| 摘要 |
<p>A process is claimed for prodn. of low fluorine content alkali phosphate solns. from pre-purified alkali phosphate solns.. The pre-purified soln. is obtd. by extn. of raw phosphoric acid with a water-immiscible organic solvent, washing the raw extract with water or alkali soln., back-extracting phosphoric acid from the extract with aq. alkali soln. at an alkali:P mol. ratio of at least 1:1, and sepg. the organic phase. - The novel step of obtaining the low fluorine content soln. comprises stirring the pre-purified soln. with an alkaline earth metal (Me2+) cpd., having a water solubility (at 20 deg. C) of more than 0.01 mol. Me2+/l. (cpds. of water solubility less than 5 g/l being used in a particle size of more than 50% below 8 microns), at 60-120 deg. C for 0.5-4 hrs. and then sepg. the resulting ppte. The alkaline earth cpd., needed for this step, is suspended or dissolved in the alkali soln. used in the back-extraction step and the reaction of this step is effected in the mixing zone of the back-extraction appts..</p> |
