Granulometric characterization of paleosols in loess series by automated static image analysis

An automated image analysis method is proposed here to study the size and shape of siliciclastic sedimentary particles of paleosols of Central European loess sequences. Several direct and indirect measurement techniques are available for grain size measurements of sedimentary mineral particles. Indirect techniques involve the use of some kind of physical laws, however, all requirements for calculations are in many cases not known. Even so, the direct manual microscopic observation and measurement of large, representative number of grains is time-consuming and sometimes rather subjective. Therefore, automated image analyses techniques provide a new and perspective way to analyse grain size and shape sedimentary particles. Here we test these indirect (laser diffraction) and direct (automated static image analysis) techniques and provide new granulometric (size and shape) data of paleosols. Our results demonstrate that grain size data of the mineral dust samples are strongly dependent on shape parameters of particles, and shape heterogeneity was different between different size classes. Due to the irregular grain shape parameters, uncertainties have arisen also for determination of grain sizes. In this paper we present a possible correction procedure to reduce the differences among the results of the laser diffraction and image analysis methods. By applying new correction factors, results of the two approaches could become closer but the unknown thickness of particles remains a problem to solve. The other presented correction procedure to assess the uncertain 3rd dimension of particles by their intensity-size relationships makes us able to reduce further the deviations of the two sizing methods

PC image-based analysis system for particle characterization of deinked pulps

Journal ArticleA low cost PC image-based particle analysis system is being developed for particle characterization of deinked pulps at the University of Utah. Initial R&D efforts of such an image analysis system were made for on-line particle characterization in the mineral processing field but now it has been found to be applicable for the analysis of deinked pulps in the wastepaper recycling industry. Both the size and shape of ink particles in hand sheets and paper pulps for all three typical wastepaper resources (newsprint, xerographic, and magazine) can easily be determined by the image analysis system. Preliminary results indicate that the system is quite successful for the evaluation of products obtained from deinking air-sparged hydrocyclone (ASH) flotation tests. Quantitative analysis can give both the size and shape of ink particles for such products. In addition, the hardware and software used to implement this image analysis system are discussed. Finally, on-line instrumentation of such a system for the direct measurement of wastepaper pulp is considered as part of future research activities

SHAPE FACTOR ANALYSIS OF ABRASIVE PARTICLES USED IN SLURRY ABRASION TESTING

The engineering components are subjected to surface damage by slurry abrasion such as transportation pipes carrying ore and mineral slurries, extruders, sand pumps and agitators, Apart from stress, abrasive particle hardness, slurry concentration, particle size and shape significantly influences slurry abrasion rate. The effect of abrasive particle shape on slurry abrasion behaviour of steels and cast irons which are widely used for wear protection has not been studied. The particle shape assumes significant importance due to fracture and fragmentation of the particles during the process of abrasion. In the present work, the particle shape characterization of silica sand abrasive particles was carried by shape factor analysis using image analysis technique. An attempt was made to correlate the different measures of shape factor with particle size of abrasive particles over a wide range. The characterization of slurry abrasion tester was carried out using slurry abrasion tester with silica sand slurry. The effect of sliding distance on slurry abrasion volume of mild steel was studied. The volume loss increased linearly with sliding distance. The scanning electron microscopic observations of worn our surfaces showed micro-ploughing and cutting as mechanism of material removal

Morphological and mineral features of nZVI induced precipitation on quartz particles

Nano Zero-Valent Iron (nZVI) is a versatile nanomaterial that can not only efficiently remove contaminants in soil, but also improve the soil’s geotechnical strength by changing their physicochemical properties. Inert solid mineral particles are the most common ingredients in soils, they present universal surface modification after the nZVI treatment. This study presents an investigation on the morphological and mineral features of nZVI induced iron mineral precipitations on quartz particles. Lead was employed as the artificial contaminant, while quartz was used to mimic the inert solid mineral particles in soil. Scanning Electron Microscope (SEM), Digital Image Analysis (DIA), Transmission Electron Microscopy (TEM), laser particle size analyzer, X-ray diffraction (XRD) and Raman spectrum were carried out for the characterization. The results indicate that iron minerals precipitated heterogeneously on the surface of quartz particles with plush-like and flake-like structure. They are made of deuterogenic plumbiferous minerals and ferriferous minerals. XRD analysis demonstrated that these minerals are amorphous. The curly flake-like mineral clusters were scatteredly distributed on the surface of quartz along with the of corroded nZVI aggregation. The thickness of the curly flake-like precipitation varied from 20 nm to 60 nm, and 20 nm to 35 nm for the plush-like precipitation. The generation of these iron mineral precipitations led to a slight increase in the average particle size and a decrease in the surface area of the soil. However, no clear difference in the shape and roughness of quartz was found after the nZVI treatment. This study is provided to improve the understanding of mass transfer from nZVI to inert solid particles in soil and its effect in soil improvement

