A growing body of research is taking place looking at how to remove and destroy Per- and Polyfluorinated Substances (PFAS) from the environment. PFAS is a group of chemicals used to make fluoropolymer coatings and products that resist heat, oil, stains, grease, and water.
“Due to their high chemical stability and useful physical properties, PFAS chemicals are found widespread in both domestic and industrial applications,” says Dr Stefan Neufeind, head of technical marketing, Liquid Purification Technologies business unit, Lanxess – a German specialty chemicals company. “This has led to an accumulation of these “forever chemicals” in the environment. Based on their supposed carcinogenicity and toxicity for reproduction these compounds exhibit a severe risk to human health.”
According to Neufeind, due to their ubiquity and potential threat to the environment and health PFAS are currently subject to “intense public and scientific discussions,” which could eventually result in tighter regulations around PFAS use and removal by authorities.
The most widely adopted method to remove PFAS is using activated carbon to capture the chemicals – a system that can be applied commercially and domestically. Other methods include ion exchange resins – a process promoted by Lanxess – which use miniature beads as a filter medium along with high pressure membranes.
In the following interview, Lanxess’s Neufeind discusses the PFAS issue and the technologies it has developed to remove these forever chemicals from our environments.
F+S: What technologies are you looking at for PFAS removal and why?
SN: As one of the leading ion exchange resin manufacturers, Lanxess has a long track record in providing solutions for contaminant removal from all kinds of waters. For several decades, our Lewatit ion exchange resins have demonstrated their reliability in ground water remediation, wastewater treatment and potable water detoxification.
Based on this experience, we have always been trying to offer solutions for the most urgent present challenge in water treatment and PFAS represents one of the major topics these days. Consequently, Lanxess developed a comprehensive portfolio of ion exchange resin for the removal of PFAS.
F+S: What are the major challenges for PFAS removal and why?
SN: PFAS is a family of substances that comprises more than 10,000 compounds. As a result, the composition of contaminated water can vary strongly from side to side, along with other parameters such as other constituents and concentrations. At the same time the target limits of treated water are often in the ppt range, which requires a case-by-case evaluation to identify the most effective and cost-efficient treatment method.
The PFAS concentrations of contaminated water are often in the ppt or ppb range, while other uncritical constituents like chloride and sulphate are present in manifold higher concentrations (several hundreds of ppm). Thus, we developed ion exchange resins that offer the necessary high selectivity for PFAS over other species and that are applicable under a broad range of conditions.
F+S: Do you see any limitations or side effects from current solutions being adopted for PFAS removal?
SN: Three major technologies for PFAS removal are activated carbon, reverse osmosis (RO) and ion exchange (IX). While the first offers low cost for the adsorbant, it has only a low selectivity for short-chain PFAS. Reverse osmosis and other membrane technologies can efficiently retain short chain PFAS, but operating costs are high, and the resulting concentrates need further treatment.
Tailormade selective ion exchange resins, on the other hand, can have high affinities to either both short and long chain PFAS or only one of them depending on the demands and economics. IX is not only applied as a standalone solution but also used in combination with other technologies to leverage the advantages of the various methods. For instance, IX resins are employed as polishing filters to capture short chain PFAS downstream of activated carbon. Highly PFAS selective once-through IX resins are also applied as polishers to treat RO permeate while these and regenerable resins are used to further increase the PFAS content in the RO concentrate.
F+S: What are the concrete advantages of your technology?
SN: Ion exchange resins usually consist of a selective functional ionic group grafted onto a cross-linked polystyrene polymer backbone. Consequently, these materials combine a purely physical adsorption of the PFAS molecule carbon chain through hydrophobic interaction with the polymer backbone with a complementary strong interaction of the ionic group of the PFAS compounds with the functional group of the IX resin.
The resulting advantages are a high selectivity of different PFAS substances (long and short chain), extremely low effluent limits (up to one-digit ppt level) and very good adsorption capacities.
The viability and reliability of this technology has already been proven by numerous installations on both small and large scale treating up to several hundreds of cubic meters of water per hour.
F+S: Which industries or sectors do you think should be targeted for PFAS removal and why?
SN: Tighter regulations require industrial producers and users of PFAS to establish suitable methods for wastewater treatment to avoid the further distribution of these substances in the environment. In areas where the excessive use of these substances already resulted in the contamination of soil, surface water and groundwater (e.g. fire fighter drill ground close to airports and airbases), remediation is a necessity.
Municipalities are also looking into processes to provide PFAS free potable water to their communities. In addition, we also see an increasing interest in domestic solutions like point-of-entry filter systems or even special cartridges for pitchers and dispensers that capture these critical substances.
F+S: Looking ahead, when would you predict that PFAS removal will 100% optimized?
SN: Over the past years, the water treatment industry has established a toolbox of different technologies to choose from depending on the actual challenge. Nevertheless, we expect that further research and development will be necessary as the awareness of this issue rises and stricter regulation imposes even lower concentration limits to protect human health and the environment.
Lanxess will continue to dedicate resources for the further optimization of our products and for the expansion of our PFAS removal resin portfolio to provide reliable and cost-efficient solutions to our customers in the water treatment industry.
Dr Stefan Neufeind was interviewed as part of the PFAS Panel Discussion in the March 2024 issue of Filtration+Separation.
