FLOCCULATION STUDY OF NATURAL QUARTZ SAMPLE USING ANIONIC POLYACRYLAMIDE

The waste sludge generated during processing of iron ore in the Omarska mine (The Republic of Srpska, Bosnia and Herzegovina) is fine-grained (15μm), containing relatively high concentrations of iron, and quartz as its major impurity. The flocculation behaviour of the primary natural raw “quartz” sample from Omarska mine was studied in the present paper. This sample is composed of major quartz which dominates over minor contents of clay minerals and feldspars, and contain 92.9% of SiO2. Particle size distribution analysis confirm that it is present as fine and ultra-fine particles. The zeta potential of quartz depends on pH value. Settling experiments were performed by using three different dispersants (Na-hexamethaphosphate, Na-pyrophosphate and Na-silicate), and anionic polyacrylamide as flocculants. The best results were achieved with Nahexametaphosphate (1000 g/t) and anionic polyacrylamide A 100. The effect of a flocculant on the settling rate depends on solid concentration. Settling rates increase significantly with the increase of the liquid component in both cases (natural settling and hindered settling by addition of a flocculant).

X-Ray Studies of Vein Quartz from Shungite Rocks

Silicon dioxide is the most common silicon compound and a major constituent of the Earth’s crust. Silicon dioxide, also known as silica, is a chemical compound that is an oxide of silicon with the chemical formula SiO2. Silica is most commonly found in nature as quartz. Quartz exists in natural and synthetic forms. More specifically α-quartz is a widely known material, which is stable at low temperatures and pressures. The α-quartz is considered competent material because over the past many years it has attracted wide attention due to its unique characteristics. The article presents the research results from comparison between one of the morphological varieties of quartz – vein quartz of shungite rocks from Zazhogino deposit of Karelia – and a reference quartz sample. Via the Rietveld method, the values of the lattice parameters are determined. Apparent coherent length for vein quartz samples having contacts with various minerals are determined by the approximation method.

The ice-nucleating ability of quartz immersed in water and its atmospheric importance compared to K-feldspar

Mineral dust particles are thought to be an important type of ice-nucleating particle (INP) in the mixed-phase cloud regime around the globe. While K-rich feldspar (K-feldspar) has been identified as being a particularly important component of mineral dust for ice nucleation, it has been shown that quartz is also relatively ice-nucleation active. Given quartz typically makes up a substantial proportion of atmospheric desert dust, it could potentially be important for cloud glaciation. Here, we survey the ice-nucleating ability of 10 α-quartz samples (the most common quartz polymorph) when immersed in microlitre supercooled water droplets. Despite all samples being α-quartz, the temperature at which they induce freezing varies by around 12 ∘C for a constant active site density. We find that some quartz samples are very sensitive to ageing in both aqueous suspension and air, resulting in a loss of ice-nucleating activity, while other samples are insensitive to exposure to air and water over many months. For example, the ice-nucleation temperatures for one quartz sample shift down by ∼2 ∘C in 1 h and 12 ∘C after 16 months in water. The sensitivity to water and air is perhaps surprising, as quartz is thought of as a chemically resistant mineral, but this observation suggests that the active sites responsible for nucleation are less stable than the bulk of the mineral. We find that the quartz group of minerals is generally less active than K-feldspars by roughly 7 ∘C, although the most active quartz samples are of a similar activity to some K-feldspars with an active site density, ns(T), of 1 cm−2 at −9 ∘C. We also find that the freshly milled quartz samples are generally more active by roughly 5 ∘C than the plagioclase feldspar group of minerals and the albite end member has an intermediate activity. Using both the new and literature data, active site density parameterizations have been proposed for freshly milled quartz, K-feldspar, plagioclase and albite. Combining these parameterizations with the typical atmospheric abundance of each mineral supports previous work that suggests that K-feldspar is the most important ice-nucleating mineral in airborne mineral dust.

Preliminary results towards the equivalence of transformed continuous-wave Optically Stimulated Luminescence (CW-OSL) and linearly-modulated (LM-OSL) signals in quartz

The present paper presents a comparative experimental study of two commonly measured Optically Stimulated Luminescence (OSL) signals in quartz. The experimental study measures both the continuous wave OSL (CW-OSL) and the linearly modulated (LM-OSL) signals from the same quartz sample for a range of stimulation temperatures between 180 and 280°C, while the former is transformed to pseudo LM-OSL (ps LM-OSL). A computerized deconvolution curve analysis of the LM-OSL and ps LM-OSL signals was carried out, and the contributions of several OSL components to the initial OSL signal (0.1 s) were shown to be independent of the stimulation temperature used during the measurement. It was also found that the composite OSL (0.1 s) signal consists mainly of the first two OSL components present in the OSL curves. The equivalence of the ps LM-OSL (transformed CW-OSL) and of LM-OSL measurements was also examined by an appropriate choice of the experimental stimulation times, and of the stimulation power of the blue LEDs used during the measurement.

