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US 6,280,630 B1Granted
Process for the treatment of effluent streams
AssigneeMintek
InventorJames Ian Ramsay
Life of this patent
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Abstract
This invention relates to a process for removing sulphates and calcium from a water stream which includes the steps of: combining the water stream and an amount of amorphous aluminum trihydroxide (Al(OH)3); allowing the formation of ettringite (3CaO.Al2O3.3CaSO4.31/32H2O) as a precipitate; and removing the precipitated ettringite from the water stream.
Claims22
A process for the removal of sulphates and calcium from a water stream, said process comprising the steps of:
- (a) adding an alkali to the water stream to raise the pH of the water stream to between 11 and 12.6;
- (b) combining the water stream with amorphous aluminum trihydroxide (Al(OH)3) to cause formation of ettringite (3CaO.Al2O3.3CaSO4.31/32H2O) as a precipitate;
- (c) removing the precipitated ettringite from the water stream;
- and
- (d) decomposing the removed ettringite to recover amorphous aluminum trihydroxide, said decomposing comprising (a) treating the ettringite with a saturation calcium sulphate solution in an amount sufficient to form a suspension of amorphous aluminum trihydroxide in a supersaturated solution of calcium sulphate and (b) recovering the suspended amorphous aluminum trihydroxide while leaving the calcium sulphate remaining in the supersaturated solution.
2 more elements
Dependencies are inferred from the claim text.