Determination of Total Halides in Brines

Importance of the Topic

Determining total halides in seawater and brine is critical for environmental monitoring, industrial process control such as alumina refinery effluents, and quality assessment in marine-related operations. Precise quantification of chloride, bromide, and iodide informs on contamination levels, ecological impact, and compliance with regulatory standards.

Objectives and Overview of the Study

This application note presents a robust thermometric titration approach to measure total halide concentration (Cl–, Br–, I–) in natural and industrial brines. The method aims to deliver accurate, reproducible results for seawater samples, including those contaminated with sodium aluminate from alumina refining processes.

Methodology and Instrumentation

Thermometric titration of an acidified brine sample with standardized 0.1 mol/L AgNO3 was performed. Key parameters included:

• Titrant delivery rate: 4 mL/min
• Delay before titration: 3 s
• Exothermic endpoints: 1
• Data smoothing factor: 40
• Stirring speed: 15 (using an 802 stirrer)
• Sample preparation: 1 mL seawater or equivalent, acidified with 5 mL 1 mol/L HNO3, diluted to ~35 mL

Instrumentation: A thermometric titrator equipped with automatic dispenser (Dosino) and temperature sensor for endpoint detection.

Key Results and Discussion

Analysis of Moreton Bay seawater and samples spiked with 2, 4, and 10 mL/L sodium aluminate showed consistent chloride concentrations around 19.07 g/L (±0.07, n=5). Contaminants did not significantly affect titration performance. The exothermic endpoint and second-derivative curve provided clear, reproducible inflection for accurate endpoint determination. Method precision was demonstrated by relative standard deviations below 0.4%.

Benefits and Practical Applications

• Rapid, accurate total halide analysis in complex matrices
• Minimal interference from refinery-derived contaminants
• High reproducibility supports quality control in environmental and industrial laboratories
• Automated titrant delivery and endpoint detection reduce operator error

Future Trends and Applications

Advancements may include integration with inline monitoring systems for real-time process control in desalination and refinery wastewater treatment. Miniaturization of thermometric sensors and improved data analytics can enhance field-deployable halide analysis. Potential expansion to other ionic species using similar thermometric endpoints is under investigation.

Conclusion

The presented thermometric titration method offers a reliable, efficient route to quantify total halides in seawater and industrial brines, even in the presence of aluminium-based contaminants. Its strong reproducibility and simplicity make it well-suited for routine environmental and process-control analysis.

References

Application Note H-078: Determination of Total Halides in Brines. Thermo Fisher Scientific.