Low Temperature Thermal Treatment of Gas-Phase Fluorotelomer Alcohols by Calcium Oxide
Riedel et al.
Chemosphere
DOI: 10.1016/j.chemosphere.2021.129859
Alongside our partner, Aerodyne Research, we continuously support the operation of our mass spectrometers for groundbreaking research. This study highlights the extensive real-time analysis capabilities of the TOFWERK Vocus CI-TOF for helping understand PFAS emissions and its disposal efforts.
Per- and polyfluoroalkyl substances (PFAS) are persistent environmental pollutants due to their resistance to degradation. Widely used in consumer and industrial products, PFAS pose significant disposal challenges. Traditional methods like landfilling and water treatment often fail to fully eliminate these substances, and incineration can create harmful byproducts. Recent research highlights calcium-based methods as a promising alternative. Calcium compounds, such as calcium oxide (CaO), can react with PFAS at lower temperatures than incineration, potentially converting them into calcium fluoride (CaF2) and carbon dioxide (CO2). This approach requires less energy and helps prevent the release of toxic byproducts.
Fluorotelomer alcohols (FTOHs), a volatile class of PFAS, are common in textiles and foams and can convert into persistent perfluorocarboxylic acids (PFCAs). Recent studies focused on using CaO to treat gas-phase FTOHs, examining their reaction at temperatures between 200 and 800°C. The results indicate that CaO-based methods are effective for destroying FTOHs and capturing fluorine, offering a viable and energy-efficient alternative to traditional thermal destruction methods. This study employed using two mass spectrometric methods to assess the efficiency of CaO treatment at temperatures between 200 and 800°C, compared to traditional thermal destruction methods. FTOHs were selected for their relevance in industrial PFAS applications and the ability of chemical ionization mass spectrometry (CIMS) using the Vocus 2R to measure them in real time. CaO was tested as a thermal treatment method for FTOHs and proved more effective than traditional thermal destruction. At higher temperatures (~800°C), CaO removed over 99% of FTOHs, and even at moderate temperatures (~400°C), removal efficiency exceeded 85%. While longer-chain FTOHs were less effectively treated, CaO still significantly reduced the formation of secondary fluorinated products and hydrofluoric acid (HF), minimizing environmental and operational issues. At lower temperatures (200-600°C), partial degradation of FTOHs led to the formation of secondary PFAS byproducts. However, at temperatures above 600°C, CaO treatment effectively prevented or removed nearly all these secondary products, demonstrating its potential for efficient PFAS destruction.
Secondary PFAS products, which often have higher vapor pressures, may contribute to air emissions and could eventually be deposited as lower volatility compounds (like PFCAs). CaO treatment offers a cost-effective solution for managing PFAS disposal gases, requiring lower temperatures and less energy compared to traditional methods. It can be integrated into stack emissions systems to capture PFAS vapors before they are released and used as a pretreatment before granular activated carbon (GAC) beds to extend GAC life and reduce reactivation frequency.
