Abstract
Technetium-99 is a radioactive isotope with a half-life of 2.13 × 105 year. 99Tc is a significant contaminant of concern to the world. For this reason, a detailed understanding of technetium chemistry is essential for the protecting the public and the environment especially after increasing the various applications and uses of isotopes in the medical practices. Therefore, treatment of waste increases prior to the safe discharge to the environment or the storage. The sorption of technetium in the form of pertechnetate on a nano manganese oxide loaded into activated carbon has been investigated. Nano manganese oxide (NMO) was synthesized from manganese chloride and potassium permanganate by co-precipitation and forming a new composite by loading a nanoparticle into a modified activated carbon by different ratios. Modifications of activated carbons using different concentrations of HNO3 (4 M, 6 M and 8 M) are used in prepared composites. Fourier transform infrared spectroscopy (FT-IR), X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM) were used to characterize the prepared composites. The adsorption of anions from low level radioactive aqueous waste was examined using batch technique. Different parameters affecting on the adsorption process were studied for the removal of . The results revealed that NMO/AC (4 M, 6 M and 8 M) has a high adsorption efficiency (93.57%, 90.3% and 90.3%) respectively compared to NMO and AC which have a lower adsorption efficiency (41% and 38.9%) respectively. Moreover, the adsorption isotherm belonged to Freundlich model, the adsorption data followed pseudo-second order model and the thermodynamic study indicated that the adsorption of on Nano-composites was an exothermic and spontaneous process.
Highlights
Technetium-99 (99Tc) is a pure β-emitter radionuclide with a half-life of 2.13 × 105 years
All chemicals were analytical grade, purchased and used as received without further purification: Potassium Permanganate KMnO4; Sigma-Aldrich, Manganese Chloride MnCl2∙4H2O; Merk, Activated Carbon (AC) commercial-grade provided by El-Gomhoria company for trade service (Cairo), 99Tc radionuclide was extracted from residual 99mTc columns from the technetium generator used in nuclear medicine centers, Ultima GoldTM (AB liquid scintillation counter (LSC)-cocktail) from Packard bioscience company, concentrated acids of A.R HNO3, HCl and NaOH were used throughout the investigations as required and freshly bi-distilled water was used through all experiments
The subsequent phase transition into different valences of manganese oxide possibly owing to the oxidative atmosphere used at the beginning of the synthesis provides a pathway to oxidize some Mn2+ present in Mn(OH)2 to Mn3+ and Mn4+ during the drying step, the reducing reaction with these carbon matrix or the acidic treatment of carbon, it seems that a partial amount of Mn3+ can be oxidized leading to Mn5O8 monoclinic phase, which stabilizes the divalent Mn ions inherited from Mn3O4
Summary
Technetium-99 (99Tc) is a pure β-emitter radionuclide with a half-life of 2.13 × 105 years It is formed in the thermal neutron fission of 235U with high yield (6%) [1] [2] and by spontaneous fission of 238U in the earth’s crust [3]. It appears environmentally from the decay of the medical radioisotope 99mTc (6.0 h half-life) [4]. Technetium-99 is very mobile in groundwater due to its existence dominantly as the anionic species, pertechnetate TcO4− [5]. The pertechnetate TcO4− is not immobilized by most common minerals or inorganic sorbents because it is repulsed by their negative charge [6]
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