If you’re concerned with water quality and are curious about how chemistry can help improve it, then this episode is for you. Dr. Jessica Ray is using creative thinking along with her full chemistry and chemical engineering skill set to develop and use new composite materials, as well as repurposing common materials, to remediate and clean up urban wastewater and storm water. This is yet another episode that touches on how chemistry can help our environment while moving us from a linear to a more sustainable circular economy.
Great scientists look at the world around them, identify problems and think about how their area of expertise can provide a solution. This is what Jessica Ray does. In her native St. Louis, she experienced regular urban flooding and grew up familiar with the problem of managing urban wastewater. When, later in life, her studies took her to California, she experienced the opposite problem of severe droughts. This is how she became interested in urban water and started applying her chemical engineering skills to deal with the problem of contaminants, such as PFAS, in urban waste waters.
The theme of the unsustainability of our linear economy – where things are made, used and discarded - returns to the podcast. This episode explores Jessica’s disruptive work on the development of cost-efficient methods for the treatment of storm water and other urban water wastes. It’s a surprising discovery of a smart combination of everyday materials and clever chemistry that promises to bring us one step closer to a more sustainable circular economy.
Dr. Jessica R. Ray 00:06
When you talk to folks, and you mentioned Seattle, they usually think of two things, storm water, and coffee. So, we're trying to combine the two in a way that is really effective, really exciting to address the real problem.
Paolo 00:22
It may not always feel like it, but water is a precious resource. And as our climate continues to change, it will only become more precious. Luckily for us, Dr. Jessica Ray is working on new, innovative ways to clean our water and lighten our impact on environment. In this Season Two episode of Bringing Chemistry to Life, we speak with another member of Chemical and Engineering News' 2020 Talented 12, about their work and trends in their field. I'm your host, Dr. Paolo Braiuca from Thermo Fisher Scientific. We began by asking Dr. Ray about her background, and how she became interested in their current work.
Dr. Jessica R. Ray 01:03
I grew up in St. Louis, and one of the main focuses of my research group is to help address contaminants present in what I call urban stormwater, what's called urban stormwater. And when I was in St. Louis, you know, it rained all the time, we had flooding often. So, I didn't think much about the very present and growing issues around the availability of water, because in St. Louis with, you know, as I said, it rains a lot. We have the Mississippi River nearby, so we have lots of water available to us, in St. Louis. And then when I moved to California, I got a very different perspective on the availability of water and the lack of water. For example, when I was there, from 2015 to 2018, California was undergoing one of the worst droughts they've had on record. And I'm sure that trend is expected to continue over the next couple of years. So, it was exciting to be a researcher interested in water quality and water treatment in a place like California that's really pushing a lot of the boundaries with respect to how we view water, how we view wastewater, how we view alternate sources of water that can, you know, help solve this very real crisis that's going on in, you know, the arid coastal cities like San Francisco, um like Seattle. So, when I, now at University of Washington, I am really thinking about this, this need for, you know, addressing contamination in different water sources to ultimately increase the urban water supply sustainability. But it was something that I had not thought of, you know, when I was a young, a young researcher, and now I understand the magnitude of the issue and really excited that I can contribute to, you know, this work. I think one of the benefits of the work that I'm doing is it's very tangible. So, you know, most folks know about the natural water cycle and stormwater, and you know, like, to some degree, the pollutants that are present in water. So, it's a very easy draw to, you know, increase awareness of these issues to young students and the general public. So very, very easy entry point.
Paolo 03:26
Can you describe what are your areas of focus, but in particular?
