THE IMPORTANCE AND CHEMICAL-MINERALOGICAL ANALYSIS OF “OSMONSOY” HEMATITE IN OBTAINING PIGMENT

ABSTRACT

This work involved research on hematite ore, a local natural mineral raw material that could be used in the production of ceramic pigment. The article focuses on the chemical-mineralogical state of hematite ore present in the Jizzakh region. Results of spectral analysis, X-ray diffraction analysis have been cited and studied. Based on the results of the analysis, it was argued that the ore content of "Osmonsoy" hematite was sufficient to contain iron (Ⅲ) oxide (Fe2O3), and its use in pigment synthesis could be promising.

АННОТАЦИЯ

Данная работа включала исследование гематитовой руды, местного природного минерального сырья, которое может быть использовано для производства керамического пигмента. В статье рассматривается химико-минералогическое состояние гематитовой руды, добываемой в Джизакской области. Приведены и изучены результаты спектрального анализа, рентгеноструктурного анализа. На основании результатов анализа было высказано предположение, что содержание гематита "Осмонсой" в руде было достаточным для содержания оксида железа (Ⅲ) (Fe2O3), и его использование в синтезе пигментов может быть перспективным.

Keywords: Ceramic pigment, hematite, spectral analysis, maghemite, amorphous silica.

Ключевые слова: керамический пигмент, гематит, спектральный анализ, маггемит, аморфный кремнезем.

1. Introduction.  In the production of ceramic products on an industrial scale, many natural and synthetic pigments are of great practical importance as coloring agents for glass, enamel and unglazed products.  Currently, many ceramic inorganic pigments are being prepared and have a wide range of applications, in particular, they are one of the necessary components for the production of traditional glazed and unglazed tiles.

When inorganic pigments are used for colored ceramic products, certain conditions are required[1-3], in particular, the pigment must be thermally stable to the firing temperature[4].   Among the synthetic inorganic ceramic pigments used in the ceramic industry, there is a limited selection for red-pink and orange colors (Cr-Sn-Ca-Si, Pb-Sb-Sn-Fe, Mn-Al systems).   They are generally easy to work with when glass is being processed, but can be sensitive to the atmosphere and high temperatures.

In recent years, interest in inclusive pigments has been developing. The main reason for this is that it makes coloring substances resistant to heat and chemical conditions in industry by introducing them into a stable vitreous or crystalline Matrix (heteromorph pigments) [4-6].

There has been much research on Iron (III) oxide. Iron (III) oxide (Fe₂O₃) has four polymorphic forms: α–Fe₂O₃, β–Fe₂O₃, γ–Fe₂O₃, and ε–Fe₂O₃[6]. Of particular importance among them are the forms α–Fe₂O₃ (hematite) and γ–Fe₂O₃ (maggemite).

Hematite occurs naturally as a crystalline mineral composed of Iron (III) oxide. It was also used by humans as a color pigment (red ocher) in burials dating to the Upper Paleolithic about 14,000 years ago[7-9]. They are often called ocher and have been used to discuss the antiquity of human symbolic behavior and for artistic purposes[10-15] it is found in sandstone, granite, quartzite or various metamorphic rocks. It is red in powder state as a pigment, but may vary in color when found in nature[16] Figure 1.

a                                                               b

     c                                                              d

Figure 1. Examples of Osmonsoy hematite. a, b) large samples c) granule d) powder state

Hematite is a cheap and low energy material in obtaining pigment [17-19]. In industry, large pieces are used mainly for the production of steel. Small pieces are used to obtain pigment in powder state. Samples of osmotic hematite X-ray diffraction results showed that there are sources of high-quality hematite in the Jizzakh region and that it is relevant to carry out studies to establish and improve the use of this material. One possible improvement is to increase the use of this material by establishing the production of pigments, which is due to the high demand for ceramic pigments and the relatively expensive cost.

The extraction of existing hematite raw material ores in the Jizzakh region is promising in obtaining pigment, and the chemical composition of the ore is mentioned in Table 1.

2. Research materials and methods.

The materials used in this research work are hematite from the "Osmonsoy" mine, limestone (CaCO₃), SiO₂ * nH₂O or microsilica (SiO₂) from Uzmetkombinat waste, boron oxide (B₂O₃).

When the physico-chemical properties of raw materials and minerals in this area are studied by X-ray phase and spectral analysis methods, it can be seen that they are sufficiently saturated with iron (III) oxide for the production of red ceramic pigment.

Table 1.

Chemical composition of the mineral hematite Osmonsoy mine

Figure 2. Spectral analysis of hematite ore

Preparation of samples. The hematite mineral was ground to a size of 0.1 mm in a ball mill. The oxides of limestone, SiO₂ * nH₂O and amorphous silicon (ⅳ) were ground separately. The components were pulled in proper proportions, and the samples were prepared at 900-1300° C by the traditional cooking method in an electric oven for 240 minutes (heating and cooling rate 20°C/min). Ready-state SiO₂ * nH₂O or amorphous silicon ( ⅳ ) oxide is used in order to accelerate reaction progress and increase surface area. For the purpose of tempering, B2O3 was added to the mass in an amount of 2%. The temperature was systematically raised and proportionally lowered [20].

X-ray diffraction lines were obtained using the traditional powder method in Cu K_α-filter radiation (λ = 0.154 nm) to determine the crystalline phases present in raw and matured samples.

X-ray diffraction patterns of pigments show that with an increase in the content of chromophores in pigments, the intensity of diffraction reflections decreases. This is due to a violation of symmetry and a violation of the crystal lattice when introducing coloring ions into the structure and the formation of solid solutions.

Figure 3. X-ray image of the hematite mineral from the Osmonsoy mine

Figure 4. X-ray images of 3CaO*Fe₂O₃*3SiO₂ ceramic pigments at different temperatures: 1000°C (A) and 1100°C (B)

3. Discussion. An X-ray of the mineral Osmonsoy hematite shows the presence of oxides Si, Fe, Al, Ca, Mg, and they are of sufficient composition in pigment synthesis. Samples cooked at different temperatures can be seen to produce mineral phases from X-ray diffraction maximums such as andradit, vallostanite, cristobalite, which imposes a color characteristic on the pigment.

Conclusion. In summary, pigments based on hematite (3CaO*Fe₂O₃*3SiO₂) were successfully prepared using a solid-state reaction method, derived from an Uzmetkombinat waste as a Silicon source, and a calcium source from limestone and using the mineral hematite. The resulting red pigment is suitable for painting ceramic tiles. However, the presence of impurities in the composition, the color intensity is not as strong as pigments, which are usually made with high purity oxides. Nevertheless, in terms of practical importance, the red color of the pigment obtained from industrial waste has a good effect compared to the pigment obtained from pure oxides. The results of the analysis showed that the synthesized pigments have good chemical and thermal stability at high temperatures. This work proved that it was possible to obtain a promising calculated ceramic pigment based on waste and local raw materials.

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