Determination of Morpholine, Ethanolamine, and Hydrazine in Simulated Nuclear Power Plant Wastewater

Significance of the Topic

In nuclear power plants, secondary and cooling water systems use organic amines and hydrazine to control pH and remove dissolved oxygen, thereby minimizing corrosion and associated maintenance costs. Monitoring trace levels of morpholine, ethanolamine, and hydrazine in process wastewater is critical for regulatory compliance and plant safety, especially in the presence of high salt loads from boiler blowdown.

Objectives and Study Overview

This study describes two ion‐exchange chromatography methods for quantifying low microgram‐per‐liter concentrations of hydrazine and morpholine and ethanolamine in a simulated nuclear plant wastewater matrix containing milligram‐per‐liter levels of common cations. Method 1 couples suppressed conductivity and integrated pulsed amperometric detection (IPAD) for hydrazine and morpholine. Method 2 uses reagent‐free IC with suppressed conductivity to quantify ethanolamine.

Methodology and Instrumentation

Both methods employ high‐capacity cation‐exchange columns and precise eluent generation:

• Method 1: Dionex ICS-3000 system with dual pumps, EG II MSA cartridge, CR-CTC II trap, IonPac CG16/CS16 (3×250 mm) column set. Eluent gradient of 15–65 mM methanesulfonic acid at 0.4 mL/min; postcolumn addition of 50 mM NaOH at 0.14 mL/min for IPAD detection on an AAA-certified Au electrode. Suppressed conductivity used upstream.
• Method 2: Dionex ICS-3000 RFIC-EG configuration with IonPac CG15/CS15 (2×250 mm) column at 50 °C. Isocratic 5 mM MSA eluent for initial ETA separation, ramping to 65 mM for matrix cleanup, flow rate 0.3 mL/min, conductivity detection with CSRS suppressor.

Key Results and Discussion

• Hydrazine and Morpholine (Method 1): LOD/LOQ were 2.3/8.6 µg/L for hydrazine and 24.8/147 µg/L for morpholine. Calibration was linear from 10–50 µg/L and 150–500 µg/L, respectively, with r²=0.9997.
• Precision and Accuracy: Seven replicates in 100% salt matrix yielded recoveries of 109% (hydrazine) and 97.2% (morpholine), with retention‐time RSDs <0.1% and area RSDs <3%.
• Robustness: Minor variations in PCR concentration, electrode lot, and column temperature produced <5% change in hydrazine response; morpholine area varied up to 27% at –2 °C. Weekly PCR preparation was required to maintain response.
• Ethanolamine (Method 2): LOD/LOQ were 13/54 µg/L; linear range 50–800 µg/L (r²=0.9997). In undiluted 100% matrix recovery was 86.4%; diluting to 80% matrix improved recovery to 101.7% with RSDs <2%.

Practical Benefits and Applications

• High sensitivity allows monitoring of μg/L levels for regulatory discharge limits.
• Reagent‐free inline eluent generation reduces manual preparation and variability.
• Dual detection in a single system streamlines analysis of multiple amines.
• Robust column chemistry prevents overload by high salt matrix.

Future Trends and Prospects

Advances in inline eluent generation and low‐dispersion tubing will further improve sensitivity and reduce noise. Integration of mass spectrometry detection may enhance selectivity for complex matrices. Automation and miniaturization of IC systems promise faster throughput and on‐line process monitoring in power plant water treatment.

Conclusion

The optimized IC methods provide accurate, precise, and sensitive quantification of key corrosion-inhibiting amines and oxygen scavenger in challenging high‐salt nuclear wastewater. The approach supports regulatory compliance and corrosion management strategies in nuclear power operations.

Instrumentation

• Thermo Scientific Dionex ICS-3000 with DP dual gradient pump and EG II MSA cartridge
• Continuously regenerated CR-CTC II cation trap
• IonPac CG16/CS16 and CG15/CS15 cation-exchange columns
• CSRS-300 suppressors for conductivity detection
• ED electrochemical detector with AAA-certified Au electrode and IPAD waveform
• Dionex Chromeleon CDS software and AS autosampler

References

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7. French Official Journal Articles on effluent limits, 2008–2009.
8. EPRI, Ion Chromatography State-of-Knowledge, 2007.