Dr. Jessica R. Ray 03:31
Sure, yes. So, we are trying to remediate per- and polyfluoroalkyl substances, or PFAS, using a holistic approach. And so, I'll describe what I mean by that. And it starts with our focus, which is PFAS present in water sources. So, this, you know, PFAS, unfortunately, are not just limited to contamination of water, you can also have PFAS contamination in the atmosphere. But with respect to water, one of the challenges with PFAS is they are very persistent in the environment. So, we know they don't degrade biologically or via even more traditional pathways that you would, for example, undergo during drinking water and wastewater treatment. So, when they end up in the environment, they tend to stay there for long periods of time. We view our mediation, our holistic remediation approach in two stages. The first stage is separation of PFAS from water and then the second stage is degradation or destruction of PFAS in water. So, to get to the first point of separation, we are trying to think about creative approaches to address this issue that I just described where PFAS tend to exist in very low concentrations compared to everything else in the water. So, if you are trying to use conventional adsorbents that are used to separate contaminants in water during water treatment that might not be effective, because they're not selective. If you have a material that's able to adsorb a wide variety of contaminants, what might happen is say you have over time, the surfaces of the adsorbent get occupied by other contaminants. And so, if a PFAS molecule comes along, it might not be able to effectively bind to that adsorbent surface. And so, you have the PFAS that are now just in the treated effluent water that we then need to contend with in in the environment. So, to get around this issue, we are trying to build selective adsorbents that target PFAS in water. And the hope there is that if we can design the material in a way that imparts this specificity and selectivity, that even if you have a lot of co-contaminants present, you still get removal of the most, you know, acutely toxic, and low concentration contaminant that you're interested in, which is the PFAS. And the way we're doing that is using this process called molecular imprinting. And essentially what you do is you have some functional materials that you start with and a template compound. So, say this template is one of the PFAS molecules that are really present in the environment. And then we build the material that incorporates the template into the structure of the adsorbent, and then afterwards, you do an extraction step to extract the template that you started with. And what you're left with is a material that has an imprint specific to the template compound. So, we refer to this as a lock and key type removal mechanisms. We have really high specificity, affinity, and selectivity for the template compound that you start with. So, what our group is doing is we are taking advantage of those material science skills that you know, I've talked about before in designing composite materials that have larger, more robust substrate supports for this molecular imprinting material that then surrounds the surface. So, we have started a couple of iterations of this material, we've tried using sand as a substrate. Sand is very commonly used in both, you know, decentralized, you know, rural low cost, resource constrained area water treatment, but also in more centralized water and drinking water and wastewater treatment applications. So, it's a very easy material to work with. And it can be easily implemented in a lot of existing infrastructure. And we're taking sand grains and essentially coating it with this selective PFAS material that we've developed. And now we're on to iteration two and three, using different substrate materials to really get to a final version of our composite materials that could impart the selectivity that we want, but on a, you know, at a level that could be used to treat large volumes of water. So that's the goal.
Paolo 08:16
So, those are all interesting concepts there. Can we discuss a bit more about the chemistry and the kind of interactions you leverage?
Dr. Jessica R. Ray 08:24
Sure, yes. So, what we are taking advantage of is using functional monomers that have some structural moieties. And similarities to for example, PFOA or PFOS to do the polymerization and imprinting process. And then we're also taking advantage of the fact that these PFAS tend to be negatively charged, and water. So, we're using the electrostatic interactions of the negatively charged PFAS with positively charged moieties on our functional monomers and our, you know, other polymerization reagents. And then we're also taking advantage of, for example, these fluorine-fluorine interactions with functional monomers that have similar structures to the PFAS that we're trying to remediate. So those, we're in the process now, as I mentioned, of doing a couple of different iterations of this material, and a lot of those iterations involve, you know, tweaking the different monomers that we use to ultimately maximize the efficacy of the imprinting step. So, there's been some interest I n a molecularly imprinted polymer material for PFAS so we have a place to start in terms of literature, where other folks have, you know, started to poke around in this area, and we are trying to find kind of the best recipe of the template and functional monomers and other ligands to use during polymerization, but mostly relying on those hydrophobic interactions and the electrostatic interactions to do so.
Paolo 10:15
It seems very tricky, because then I'm assuming you, well, you, you use, your resin, or your, your, your capturing affinity material in an extremely uncontrolled environment, right? So, I'm assuming there's a lot of variability in in the wastewater. You could have shifts in pH, you have 1000s of compounds in there that could potentially, you know, bind to your to your material and, and even displace the PFAS somehow or, or kind of changing the affinity, right, so that the importance of the macro and microenvironment must, must be huge. So, do you have a sense for the kind of performance in the range of conditions typical range of conditions that that you experience in in a real-world application?
Dr. Jessica R. Ray 11:05
That's a great question. And it's where we're headed very soon. So right now, we're still in the development phase, we have done some testing. For example, if you use, let's say, PFOS as a template compound, but then you have, you then use the polymer material composite that we've created to treat water that contains PFOS, but other short and long chain PFAS derivatives, you know, how selective is the material for PFOS and so we see preferential PFOS absorption, but we also see some absorption of those other PFAS compounds as well. Which in this case, it's not a bad thing, because we want to get rid of them. Right? We're trying to catch them all. So yeah, and this case, it's not a bad thing. And the next stage would be to assess the performance when you have other organic and inorganic co-contaminants that don't look like PFAS. And then the next step would be to investigate these materials in different water matrices. As you mentioned, there's a lot of variability depending on if you're treating contaminated groundwater contaminated surface water or contaminated wastewater with PFAS. So, we want to understand the impact of those aquatic conditions on the ability of our material to remove PFAS. So that's where we're going very soon.
Paolo 12:36
And so, you capture these, these, these PFAS, and you can concentrate them, right, and then you can wash them out to your adsorbent, so that you can reuse the adsorber in a new cycle of treatment. And then you have this concentrated solution of your contaminants. And at that point, you need to get rid of them. To me, they sound, or they look actually as pretty stable compounds, right? What do you actually do with them?
