended to separate dissolved and particulate forms of radium soon after the sampling and to prefer polyethylene to glass as container material for storage of dissolved forms of radium.     

Biochar derived from waste bamboo shoots for the biosorptive removal of ferrous ions from aqueous solution

With the ongoing global demands for modern commodities, anthropogenic activities by industries and humans have brought a colossal pressure to the natural water bodies. Though numerous scientific interventions or treatment techniques have been proposed, the need for a viable low-cost method has been a quest for many researchers. Adsorption as such has been in the limelight as an effective method in recent times using various feedstock biomass waste. Our present piece of research aims to use the non-edible biomass waste generated from bamboo shoots as a sustainable low-cost biochar adsorbent and examine its efficiency in the removal of ferrous (Fe²⁺) ions from an aqueous solution. The batch adsorption study was conducted and the optimum dose and concentration were found to be 0.2 g and 7 mg L^?1 with the Langmuir isotherm model best describing the experimental data. Furthermore, kinetic study suggests that the overall sorption rate predominantly follows the chemisorption pathway. Multiple studies suggest bamboo is an excellent adsorbent for treating various inorganic & organic contaminants; here we have highlighted the multifaceted applications of waste bamboo shoots as an effective adsorbing material. The obtained results can lead to additional benefits and usage of bamboo shoots (waste) with future research prospects.     

Interaction of radium with freshwater sediments and their mineral components

A radiotracer method was used for investigation of the adsorption and desorption of radium on stream sediments under conditions similar to those prevailing in waste and surface waters. The effects of pH, ionic strength and Ca²⁺ or SO ₄ ^2– ions were studied. The results were compared with analogous data characterizing radium interaction with model solids representing components of the sediments. It has been found that the adsorption affinity of the sediments for radium cannot be easily derived from their composition or other properties. No simple correlation with specific surface area, organic matter, oxidic coatings or other components of the sediments was observed. However, an exceptional role of barite (barium sulfate) in the sediments was noted. In the presence of sulfate ions (60 mg/l) this component was responsible for the uptake of predominant or at least significant part of radium, depending on the barite content of sediments. In the absence of added sulfate ions, the adsorption of radium at ph 5–9 on sediments containing barite was lower than on similar sediments without this component, indicating that other components may be more efficient in radium adsorption.     

Use of local soil for the decontamination of liquid radioactive wastes at PINSTECH

The use of locally available mineral clay for the removal of radionuclides from the low and intermediate level liquid waste has been studied. Adsorption behavior of this naturally available inorganic adsorbent is reported. The factors such as contact time, nature of the waste, pH and adsorption capacity have been considered. These optional physico-chemical conditions suggest an effective use of this locally available adsorbent for the decontamination of the liquid radioactive waste at Pakistan Institute of Nuclear Science and Technology (PINSTECH), Islamabad.     

High Sorption and Selective Extraction of Actinides from Aqueous Solutions

The selective elimination of long-lived radioactive actinides from complicated solutions is crucial for pollution management of the environment. Knowledge about the species, structures and interaction mechanism of actinides at solid–water interfaces is helpful to understand and to evaluate physicochemical behavior in the natural environment. In this review, we summarize recent works about the sorption and interaction mechanism of actinides (using U, Np, Pu, Cm and Am as representative actinides) on natural clay minerals and man-made nanomaterials. The species and microstructures of actinides on solid particles were investigated by advanced spectroscopy techniques and computational theoretical calculations. The reduction and solidification of actinides on solid particles is the most effective way to immobilize actinides in the natural environment. The contents of this review may be helpful in evaluating the migration of actinides in near-field nuclear waste repositories and the mobilization properties of radionuclides in the environment.     

Endlagerung radioaktiver Abfälle

Shales, granites and rock salt are currently under investigation as host rocks for radioactive waste. With respect to heat‐producing waste (spent fuel, high‐active waste) these rock types comprise contrasting mechanical and chemical behavior. The differences are due to the respective geological formations: Shales form by slow accumulation of fine‐grained minerals from seawater with subsequent compaction and diagenesis; crystallization of deep‐seated magmas at 700 to 850°C is the process that generates granitic rocks in the upper 20 km of the earth's continental crust; rock salt is a chemical sediment which forms by precipitation of chloride and sulfate minerals from seawater evaporation in shallow marine basins under arid conditions. The extent of chemical reactions between granitic rocks and migrating saline fluids upon canister‐induced heating is quite small. However, thermally induced reactions between sheet silicate minerals in shales may result in a gradual loss of adsorption capacities for released radionuclides. Canister‐induced temperature gain in rock salt results in increasing creep rates which lead to an enhanced enclosure process. Great care has to be taken in the selection of salt formations as host rocks with respect to brines; depending on their composition and temperature brines might react with e.g. potash‐seams.     

