REVERSIBLE FLOCCULATION AND REDISPERSION OF CHRYSOTILE ASBESTOS

A method of treating chrysotile asbestos comprises the preparation of an aqueous colloidal dispersion of up to 5% by weight chrysotile asbestos fibres, adjusting the pH to 6.0-10.5, therebc flocculating the asbestos fibres, filtering and drying these fibres. In the flocculation step, a water-soluble alkaline reagent is used to adjust the pH. Suitable materials are ammonium hydroxide, sodium hydroxide, sodium carbonate, sodium phosphate, potassium hydroxide, potassium carbonate, potassium hydroxide, potassium carbonate, and strontium hydroxide. The fibres can be redispersed by taking up to 5% by weight of filtered fibres and adding to water which contains no more than 100 p.p.m. of monovalent anions and no more than 10 p.p.m. of multivalent anions, such as deionized or distilled water. The dispersion is stable in the pH range 4.0 to 6.0. Adjustment of pH to this range may be made with any monobasic carboxylic acid having up to six carbon atoms or with inorganic acids such as nitrous or hydrochloric acid. Formic and acetic acid are the preferred organic acids.