Recovery of calcium fluoride from phosphate operation waste water

A method of recovering calcium fluoride from pond waters comprising from about 0.1 to about 5.0% fluorine, from about 0.1 to about 5.0% P.sub.2 O.sub.5, from about 0.1 to about 2.5% SiO.sub.2, from about 0.1 to about 0.5 dissolved calcium, from about 0.1 to about 0.5% soluble sulfate salts, and soluble metallic compounds of iron, aluminum, and magnesium, said method comprising the steps of:

• (a) adding with agitation to the pond water calcium carbonate in sufficient amounts so that between about 0.3 to about 0.8 equivalent of calcium is added per equivalent of fluorine whereby soluble calcium salts are formed;
• (b) adding, with agitation to the calcium carbonate treated pond water of step (a), additional aounts of calcium carbonate corresponding to about 0.1 to about 2.0 equivalents of calcium per equivalent of fluorine so that the total calcium equivalent added in steps (a) and (b) is from about one to about two;
• whereby solids are formed comprising calcium fluoride, calcium phosphate, and silicon, iron, aluminum and magnesium values;
• (c) separating the solids from the pond water, said solids containing at least 85% of the initial fluorine present in the pond water as calcium fluoride;
• and
• (d) purifying the calcium fluoride in the solids by treating the solids with an aqueous mineral acid to remove the acid soluble values therefrom and thereby yielding mineral acid washings, and thereafter washing the acid treated solids with water to remove the mineral acid and the water soluble values therefrom thereby yielding water washings and resulting in solids containing up to about 45% fluorine as calcium fluoride.

A method of recovering calcium fluoride from pond water comprising from about 0.1 to about 5.0% fluorine values and from about 0.1 to about 5.0% P.sub.2 O.sub.5 values comprising the steps of:

• (a) adding with agitation to the pond water calcium carbonate in sufficient amounts such that between about 0.3 to about 0.8 equivalent of calcium is added per equivalent of the fluorine values whereby soluble calcium salts are formed;
• (b) adding, with agitation to the calcium carbonate treated pond water from step (a), additional calcium carbonate corresponding to about 0.1 to about 2.0 equivalents of calcium per equivalent of the fluorine values present in the pond water to form solids containing calcium fluoride and calcium phosphate values, such that the total equivalent of calcium added in steps (a) and (b) is no less than about 0.8 equivalent per equivalent of fluorine values in the pond water, provided that when the total equivalent of calcium added in steps (a) and (b) is about 0.8, the amount added in step (a) is less than the total amount added in step (a) and step (b);
• and
• (c) separating solids from the pond water, said solids containing the major part of the initial fluorine values in the pond water as calcium fluoride.

A method of recovering calcium fluoride from pond water comprising from about 0.1 to about 5.0% fluorine values and from about 0.1 to about 5.0% P.sub.2 O.sub.5 values comprising the steps of:

• (a) adding with agitation to the pond water a calcium containing compound selected form the group consisting of calcium carbonate, calcium oxide, and combinations thereof in sufficient amounts such that between about 0.3 to about 0.8 equivalent of calcium is added per equivalent of the fluorine values whereby soluble calcium salts are formed;
• (b) adding, with agitation to the treated pond water from step (a), additional calcium containing compound selected from the group consisting of calcium carbonate, calcium oxide, and combinations thereof corresponding to about 0.1 to about 2.0 equivalents of calcium per equivalent of the fluorine values present in the pond water to form solids containing calcium fluoride and calcium phosphate values, such that the total equivalent of calcium added in steps (a) and (b) is no less than about 0.8 equivalent per equivalent of fluorine values in the pond water, provided that when the total equivalent of calcium added in steps (a) and (b) is about 0.8, the amount added in step (a) is less than the total amount added in step (a) and step (b);
• (c) separating solids from the pond water, said solids containing the major part of the initial fluorine values in the pond water as calcium fluoride;
• and
• (d) purifying calcium fluoride in the solids recovered in step (c).

A method of recovering calcium fluoride from pond water comprising from about 0.1 to about 5.0% fluorine values and from about 0.1 to about 5.0% P.sub.2 O.sub.5 values comprising the steps of:

• (a) adding with agitation to the pond water a calcium containing compound selected from the group consisting of calcium carbonate, calcium oxide, and combinations thereof in sufficient amounts such that between about 0.3 to about 0.8 equivalent of calcium is added per equivalent of the fluorine values whereby soluble calcium salts are formed;
• (b) adding, with agitation to the treated pond water from step (a), additional calcium containing compound selected from the group consisting of calcium carbonate, calcium oxide, and combinations thereof corresponding to about 0.1 to about 2.0 equivalents of calcium per equivalent of the fluorine values present in the pond water to form solids containing calcium fluoride and calcium phosphate values, such that the total equivalent of calcium added in steps (a) and (b) is no less than about 0.8 equivalent per equivalent of fluorine values in the pond water, provided that when the total equivalent of calcium added in steps (a) and (b) is about 0.8, the amount added in step (a) is less than the total amount added in step (a) and step (b);
• (c) separating solids from the pond water, said solids containing the major part of the initial fluorine values in the pond water as calcium fluoride, said solids containing from about 15 to about 35% fluorine;
• and
• (d) purifying calcium fluoride in the solids recovered in step (c) by treating said solids recovered in step (c) with an aqueous solution of a mineral acid to remove acid soluble values therefrom and thereby yielding aqueous mineral acid washings, and thereafter washing such acid treated solids with water to remove mineral acid and water soluble values therefrom thereby yielding water washings and resulting in solids containing up to about 45% fluorine as calcium fluoride.