Use of radioactive thermal water after226Ra removal

The paper describes the possibility of efficient and safe use of geothermal water at a location in the town of Zagreb. Geothermal water is used exclusively for the purpose of sport and recreation. Due to elevated²²⁶Ra concentrations, the raw geothermal water must be used in limited proportions so as to exclude any potential health risk for the pool users. With application of adequate treatment methods, such as intense aeration (²²⁶Ra removal efficiency 13.7±3.5%) and filtration of aerated water with high pressure sand filters (removal efficiency 39.5±7.9%), the elevated²²⁶Ra content would be maximally reduced. The decrease of radioactivity enables that the proportion of geothermal water would be increased without any health risk, ensuring great cost reduction spent on the warming of pool waters.     

Studies on adsorptive removal of radioactive cobalt from alkaline waste generated in sodium cooled fast breeder reactors

The removal of radioactive cobalt from alkaline waste containing sodium has been studied in batch process using two different inorganic compounds (a) hydrous manganese oxide (HMO), and (b) copper hexa-ferrocyanide (CFC) and compared with a strongly acidic cation exchange resin (Dowex50W×8). The percentage removal of cobalt was examined by varying experimental conditions, viz. pH of the solution, contact time and interfering ions. The studies showed that HMO can be used as an efficient adsorbent for the removal of cobalt from sodium containing wastes.     

Determination of radioactive cobalt in reactor coolant water by solvent extraction

A rapid extraction separation method is described for the radiochenaical determination of cobalt-58 and cobalt-60 in reactor coolant water. After adjustment of the pH of the sample water to 5.0-5.5, cobalt diethyldithiocarbamate is extracted with benzene. Other nuclides, e.g., manganese-54 and -56, copper-64 and iron-59, which are usually present in reactor coolant water, are also extracted together with cobalt. However, they can be readily removed by washing the extract with mercury(II) chloride solution. The cobalt-58 and -60 activities are measured by gamma counting of an aliquot of the washed extract. Trace amounts of radioactive cobalt in 500 ml of sample water can be quantitatively extracted without the use of carrier. The separation could be finished in 15 min and an average recovery of 99.5 % was obtained, with a relative standard deviation of 1.4% (25 experiments).     

Use of radioactive thermal water after226Ra removal

The paper describes the possibility of efficient and safe use of geothermal water at a location in the town of Zagreb. Geothermal water is used exclusively for the purpose of sport and recreation. Due to elevated²²⁶Ra concentrations, the raw geothermal water must be used in limited proportions so as to exclude any potential health risk for the pool users. With application of adequate treatment methods, such as intense aeration (²²⁶Ra removal efficiency 13.7±3.5%) and filtration of aerated water with high pressure sand filters (removal efficiency 39.5±7.9%), the elevated²²⁶Ra content would be maximally reduced. The decrease of radioactivity enables that the proportion of geothermal water would be increased without any health risk, ensuring great cost reduction spent on the warming of pool waters.     

Determination of radioactive cobalt in mixtures of radionuclides

A detailed procedure for the separation of radioeobalt from other active material is described. Precipitation as the mercurithiocyanate and as the anthranilate have been compared, and the latter has been shown to be somewhat preferable.     

Selective cation exchange isolation of radioactive mercury from cobalt,scandium and europium

Distribution of Hg²⁺, Co²⁺, Sc³⁺ and Eu³⁺ between the cation exchanger Dowex-50X8, [H⁺] (100–200 mesh), and 1M HNO₃ solution containing different benzylamine (BA) concentrations has been studied. The distribution coefficient, D, for Co²⁺, Sc³⁺ and Eu³⁺ is very small and does not vary seriously with the BA concentration. It is also found that Hg²⁺ is highly taken by the resin from the media studied. In this respect, D increases with increasing BA concentration to reach a maximum at 0.5% BA in 1M HNO₃. This behaviour is explained by the exchange of molecular species between the cation exchanger and the aqueous phase. Based on the results, a radiochemical separation procedure for the selective isolation of Hg²⁺ from Co²⁺, Sc³⁺ and Eu³⁺ has been developed. The radiochemical purity is not less than 99.8% and the chemical yield more than 95% for the separated²⁰³Hg.     

