Chemical treatment of sand

#This invention relates to the chemical treatment of sand.

#Many techniques exist for the production of high quality silica sand and beneficiation methods are normally related to the level of contaminant in the raw material. Generally, the industrial processing routes follow a basic pattern and include the washing of sand by a variety of techniques. Essentially, the washing of sand is undertaken using simple settling cones, upward current washing or screw classifiers. Each of these techniques is normally employed to remove the finer fraction material and relies largely on differential settling based mainly on size distribution of mono-mineralic material. Further, as the product will be granular in a size range exceeding 75 .mu.m, settling will also remove the materials of low specific gravity such as clays and organic material.

#Numerous methods for the further treatment of sand have also been utilized using chemical and mechanical means.

#The invention will now be illustrated by the following Examples.

#The following process conditions were employed in the Examples

#A sample of raw sand was washed through an 18 mesh laboratory test sieve into a laboratory flotation cell and water was added until the pulp density was 20% solids by weight. Agitation of the pulp was carried out at 1700 rpm using the standard flotation assembly for a period of 2.5 minutes, after which time the agitation was ceased, the impeller assembly removed from the cell (any sand particles adhering to the unit were washed back into the cell). The suspension in the cell was allowed to settle for 30 seconds and then the supernatant liquor was decanted off--the settled sand was then washed by decantation with tap water for a further three times and the final washed sand was filtered. This washing procedure was repeated on several batches of sand in order to produce a large washed sample, which was carefully mixed to ensure homogeneity. A small sub-sample of the material was taken to provide a washed, chemically unprocessed head sample for chemical analysis.