Investigation of thermoluminescence glow curves in quartz extracted from the Central Eastern Desert, Egypt.

The current study investigated the thermoluminescence (TL) properties of milky quartz samples collected from the Central Eastern Desert, Egypt. The crystallinity and the elemental concentrations of the milky quartz samples were examined using X-ray diffraction and an atomic absorption spectrometer. Samples were irradiated using a gamma source at different doses from 250 mGy up to 2 kGy. For annealing, the samples were heated at 400°C for 1 h, followed by slow cooling. Kinetic analyses for the TL glow curves were performed using new designed TL deconvolution software. The glow curves were composed of six overlapped trapping sites at 428, 468, 498, 545, 586, and 639 K. The samples also displayed a linear dose-response from 0.25 Gy up to 20 Gy and a supralinear response from 20 Gy up to 200 Gy. The samples exhibited very low sensitivity for gamma radiation compared with LiF and the minimum detectable dose was 545 µGy. From its linear nature, it was observed that the sensitivity had changed. This study recommends starting measurements of these milky quartz samples after 4 days to give established measurements.

Fossils as candidate material for orthopedic applications.

Ceramic powders from fossil deposits were thoroughly characterized from the material point of view and sintered to produce massive components. The raw material, a mixture of apatite minerals, feldspars, and quartz, seems ideally suitable to obtain a biologically compatible glass ceramic. Preliminary in vitro tests of proliferation and adhesion of MG63 human osteoblast-like cell line on a selected sample are encouraging. Results are correlated with sintering conditions and phase composition: the fossil can be sintered to almost full density at temperatures as low as 900 °C and seems to quickly promote cell activation with respect to hydroxylapatite.

Further purification of industrial quartz by much milder conditions and a harmless method.

A much "greener" and harmless leaching method for removing impurity aluminum further from industrial quartz sands by very dilute mixed acids has been presented. With the help of supersonic, the percentage of removal aluminum reached up to 52.5%/53%, that is, 17.4 ppm/17.7 ppm at 30 °C/80 °C, respectively. These results are 4.4/4.7 ppm lower than that supplied by a world famous quartz sands supplier, and the leaching conditions are much milder compared with other comparable methods: the concentration of hydrogen chloride in the mixed acid is only 10% of the others, the leaching temperature is much lower; at the same time, the operating time is only 13-20% of the others, thereby pollution of industrial strong acids and thermo-scattering is reduced substantially.

Toxicity of a quartz with occluded surfaces in a 90-day intratracheal instillation study in rats.

This 90-day study was aimed at characterizing the differences in biological activity between a crystalline ground reference quartz (DQ12) and a quartz with occluded surfaces (quartz isolate) obtained from a clay deposit formed 110 to 112 million years ago. In different test groups, rats were dosed with the same total mass and quartz level by intratracheal instillation, with a total high dose of 15.2 mg/kg (body weight, bw) or approximately 4.7 mg/rat of each quartz species in a saline suspension. The reference quartz was mixed with titanium dioxide to achieve a positive control mixture, which contained the same quartz content as in the quartz isolate. At 3 days post dosing, both quartz groups showed a significant inflammatory response based on total and differential cell counts from bronchoalveolar lavageate (BAL) analysis. At 28 and 90 days, the quartz isolate values were no longer statistically different from vehicle control group values; however, the positive control group values were approximately 12 and 65 times greater than those of the control group, respectively. After 28 days, histopathological evaluation showed moderate effects in the quartz isolate group compared to the saline control animals. These effects did not progress in severity at 90 days. In contrast, the positive control group exhibited more severe effects than the quartz isolate group and these effects showed a progression to a persistent and self-perpetuating inflammatory state. The toxicological properties of quartz particles can vary significantly dependent on their surface characteristics. Toxicity can range from a high-dose-induced, modest, transient inflammation from quartz with occluded surfaces, to a severe and persistent inflammatory state caused by ground quartz with fractured surfaces.

