Metallic ion removal from phosphoric acid
AssigneeOccidental Chemical Corporation
InventorHarold E. Mills
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Abstract
Metal ion impurities are removed from phosphoric acid by adding to the acid a precipitant comprising ions of calcium and fluorine to cause precipitation of a fluoride solid which contains ions of magnesium, and other metals (e.g., Al, N.sub.a) which were in the impure acid. A preferred precipitant comprises calcium fluoride, such as the sludge obtained by treating pond water from a phosphoric acid plant with calcium ions (e.g. lime and/or limestone).
Claims21
A process for the removal of at least one metallic ion impurity from phosphoric acid comprising the steps of:
- (a) adding to the acid a sludge precipitant comprising at least 50% by weight calcium fluoride on a dry basis;
- (b) allowing the formation of a precipitate containing the impurity;
- and
- (c) separating the precipitate from the acid.
Process for removal of magnesium ions from impure wet process phosphoric acid, said process comprising
- adding to the acid a precipitant comprising the sludge comprising calcium and fluoride ions obtained by addition of calcium ions to a fluoride containing pond water, said sludge also containing compounds of phosphorous, magnesium, iron, aluminum, sodium, silica and sulfur and, having a weight ratio MgO to F in the range of about 1 to 23 to about 1 to 260 and a molar ratio of calcium to fluorine of about 1:2;
- maintaining said acid, after adding said precipitant, at a temperature in the range of about 115.degree. to 160.degree. F. for sufficient time to permit a precipitate to form;
- and,
- separating said precipitate from the purified acid.
A process for removing magnesium ions and aluminum ions from phosphoric acid comprising the steps of:
- (a) treating phosphoric acid containing aluminum and magnesium ions by adding to the phosphoric acid a wetted precipitant comprising calcium and fluorine in a molar ratio of fluorine to calcium of about 2:1 in an amount sufficient to yield a molar ratio of fluorine ions to magnesium ions in the treated phosphoric acid mixture of from 3.8 to 5;
- (b) maintaining the treated phosphoric acid at an elevated temperature for a sufficient time to form a precipitate containing magnesium and aluminum;
- and
- (c) separating formed precipitate from the treated phosphoric acid.
A process for removing impurities from wet process phosphoric acid comprising 38 to 54% by weight P.sub.2 O.sub.5, 0.3 to 1.75% by weight MgO, as well as sodium, iron, and aluminum, comprising the steps of:
- (a) precipitating sludge from a fluoride containing wet process phosphoric acid plant pond water by adding a calcium compound to the pond water, the sludge comprising calcium and fluoride ions in a molar ratio of calcium to fluoride ions of about 1:2, and also containing compounds of phosphorus, magnesium, iron, aluminum, sodium, silica and sulfur, and having a weight ratio of MgO to F in the range of about 1:23 to about 1:260;
- (b) treating the phosphoric acid by combining the phosphoric acid with a sufficient quantity of such sludge for forming a precipitate;
- (c) maintaining the treated phosphoric acid at a temperature in the range of about 115.degree. to 140.degree. F. for a period of time in the range of about 2 to 6 days for forming a precipitate comprising sodium, aluminum, and magnesium;
- and
- (d) removing formed precipitate from the phosphoric acid.
Dependencies are inferred from the claim text.