Posted: Friday, 19 January 2024
Per- and polyfluoroalkyl
substances (PFAS), including perfluorooctanesulfonic acid (PFOS) are chemicals commonly found in various industrial
and consumer products. Studies have shown that they notoriously remain persistent in the environment and the
human body, earning them the nickname "forever chemicals". We took an
initial look at the challenge in a 2022 blog, but the quest for effective and
sustainable methods to break down PFAS compounds has led to an increasing
interest in advanced technologies like Ultraviolet (UV) light and Advanced
Oxidation Processes (AOP). Here we look at the technologies and their current
challenges towards being able to contribute to a solution in a commercial environment.
The
Mechanism of UV and AOP Technologies
Ultraviolet
(UV) Light
Ultraviolet
light, particularly in the C spectrum (UV-C), is known for its germicidal
properties. This spectrum of light has the capability to break chemical bonds,
making it a potential tool for degrading complex PFAS molecules. When UV light
is absorbed by PFAS compounds, it can initiate photolysis, leading to the
breakdown of the carbon-fluorine bond, which is one of the strongest in organic
chemistry.
Advanced
Oxidation Processes (AOP)
AOPs are
characterized by the production of highly reactive species like hydroxyl
radicals. These radicals are capable of attacking most organic compounds,
including PFAS, leading to their degradation. AOP technologies combine various
methods such as UV light, hydrogen peroxide, and sometimes catalysts to enhance
the degradation process.
Current
Status of the Technology
Recent
studies have shown promising results in using UV and AOP technologies to
degrade PFAS compounds. Laboratory-scale experiments have demonstrated
significant breakdown of these chemicals under controlled conditions. See the
list of relevant sources of studies at the bottom of this blog if you would
like to read into this in more depth. However, several challenges remain:
Efficacy at
Scale: Scaling these technologies from lab experiments to full-scale
environmental remediation remains a challenge. The effectiveness of UV and AOP
in varied environmental matrices (like soil, groundwater, etc.) is still under
research.
Energy
Efficiency: UV and AOP methods can be energy-intensive. Making these processes
energy-efficient is crucial for their practical application.
By-product
Management: The degradation of PFAS can lead to the formation of smaller,
potentially harmful by-products. Better understanding and managing of these
by-products are essential for the safe application of the technologies.
Cost: Higher
operational costs, primarily due to energy consumption and the need for
specialised equipment, currently limit the widespread adoption of these
technologies.
Path to
Commercial Viability
Research
and Development
Ongoing
research focusing on optimising UV/AOP systems for different environmental
conditions and PFAS types is crucial. This includes developing more efficient
catalysts, identifying optimal operational parameters, and integrating these
systems with existing water treatment infrastructures.
Regulatory
Framework
A clear
regulatory framework that outlines acceptable levels of PFAS in the environment
and guidelines for remediation technologies can drive innovation and investment
in this field is required. This will help provide a clearer direction of travel
for companies to invest their time and resources.
Public-Private
Partnerships
Collaborations
between governments, research institutions, and private companies can
accelerate the development and deployment of these technologies. Funding and
resources from these partnerships can be pivotal in overcoming current
limitations.
Timeline
for Commercialisation
Given the
current pace of research and growing regulatory pressures to address PFAS
contamination, we could see viable commercial applications of UV and AOP
technologies in the next 5-10 years. This timeline could be expedited with
increased investment and focused collaborative efforts in this field.
Conclusion
While the
complete destruction of PFAS compounds remains a formidable challenge, the
advancements in UV and AOP technologies offer a ray of hope. With continued
research, innovation, and supportive policy frameworks, these technologies hold
the potential to play a critical role in mitigating the PFAS crisis. The
journey from laboratory findings to real-world applications is often long and
complex, but the environmental and health benefits of successfully tackling
PFAS pollution justify the effort and investment required to advance these
promising technologies.
Here are
some references to research studies and articles that provide valuable insights
into the use of UV and AOP technologies for the degradation of PFAS compounds:
Trojanowicz,
M., Bojanowska-Czajka, A., Capodaglio, A. G., et al. (2018). "Advanced
oxidation/reduction processes treatment of aqueous solutions contaminated with
perfluorinated compounds (PFCs) – A review." Chemical Engineering Journal,
334, 1498-1511.
This review
article provides a comprehensive overview of various advanced oxidation and
reduction processes, including UV-based methods, for the treatment of water
contaminated with perfluorinated compounds.
Hori,
H., Hayakawa, E., Einaga, H., et al. (2008). "Degradation of
Perfluorooctane Sulfonate and Perfluorooctanoic Acid by Advanced Oxidation
Processes." Environmental Science & Technology, 42(13), 4976-4981.
This study
investigates the degradation of PFOS and PFOA using various advanced oxidation
processes, highlighting the effectiveness and challenges of these methods.
Park,
S., Lee, L. S., Medina, V. F., et al. (2016). "Degradation of
Perfluorooctanesulfonic Acid by Reactive Species Generated Through Catalyzed
H2O2 Propagation Reactions." Environmental Science & Technology
Letters, 3(2), 38-42.
This
research explores the degradation of PFOS using catalyzed hydrogen peroxide
propagation reactions, a subset of AOP, and discusses the potential of these
reactions in PFAS treatment.
Vecitis,
C. D., Park, H., Cheng, J., et al. (2009). "Treatment Technologies for
Aqueous Perfluorooctanesulfonate: A Critical Review Including Incentives and
Practicalities of Using High-Energy Electrons and Pulsed Power."
Environmental Science & Technology, 43(23), 7048-7056.
This
critical review discusses various treatment technologies, including high-energy
electrons and pulsed power (aspects of AOP), for aqueous PFOS remediation.
Rayaroth,
M. P., Aravind, U. K., Aravindakumar, C. T. (2017). "AOPs and RFPS for the
Degradation of PFOA and PFOS in Water: A Review." Reviews in Environmental
Science and Bio/Technology, 16, 429-454.
This review
focuses on the application of advanced oxidation and reduction processes for
the degradation of PFOA and PFOS in water, emphasizing the progress and
challenges in the field.
Appleman,
T. D., Higgins, C. P., Quiñones, O., et al. (2014). "Treatment of Poly-
and Perfluoroalkyl Substances in U.S. Full-Scale Water Treatment Systems."
Water Research, 51, 246-255.
This study
examines the effectiveness of full-scale water treatment systems, including
AOPs, in removing PFAS compounds from water, providing insights into the
practical application of these technologies.
These
references offer a mix of review articles and specific studies, providing a
broad understanding of the current state of research and the challenges in
using UV and AOP technologies for PFAS degradation. They serve as excellent
starting points for a deeper exploration into the subject.