| 摘要 |
<p>A method for purification of phosphoric acid, characterized as comprising contacting a crude phosphoric acid containing arsenic with hydrogen halide to remove the arsenic from the crude phosphoric acid; and a method for purification of phosphoric acid, characterized as comprising contacting a crude phosphoric acid containing arsenic with hydrogen halide in the presence of a compound which can produce hydrogen halide under an acidic condition. The above methods provide novel methods for removing arsenic from a crude phosphoric acid which does not require any of a filtering and a degassing processes which are necessary in the sulfide precipitation method, does not give a large amount of residual sodium, can be applied to a crude phosphoric acid having a high concentration of phosphorus pentoxide, particularly to polyphosphoric acid, and can be practiced at a low cost; and thus they can be used for producing a high purity polyphosphoric acid having an arsenic (As) content of 1 ppm or less and also low contents of heavy metals, silica, sodium and the like.</p> |
