Negev Phosphates Ltd.

Iosef Alexander

Menachem Bar-on

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.

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Arad, Israel

Iosef Alexander