Optimization and evaluation of the method for the determination of the manganese content in manganese ores and concentrates as described in ISO 4298:1984

It has been 36 years since ISO 4298:1984 was published, yet the role of sodium pyrophosphate in the oxidation of manganese(II) by potassium permanganate in this standard has not been fully recognized. The sample and reagent dosages exceed the actual detection needs, which creates challenges in the test operation and waste liquid treatment. In this study, a more scientific expression for the principle and reaction and the dosage of pyrophosphate in ISO 4298:1984 are discussed. The pyrophosphate ligand is involved in the oxidation of manganese(II) by potassium permanganate, and plays a role in preventing Mn(II) precipitation or Mn(III) dismutation during the whole reaction. The most appropriate amount of saturated sodium pyrophosphate is 150 mL for the test of manganese ores and concentrates with manganese content from 15% to 60%. The method developed by reducing sample size and reagent consumption was evaluated with ten certified reference materials, showing high accuracy and meeting the analytical performance requirements. These results can provide technical support for the revision of ISO 4298:1984.