Dr. Jessica R. Ray 13:04
Yes, that's a, you're, right? They are extremely stable, that's posed a huge problem in wastewater treatment, because our conventional approaches to degrade contaminants during, you know, the oxidation and disinfection stage of treatment is not effective to, you know, degrade these compounds. So, we're looking at the literature and what's been investigated at the lab scale and is slowly moving its way towards the field scale, is using what's called advanced reduction processes for PFAS. So, what you're doing is using a photosensitizer, or chemical mediator, for example, that is being excited by UV light, and that reaction generates a highly reactive reducing species called solvated electrons or hydrated electrons. And what the literature has shown is that these solvated electrons are very effective at cleaving the carbon-carbon center most carbon-carbon bonds within, for example, PFOS or PFOA, but they can also cleave those carbon-fluoride bonds that are very difficult to degrade otherwise, so there's been a lot of interest in trying to increase the efficacy of these solvated electrons that are very short lived species and water but are very effective at degrading PFAS. The bulk of the work has been, as I described, you know, UV light, you add some chemical mediators, say for example, sulfite or iodide, and you expose that to UV light and that generates the solvated electrons in the water that is also contaminated with PFAS and there's been a lot of studies to show the efficacy of degradation, how fast this occurs, etc. And more recently, there has been work looking at the use of some kind of substrate or material to help facilitate this process. Because if you do the approach that I just described, what you're relying on is the solvated electron, the short-lived species that's generated in water to find PFAS in solution. And on the way that solvated electron can be scavenged by, you know, protons, dissolved oxygen, a lot of other species that are probably going to coexist in the water with PFAS. And so that limits the efficacy of treatment. And what recent work has found is that if you have some sort of substrate material, for example, a very effective adsorbent for PFAS, then what you're doing is you're fixing the PFAS to a certain location right on the surface of the substrate. And now if you generate the solvated, electrons and water, they can more easily target the PFAS because the PFAS are all stuck on the surface of the substrate. And that has extremely increased the rate of PFAS degradation and the efficacy of PFAS degradation. And this project that we've been working on for the last year or so it's finally coming together. We'll hope to publish this soon. But we are using these two-dimensional nanomaterials that are really effective adsorbents for PFAS, but also possess very high charge transfer kinetics and electron shuttling abilities. And what we found is that without the need for UV light, if you just add in an oxidant to this water, let's say that has PFAS, and these two-dimensional nanomaterials that they can generate solvated electrons near where the PFAS are co-located, to rapidly degrade PFAS to near 100% defluorination efficacy. So, we are using this material called MXene and it's a metallic carbide or nitride layered material. Its morphology is similar to graphene nanosheets, for example. And we're taking advantage of the carbon kind of two dimensional nanosheet morphology as an effective adsorbing for PFAS, but also the rapid charge transfer kinetics of this material to produce those solvated electrons near where the PFAS are adsorbed to really really boost the mineralization efficiency. So that was, it's been a long journey we were we were observing all of these different phenomena with this system. And we're trying to understand what was happening. And yeah, it's really coming together in the last, you know, couple months or so we're excited to share this work with the public soon.
Paolo 18:12
We hope you're enjoying this episode of Bringing Chemistry to Life. Please remember that you can find more information about Jessica and her work in our episode technical sheet. And also, as a listener, you can get a free Bringing Chemistry to Life T-shirt, a fun way to show your love for science. Just stay tuned until the end of the episode for instructions. And now back to our conversation.
How far are we from a real-world application?
Dr. Jessica R. Ray 18:39
With the selective adsorption material, I think maybe in the next couple of years, we could, you know really confidently say we've characterized this material enough to know where it works, where it doesn't work so well, under what conditions could you optimize PFAS absorption. For the degradation technologies, those are going to be a little bit of a ways off, we're still very much in the proof-of-concept phase for that technology. On the flip side, for the materials that we're developing to remove contaminants in stormwater; so that's something I haven't talked about yet, but we're kind of going to the reverse or opposite kind of thought process with those materials that we're developing. Because for stormwater, you really need something that is going to remove a wide variety of contaminants because unfortunately, we have a wide variety of contaminants present in urban stormwater. So, we don't want specificity, we want something that is, you know, more along the lines of your activated carbon. Something that can remove a wide variety of contaminants. So, for those technologies, those could be field ready in the next year or so. Because we've been we've designed them to have this broad range of contaminant removal properties, but also, we've intentionally designed them to be implemented and amended in existing green stormwater infrastructure, for example, a rain garden or a bioswale.
Paolo 20:10
So, they do they do they have a way to recycle themselves?