Determination of macroconstituents and trace elements in naturally occurring radioactive material in oil exploration waste products

Naturally occurring radioactive materials (NORM) contain radionuclides, such as radium, thorium, and uranium. The existence of NORM remains an issue for oil and gas exploration because once the material becomes concentrated through technological activity, it becomes a radioactive contamination hazard or a radioactive waste. Pipes and tanks used to handle large volumes of produced water at some oil-field sites are coated with scale deposits that contain high levels ²²⁶Ra, ²²⁸Ra and ²¹⁰Pb. Experiments were conducted using thermal and epithermal neutron activation analysis and Compton suppression for the determination of macroconstituents and trace elements in the radioactive scale sample.     

Treatment of an aqueous radioactive waste solution with elevated levels of226Ra and228Ra

Treatment of an aqueous radioactive waste solution to remove radium prior to discharge was conducted at a laboratory scale. The actual solution is mainly composed of combined radium (²²⁶Ra and²²⁸Ra) with high concentrations of manganese, iron and calcium, which are present as chlorides in dilute hydrochloric acid. Direct precipitation by sulfate anions was selected to be the more viable treatment technique. Sulfate anion concentration, free acidity, temperature and aging of the sulfate precipitate in the supernate prior to filtration are factors that were investigated for their effect on the separation efficiency. The data obtained are discussed in detail.     

Adsorption of La(III) onto GMZ bentonite: effect of contact time,bentonite content,pH value and ionic strength

Bentonite has been studied extensively because of its strong adsorption capacity. A local Na-bentonite named GMZ bentonite, collected from Gaomiaozi County (Inner Mongolia, China), was selected as the first choice of buffer/backfill material for the high-level radioactive waste repository in China. In this research, the adsorption of La (ΙΙΙ) onto GMZ bentonite was performed as a function of contact time, pH, solid content and metal ion concentrations by using the batch experiments. The results indicate that the adsorption of La (III) on GMZ bentonite achieves equilibration quickly and the kinetic adsorption follows the pseudo-second-order model; the adsorption of La (III) on the adsorbent is strongly dependent on pH and solid content, the adsorption process follows Langmuir isotherm. The equilibrium batch experiment data demonstrate that GMZ bentonite is effective adsorbent for the removal of La (III) from aqueous solution with the maximum adsorption capacity of 26.8 mg g⁻¹ under the given experimental conditions.     

Study of the immobilization of226Ra

A study of the immobilization for²²⁶Ra waste has been carried out. Cement-based concrete was used as a matrix for the solidification of radium waste. The experimental results show that the cement mixture with water/cement between 0.46–0.54 has higher strengh (above 20 MPa), and the compressive strength was not reduced by addition of 1% barite or the radium waste (RaSO₄) into the concrete solid.Sponsored by the National Nuclear Corporation of China.     

Laws and mechanism of adsorption of cations by different ion-exchange forms of silica gel

Using radioactive tracer method, the regularities of adsorption of over 30 mono-, di- and trivalent cations including transition metal and lanthanide ions on the H, Ca- and Al-forms of silica gel are established. It has been shown that the affinity of cations of the same charge to the silica gel surface depends both on the nature of the adsorbing ion and the nature of exchangeable cation on the surface. Adsorption of alkali earth metal ions on the Ca-form of silica gel increases with a decrease of their radius i.e. an inversion of the sequence of adsorption compared to H- or Al-form of this adsorbent or polymeric cation-exchange resins takes place. For lanthanide ions the sequence of adsorption is the same for all ion-exchange forms of the silica gel studied, namely, an increase of adsorption with a decrease of their crystallographic radius, i.e. from La ³⁺ to Lu ³⁺ takes place. The laws observed are explained by taking into account the fact that adsorption of cations by silica gel is determined by both electrostatic interactions and additional covalent/donor–acceptor interactions between the surface and cations. The latter is due to formation of π-bonds between the electron pair in surface oxygen and vacant p-, d- or f-orbital of adsorbing cations.     

Waste cigarette filters: activated carbon as a novel sorbent for uranium removal

Uranium is important in the nuclear fuel cycle as both as an energy source and as radioactive waste. Herein, activated carbon (AC) prepared from waste cigarette filters by convenient carbonization and functionalization was chosen as the raw materials for radionuclides adsorption. Batch adsorption experiments showed that AC presented comparable UO₂²⁺ adsorption capacity (106 mg g^?1) and very outstanding selectivity. The adsorption process accorded with Langmuir model and the pseudo-second-order kinetics model well. This work combines the waste cigarette filters with the radioactive nuclear treatment materials, which may provide a new strategy for the future treatment of waste cigarette butts.