Biosorption of Cr(III) and Fe(III) in single and binary systems onto pretreated orange peel.

Trivalent chromium and iron are the products of the traditional reduction of hexavalent chromium by ferrous salts in industrial wastewater. Although there have been a few studies of Cr(III) adsorption, none have considered the effect of Fe(III) on Cr(III) adsorption in a binary system representing expected products of hexavalent chromium in industrial wastewater. The biosorption of Cr(III) and Fe(III) ions onto pretreated ground orange peel in single and binary systems was studied in batch experiments using a variety of techniques. The kinetic results showed a rapid rate of biosorption of Cr(III) and Fe(III) in single and binary systems and mutual interference effects in the competitive binary Cr(III)-Fe(III) system. Second order kinetic models showed the best fit for all systems. The behavior of competitive Cr(III)-Fe(III) biosorption were successfully described by the multicomponent Langmuir model, obtaining maximum capacities for Cr(III) and Fe(III) of 9.43 and 18.19 mg/g respectively. SEM/EDS results confirmed that the metals adsorb on the surface and FTIR identified the hydroxyl groups on the carboxylic acids as the active binding sites.

Dosimetric evaluation of lithium carbonate (Li2CO3) as a dosemeter for gamma-radiation dose measurements.

This work reports the possibility of using lithium carbonate as a dosimetric material for gamma-radiation measurements. Carboxi-radical ions, CO(2)(-) and CO(3)(-), arise from the gamma irradiation of Li(2)CO(3), and these radical ions can be quantified by electron paramagnetic resonance (EPR) spectrometry. The EPR-signal response of gamma-irradiated lithium carbonate has been investigated to determine some dosimetric characteristics such as: peak-to-peak signal intensity versus gamma dose received, zero-dose response, signal fading, signal repeatability, batch homogeneity, dose rate effect and stability at different environmental conditions. Using the conventional peak-to-peak method of stable ion radicals, it is concluded that lithium carbonate could be used as a gamma dosemeter in the range of 3-100 Gy.

Cr(VI) and Cr(VI)-diphenylcarbazide removal from aqueous solutions using an iron rotating disc electrode.

This paper presents the results of the investigation on the removal of Cr(VI) and the complex Cr(VI)-diphenylcarbazide from aqueous solutions using an electrochemical reactor, with iron electrodes. A maximum value of 99% Cr(VI) removal from aqueous solutions is observed for both Cr(VI) and Cr(VI)-diphenylcarbazide, at initial concentrations from 150 to 800 mg l(-1). Cyclic voltammetry experiments of water show the presence of electroactive species in the oxidation and reduction zones previous to the treatment and how this presence diminishes as the electrochemical treatment is applied to the wastewater. UV-Vis analyses corroborate the improvement on the quality of aqueous solutions treated. Finally, scanning electron microscopy and energy dispersion spectra show that Cr and Fe are present as constituents of the sludge formed during the electrochemical treatment. It was demonstrated that the use of electrochemical methods for the treatment of Cr(VI) and Cr(VI)-diphenylcarbazide aqueous solutions is an effective and economical method.

Genotoxicity of neutrons in Drosophila melanogaster. Somatic mutation and recombination induced by reactor neutrons.

This paper describes the observation of a direct relationship between the absorbed doses of neutrons and the frequencies of somatic mutation and recombination using the wing somatic mutation and recombination test (SMART) of Drosophila melanogaster. This test was used for evaluating the biological effects induced by neutrons from the Triga Mark III reactor of Mexico. Two different reactor power levels were used, 300 and 1000 kW, and two absorbed doses were tested for each power level: 1.6 and 3.2 Gy for 300 kW and 0.84 and 1.7 Gy for 1000 kW. A linear relationship was observed between the absorbed dose and the somatic mutation and recombination frequencies. Furthermore, these frequencies were dependent on larval age: In 96-h-old larvae, the frequencies were increased considerably but the sizes of the spots were smaller than in 72-h-old larvae. The analysis of the balancer-heterozygous progeny showed a linear absorbed dose- response relationship, although the responses were clearly lower than found in the marker-trans-heterozygous flies. Approximately 65% of the genotoxicity observed is due to recombinational events. The results of the study indicate that thermal and fast neutrons are both mutagenic and recombinagenic in the D. melanogaster wing SMART, and that the frequencies are dependent on neutron dose, reactor power, and the age of the treated larvae.