Update on the Performance of the SUERC In Situ Cosmogenic 14C Extraction Line

In this paper, we describe improvements to the in situ cosmogenic radiocarbon extraction system at SUERC made since 2004, highlighting the factors that potentially control the reduction of analytical variability. We also present new results on system blanks and of measurements of in situ14C in shielded quartz and a surface quartz sample used at the University of Arizona as an in situ14C standard (PP-4). The SUERC in situ14C extraction system was built in 2001 and is based on a combustion technique following the design of the extraction system at the University of Arizona. Our preliminary results suggest that the continuous running of the extraction system and the monitoring of gas collecting time and of the temperature of the cryogenic traps used in the gas cleaning steps are key to maintaining low and stable system blanks. Our latest average system blank is 2.02 ± 0.23 x 10514C atoms. This is consistent with those recently published by the University of Arizona and ETH in situ14C labs. Measurements of in situ14C concentrations in sample PP-4 yield an average of 3.82 ± 0.23 x 105 atoms g–1 quartz, again consistent with published values.

Mist-Abrasion Machining of Brittle Material and Its Application in Corrective Figuring of Optical Parts

Polished surfaces are usually used for corrective figuring in ultraprecision machining, but in this research, corrective figuring of a rough quartz sample has been preformed before the polishing process. A capacitor probe has been used to measure out the flatness of a rough quartz sample since the laser interferometer measuring device restrictions. Mist-abrasion machining method is proposed for corrective figuring of the optical materials. By the new figuring method, not only the polishing time decreases but also its efficiency increases by bigger abrasive grain size. The fundamental characteristics and its applicability for corrective figuring of a flat quartz sample are investigated. Flatness of the rough quartz sample is improved from PV=0.4μm to PV=0.1μm before the polishing process by mist-abrasion figuring.

Component Resolved IR Bleaching Study of the Blue LM-OSL Signal of Various Quartz Samples

Component Resolved IR Bleaching Study of the Blue LM-OSL Signal of Various Quartz Samples The present work provides an initial component resolved analysis concerning the effect of infra-red (IR) exposure at elevated temperatures on the blue LM-OSL signal of quartz (stimulated at 470 nm). The study was performed on a total of seven quartz samples, among which five originated from Turkey, one from Greece and one synthetic quartz sample. For these quartz samples, the presence of 6 or even 7 independent LM-OSL components was previously reported, after the application of a computerized decomposition analysis. IR bleaching of each one of these components is studied and compared to the respective signal reduction due to the same thermal treatment solely. It is clearly demonstrated that IR stimulation at temperatures above 50°C does not deplete only the fast component in most sedimentary quartz samples studied. Net depletion of fast and medium components resulting from IR exposure is sample-dependent and occurs faster as the stimulation temperature increases. Weak IR bleaching of slow components is also reported in some cases, being more effective for stimulation temperatures up to 100°C. No depletion of either the medium or the slow components was detected for stimulation temperatures above 150°C. Finally, IR does not stimulate any of the LM-OSL components in the case of the synthetic quartz sample.

Heterogeneities in Adsorption from Aqueous Solution — An Example of the Effect of Surface Coverage

Studies of the interaction of uranyl species with the surface of quartz are reported. Two approaches were applied. These were (i) the classical static batch adsorption approach in which only the forward adsorption uptake reaction is usually studied and (ii) a dynamic column approach in which the retention of a solute during its migration through a porous medium is investigated and where adsorption and desorption are both relevant for the final breakthrough curve. In this paper, we present the results of a column study at pH 4. Under these conditions, the interference of the carbonate ion (via the formation of dissolved or adsorbed uranyl-carbonato species), the effects of quartz surface charge (quartz/silica is virtually uncharged under these conditions) and the potential effects of quartz dissolution on uranyl speciation (via the formation of dissolved or adsorbed uranyl-silicato species) are minimised. The reported batch adsorption results are reasonably predicted by a model which under similar conditions successfully described batch and column data on a quartz sample with grains smaller than the quartz particles used in the present study by a factor of ca. 25. However, this model was incapable of describing the breakthrough behaviour of uranyl species. This failure was attributed to the heterogeneity of the quartz particles used, which may be more important for column breakthrough than for batch adsorption data.