| 摘要 |
<p>An aqueous solution of phosphoric acid is clarified by treating the solution with a reducing agent capable of converting Fe, V, Cr and As to their lower valency and insoluble states, a flocculating agent and fine crystals of calcium or barium sulphate in such amount that a homogeneous slurry is obtained, and then separating the solution thus clarified from the solid material of the slurry. The reducing agent is preferably an alkali metal or alkaline earth metal sulphide, a hydrosulphite, a thiosulphate, Al, Zn, Mg or Fe in subdivided form, hydrazine or hydroxylamine. The flocculating agent is preferably a resin which is stable in the presence of the solutions undergoing treatment and preferably in an acid medium, up to 60 DEG C., e.g. an acrylic resin. An adsorbent material e.g. a bleaching earth, active carbon, an adsorbent resin or an organic chelating agent, may also be added to the solution to be clarified.</p> |
