Adsorption capacities of poly-γ-glutamic acid and its sodium salt for cesium removal from radioactive wastewaters

Publication date: December 2016
Source:Journal of Environmental Radioactivity, Volume 165
Author(s): Shigeki Sakamoto, Yoshinori Kawase
Cesium removal from radioactive wastewaters was examined using water-insoluble poly-γ-glutamic acid (γ-PGA) and water-soluble sodium salt form poly-γ-L-glutamic acid (γ-PGANa) as biosorbents. The maximum adsorption capacities at equilibrium of γ-PGA and γ-PGANa for Cs were 345 mg-Cs(g-γ-PGA)⁻¹ at pH 6.0 and 290 mg-Cs(g-γ-PGANa)⁻¹ at pH 9.0, respectively. At lower pH < pKa, the carboxyl groups of γ-PGA primarily remained in the protonated form and adsorption of Cs only slightly occurred. At higher pH > pKa, the adsorption of Cs was significantly facilitated due to ionization of carboxyl groups to carboxylate ion. Adsorption of Cs at pH > 9.0 was inhibited due to the hydrolysis of Cs. The Langmuir model could successfully describe the isotherm data. For γ-PGA and γ-PGANa, the maximum adsorption capacities at equilibrium in the Langmuir model were 446 and 333 mg-Cs(g-adsorbent)⁻¹, respectively. The high adsorption capacities confirmed a potential utilization of γ-PGA and γ-PGANa for Cs removal. The adsorption of Cs by both γ-PGA and γ-PGANa attained the equilibrium within 0.5 min. The very quick equilibration is a benefit from the viewpoint of practical application. The spectra of FT-IR and XPS before and after adsorption confirmed the adsorption of Cs onto γ-PGA and γ-PGANa via electrostatic interaction with carboxylate anions.

Graphical abstract

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Distribution of radionuclides between atmosphere and ash during combustion of contaminated vegetation

Publication date: December 2016
Source:Journal of Environmental Radioactivity, Volume 165
Author(s): Liufang (Jenny) Zhou, Raghu Rao, Emily Corcoran, David Kelly
A series of laboratory-scale combustion tests were conducted under well-controlled conditions to measure the release of ⁹⁰Sr and ¹³⁷Cs nuclides to the atmosphere (air) from combustion of vegetation and organic soil samples contaminated with radioactivity. These vegetation and soil samples were collected from a controlled contaminated forest area within the Canadian Nuclear Laboratories – Chalk River site. The combustion products including ash and smoke particulates, along with gaseous emissions, were collected and then analyzed for ¹³⁷Cs and ⁹⁰Sr concentrations by radiometric techniques. The experimental results reveal that the releases of ⁹⁰Sr to the atmosphere (air) from combustion of vegetation are very low with most of the ⁹⁰Sr activity remaining in ash residues, even at a temperature of 800 °C. The detailed combustion experiments with surface litter and twigs, alder twigs, alder leaves, and organic soil indicate that 0.5 ± 0.1%, 0.3 ± 0.1%, 0.9 ± 0.1%, and 0.3 ± 0.1% of ⁹⁰Sr is released to the atmosphere (air), respectively. On the other hand, the releases of ¹³⁷Cs are found to be highly dependent on the combustion temperature as well as the nature of vegetation. The releases of ¹³⁷Cs obtained at 800 °C are 45 ± 7%, 77 ± 9%, 92 ± 5%, and 2.4 ± 0.5% for surface litter and twigs, alder twigs, alder leaves, and organic soil, respectively. The mechanism associated with the high release of ¹³⁷Cs at a high temperature of 800 °C was explored.



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Experimental evidence for ternary colloid-facilitated transport of Th(IV) with hematite (α-Fe2O3) colloids and Suwannee River fulvic acid

Publication date: December 2016
Source:Journal of Environmental Radioactivity, Volume 165
Author(s): Hilary P. Emerson, Katherine A. Hickok, Brian A. Powell
Previous field experiments have suggested colloid-facilitated transport via inorganic and organic colloids as the primary mechanism of enhanced actinide transport in the subsurface at former nuclear weapons facilities. In this work, research was guided by the hypothesis that humic substances can enhance tetravalent actinide (An(IV)) migration by coating and mobilizing natural colloids in environmental systems and increasing An(IV) sorption to colloids. This mechanism is expected to occur under relatively acidic conditions where organic matter can sorb and coat colloid surfaces and facilitate formation of ternary colloid-ligand-actinide complexes. The objective of this work was to examine Th transport through packed columns in the presence of hematite colloids and/or Suwannee River fulvic acid (SRFA). In the presence of SRFA, with or without hematite colloids, significant transport (>60% recovery within the effluent) of thorium occurred through quartz columns. It is notable that the SRFA contributed to increased transport of both Th and hematite colloids, while insignificant transport occurred in the absence of fulvic acid. Further, in the presence of a natural sandy sediment (as opposed to pure quartz), transport is negligible in the presence of SRFA due to interactions with natural, clay-sized sediment coatings. Moreover, this data shows that the transport of Th through quartz columns is enhanced in ternary Th-colloid-SRFA and binary Th-SRFA systems as compared to a system containing only Th.