COMPARISON OF PARTICLE SHAPES OF CONVENTIONALLY GROUND BARITE, CALCITE AND TALC MINERALS BY DYNAMIC IMAGING TECHNIQUE: A REVIEW

Shape of particles made by grinding is one of the important measures for determining the utilizations of industrial minerals namely barite, calcite, and talc particles, particularly at production (like coating pigments, paints, rubber and paper) and processing stages (beneficiation by flotation). Therefore, measurement of particle characteristics is a critical issue in the development and control of industrial mineral products in most of the industries for some demanding applications. Ball and rod mills are commonly used as conventional grinding mills to produce a controlled grind size for the flotation circuit in the beneficiation of industrial minerals. Dynamic Image Analysis (DIA) offers reproducible results of a huge number of particles for some industrial minerals namely, barite [1], calcite [2] and talc [3] particles, whose shapes are crucial for some industries utilized as fillers. Thus, this review is about the comparison of shape values in terms of circularity (C) and bounding rectangle aspect ratio (BRAR) determined by the real time DIA. It was found that the shape results of the previous studies for the same samples by SEM measurement [4] were in good agreement with DIA results. It was concluded that the more rounded particles were encountered in the rod milled products for calcite and barite minerals. On the other hand, the more elongated particles were found in the ball milled products for talc mineral. It was attributed to the material type since the same mills were used for all tests. Hence, DIA can be used as a useful tool, which is easy, fast and highly accurate to control the particle shape distributions whether the required powder is fit for us

Identification of Saharan dust particles in Pleistocene dune sand- paleosol sequences of Fuerteventura (Canary Islands)

Automated static image analysis and newly introduced evaluation techniques were applied in this paper to identify Saharan dust material in the unique sand-paleosol sequence of Fuerteventura (Canary Islands). Measurements of ~50,000 individual mineral particles per samples provided huge amount of granulometric data on the investigated sedimentary units. In contrast to simple grain size and shape parameters of bulk samples, (1) parametric curve-fitting allowed the separation of different sedimentary populations suggesting the presence of more than one key depositional mechanisms. Additional (2) Raman-spectroscopy of manually targeted individual particles revealed a general relationship among grain size, grayscale intensity and mineralogy. This observation was used to introduce the (3) intensity based assessment technique for identification of large number of quartz particles. The (4) cluster and (5) network analyses showed that only joint analysis of size, shape and grayscale intensity properties provided suitable results, there is no specific granulometric parameter to distinguish Saharan dust due to their irregular shape characteristics. The presented methods allowed the separation of Saharan dust-related quartz grains from local sedimentary deposits, but due to the lack of robust granulometric characterization of coarsest fractions and due to the diverse geochemical properties of North African sources, exact volumetric amount of deposited dust material and sedimentation rates could not be determined from these data

Geometallurgical methodology to improve the small-scale gold mining process of the Gualconda mine in Nariño – Colombia

In the gold beneficiation processes, the degree of particle size reduction is strongly influenced by the size and shape of the mineral species associated with the economically important metals. The capacity, energy consumption, and costs of the gold-bearing ore processing depend mainly on the operational parameters of the equipment of comminution and gravimetric concentration; therefore, it is essential to characterize the liberation degree of the minerals of interest as function of particle size. The small-scale mining beneficiation plants usually do not consider the liberation of sulfide particles as a requirement to define the grinding size reduction ratio, this is determined empirically, evaluating in which size a higher percentage of gold recovery is obtained. The methodology proposed in this paper constitutes a low cost analytical technique, using the free software IMAGE-J, to determine the appropriate liberation size for sulfide particles and associated gold particles, as well as the size distribution of gold ore particles. Additionally, the Molycop-Tools software was used to simulate the best grinding strategy based on the liberation results obtained. Through the methodology of automatic image analysis to determine the liberation degree of sulfides, the mineralogical characterization, and the recommendation of a metallurgical processing strategy for the gold-bearing ore based on steady-state simulations, it was possible to establish the appropriate parameters of ball mill grinding and gravimetric concentration of the Gualconda mine in the Department of Nariño, in order to improve the gold recovery and increase the plant capacity.En los procesos de beneficio del oro, el grado de reducción del tamaño de partícula está fuertemente influenciado por el tamaño y la forma de las especies minerales asociadas con los metales de importancia económica. La capacidad, el consumo de energía y los costos del procesamiento del mineral aurífero dependen principalmente de los parámetros operativos de los equipos de conminución y concentración gravimétrica; por lo tanto, es esencial caracterizar el grado de liberación de los minerales de interés en función del tamaño de partícula. Las plantas de beneficio mineral en pequeña escala generalmente no consideran la liberación de las partículas de sulfuros como un requisito para definir la relación de reducción del tamaño de molienda, esto se determina empíricamente, evaluando en qué tamaño se obtiene un mayor porcentaje de recuperación de oro. La metodología propuesta en el presente artículo constituye una técnica analítica de bajo costo, utilizando el software libre IMAGE-J, para determinar el tamaño de liberación apropiado para las partículas de sulfuros y las partículas de oro asociadas, así como la distribución de tamaño de las partículas oro. Adicionalmente, fue utilizado el software Molycop-Tools para simular la mejor estrategia de molienda basada en los resultados de liberación obtenidos. A través de la metodología del análisis automático de imágenes para determinar el grado de liberación de sulfuros, la caracterización mineralógica y la recomendación de una estrategia de procesamiento metalúrgico para el mineral aurífero basado en simulaciones en estado estacionario, fue posible establecer los parámetros apropiados de la bola molienda y concentración gravimétrica de la mina Gualconda en el departamento de Nariño, para mejorar la recuperación de oro y aumentar la capacidad de la planta. &nbsp

