RESUMEN
Radiation-induced luminescence signals in beige sepiolite samples were investigated using optically stimulated luminescence. A thermally stable, light-sensitive radiation-induced signal was detected, and radiation dose response and thermal properties of this signal were studied. The thermal stability and dose sensitivity of the signal implies the potential of the material for dating and retrospective radiation dosimetry.
Asunto(s)
Luminiscencia , Silicatos de Magnesio/química , Silicatos de Magnesio/efectos de la radiación , Óptica y Fotónica , Dosimetría Termoluminiscente/métodos , Relación Dosis-Respuesta en la Radiación , Humanos , Ensayo de Materiales , Dosis de Radiación , Monitoreo de Radiación , Dosificación Radioterapéutica , TurquíaRESUMEN
Energy response of LiF:Mg,Ti, LiF:Mg,Cu,P and Mg2SiO4:Tb thermoluminescence dosemeters (TLDs) was measured in the range 10-150 keV for monoenergetic photons at SPring-8 of an 8-GeV synchrotron radiation facility. The photon beam was monitored by a parallel-plate free-air ionisation chamber calibrated with an uncertainty of 3%. Owing to the small dimension of the beam, a rotating holder was designed in order to irradiate TLDs uniformly. The measured responses of LiF to energy were approximately in agreement with the calculated dose absorption dependence in the soft tissue. However, two types of LiF TLDs presented the different luminescent responses to the photon energy. The response of LiF:Mg,Ti had a smooth curve, and that of LiF:Mg,Cu,P presented a local maximum at 30 keV and a local minimum at 100 keV. The Mg2SiO4:Tb response was nearly bone equivalent. Linearity of dose responses was also confirmed up to 2 Gy on each TL material.
Asunto(s)
Fluoruros/efectos de la radiación , Transferencia Lineal de Energía/efectos de la radiación , Compuestos de Litio/efectos de la radiación , Silicatos de Magnesio/efectos de la radiación , Fotones , Protección Radiológica/instrumentación , Dosimetría Termoluminiscente/instrumentación , Relación Dosis-Respuesta en la Radiación , Diseño de Equipo , Análisis de Falla de Equipo , Fluoruros/química , Compuestos de Litio/química , Silicatos de Magnesio/química , Ensayo de Materiales , Dosis de Radiación , Protección Radiológica/métodos , Reproducibilidad de los Resultados , Sensibilidad y Especificidad , Dosimetría Termoluminiscente/métodosRESUMEN
The aim of the present study is to enhance the methylene blue (MB) adsorption of sepiolite by ultrasonic treatment. The natural sepiolite was pretreated by sonication to improve the surface characteristics and enhance the dye uptake capacity. Sonication process resulted in a significant increase in the specific surface area (SSA) of sepiolite. The FTIR spectrum of the sonicated sepiolite indicates that the tetrahedral sheet is probably distorted after sonication process. The effect of various parameters such as sonication, pH, initial dye concentration and temperature on dye adsorption has been investigated. The adsorbed amount of MB on sepiolite increased after sonication as well as with increasing pH and temperature. The experimental data were evaluated by applying the pseudo-first- and second-order, and the intraparticle diffusion adsorption kinetic models. Adsorption process of MB onto sepiolite followed the pseudo-second-order rate expression. The experimental data were analyzed by Langmuir and Freundlich isotherms, and found that the isotherm data were reasonably well correlated by Langmuir isotherm. Maximum monolayer adsorption capacity of sepiolite for MB increased from 79.37 to 128.21 mg/g after the sonication. Various thermodynamic parameters, such as Delta G(0), Delta H(0) and DeltaS(0) were calculated. The thermodynamics of MB/sepiolite system indicated spontaneous and endothermic nature of the process. Adsorption measurements showed that the process was very fast and physical in nature.