| 摘要 |
<p>Wet process phosphoric acid, after filtering and cooling, is treated with finely powdered phosphate rock (phosphorite), CaSO4.2H2 to give an H2SO4 content of 1.4 plus-or-minus 0.2%, and with the precise quantity of Na ions, obtd. from a soluble salt, required to eliminate F- and SiO2 as Na2SiF6; the supersatd. suspension of the solids formed by the CaSO4.2H2O, Na2SiF6 and a small quantity of monocalcium phosphate dihydrate is maintained by vigorous agitation for >=8 hrs., and the purified phosphoric acid is sepd. from the sludge with opt. recovery of the phosphoric acid contained in the sludge. Very pure phosphoric acid is obtd. with a low content of organic material, SO4=, F-, SiO2, and Ca++.</p> |
