PFAS Treatment Technologies And Methods: Removal, Separation, Destructions, And Beyond
In this contexts, we mainly cover methods and technologies adopted for PFAS treatment, therefore it will be a general introduction of PFAS removal/separation, PFAS destructions, and sequestration, and the core part of this content is about the electrocehmical oxidation processes technologies for PFAS treatment.
Before we walk you through the major PFAS treatment methods, learn more about PFAS to comprehend why it’s critical to select PFAS treatment methods.
Comprehensive Introduction About PFAS & Why Selecting Proper PFAS Treatment Technologies Matters
Check the comprehensive introductions about PFAS(Per- and Polyfluoroalkyl Substances) mainly cover the concept of PFAS, PFAS types and variations, impacts of PFAS to the environment and human health, and the reason why PFAS are refractory and hard to remove/destroy, address all your questions:
What is PFAS? Application Ranges of PFAS, And PFAS Types, Impacts of PFAS To Environment
PFAS, or per- and polyfluoroalkyl substances, well known for their water, stain, and grease-resistant properties, were invented in the 1940s, are a group of man-made chemicals.
There are some 10,000 types of PFAS, typically PFAS could be classified into two categories, firstly, we have polymeric PFAS with a polymer backbone with fluorines directly attached to carbon atoms, and the other category is smaller, easily adsorbed Non-polymeric PFAS, PFAS have been used in various consumer goods and industrial usages.
Check major PFAS and application ranges of these PFAS we listed below:
PFOA (perfluorooctanoic acid) and PFOS (perfluorooctane sulfonic acid) are key components of Teflon and different non-stick coatings of non-stick cookwares.
Some PFOA and PFOS substances are banned in EU and the US.
Grease-resistant nature of PFAS make them basic element for food packagings, for instance, paper and cardboard.
Perfluorooctanesulfonic acid,aka PFOS is a type of main ingredients in firefighting foams, a type of aqueous film-forming foam (AFFF), adopted to extinguish fire.
PFAS were adopted to manufacturing processes of producing textiles and carpets, mainly for their waterproof and stain-resistance nature.
Certain types of PFAS can be utilized to manufacture cosmetics and personal care products.
Water-resistant PFAS are adopted to manufacture paints, sealants, and varnishes to enhance durability of these merchandises.
PFHxS (perfluorohexane sulfonic acid)is an alternative for PFOS in certain applications.
PFNA (perfluorononanoic acid) is another PFAS adopted for various implements.
GenX (hexafluoropropylene oxide dimer acid) is invented to relacing older PFOA in some manufacturing and application processes.
PFBS (perfluorobutane sulfonic acid): Another PFAS, often used as a replacement for PFOS.
PFBA (perfluorobutyric acid) is a type of PFAS.
PFHxA (perfluorohexanoic acid) is a type of PFAA, it’s a short-chain PFAS.
Perfluoroalkyl acids (PFAAs): The least complex PFAS molecules.
Environmental Impact
Given the truth that the PFAS has some stable C-F bonds/chains, PFAS are persistent organic pollutants widely exist in water, soil, even air
Reproductive and immune systems of different species will be seriously affected by PFAS contaminated water, soil and etc, Bioaccumulate in wildlife**, affecting
PFAS contaminate drinking water
PFAS Treatment Methods: Removal/Separations, Destruction, and Sequestration
Persistent nature of PFAS (Per- and Polyfluoroalkyl Substances) makes thos group of pollutatns heat, oil and stain resistance, and waterproof, PFAS treatment challenging, which means to tackle the challenges with PFAS, people need to find alternative technologies and solution way more complicated than conventional water treatment methods.
PFAS are with extremely strong carbon-fluorine bonds, resistant to heat, acids, and traditional water treatments such as chlorination and biological degradation processes are proven to be ineffective when it comes to PFAS treatment.
We discuss major treatment technologies and methods to remove or destroy PFAS from contaminated water, there are three typical approaches, that is removal/separation, destructions, and sequestration.
These treatment methods range from psychic, chemical and other ranges of treatment methods, we are going to explore various types of treatment methods in this exact content, and incumbent and emerging methods as well.
Removal/Separations, PFAS Treaent in An Non-Destructive Fashion
PFAS removal/separation, one category of the primary PFAS treatment approach, is all about capturing and separating PFAS from contaminated water or other matrices in a physical way, that is prevent them from further ingestion, instead of destroying the persistant chemical bonds. The removal/separation processes involve capturing or concentrating the PFAS for further management or disposal. PFAS removal from water is mainly accomplished via activated carbon filtration, ion exchange resins, and high-pressure membrane systems like reverse osmosis and nanofiltration.
