Abstract: A process for the treatment of phosphoric acid plant pond water where an increased recovery of phosphorus values from the input pond water is achieved through the dilution of the initial pond water with clarified water from the product generation stage and/or the final stage clarified water. The recycle of the product generation stage and/or final stage waters to dilute the feed pond water mitigates or eliminates the problems of silica gel formation and precipitation that occur when undiluted pond waters are processed. In addition, the dilution reduces phosphate losses in the first liming or neutralization stage rejected solids thereby increasing the yield of Di-Calcium Phosphate or ammonium magnesium phosphate or potassium magnesium phosphates.

Abstract: A process for the treatment of phosphoric acid plant pond water facilitating the recovery of phosphorus values from the input pond water. In certain aspects the process recycles solids from a later stage neutralization and separation into the clarified liquid stream from an initial clarification and neutralization stage. A sufficient amount of solids are added to the clarified liquid stream to effect the pH-dependent precipitation of a phosphate product. In alternative aspects an intermediate pH-dependent precipitation of a phosphate product is achieved through the addition of a neutralizing agent. The phosphate product is further characterized by a low concentration of fluoride. In addition the phosphate product can be further processed to a high purity technical grade phosphoric acid. In certain aspects the process employs flocculating agents to enhance the formation of precipitates. In further aspects, methodologies taught herein facilitate the reduction of silica in the process streams.

Abstract: A process for the partial purification of contaminated phosphoric acid plant pond water is described, in which the pond water is treated sequentially, with two basic compounds, clarified, aged, clarified again and re-acidified. The thus treated pond water, still containing the majority of the phosphate originally present, can then be concentrated via the removal of essentially pure water, using any conventional means of concentration, without the formation of solid precipitates.

Abstract: A simplified process for the partial purification of contaminated phosphoric acid plant pond water having a molar calcium plus magnesium to fluorine ratio greater than or equal to about 0.60, is described, in which the pond water is treated with a basic compound, clarified, aged, clarified again and re-acidified. The thus treated pond water, still containing the majority of the phosphate originally present, can then be concentrated via the removal of essentially pure water, using any conventional means of concentration, without the formation of solid precipitates.

Abstract: A process for the partial purification of contaminated phosphoric acid plant pond water is described, in which the pond water is treated sequentially, with two basic compounds, clarified, aged, clarified again and re-acidified. The thus treated pond water, still containing the majority of the phosphate originally present, can then be concentrated via the removal of essentially pure water, using any conventional means of concentration, without the formation of solid precipitates.

Abstract: The present process stabilizes merchant acid from bottoms solutions against post-precipitation by heating the acid to a temperature of at least about 180.degree. F. for about 12 to about 48 hours. The stabilized acid product exhibits less than about 1 wt % solids precipitation after even 14 days of standing at about 70.degree. F.

Abstract: A method for defluorinating wet process phosphoric acid. Phosphatic waste clay from phosphate rock beneficiation is mixed with the wet process phosphoric acid. The mixture is heated for a time sufficient to remove fluorine from the acid as gaseous silicon tetrafluoride. Phosphate is liberated from the phosphatic waste clay and thus is recovered in the defluorinated wet process phosphoric acid.

Abstract: An improved process for the thermal defluorination of phosphate rock is provided. The process comprises adding ammonia to the phosphoric acid fed to the kiln, the amount of ammonia added being effective for forming a eutectic with the fused ring and ball materials and heating the mixture with agitation to defluorinating temperatures for a period of time sufficient to defluorinate the rock and recovering the defluorinated rock.

Abstract: A method of removing aluminum, magnesium, iron and other impurities from wet process phosphoric acid is provided. The method comprises partially ammoniating the acid and reacting the acid with a fluoride ion donating compound to precipitate aluminum- and magnesium-containing ralstonite and ammonium fluorosilicate which can be easily separated from the acid thereby producing a partially ammoniated wet process phosphoric acid of reduced impurities content.

Abstract: An improved method of defluorinating wet process phosphoric acid using silica-containing dust which is obtained as a waste product collected from the fumes of a submerged arc furnace process of making silicon metal alloys. The silica-containing dust has a very small particle size, and contains at least about 60% by weight silica (SiO.sub.2), and has a very high surface/mass ratio which increases the efficiency of the defluorination reaction.The defluorination reaction using this silica-containing fume takes less time than required using prior methods employing diatomaceous earth as the silica source. The presence of silicon metal alloy particles in the dust are thought to have a catalytic effect on the defluorination reaction.