Aqueous phosphate-stabilized polyaluminum sulfate solutions and preparation thereof

A process for preparing an aqueous chloride-free, phosphate stabilized polyaluminum sulfate solution, useful as a coagulant in water treatment, having the formula:

• Al(OH.sub.x)(SO.sub.4).sub.y (H.sub.2 PO.sub.4).sub.z
• wherein
• x is about 1.2 to 1.62;
• y is about 0.595 to 0.87;
• and
• z is about 0.06 to 0.19,
• comprising blending an overbasified aqueous chloride-free phosphate-stabilized polyaluminum sulfate solution with an aqueous chloride-free, alum solution, with the proviso that the sum of x+2y+z is 3.

A process for preparing an aqueous chloride-free, phosphate-stabilized polyaluminum sulfate solution, useful as a coagulant in water treatment, of a composition having the formula:

• Al(OH).sub.x (SO.sub.4).sub.y (H.sub.2 PO.sub.4).sub.z
• wherein
• x is about 1.2 to 1.62;
• y is about 0.595 to 0.87;
• and
• z is about 0.06 to 0.19
• which comprises:
• reacting Al.sub.2 O.sub.3.nH.sub.2 O, wherein n is at least 3, with chloride-free phosphoric acid, in a ratio of about 3 to 10 moles of H.sub.3 PO.sub.4 per mole of Al.sub.2 O.sub.3.nH.sub.2 O;
• and
• mixing the resultant reaction product with an aqueous chloride-free polyaluminum sulfate solution, with the proviso that the sum of x+2y+Z is 3.

A process for preparing aqueous phosphate-stabilized polyaluminum sulfate/chloride solutions, useful as a coagulant in water treatment, comprising

• blending an aqueous chloride-free phosphate-stabilized polyaluminum sulfate solution of a composition having the formula
• Al(OH).sub.x (SO.sub.4).sub.y (H.sub.2 PO.sub.4).sub.2
• wherein
• x is about 1.2 to 1.62;
• y is about 0.595 to 0.87;
• and
• z is about 0.06 to 0.19
• with the proviso that the sum x+2y+7 is 3, with an aqueous aluminum trichloride solution .