Sorption of radioactive cobalt in natural Mexican clinoptilolite

The ability of a natural Mexican clinoptilolite to sorb radioactive cobalt from aqueous solution was studied. The zeolite was stabilized partially with sodium and the content of Na⁺ in the samples was determined by neutron activation analysis. Ion exchange experiments were performed with solution labeled with radioactive⁶⁰Co at pH 6.5. XRD patterns were used to verify if the crystallinity of the aluminosilicate was affected by ionic exchange. A fast sorption uptake was observed and it was found that 0.408 meq/g of zeolite of Na⁺ ions were replaced by cobalt ions, followed by a desorption process where the uptake decrease to 0.314 meq/g of zeolite. This behavior is a consequence of the partial dehydration of the zeolite.     

Continuous removal of radiolytic products from TBP extraction systems

In the actinide separation process using TBP as extractant, hydrolytic and radiolytic reactions cause a gradual decomposition of the extractant, resulting in the formation of degradation products which can affect process performance adversely. The TBP diluent has to be cleaned from these degradation products before it is reused. This paper deals with a procedure for solvent cleanup, using a fourstage continuous contactor for increasing the scrubbing efficiency.     

Removal of cobalt from liquid radioactive waste by in situ electrochemical synthesis of ferrite

This study combined electrochemical synthesis with traditional ferrite method to remove Co²⁺ from simulated liquid radioactive waste (LRW). The experiment investigated the effects of various reaction conditions including current density, reaction time for electrosynthesis, reaction temperature, initial pH value and boric acid concentration as well as the type of power supply by measuring the concentration of Co²⁺ in the effluent, explored the reaction mechanism by measuring particles using XRD. The results showed that it was feasible to remove Co²⁺ from simulated LRW by electrochemical synthesis of ferrite. The best removal efficiency of 99.99% (the concentration of Co²⁺ in the effluent was 0.447 μg/L) was achieved under the optimal reaction conditions, the sediment was mainly composed of the mixture of CoFe₂O₄ and Fe₃O₄.     

Inorganic ion exchangers for strontium removal from radioactive waste : a review

Journal of Radioanalytical and Nuclear Chemistry - 90Sr is the most hazardous radioactive isotope of strontium that is produced during the normal operation of nuclear reactors. It can also spread...     

Molecular cobalt pentapyridine catalysts for generating hydrogen from water

A set of robust molecular cobalt catalysts for the generation of hydrogen from water is reported. The cobalt complex supported by the parent pentadentate polypyridyl ligand PY5Me(2) features high stability and activity and 100% Faradaic efficiency for the electrocatalytic production of hydrogen from neutral water, with a turnover number reaching 5.5 × 10(4) mol of H(2) per mole of catalyst with no loss in activity over 60 h. Control experiments establish that simple Co(II) salts, the free PY5Me(2) ligand, and an isostructural PY5Me(2) complex containing redox-inactive Zn(II) are all ineffective for this reaction. Further experiments demonstrate that the overpotential for H(2) evolution can be tuned by systematic substitutions on the ancillary PY5Me(2) scaffold, presaging opportunities to further optimize this first-generation platform by molecular design.     

Methylphenols removal from water by low-cost adsorbents

A comparative study on the adsorption of methylphenols on adsorbents prepared from several industrial wastes has been carried out. The results show that extent of adsorption on carbonaceous adsorbent prepared from fertilizer industry waste has been found to be 37.3, 40.5, 65.9, and 88.5 mg/g for 2-methylphenol, 4-methylphenol, 2,4-dimethylphenol, and 2,4,6-trimethylphenol, rspectively. As compared to carbonaceous adsorbent, the other three adsorbents viz. blast furnace sludge, dust, and slag adsorb methylphenols to a much smaller extent. This has been accounted for due to the carbonaceous adsorbent having a larger porosity and consequently higher surface area. The adsorption of phenols on this carbonaceous adsorbent as a function of contact time, concentration, and temperature has been studied by the batch method. The adsorption has been found to be endothermic and data conform to the Langmuir equation. The analysis of data indicates that adsorption is a first-order process and pore diffusion-controlled. The efficiency of the carbonaceous adsorbent was assessed by comparing the results with those on a standard activated charcoal sample. It was found that the carbonaceous adsorbent is about 45% as efficient as standard activated charcoal and can therefore be employed for the removal of methylphenols from wastewaters.     

