Determination of Ferric Ion in Hydrometallurgical Leach Liquors

Significance of the Topic

Determination of ferric ion in hydrometallurgical leach liquors is critical for controlling metal recovery, ensuring process efficiency and meeting environmental regulations. Accurate titrimetric analysis of Fe(III) supports real‐time monitoring and quality assurance in mineral processing operations.

Objectives and Study Overview

This application note outlines a validated titration procedure for quantifying Fe(III) in acidic leach solutions. The goals are to demonstrate method precision, describe standardization of titrant, and present representative results for typical process liquors.

Methodology

A 25 mL aliquot of acidic leach liquor is transferred to a polypropylene titration vessel and acidified with 2 mL glacial acetic acid. Potassium iodide is added to reduce Fe(III) to Fe(II), liberating iodine. The released iodine is back‐titrated with 1 mol/L sodium thiosulfate to an exothermic endpoint detected by temperature change and second‐derivative criteria. Key operational parameters include a titrant delivery rate of 4 mL/min, a data smoothing factor of 40, stirring speed setting 8 on the 802 stirrer, and a 10 s delay after KI addition.

Used Instrumentation

• Automated titrator equipped with a Dosino dispenser unit for precise aliquot delivery
• 814 sample rack accommodating PP titration tubes
• Tiamo™ software for endpoint detection and standardization calculations
• Temperature sensor and second‐derivative (ERC) algorithm for exothermic endpoint recognition

Main Results and Discussion

Standardization of the 1 mol/L Na2S2O3 titrant was performed using potassium iodate (0.04 mol/L) in volumes from 5 to 20 mL. Linear regression of consumed thiosulfate versus known IO3– moles confirmed titrant molarity with high linearity. Application to a process sample containing multiple metal ions yielded an Fe(III) concentration of 9.53 ± 0.01 g/L (n = 5), demonstrating excellent precision and specificity in the presence of Mg, Al, Mn, Cr, Cu, Co and Ca.

Benefits and Practical Applications

This titrimetric method offers:

• High accuracy and reproducibility for routine quality control
• Rapid turnaround suitable for process monitoring
• Minimal interferences through selective reduction and endpoint detection
• Compatibility with automated titration platforms for high throughput

Future Trends and Potential Applications

Advances in sensor technology and digital titration control may enable inline ferric ion monitoring and feedback loops for process optimization. Integration with predictive analytics and coupling with spectroscopic detectors could further enhance selectivity and reduce sample handling. Miniaturized flow‐through titration systems represent another emerging direction for real‐time industrial analytics.

Conclusion

The described redox titration protocol provides a robust, precise and automated approach for determining Fe(III) in hydrometallurgical leach liquors. Its implementation supports improved process control and product quality in mineral extraction and refining operations.