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(1) Washing: Mercury pastes, especially those obtained by mercury traps and amalgamation cartridges, often contain a large amount of heavy sand, gangue and other impurities, which must be washed and removed.
The mercury paste obtained from the mercury-mixing cylinder is usually washed with a sharp-bottomed gold pan, and the mercury paste is separated from the heavy sand by the density of the specific gravity sand.
The mercury paste scraped from the mercury-mixed plate is relatively clean and the washing is carried out on a rectangular table. Laying thin copper plate mesa, the mesa four weeks 20 to 30 mm high nailed strips of wood, to prevent the mercury spill out during operation. The mercury paste is first placed in a porcelain dish and repeatedly rinsed with water, and the operator wears gloves repeatedly to make it possible to wash out the impurities in the mercury paste to the greatest extent possible. Washing is continued until the amalgam is bright and clean.
(2) Pressure filtration: The washed mercury paste still contains a large amount of excess mercury. The purpose of pressure filtration is to remove this mercury.
Filter press equipment depends on the scale of production. The production scale is small, and manual pressure filtration can be used. That is, the mercury paste is wrapped with a filter cloth and manually squeezed to recover excess mercury outflow. If the production scale is large, it will be filtered by a screw press, and the mercury solution by pressure filtration will contain 0.1%~2% of gold, which can be used for amalgamation. The filter cake is sent to the distillation.
(3) Distillation: The mercury paste after pressure filtration still contains a considerable amount of mercury (20% to 50%), some of which are filtered and unfiltered mercury, and the other part forms a solid solution with gold. To remove this mercury, it must be used. The method of distillation. Distillation is based on the boiling point of the mercury paste (357 ° C), which is much lower than the gold melting point (1064 ° C) and the boiling point (2860 ° C). When the temperature exceeds the boiling point of mercury, the mercury is vaporized and sublimated from the mercury paste. After sublimation of mercury, the spheroidal droplets are dripped into the container and recovered. The distillation time is about 5 to 6 hours.
Distillation equipment depends on the scale of production. A small-scale available distillation tank, a large-scale available distillation furnace.
The distilled mercury paste becomes sponge gold, which remains in the solid state in the distillation apparatus and still contains some non-volatile impurities.
Pretreatment of mercury amalgam
Mention amalgamation gold amalgam products are obtained, the excess amalgam containing mercury and other impurities. The purpose of amalgam treatment is to remove impurities, extract gold and recover mercury. Processing operations generally include the following three steps: