Washing

washing

1. something, such as gold dust or metal ore, that has been obtained by washing

2. a thin coat of something applied in liquid form

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washing [′wäsh·iŋ]

(analytical chemistry)

In the purification of a laboratory sample, the cleaning of residual liquid impurities from precipitates by adding washing solution to the precipitates, mixing, then decanting, and repeating the operation as often as needed.

The removal of soluble components from a mixture of solids by using the effect of differential solubility.

(chemical engineering)

In a process operation, cleaning of a solids bed (settler) or cake (filter) with a liquid in which the solid is not soluble.

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Washing 

the process during which water is used to remove contaminating impurities, chiefly clayey impurities, from minerals. Impurities are first ground (usually by mechanical means), then converted into suspensions and finally drained from the mineral. Washing is used in the process of enriching minerals if seams, layers, lenses, and clay karsts are present in the mineral stratum under exploitation.

The plastic properties of a clayey impurity are characterized by the plasticity index and plasticity limit of the impurity; these indicators determine the washability of a material. Readily washable materials may be effectively washed (90 percent clay recovery) on screens using a combination of screening, washing, and dehydration. Trough-shaped, vibrating, and drum washers are utilized to wash materials exhibiting average, low, and very low washability. It is economical to use the dry method in extracting ball clay from materials with low washability. The particle size and content of clay determine when washing is to be introduced into the production process: given an impure raw material with a clay content of more than 10 percent, washing is conducted at the beginning of dressing after the first stage of crushing. Scrubbers and wash trommels are used for washing materials made up of large particles reaching 250 mm.

Fine materials, including those that are not classified, from 0 to 60 mm in size are washed in trough-shaped inclined or horizontal washers at the end of the production process. Sand with a particle size of 0–5 mm is washed in spiral classifiers. Materials should be premoistened in order to improve the effectiveness of washing.

REFERENCES

Sergo, E. E. Promyvka rud chernykh metallov. Moscow, 1963.
Troitskii, V. V., V. V. Oliunin, and M. G. Mikhal’chenko. Promyvka ne-
rudnykh stroitel’nykh materialov. Moscow, 1972.
Grocksch, R., and G. Paulisch. Aufbereitungsmaschinen. Berlin, 1954. (Baumaschinen—Handbuch, vol. l.)

V. V. OLIUNIN