Determination of Mercury in Cement Raw Meal, Flue Ash, and Clay Slate/Coke Mixture

Significance of the Topic

The accurate determination of mercury in cement raw materials and by-products is crucial for environmental compliance and worker safety. Mercury releases during cement production can contribute to airborne pollution and long-term soil and water contamination. Regulatory limits for mercury content in industrial materials demand reliable, sensitive, and rapid analytical approaches capable of meeting detection thresholds down to sub-ppm levels.

Study Objectives and Overview

This application note describes a streamlined procedure for quantifying total mercury in cement-related matrices using direct thermal decomposition, gold amalgamation, and atomic absorption spectroscopy. The goals are to validate instrument calibration, assess method precision and accuracy in representative materials (flue ash, raw meal, clay-coke blends), and demonstrate compliance with expected mercury concentration ranges.

Methodology and Instrumentation

Instrument Used:

• LECO AMA254 Mercury Analyzer (thermal decomposition with gold amalgamation and AAS detection)

Sample Preparation and Analysis Workflow:

• Sample weight: ~100–200 mg placed in a large nickel boat
• Blank determination: three successive blank measurements to purge residual mercury
• Calibration: using certified reference materials (fly ash, BCR-143r, NIST 2781 sludge) across required dynamic range
• Analysis parameters: drying 60 s, decomposition 200 s, cuvette clear 45 s, automatic cell selection, peak area quantitation
• Sequence: blank → calibration standards → samples → verification of calibration by replicate standard analysis

Main Results and Discussion

Three typical matrices were evaluated:

• Flue Ash (expected <0.5 ppm): mean 0.281 ppm, SD 0.004 ppm, RSD 1.25%
• Preheated Raw Meal (expected <0.05 ppm): mean 0.00082 ppm, SD 0.00003 ppm, RSD 3.23%
• Clay/Slate-Coke Blend (expected ~0.1 ppm): mean 0.0938 ppm, SD 0.0042 ppm, RSD 4.44%

These results demonstrate the method’s sensitivity and repeatability across low and higher concentration ranges. The low RSD values confirm robust precision, while close agreement with expected values validates accuracy.

Benefits and Practical Applications

• Chemical-free sample preparation reduces waste and exposure risk.
• Short analysis time (~8 minutes per sample) enhances throughput for routine QA/QC.
• Wide dynamic range accommodates diverse cement-related materials without matrix separation.
• Minimal maintenance and straightforward operation support industrial laboratory workflows.

Future Trends and Potential Applications

Advances may include integration with automated sample loaders for higher throughput, development of field-portable analyzers for on-site screening, and coupling with speciation modules to distinguish inorganic versus organic mercury species. Stricter environmental regulations and the need for continuous emissions monitoring will drive further enhancements in detection limits and real-time analysis.

Conclusion

The described thermal decomposition–amalgamation AAS method on the LECO AMA254 platform offers a reliable, efficient, and precise solution for total mercury determination in cement production streams. Its rapid turnaround, minimal sample preparation, and strong performance metrics make it well suited for routine industrial monitoring and regulatory compliance.

Reference

• LECO Corporation. AMA254 Operating Manual, Form No. 203-821-115, Rev. 3, 2010.
• European Commission. BCR-143r Certified Reference Material for Fly Ash, 2002.
• National Institute of Standards and Technology. SRM 2781: Domestic Sludge, 2003.