Stimulant sensitive flocculation and consolidation
The present invention relates to methods for the separation of materials from heterogeneous fluids and provides a means of effecting stimulant-sensitive flocculation and consolidation of solid suspensions within a liquid medium. Specifically, the present invention provides a method of controlling the state of a suspension of solid particles in a liquid, including applying to the suspension a stimulus adapted to control inter-particle forces between the solid particles. The stimulus is reversibly operable to control attraction and/or repulsion. Means of consolidating a sediment bed and of separating the resultant liquids-rich and solids-rich phases are also within the ambit of the invention.
1. A method of controlling the condition of a suspension of solid mineral particles within a liquid by flocculation and/or coagulation, said method comprising contacting said solid mineral particles with a chemical additive consisting of a stimulus-sensitive polymer, the stimulus-sensitive polymer consisting of a polymer selected from the group consisting of a cationic, anionic, non-ionic, and a combined polyelectrolyte, and applying a stimulus, said polymer adapted to control inter-particle forces between said solid mineral particles in response to said stimulus, wherein said inter-particle forces consist of attraction and repulsion, and wherein said stimulus is selectively and repeatedly added and removed to effect reversibly operable conditioning between an initial state of said solid mineral particles and said polymer prevailing prior to applying said stimulus and a conditioned state resultant from applying said stimulus, thereby to control interaction between said solid mineral particles and said polymer within said liquid.
2. A method according to claim 1 , further comprising separating said solid mineral particles from the liquid after the method according to claim 1 for a predetermined time thereby to provide a solids-rich phase and a liquids-rich phase and then separating the solids-rich phase and the liquids rich phase.
3. A method of controlling the consolidation of a bed of solid mineral particles within a liquid by flocculation and/or coagulation, said method comprising contacting said solid mineral particles with a chemical additive consisting of a stimulus-sensitive polymer, the stimulus-sensitive polymer consisting of a polymer selected from the group consisting of a cationic, anionic, non-ionic, and a combined polyelectrolyte, and applying a stimulus, said polymer adapted to control inter-particle forces between said solid mineral particles in response to said stimulus, wherein said inter-particle forces consist of attraction and repulsion, and wherein said stimulus is selectively and repeatedly added and removed to effect reversibly operable conditioning between an initial state of said solid mineral particles and said polymer prevailing prior to applying said stimulus and a conditioned state resultant from applying said stimulus, thereby to control interaction between said solid mineral particles and said polymer within said liquid, said stimulus being applied for a predetermined time thereby to liberate at least some liquid otherwise trapped within said bed.
4. A method according to claim 3 , wherein said bed is a sediment bed, a filtercake, or the product of a centrifuge.
5. A method according to claim 1 or claim 3 , wherein said stimulus is applied for a predetermined time, thereby to induce the desired attraction or repulsion and is subsequently removed or altered, thereby to effect said reversibility.
6. A method according to claim 1 or 3 , wherein said polyelectrolyte is adsorbable onto the surface of said solid mineral particles as to create steric or electrostatic repulsion between said solid mineral particles.
7. A method according to claim 1 or 3 , wherein said polyelectrolyte is soluble at pH values where it is charged, thereby to effect dispersion of said suspension or wherein said polyelectrolyte is insoluble at pH values where it is uncharged, thereby to effect flocculation of said suspension.
8. A method according to claim 1 or 3 , wherein said polyelectrolyte is selected from the group consisting of chitosan, polyacrylic acid, polyacrylamides and derivatives thereof, polymethacrylic acid, poly sodium acrylate, polystyrene sulfanate, polysulfanamide, poly(2-vinyl pyridine), poly(vinylpyridinium bromide), poly(diallyldimethylammonium chloride)(DADMAC), poly(diethylamine), poly(epichlorohydrin), polymers of quarternised dimethylaminoethyl acrylates, polymers of quarternised dimethylaminoethyl acrylamides, poly(ethyleneimine), polyglucose amine, homo-and copolymers prepared from ethylenic unsaturated monomers including methacrylic acid and salts thereof, methacrylamide, acrylamido methyl propyl sulfonic acid (AMPS) and/or styrene sulfanate and salts thereof, xanthan, carragenan, agarose, agar, pectin, guar gum, starches, alginic acid, carboxy methyl cellulose and hydroxy propyl guar.
9. A method according to claim 3 , wherein removal of or a change in said stimulus provides for further settling/consolidation of said solid mineral particles within said bed.
10. A method according to claim 3 , wherein said polymer is added to a suspension prior to formation of said sediment bed, thereby to effect thorough mixing of said chemical additive within said bed.