Derivatography is a method of water structure study on solid mineral surfaces


The current issue with the dewatering and fine dispersing materials process intensification is the development of reliable methods for valuing the water structure on solid mineral surfaces, especially coal surfaces. The question of correlation between the amount of superficial moisture that can be mechanically removed stands especially rough, and that which is not removable by mechanical methods – filtration, centrifugal, etc. The last one is presented by the structured (limited) pellicles.

Previously, this issue was investigated by a group of authors (Bochkov 1996, Bejlin 1969, Ivanova 1974, Derivatogramms 1992, Kazanskij 1961, and Deriagin 1989), however, the distinction between qualitative and quantitative estimation of pellicle moisture remains ambiguous. Today, there are several quantitative estimation methods for different types of moisture. There are methods for efficiently determining strongly combined (hygroscopic) moisture, for example according to GOST 8719-70 and its equivalents. For other moisture forms, the lack of clear boundaries between separate moisture types leads to difficulty in quantitative appreciation.

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Secondly, there is an attempt to identify moisture types and their quantitative determination, which was made by Bejlin 1969 and Kazanskij 1961 with the help of isothermal drying thermograms of silica gel. According to M.I. Bejlin (Bejlin 1969), thermo-grams allow to differ various kinds of capillary moisture: “internal capillary moisture” (moisture of capillary escalation); capillary joint moisture and hyal The identification of moisture that is strongly combined is a challenging task in the context of non-clear thermo-grams bends in mineral system drying. Today, the only method of moisture determination that is not dependent on mechanical methods is the method of maximum molecular moisture capacity (MMMC) (Bochkov 1996) What is widely used in theory and practice? This method is an integral estimation of the moisture content of row species, including but not limited to capillary, internal, and partly external, film moisture, which cannot be extracted mechanically.

The estimation of their differential using the MMMC method is unfeasible. Despite having a tangible and practical significance, this technique is ineffective for the theoretical analysis of diverse moisture types. Therefore, our brief survey demonstrates the existence of distinct methods for estimating diverse moisture types and the limitations of their utilization. Simultaneously, the moisture pellicle that is commonly referred to as "thin" and "thick" (without referring to their potential constituents) cannot be identified by conventional methods, despite their apparent differences in the energy of contact with a hard surface (Deriagin 1989)

The exposure of fundamental materials.
On the practice of physical-chemical investigations of minerals and especially coal, the method of derivatography is widely used (Ivanova 1974 and; Derivatogramms 1992) One of its functions pertains to the determination of moisture and hydroxides content in minerals, as stated by Derivatogramms in 1992. We offered derivatography as a method for estimation of water phase structure on coal surface. For this purpose, coal analytical samples of stamp " (fat)" from mine Samsonivska-Zahidna #1 were investigated with ash content 9.5% During one month, fresh coal crashed and oxidized on air by 20 o was used. For the purposes of coincidence determination, experiments were duplicated. For moisturizing, coal had been used, with water pH 7.

The maximums of water evacuation for samples exhibit significant variations in terms of intensity, configuration, and particularly the extent of symmetry and area under curves. Let us discuss this characteristic in greater detail. The intensity of DTG peaks determines the maximum speed of moisture removal, and the area under the curve indicates the mass of moisture that is removable. The effect of non-symmetry is related to the presence of different moisture types on the coal surface. Since different kinds of moisture have different energy of connection with the solid surface, they are removed at different temperature intervals. Particularly in this location, distinct temperatures occur, which correspond to the maximum rate of moisture removal for various types of moisture (the points on the basic line that correspond to the tops of peaks) Every kind of moisture is characterized by its own peak of moisture removal, and their overlap leads to non-symmetric peaks on DTG. Therefore, it is possible to identify separate moisture forms by decomposing non-symmetric peaks of DTG into Gauss curves. We will analyze these peaks of moisture-removing using DTG curves.

The moisture-removing peak for air dry coal (sample 1, Figure 2a) exhibits a small intensity and soft fronts of DTG, which are practically symmetric. The last, obviously, attested to a homogeneous water structure, which in this case represents only as pellicle moisture. The small intensity (amplitude) and some plane of peak leads to a low rate of moisture removal. This is precisely characterized for strongly combined moisture. Additionally, the maximum rate of moisture-removing is observed at higher temperatures (135 o), which also testifies the highpower connection of contacting phases “watersolid”.

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