Negev Phosphates Ltd.

Menachem Bar-on

Alexander Iosef

Dagobert Kellerman

Iosef Alexander

Jacob Oren

The present invention relates to a process for the manufacture of disodium phosphate of a high purity without utilizing organic solvents. According to the process, monosodium sulfate is reacted, at a temperature, in the range of 40 to 100 degrees C. with a phosphate constituent selected from phosphate rock, dicalcium phosphate or mixtures thereof, in the presence of phosphoric acid. The common metal impurities, organic matter and fluorides present in the starting phosphate rock are substantially complete eliminated with the solid gypsum or dicalcium phosphate resulted thereto. After separating said solid, the filtrate is treated in two neutralization stages: first by a calcium constituent selected from calcium carbonate, calcium hydroxide or mixtures thereof and separating the formed dicalcium phosphate, followed by a second neutralization with an alkali sodium constituent selected from sodium hydroxide, sodium carbonate and sodium bicarbonate or mixtures thereof at a pH in the range of 8.0 to 9.5. From the resulted filtrate, pure disodium phosphate is obtained by crystallization. The process is characterized by a high recovering of the P.sub.2 O.sub.5 and Na.sub.2 O values, the resulted product being substantially free of chloride ion.

Process for the manufacture of disodium phosphate

The present invention relates to a process for the manufacture of monopotassium phosphate of a high purity without utilizing organic solvents. According to the process, monopotassium sulfate is reacted, at a temperature in the range of between 40 to 100 degrees with a phosphate constituent selected from phosphate rock, dicalcium phosphate or mixtures thereof in the presence of phosphoric acid. The common metal impurities, organic matter and fluorides present in the starting phosphate rock are substantially elininated, with the calcium sulfate resulted thereto. After separating out the calcium sulfate, the filtrate is neutralized to a pH in the range of between 3 to 7, with a calcium-containing compound comprising Ca(OH).sub.2, CaO or CaCO.sub.3, or mixtures thereof. From the filtrate obtained, pure monopotassium phosphate is crystallized out. The process is characterized by a high recovery of the P.sub.2 O.sub.5 and K.sub.2 O values, the monopotassium phosphate produced being completely free of chloride ion.

Process for the manufacture of monopotassium phosphate

The present invention relates to an improved process for the manufacture of purified phosphoric acid from phosphate rock. According to the invention, phosphate rock is decomposed by a mineral acid selected from hydrochloric acid, sulfuric acid or mixtures thereof. The dissolution liquor obtained is reacted with a calcium-containing compound such as calcium oxide, calcium carbonate, tricalcium phosphate and fines of phosphate rock producing an aqueous solution containing monocalcium phosphate in an amount corresponding to between 0.4% to 5.5% by wt CaO. After the separation of the precipitated solids, the clarified solution is extracted by an organic solvent having the property to extract the phosphate component. The phosphoric acid is subsequently recovered from the solvent extract by known methods such as washing or distillation.

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