Determination of Magnesium in Hydrometallurgical Leach Liquors

Significance of the topic

Hydrometallurgical leach liquors often contain multiple metal ions whose accurate quantification is critical for process control, product quality, and environmental compliance. Magnesium determination is particularly important because it influences downstream precipitation steps, impacts purity of recovered metals, and can interfere with other analytical measurements.

Aims and overview of the study

This application note describes an automated titrimetric method using EDTA to determine magnesium in acidic hydrometallurgical leach solutions. The goals are to achieve high accuracy, precision, and throughput, and to compare results with alternative techniques such as atomic absorption spectroscopy (AAS) and manual titration.

Methodology and instrumentation

The procedure involves complexation, masking, reduction of interferences, and EDTA titration under controlled pH and temperature. Key steps include:

• Aliquot preparation: 5 mL sample plus ascorbic acid and water.
• Sequential reagent additions: sodium gluconate to complex residual ions, NH₃/NH₄Cl buffer to raise pH to ~10.5, and KCN to mask Fe(III).
• Reduction of Fe(III) to Fe(II) with ascorbic acid.
• EDTA titration at controlled delivery and stirring rates, with end point detection via enthalpimetric second-derivative measurement.

Instrumentation:

• Thermo Titration System equipped with an 802 magnetic stirrer.
• 814 Sample Processor for automated reagent addition and sample handling.
• PP titration tubes and temperature-controlled titration cell.

Reagents include 1 mol/L Na₄EDTA titrant, sodium gluconate complexant, NH₃/NH₄Cl buffer, 20% KCN masking solution, and 5% ascorbic acid reducing solution.

Main results and discussion

Standardization of the EDTA titrant yielded a concentration of 1.03984 mol/L with R² = 1.0000. Analysis of a multi‐element leach liquor returned Mg = 20.35 ± 0.05 g/L (n=6), in close agreement with AAS (21.5 g/L) and manual titration (~20 g/L). The automated method demonstrated excellent precision, minimal operator intervention, and robust interference control.

Benefits and practical applications of the method

• High accuracy and precision suitable for QA/QC in metallurgical plants.
• Reduced analysis time and labor through automation.
• Effective masking and reduction steps minimize Fe and other metal interferences.
• Cost‐effective alternative to AAS for routine monitoring.

Future trends and applications

Advances may include integration with inline sampling for real‐time process control, expansion to simultaneous multi‐ion determinations via multiplexed titration or spectroscopic end‐point detection, and enhanced data analytics for predictive maintenance. Development of safer masking agents to replace cyanide and novel sensor technologies could further improve environmental and operator safety.

Conclusion

The described automated EDTA titration method provides a reliable, precise, and efficient approach for magnesium determination in complex hydrometallurgical matrices. Its strong correlation with established techniques and adaptability to high‐throughput workflows make it valuable for industrial quality control.

References

No external literature references were provided in the source text.