Physicochemical and mineralogical characterization of test materials used in 28-day and 90-day intratracheal instillation toxicology studies in rats.

Two recent intratracheal instillation toxicology studies in rats clearly show that a naturally occurring quartz, with occluded crystal surfaces (quartz isolate), produced significantly less inflammatory response than a crushed reference quartz (DQ12). Respirable-size quartz isolate was isolated from bentonite parent rock, without crushing or the use of chemicals, to ensure that the surface properties of the quartz particles were unaltered. The isolation technique utilized gentle mechanical dispersion followed by sedimentation in an aqueous medium. Extensive mineralogical and chemical characterizations were undertaken to define the physicochemical properties of the test materials. The characterizations showed significant, measurable physicochemical differences between the two quartz types. These differences may help to explain the difference in toxicological response associated with these materials. The evaluation methods and resulting data that characterized the chemical and physical properties of the instillation test materials are discussed. The data presented show that such characterizations are essential if meaningful correlations are to be made between test materials and their toxicological profiles.

The effects of Fe(II) and Fe(III) concentration and initial pH on microbial leaching of low-grade sphalerite ore in a column reactor.

In this study the effects of initial concentration of Fe(II) and Fe(III) ions as well as initial pH on the bioleaching of a low-grade sphalerite ore in a leaching column over a period of 120 days with and without bacteria were investigated. Four different modifications of medium were used as column feed solutions to investigate the effects of initial concentration of Fe(II) and Fe(III) ions on zinc extraction. The experiments were carried out using a bench-scale, column leaching reactor, which was inoculated with mesophilic iron oxidizing bacteria, Acidithiobacillus ferrooxidans, initially isolated from the Sarcheshmeh chalcopyrite concentrate (Kerman, Iran). The effluent solutions were periodically analyzed for Zn, total Fe, Fe(II) and Fe(III) concentrations as well as pH values. Bacterial population was measured in the solution (free cells). Maximum zinc recovery in the column was achieved about 76% using medium free of initial ferrous ion and 11.4 g/L of ferric ion (medium 2) at pH 1.5. The extent of leaching of sphalerite ore with bacteria was significantly higher than that without bacteria (control) in the presence of ferrous ions. Fe(III) had a strong influence in zinc extraction, and did not adversely affect the growth of the bacteria population.

Recycling of waste products in the induction of biofilms to remediate the visual impact generated by quartz mining.

The present study was undertaken to investigate the viability of the use of two waste products, cheese whey and composted organic waste, as nutrient sources in the induction of biological films on quartz surfaces, with the final aim of reducing the visual impact generated by quartz mining. Experiments were carried in laboratory in which quartz samples were colonized with microorganisms (mainly cyanobacteria) forming biofilms. Previous studies have shown that a nutritional supplement must be added for good development of biofilms and, therefore, application of the two waste products was compared with application of the chemical nutrient medium on which these types of microorganisms are usually cultivated. Both products provided better results than the culture medium, in terms of the speed of formation of the biofilm, faster with the waste products, and the degree of cover of the brilliant white colour of the quartz, better masked by the biofilms formed when the waste products were applied as a darker biofilm was obtained.

Search for common characteristics in the glow curves of quartz of various origins.

The thermoluminescence (TL) glow curves of quartz of various origins were measured under two different conditions, (1) unannealed samples and (2) samples annealed at 500 degrees C and 900 degrees C. The different glow curves obtained were analysed using first order kinetics and glow curve deconvolution (GCD) analysis. The comparison of the glow curves obtained was mainly concentrated in studying the sensitivities of the glow peaks as a function of the annealing temperature, and in obtaining the kinetic parameters of the glow peak at '110 degrees C'. Furthermore, in four samples the detailed comparison was extended to the trapping parameters of all existing glow peaks. It was found that despite their different origin and the different shapes of the glow curves, there are several basic characteristics that are common to all samples studied.