Incidence of rough and irregular atmospheric ice particles from Small Ice Detector 3 measurements

NERC, NE/E011225/1 © Author(s) 2013. This work is distributed under the Creative Commons Attribution 3.0 LicenseThe knowledge of properties of ice crystals such as size, shape, concavity and roughness is critical in the context of radiative properties of ice and mixed phase clouds. Limitations of current cloud probes to measure these properties can be circumvented by acquiring two-dimensional light scattering patterns instead of particle images. Such patterns were obtained in situ for the first time using the Small Ice Detector 3 (SID-3) probe during several flights in a variety of mid-latitude mixed phase and cirrus clouds. The patterns are analyzed using several measures of pattern texture, selected to reveal the magnitude of particle roughness or complexity. The retrieved roughness is compared to values obtained from a range of well-characterized test particles in the laboratory. It is found that typical in situ roughness corresponds to that found in the rougher subset of the test particles, and sometimes even extends beyond the most extreme values found in the laboratory. In this study we do not differentiate between small-scale, fine surface roughness and large-scale crystal complexity. Instead, we argue that both can have similar manifestations in terms of light scattering properties and also similar causes. Overall, the in situ data is consistent with ice particles with highly irregular or rough surfaces being dominant. Similar magnitudes of roughness were found in growth and sublimation zones of cirrus. The roughness was found to be negatively correlated with the halo ratio, but not with other thermodynamic or microphysical properties found in situ. Slightly higher roughness was observed in cirrus forming in clean oceanic airmasses than in a continental, polluted one. Overall, the roughness and complexity is expected to lead to increased shortwave cloud reflectivity, in comparison with cirrus composed of more regular, smooth ice crystal shapes. These findings put into question suggestions that climate could be modified through aerosol seeding to reduce cirrus cover and optical depth, as the seeding may result in decreased shortwave reflectivity.Peer reviewe

Influence of petrographic textures on the shapes of impact experiment fine fragments measuring several tens of microns: Comparison with Itokawa regolith particles

In 2010, fine regolith particles on asteroid Itokawa were recovered by the Hayabusa mission. The three-dimensional microstructure of 48 Itokawa particles smaller than 120 µm was examined in previous studies. The shape distribution of Itokawa particles is distributed around the mean values of the axial ratio 2:√2:1, which is similar to laboratory impact fragments larger than several mm created in catastrophic disruptions. Thus, the Itokawa particles are considered to be impact fragments on the asteroid's surface. However, there have never been any laboratory impact experiments investigating the shapes of fine fragments smaller than 120 µm, and little is known about the relation between the shapes of fine fragments and the petrographic textures within those fragments. In this study, in order to investigate the relation between the petrographic textures and the shapes of fine fragments by impacts, the shapes of 2163 fine fragments smaller than 120 µm are examined by synchrotron radiation-based microtomography at SPring-8. Most samples are fine fragments from basalt targets, obtained in previous laboratory impact experiments by Michikami et al. (2016). Moreover, two impacts into L5 chondrite targets were carried out and the shapes of their fine fragments are examined for comparison. The results show that the shape distributions of fine fragments in basalt targets are similar regardless of impact energy per target mass (in contract to the shape distribution of relatively large fragments, which are affected by impact energy), and are similar to those in L5 chondrite targets and Itokawa regolith particles. The physical process producing these fine fragments would be due to multiple rarefaction waves in the target. Besides, the petrographic textures do not significantly affect the shapes of fine fragments in our experiments. On the other hand, according to Molaro et al. (2015), the shapes of the fragments produced by thermal fatigue by the day-night temperature cycles on the asteroid surface are influenced by the petrographic textures. Therefore, we conclude that the Itokawa particles are not the products of thermal fatigue but impact fragments on the asteroid surface