Inline analysis of borate and sulfate solutions with Raman spectroscopy

Importance of the topic

Boron-containing compounds, particularly boric acid derived from borax, are integral to industries such as glass manufacturing, electronics, and detergents. Efficient, real-time monitoring of borate and sulfate concentrations during production is essential for optimizing yield, minimizing environmental impact, and reducing costs.

Objectives and study overview

This study demonstrates the application of inline Raman spectroscopy using the Metrohm PTRam Process Analyzer to quantify H3BO3 and Na2SO4 in process solutions at low concentrations (<100 mg/L). The objectives were to establish a simple calibration model, assess detection limits, and compare performance with traditional methods.

Methodology

Single-channel Raman measurements were performed with a 785 nm laser. Minimal reference measurements were collected to calibrate chemometric models. Key Raman bands at 880 cm−1 (borate) and 993 cm−1 (sulfate) were targeted for quantitative analysis.

Instrumentation used

The Metrohm PTRam Process Analyzer equipped with a 785 nm laser, a lab fiber-optic probe, and Vision software was employed for inline measurements. The system supports automated self-calibration and performance validation.

Main results and discussion

Distinct Raman peaks for boric acid and sodium sulfate enabled accurate quantification. Limits of detection for H3BO3 and Na2SO4 were determined at approximately 14.5 mg/L and 6.9 mg/L (ion basis), respectively. Standard error of prediction values confirmed reliable performance in mixed and single salt solutions.

Benefits and practical applications

• Real-time inline monitoring without reagent consumption
• Rapid analysis and reduced sample preparation
• Improved process control, yield, and cost efficiency

Future trends and applications

Advancements may include integration with automated process control, AI-driven chemometric analysis, expanding inline spectroscopy to additional analytes, and adopting fiber-optic probes for extreme conditions in industrial environments.

Conclusion

Inline Raman spectroscopy with the PTRam Process Analyzer offers a robust, reagent-free method for continuous monitoring of borate and sulfate in boric acid production. This approach enhances process efficiency and supports environmental sustainability.

References

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• Precedence Research. Boric Acid Market Size to Worth Around US$1,169.89 Million by 2030. Accessed July 22, 2022.
• Mergen A.; Demirhan M. H.; Bilen M. Processing of Boric Acid from Borax by a Wet Chemical Method. Advanced Powder Technology, 2003, 14(3):279–293.
• Britannica. Gravimetric analysis | Definition, Steps, Types, & Facts. Accessed August 21, 2023.
• Childs M. P. Quantification of Boric Acid Concentration and Losses Due to Vaporization in the PASTA Facility. Texas A&M University, 2016.
• ISO. Sodium Sulphate for Industrial Use — Determination of Sulphates Content — Calculation Method and Barium Sulphate Gravimetric Method. 1975.