Lithium carbonate Li 2 CO 3 as a material for thermal neutron fluence measurements.

A possibility to use the electron paramagnetic resonance (EPR) signal of neutron-irradiated lithium carbonate for thermal neutron fluence measurements has been investigated. The following aspects of the system have been studied: peak-to-peak signal amplitude as a function of thermal neutron fluence, signal fading, signal repeatability, sample batch homogeneity, and zero-fluence response of the probes. It has been concluded that lithium carbonate can be used as a material sensitive to thermal neutron fluences.

Cr(VI) removal from wastewater using low cost sorbent materials: roots of Typha latifolia and ashes.

This work presents conditions for hexavalent chromium (Cr(VI)) removal from aqueous solution using different sorbent materials, namely: pyrolytic ashes of an industrial sludge from wastewater treatment and roots of Typha latifolia. The sorbent materials were characterized using scanning electron microscopy (SEM) and surface area using the Brunauer-Emmett-Teller (BET) technique, before and after the contact with the chromium-containing aqueous media. An overall Cr(VI) concentration reduction of 45% was achieved using the roots of Typha latifolia whereas in the case of pyrolytic ashes a 60% removal was observed. The percentage removal was found to depend on the initial Cr(VI) concentration in aqueous solution, pH and temperature. The Cr(VI) uptake process was maximum at pH 2 and a temperature of 40 degrees C for both sorbents. These materials showed a Cr(VI) adsorption capacity that was adequately described by the Langmuir adsorption isotherm. It was demonstrated that the use of waste materials for the treatment of Cr(VI)-containing wastewater is an effective and economical alternative method.

Determination of neutron absorbed doses in lithium aluminates.

Lithium-based ceramics have been proposed as tritium breeders for fusion reactors. The lithium aluminate (gamma phase) seems to be thermally and structurally stable, the damages produced by neutron irradiation depend on the absorbed dose. A method based on the measurement of neutron activation of foils through neutron capture has been developed to obtain the neutron absorbed dose in lithium aluminates irradiated in the thermal column facility and in the fixed irradiation system of a Triga Mark III Nuclear Reactor.

Intercomparison of absorbed dose to water measurements for 60Co gamma rays using Fricke, alanine and radiochromic dye film dosimetry.

Measurements of absorbed dose at 5 cm depth in a 30 x 30 x 30 cm3 water phantom have been performed using three independent dosimetric techniques: Fricke, alanine and radiochromic dye film (GafChromic HD-810). The measurements were carried out in the secondary standard dosimetry laboratory at ININ Mexico using a collimated 60Co gamma source with a radiation field of 10 x 10 cm2 at the phantom front surface. The source to phantom distance was set at 100 cm. The reference absorbed dose at 5 cm depth in the water phantom was obtained using a 0.6 cm3 ionisation chamber. The absorbed dose to water for the test dosimetry techniques was around 100 Gy. The deviations of the dose obtained from these dosimetry techniques were within 4%. The reasons for these deviations are discussed.

Genetic effects induced by neutrons in Drosophila melanogaster I. Determination of absorbed dose.

A method to obtain the absorbed dose in Drosophila melanogaster irradiated in the thermal column facility of the Triga Mark III Reactor has been developed. The method is based on the measurements of neutron activation of gold foils produced by neutron capture to obtain the neutron fluxes. These fluxes, combined with the calculations of kinetic energy released per unit mass, enables one to obtain the absorbed doses in Drosophila melanogaster.

EPR signal enhancement of alanine irradiated with thermal neutrons.

A method to enhance the electron paramagnetic resonance signal amplitude response of alanine to thermal neutrons is presented. The method is based on the production of additional free radicals caused by alpha-particle and 7Li interactions on the alanine. These particles emerge from the neutron capture 10(5)B (n, alpha) 7(3)Li reaction. For this purpose, alanine and boric acid are intimately mixed. Mixture intimacy is critical for optimum enhancement. A way to achieve good mixture intimacy is suggested. A signal enhancement up to 2200% is obtained.