Activated Carbon Adsorption (GAC/PAC) utilizes the large surface area of activated carbon to attract and hold PFAS molecules, Granular Activated Carbon (GAC) is a typical method to adsorbe PFAS, especially long-chain PFAS to their surface, effectively removing them from the water in a cost-effective and easy operation way, however GAC usually demands huge space when it comes regular operations, and provened to less effective on short-chain PFAS.
Powdered Activated Carbon (PAC), however have less efficiency in PFAS adsorptions, it could be combined with other wastewater treatment methods, it transfers the PFAS to the carbon, creating a new waste stream requiring disposal.
Ion Exchange Resins (IX) utilizing porous polymeric materials to realize some chemical exchange process, replacing existing ions with PFAS molecules, effectively that is to capture PFAS by replacing ions within the electrolytes/solution with the PFAS molecules, Ion exchange resins are proven to be highly effective at removing a wide range of PFAS, including long-chain ones and especially shorter-chain PFAS. These resins are specifically designed to bind to PFAS molecules, often used in whole-house treatment systems, where they can be attached to the water inlet to filter PFAS from all water entering the house, like household water filtration system, Ion exchange resins treatment systems may demand frequent regeneration or replacing than other methods.
Membrane Filtration (Reverse Osmosis/Nanofiltration): These advanced membrane-based processes use semi-permeable membranes, utilizing pressures to force water go through these membranes with small pores, to physically block PFAS compounds based on their size, that is PFAS molecule filtrations. They are highly particularly effective at removing both long- and short-chain PFAS, however these treatment methods generate a concentrated waste stream, and what is more, given the sophistication of membrane system, these can be expensive and consumes more energy within the PFAS treatment processes.
Surface Active Foam Fractionation (SAFF) exploits differences in surface activity to selectively capture and concentrate PFAS into a foam, which is then removed from the water.
Destruction,Breaking Down As A PFAS Treatment Solution
Destruction of PFAS, is an approach to break persistent PFAS molecules into fluoride ions, carbon deoixdes, water and otehr inorganic compounds, one of the major method is mineralization of strong carbon-fluorine bonds into intermediates and substances that are less harmful.
In this part of contexts, we are gonna name several PFAS destruction methods and techologies, and then focus mainly on electrochemical oxidation, as we will find the right time and place to discuss other PFAS treatment method within the destruction categories.
Supercritical Water Oxidation (SCWO) utilizeds high pressure and temperature with water in a supercritical state to break down PFAS.
Hydrothermal Alkaline Treatment (HALT) uses compressed water, high temperatures, and an alkaline reagent to break the carbon-fluorine bonds.
Advanced Oxidation Processes (AOPs) generate highly reactive species like hydroxyl radicals to degrade PFAS. Examples include combinations of UV light with other oxidizing agents like hydrogen peroxide.
Electrochemical Oxidation for PFAS Treatment
Electrochemical oxidation(EO)，uses an electrical current to generate reactive species that can directly oxidize PFAS or facilitate their breakdown, is an effective method for treating high-concentration PFAS streams, offering high removal efficiencies and the potential for mineralization of PFAS compounds. EO works by using an electric current to oxidize PFAS molecules, breaking them down into simpler, less toxic compounds.
How Electrochemical Oxidation Works In PFAS Treatment
Direct Oxidation of PFAS Molecules Within Electrochemical Oxidation Processes for PFAS Treatment
Electrochemical oxidaiton processes requires implements of electric currents into the electrochemical reactor, once electric current applied, PFAS molecules are adsorb onto the surface of the anodic side of the electrochemical cell, and undergo direct electron transfer among the PFAS molecules and the anode, losing eletrons leading to direct oxidation and degradation into less complex substances and molecules.
Direct Oxidation of PFAS Molecules Within Electrochemical Oxidation Processes for PFAS Treatment
Strong oxidizing agents such as hydroxyl, oxygen radicals, sulfate radicals, and carbonate are eletro-generated in bulk within the electorchemical cell, these reactive oxidants react with PFAS molecules in the electrolytes, breaking down the persistent molecules into intermediates, and constant oxidation of these intermediates degrade the compounds into degradeable, less harmful compounds, water, and etc.
Boron-Doped Diamond BDD electrode, as the next gen n0n-active catalyst electrode material with robust oxidation capability and massive molecule adsorption surface, is often adopted as anodes in eletrochemical reactor for electrochemical oxidation treatment of PFAS.
Key Advantages of Electrochemical Oxidation Processes for PFAS Treatment:
High Removal Efficiency: Electrochemical oxidation achieved relatively high PFAS removal rates, check the treatability testing results from Boromond laboratory and our customers:
Preliminary results we achieved at our laboratory indicated a complete electrochemical oxidation of PFAS at 1 mg/l after 2 hours, without formation of intermediate compounds.
One of our customers utilized boron doped diamond BDD electrodes on X-Gen or say Gen-X (hexafluoropropylene oxide dimer acid) and located a good oxidation results, PFOA (perfluorooctanoic acid), and electrochemical oxidation degradation of Gen-X is slower than in the case of PFOA since the testing were conducted simultaneously.