Splitting water with cobalt

The future of energy supply depends on innovative breakthroughs regarding the design of cheap, sustainable, and efficient systems for the conversion and storage of renewable energy sources, such as solar energy. The production of hydrogen, a fuel with remarkable properties, through sunlight-driven water splitting appears to be a promising and appealing solution. While the active sites of enzymes involved in the overall water-splitting process in natural systems, namely hydrogenases and photosystem II, use iron, nickel, and manganese ions, cobalt has emerged in the past five years as the most versatile non-noble metal for the development of synthetic H(2)- and O(2)-evolving catalysts. Such catalysts can be further coupled with photosensitizers to generate photocatalytic systems for light-induced hydrogen evolution from water.     

Studies on removal of cobalt from an alkaline waste using synthetic calcium hydroxyapatite

The removal of cobalt from an alkaline waste solutions containing sodium was carried out using a radiotracer in a batch method using synthetic calcium hydroxyapatite (HAP). The influence of different parameters such as solution pH, contact time, cobalt concentration, and presence of other ions like sodium on cobalt removal was studied. The sorption process followed pseudo-second-order kinetics with necessary time of around 23–25 h to reach equilibrium and the cobalt uptake was quantitatively evaluated using the Freundlich model. The results indicated that the mechanism of cobalt removal by HAP was mainly due to chemisorption on a heterogeneous surface. In the presence of sodium, the sorption of cobalt on HAP was not affected. The sorption of cobalt on HAP was pH independent in the range from 4 to 8, because of its buffering properties. The adsorption of cobalt on HAP was fast and the percentage of cobalt sorption was >97 % during the first 30–40 min of the contact time.     

放射性废水中铯的去除方法研究进展

随着核工业的发展,放射性废液的去除越来越受到重视。本文介绍了离子交换法、溶剂萃取法、吸附法、膜分离法和化学沉淀法以及组合工艺等放射性废水中铯的去除方法,对每种方法的原理、特点及应用情况进行了评述,对放射性铯去除方法的研究方向和发展趋势进行了展望。本文对于针对不同情况的放射性污染科学选用放射性铯的去除方法具有较大参考价值。     

Kinetics of removal of dissolved iron from natural water

The relationships of iron(II) oxidation in water using a new type of aerator based on a disk disperser were studied. The oxidation rate constants and the iron(II) to iron(III) half-conversion time were determined. The iron(II) oxidation in water follows a first-order rate equation. Changes in the water quality parameters depending on the conditions of the iron(II) oxidation were analyzed.     

Iranian clinoptilolite-rich tuffs for radionuclide removal from water

Three Iranian natural zeolites were characterized and evaluated for their abilities to take up Ba⁺², Ca⁺², K⁺ and Na⁺ from radioactive waste waters. The distribution coefficient values (K _d ) of the cations were measured and investigated as a function of pH. Four different cationic forms (Na, K, NH₄, and Ca) were also prepared and theirK _d values were determined. Some cations such as potassium presented highK _d values both in natural and exchanged zeolites. In sodium and ammonium exchanged forms theK _d values increased between 7 to 100 times with respect to the untreated zeolite.     

连续式超临界水反应器中褐煤制氢过程影响因素的研究

建立了煤处理量为1kg/h的连续式超临界水反应装置并实现稳定运行,考察了反应温度（500℃～650℃）、反应压力(20MPa～30MPa)、水煤浆浓度(20%~50％)以及KOH添加量对小龙潭褐煤在超临界水中连续化制氢的影响。实验结果表明,反应进行20min后连续装置达到稳定运行状态。反应温度和KOH添加量是影响超临界水中褐煤制氢的关键因素。随着反应温度从500℃提高到650℃,氢气的体积分数与产率分别由11%和25mL/g增加到29%和110mL/g。添加0.5%KOH可明显提高碳气化率以及氢气的产率,但随着KOH加入量进一步增加,氢气产率增加的幅度减小。随着压力增加,甲烷产率有升高的趋势,氢气产率变化不大,提高水煤浆的浓度,碳气化率降低。