METHOD FOR REMOVING CADMIUM FROM EXTRACTED RESIDUE SOLUTION OR REEXTRACTED RESIDUE SOLUTION

摘要

PURPOSE:To purifying a solution of phosphoric acid of wet type of extracting it with an organic solvent, to remove Cd readily without requiring water insolubilization newly, by diluting an extracted residue solution or reextracted residue solution with water at a specific temperature, carrying out pH adjustment and filtering off precipitated sediment. CONSTITUTION:Phosphoric acid of wet type obtained by decomposing ore of phosphorus with a mineral acid such as sulfuric acid, etc., is extracted with an organic solvent and purified. In the operation, the produced extraction residue solution or the reextracted residue solution obtained by reextracting the extracted residue solution is diluted with water while keeping it at =50 deg.C with stirring, pH is adjusted to 0.5-1.0 and precipitated sediment is filtered off. The precipitated sediment is a compound consisting essentially of cadmium phosphate and is water-insoluble so insolubilization is not required. According to this process, operation is simpler than the conventional method to use a water-soluble solfide and a device is also simple. Further, the separated Cd- containing compound requires no insolubilization newly and Cd can be simply removed.