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Dose assessment to workers in a dicalcium phosphate production plant

Publication date: December 2016
Source:Journal of Environmental Radioactivity, Volume 165
Author(s): D. Mulas, J. Garcia-Orellana, N. Casacuberta, A. Hierro, V. Moreno, P. Masqué
The production of dicalcium phosphate (DCP) uses phosphate rock (PR) as a raw material. Sedimentary phosphate rocks are enriched with relevant concentrations of natural radionuclides from the ²³⁸U decay chain (around 10³ Bq·kg⁻¹), leading to the need of controlling potential exposures to radiation of workers and members of the public in accordance with IAEA safety standards. Indeed, phosphate industries are classified as Naturally Occurring Radioactive Material (NORM) industries. Thus, the aim of this work is to assess the radiological risk of the workers in a DCP production plant located in the Iberian Peninsula (South-West Europe), which digests PR with hydrochloric acid. In the present study ²³⁸U, ²³⁰Th, ²²²Rn, ²¹⁰Pb and ²¹⁰Po concentrations in aerosols (indoor and outdoor areas) are reported. Aerosols showed concentrations between 0.42–92 mBq·m⁻³ for ²³⁸U, 0.24–33 mBq·m⁻³ for ²³⁰Th, 0.67–147 mBq·m⁻³ for ²¹⁰Pb and 0.09–34 mBq·m⁻³ for ²¹⁰Po. Long-term exposure (four months) of passive ²²²Rn detectors provided concentrations that ranged from detection limit (< DL) to 121 Bq·m^-3 in outdoor areas and from < DL to 211 Bq·m⁻³ in indoor areas, similar to concentrations obtained from short-term measurements with active detectors from < DL to 117 Bq·m⁻³ in outdoor areas and from < DL to 318 Bq·m⁻³ in indoor places. ²²⁶Ra accumulation in ebonite and pipe scales were the most important contributions to the ambient dose equivalent H*(10), resulting in 0.07 (background)–27 μSv·h⁻¹ with a median value of 1.1 μSv·h⁻¹. Average ²²²Rn air concentrations were lower than the 300 Bq·m⁻³ limit and therefore, according to European Directive 2013/59/EURATOM, ²²²Rn concentration is excluded from the worker operational annual effective dose. Thus, considering the inhalation of aerosols and the external dose sources, the total effective dose determined for plant operators was 0.37 mSv·y⁻¹.



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Monteggia fracture-dislocation with intercondylar fracture of the ipsilateral humerus: a new type III Monteggia equivalent

2016-10-08T18-09-54Z
Source: The Southeast Asian Journal of Case Report and Review
Dr.Aakash Mugalur, Dr.Binoti A Sheth.
Monteggia fracture dislocations are rare but complex injuries usually involving a fracture of the ulna and dislocation of the radial head. Monteggia Fracture dislocations are associated with other concomitant injuries in the ipsilateral upper limb. However, ipsilateral distal intercondylar fracture of the humerus and Monteggia fracture dislocation in adults are very rare with only 4 cases described in literature till date. We presented an exceptionally rare case of type III Monteggia fracture dislocation with intercondylar distal humerus fracture with posterior interosseous nerve palsy. The patient was treated with open reduction and internal fixation with post operative physiotherapy. The posterior interosseous nerve palsy recovered without any operative intervention. The patient had good functional outcome with no disability. We consider it to be a type III Monteggia equivalent adding to the expanding list of equivalent lesions.


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Monteggia fracture-dislocation with intercondylar fracture of the ipsilateral humerus: a new type III Monteggia equivalent

2016-10-08T18-09-54Z
Source: The Southeast Asian Journal of Case Report and Review
Dr.Aakash Mugalur, Dr.Binoti A Sheth.
Monteggia fracture dislocations are rare but complex injuries usually involving a fracture of the ulna and dislocation of the radial head. Monteggia Fracture dislocations are associated with other concomitant injuries in the ipsilateral upper limb. However, ipsilateral distal intercondylar fracture of the humerus and Monteggia fracture dislocation in adults are very rare with only 4 cases described in literature till date. We presented an exceptionally rare case of type III Monteggia fracture dislocation with intercondylar distal humerus fracture with posterior interosseous nerve palsy. The patient was treated with open reduction and internal fixation with post operative physiotherapy. The posterior interosseous nerve palsy recovered without any operative intervention. The patient had good functional outcome with no disability. We consider it to be a type III Monteggia equivalent adding to the expanding list of equivalent lesions.


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Unintentional household poisoning due to rodenticide in a child

2016-10-08T18-09-54Z
Source: The Southeast Asian Journal of Case Report and Review
Nisreen A Rahman, Vinod A Chaudhari, Bhawana A Badhe, Kusa K Shaha.
Introduction: The household poisoning is a major problem in India, and the awareness of these poisons among the people is meager and sometimes they ignorant and careless regarding these poisons. The various types of rat killer or rodenticides used in household, and their improper usage and safety may pose serious health issues. The rat killer poisoning with phosphide, warfarin, and superwarfarin are increasing day by day. Case report: A three years old boy unintentionally consumed rat killer paste, when his mother was out of the house. He had complaints of nausea and vomiting, and he admitted in a primary health care center. Then he was referred to tertiary care center and during the treatment he developed the features of acute renal failure and hepatotoxicity due to the rat killer poison and succumbed on a second day of admission. The features of rat killer poison that is zinc phosphide were evident on thorough autopsy examination, clinical findings, and ancillary examinations. Discussion: There is a need for proper preventive and treatment strategies to reduce the number of exposures, morbidity and mortality due to household poisons including rat killer poisons. In medical practice identifying the rat killer poisoning cases, their proper management, and its medicolegal aspects are very important.


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