Determination of Ferrous Ion in Hydrometallurgical Leach Liquors

Significance of the Topic

Determination of ferrous iron in hydrometallurgical leach liquors is critical for process control and quality assurance in metals extraction. Accurate Fe(II) measurement ensures optimized recovery, reduced reagent consumption and reliable monitoring of redox conditions throughout leaching operations.

Study Objectives and Overview

This application note describes a standardized titrimetric method to quantify Fe(II) in acidic leach solutions. The procedure employs potassium dichromate as titrant and relies on an exothermic endpoint detection to deliver precise, reproducible results suitable for industrial and research laboratories.

Methodology

The assay begins with aliquoting 15 mL of sample into a polypropylene titration cell, followed by addition of 5 mL sulfuric acid (25% v/v) and 10 mL deionized water. After mixing, the solution is titrated with 0.1 mol/L K2Cr2O7 at 4 mL/min. Reaction stoichiometry: one mole dichromate oxidizes six moles ferrous ion under acidic conditions, releasing heat to signal the endpoint.

Instrumentation

• Automated titrator equipped with an exothermic endpoint sensor
• Volumetric glass pipette and polypropylene titration tubes
• Magnetic stirring at speed setting 8
• Data smoothing factor set to 50
• Delay before titration start: 10 seconds

Results and Discussion

Using a sample containing Fe(II) alongside Fe(III), Mg, Al, Mn, Cr, Cu, Co and Ca, the method yielded an average Fe(II) concentration of 10.66 ± 0.02 g/L (n=5). The single exothermic endpoint provided clear differentiation even in the presence of potential interferents. The calculated iron content closely matched expected values, demonstrating method accuracy and robustness.

Benefits and Practical Applications

• High precision and linear response for Fe(II) levels common in leach liquors
• Minimal sample preparation and rapid throughput
• Simplicity of titration setup compatible with routine QA/QC
• Resistance to interferences from common metal ions

Future Trends and Opportunities

Advancements may include integration of flow injection analysis for higher sample throughput, miniaturized sensor technology for on-line process monitoring, and adaptation to nonaqueous systems. Combining titrimetry with spectroscopic endpoints could further enhance selectivity and automation.

Conclusion

The described titration method provides an efficient, accurate determination of ferrous ion in hydrometallurgical leach liquors. Its straightforward implementation, robust performance and industrial relevance make it a valuable tool for metallurgical laboratories and process engineers.

References

Thermo Scientific Titration Application Note No. H-107: Determination of Ferrous Ion in Hydrometallurgical Leach Liquors