And what is more, this customer disclosed that they had not detected significant values of intermediate compounds of degradation, which indicates a quite complete oxidation result, which means electrochemical oxidation processes has the potential to, not only breaking down PFAS molecules, but also accomplishing complete mineralizations of these persistent molecules into basic substances.
Reduced Waste Generation: By breaking down PFAS into less toxic compounds, EO can minimize the need for specialized waste disposal methods.
Scalability and Efficiency: EO is a scalable technology that can be adapted for various applications, from laboratory experiments to full-scale treatment plants.
Effective in Complex Matrices: EO can be effective even in the presence of other contaminants like natural organic matter (NOM).
Potential for Non-Toxic Byproducts: ECO aims to completely mineralize PFAS, transforming them into less harmful compounds like carbon dioxide, fluoride, and water.
Versatility and Adaptability: ECO can be used to treat various PFAS, different water matrices, and can be integrated with other technologies.
Factors Affecting Electrochemical Oxidation Efficiency Toward PFAS Treatment:
Selection of Electrode Material: Boron-doped diamond (BDD) electrodes are commonly used due to their high chemical and mechanical stability, robust performances, wider potential window and ability to generate strong oxidizing species. Other electrode materials, like titanium and lead-based electrodes, are also being explored.
Current density: The amount of electric current applied during the process significantly impacts the efficiency of PFAS degradation.
Solution pH: The pH of the solution can affect the generation of reactive oxidizing species and the overall efficiency of the process.
Electrolyte concentration: The exact type of electrolyte and electrolyte concentration can affect the conductivity of the solution and the electro-generation of oxidizing species.
Electrochemical cell/reactor design: Parameters such as flow rate, retention time, electrode spacing and etc will impact the comprehensive electrochemical oxidation efficiency.
Challenges and Considerations:
Cost and Energy Consumption: Developing cost-effective electrode materials and optimizing energy consumption are ongoing areas of research. [1]
Potential Byproducts: The formation of transformation byproducts during EO needs to be carefully monitored and managed. [1]
Effect of Water Chemistry: Factors like pH, electrolyte, and the presence of other dissolved substances can affect the efficiency of EO. [10]
Developing Cost-Effective Electrode Materials: Finding cost-effective and high-performance electrode materials is an ongoing research area.
Optimizing Energy Consumption: Minimizing energy requirements for ECO is crucial for its scalability and economic viability.
Understanding Transformation Byproducts: It’s important to carefully study and manage potential transformation byproducts generated during ECO.
Overall, EO is a promising technology for treating high-concentration PFAS streams, offering high removal efficiencies, the potential for mineralization, and a reduced environmental footprint compared to other PFAS treatment methods.
Electrochemical oxidation (ECO) shows promise as a technology for treating high-concentration PFAS streams, offering high removal rates and potential for non-toxic byproducts. ECO uses an electrochemical cell to generate an electric current between an anode and cathode, leading to PFAS degradation through direct electron transfer at the anode surface and the generation of oxidizing species in the bulk liquid.
Integrating with Other Technologies:
Combining ECO with other technologies, like foam fractionation, can further enhance PFAS treatment efficiency.
Sequestration (Containment/Immobilization):
Concept: These methods aim to contain or immobilize PFAS within a specific area, preventing their migration into the environment.
Examples:
Adsorption/Stabilization: Sorbents like activated carbon, biochar, and modified clays are added to the soil to adsorb and immobilize PFAS, reducing their leaching potential.
Encapsulation/Stabilization in Concrete: PFAS concentrates can be mixed with proprietary ingredients and cast into concrete, potentially encapsulating and stabilizing the PFAS permanently.
Landfill Disposal: While not ideal, some jurisdictions still allow landfill disposal of PFAS-containing waste or treatment media. However, newer approaches focus on capturing PFAS at the source within landfills and potentially recirculating treated leachate back into the landfill or further treating the leachate for destruction or permanent sequestration.
No single technology is a universal solution for all PFAS types and complexity, therefore Boromond team are inviting wastewater treatment experts from wastewater treatment companies, environmental services, environmental engineering consulting companies, to join Boromond’s PFAS and persistent organic pollutants removal plan to:
Enables direct PFAS removal and/or destruction in wastewater instead of simply collecting PFAS for hazardous disposal or secondary destruction.
Explore possible solution to coupling different technolgies to find effective approach for PFAS treatment.
Constant research and development, and updating advancements of PFAS treatment methods and technologies.
Strategical combination and consideration of cost-effectiveness, scalability, and the mitigation of by-products.
Boromond team is ready to team up with you to explore more about PFAS treatment, contact Boromond via enquiry@boromond.com to discuss more details.
