초록 ▼

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).sub.3); allowing the formation of ettringite (3CaO.Al.sub.2 O.sub.3.3CaSO.sub.4.31/32H.sub.2 O)

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).sub.3); allowing the formation of ettringite (3CaO.Al.sub.2 O.sub.3.3CaSO.sub.4.31/32H.sub.2 O) as a precipitate; and removing the precipitated ettringite from the water stream.

대표청구항 ▼

[ What is claimed is:] [1.]1. 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 trihyd

[ What is claimed is:] [1.]1. 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).sub.3) to cause formation of ettringite (3CaO.Al.sub.2 O.sub.3.3CaSO.sub.4.31/32H.sub.2 O) 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.