Determination of Water-Extractable Total Organic Carbon Content in Recycled Black Mass

Significance of the Topic

Black mass from lithium-ion battery recycling contains valuable metals and residual organic compounds. Quantifying water-extractable total organic carbon (TOC) is essential to control recycling quality, prevent process inefficiencies, and minimize environmental impact.

Objectives and Study Overview

This study evaluates methods for measuring water-extractable TOC in recycled black mass according to China standard GB/T 45203-2024. It compares the conventional total carbon minus inorganic carbon method with a streamlined non-purgeable organic carbon (NPOC) approach, using a Shimadzu TOC-L analyzer and ASI-L auto-sampler.

Used Instrumentation

• Shimadzu TOC-L total organic carbon analyzer with combustion oxidation and nondispersive infrared detection
• ASI-L automatic sample changer
• High-density polyethylene containers, quantitative filter papers, PTFE syringe filters

Methodology

Samples of 8 g black mass were shaken with 80 mL water for 18 hours, then filtered through 5C paper and 0.22 µm PTFE membrane. For the TC-IC method, the filtrate was acidified, aerated, and analyzed for total and inorganic carbon separately. The NPOC method automates acid addition and aeration, eliminating manual pretreatment steps. Calibration used seven-point curves for TC, IC, and TOC.

Main Results and Discussion

• Calibration curves exhibited linearity with correlation coefficients ≥ 0.9999
• Blank tests confirmed background TOC below the quantification limit of 0.2 mgC/L
• Both methods produced equivalent TOC values for unspiked and spiked samples
• Spiked recovery rates were 97.6 percent for TC-IC and 99.9 percent for NPOC
• Measured water-extractable TOC in the commercial sample was below 0.01 percent, well under the 0.10 percent criterion

Benefits and Practical Applications

The NPOC method reduces sample handling and analysis time while retaining accuracy, making it suitable for high-throughput quality control. Automated sampling enhances laboratory efficiency in battery recycling workflows.

Conclusion

Both TC-IC and NPOC methods reliably quantify water-extractable TOC in recycled black mass. The NPOC approach, coupled with auto-sampling, streamlines operations without sacrificing data quality.

Future Trends and Applications

Future developments may integrate inline auto-sampling with real-time data processing, extend NPOC workflows to other recycled matrices, and improve detection limits through advanced catalysts. Enhanced automation and methodological standardization will support sustainable battery material recovery.

Reference

• GB/T 45203-2024 Recycled Black Mass for Lithium-Ion Battery