Determination of Nickel in Hydrometallurgical Leach Liquors

Importance of the topic

Hydrometallurgical processes generate leach liquors containing valuable metals such as nickel along with a range of potential interferences. Accurate determination of nickel concentration is essential for process control, resource recovery and quality assurance in mining, battery production and metallurgical industries.

Objectives and Overview

This study presents a titrimetric procedure for quantifying nickel in acidic hydrometallurgical leach liquors. The method aims to overcome common interferences from iron and other metals by employing an oxidation step, selective masking agents and an exothermic titration endpoint using disodium dimethylglyoximate as the titrant.

Methodology and Instrumentation

The analytical workflow comprises the following steps:

• Oxidation: Addition of 30 % H2O2 to convert Fe(II) to Fe(III).
• Masking: Introduction of 1 mol/L potassium pyrophosphate to complex Fe(III) and other interfering cations.
• pH adjustment: Use of 5 mol/L ammonium acetate to optimize conditions for nickel precipitation.
• Titration: Automated addition of 0.5 mol/L disodium dimethylglyoximate at 6 mL/min until an exothermic endpoint is detected.

Key operational parameters include a stirring speed of 14 (802 stirrer), data smoothing factor of 30, and a 10 s delay before titration start. Sample automation is achieved with the Thermo Scientific 814 Sample Processor.

Main Results and Discussion

Standardization of the dimethylglyoximate titrant demonstrates excellent linearity (r > 0.999) across nickel aliquots from 1 to 5 mL of a 0.2 mol/L Ni solution. The method yields a precision of ±0.06 g/L (n=5) for the analysis of real acidic leach liquors containing Fe, Mg, Al, Mn, Cr, Cu, Co and Ca. Exothermic titration curves show a sharp thermal peak corresponding to the nickel dimethylglyoximate formation, with minimal baseline noise when using high stirring rates.

Benefits and Practical Applications

The titrimetric approach offers:

• High specificity for Ni in complex matrices due to effective masking and oxidation steps.
• Rapid, fully automated workflow suitable for routine process control.
• Minimal sample preparation and robust endpoint detection via thermal monitoring.

This method is directly applicable in metallurgical operations, hydrometallurgical pilot plants and quality control laboratories.

Future Trends and Applications

Advancements may focus on integrating real-time data analytics and inline process monitoring. Miniaturized thermal sensors and enhanced automation could enable higher throughput and deployment at remote plant sites. Adaptation to determine other transition metals by selecting appropriate ligands and titrants is a promising extension.

Conclusion

The exothermic titration using disodium dimethylglyoximate provides a reliable, selective and automated solution for nickel determination in hydrometallurgical leach liquors. The protocol demonstrates strong correlation, precision and operational simplicity, supporting its adoption in industrial quality assurance and research settings.