Dr. Jessica R. Ray 20:13
So I'll briefly describe the two materials that we're developing. The first is actually an analogue to activated carbon. We wanted a material that had all the benefits of activated carbon, but was not sourced from coal, which is where a lot of activated carbon is sourced from. So, for that we are using used coffee grounds. And we are pyrolyzing and activating them to create our own activated charcoal material. And we've done direct comparison to commercial granular activated carbon have basically comparable performance to, you know, be activated carbon. We're doing these longevity studies in the lab right now, basically, creating small filtration systems packed with our used coffee ground material, and we are flowing, synthetic, contaminated stormwater through, through these columns. And we've been treating, for example, we started this process in January. So, it's been what 5 to 6, 5 months already, we're still treating the water, it's still removing contaminants. So yeah, those that material is very promising and has a lot of very valuable benefits. Because it's, you know, it's very widely available. Coffee, you can find everywhere I happen to live in the coffee capital. Right, there's, but it's great, because what our studies have shown is that a little goes a long way in terms of, you know. For example, the system I just described, we're treating stormwater now for the past five months, has only used four grams of the used coffee ground material.
Paolo 22:06
And this is amazing, because, you know, besides you know how brilliant this is, right? Using coffee in Seattle. But you're, you're using a waste material, right? That would go to waste. To treating waste. Yes. So, you get double value out of two different waste streams. Which, which is amazing if… This is what science can do. Yeah, I'm really impressed. So, you obviously treat these grounds somehow, what is really happening? Why, what is it that makes these materials so long lasting?
Dr. Jessica R. Ray 22:41
With the used coffee grounds, and with the generation of activated carbons, we are lucky in the fact that the used coffee grounds happen to be very carbon rich in nature. And that's really something that you want, if you're trying to make your own activated charcoal material. You want to start with the feedstock that's very rich in carbon. Because what that does is when you burn that feedstock, at very high temperatures, you are really kind of exposing the carbon in a way that is really effective for hydrophobic interactions with organic compounds, for example, or organic contaminants in the water that you're treating. And what we've done then is we, so we examined, for example, a range of the like temperatures used to create the charcoal material to see what works best in terms of contaminant removal and water. And we found that for some organic compounds, even if you just you know pyrolyze the material at high temperature, and by high temperature, we're using low temperature and what we found is even at that low temperature, we have a fairly high removal capacity for certain types of organic compounds, say those that are tend to be more hydrophobic, those are actually pretty well removed even with just that material. But to target contaminants like PFAS in water, what we've done is we've taken that 400 degrees Celsius burned material and then we have mixed in potassium hydroxide. And potassium hydroxide, you know, similar to lye, for example, as a caustic material, we're using very low amounts of those. So, we take a gram of the pyrolyzed uses coffee grounds and a gram of the potassium hydroxide, we mix those and then do another pyrolysis step to generate an activated material and what the what that does is the potassium hydroxide reacts with the kind of the trapped carbon in the material. So, what you get in the final product is, you still have that high carbon nature imparted on the material. But you have significantly increased the porosity and the surface area of the material due to this kind of trapped carbon escaping during the, the second pyrolysis. And so, what we've observed is a 300% increase in surface area if you do this second activation step. Which is I should say similar to activation processes use for granular activated carbon, we're just using significantly lower concentrations of our activating agent, which is that potassium hydroxide, so.
Paolo 25:44
And your your original source is also much more sustainable?
Dr. Jessica R. Ray 25:47
Yes, exactly. So, yep, we we're using the used coffee ground activated carbon material primarily for the stormwater treatment. But for example, it could also be used as a substrate for our selective PFAS polymer coating, because another benefit that we were very pleased with the used coffee ground material is that it's very mechanically robust. And it does not adsorb water, to the same degree as other bio-char adsorbents, for example, or even some activated carbon. So, we're not significantly impacting the flow of water when we use this material. And because it's so sturdy and robust, it could be used, for example, in a packed column, or packed bed or packed column to do other sorts of water treatment application.
Paolo 26:45
So, are we looking at the future of urban water cycle, which is made of a sort of mix of low, broad scope adsorbents, possibly of sustainable nature, your coffee ground technology? Plus, you know, a range of selective materials, that are looking at capturing the very specific contaminants that would be otherwise be completely lost. And so, in somehow in an integrated system that are going to change the fundamental way we are looking at our cities, right, how we build them up and the infrastructure that sustains it.
Dr. Jessica R. Ray 27:24
Right, exactly. We, I think going forward, what really needs to happen is a mix of a bunch of different things. So, using more sustainable technologies, like the used coffee ground material, using in the cases where needed more selective materials to target certain pollutants, that needs to happen in conjunction with folks who are doing this kind of green chemistry work where instead of purposely synthesizing you know, these PFAS, which serve a very practical function. If we could do so in a way that is less, you know, harmful to the environment, but still has the same benefit of the intended application that needs to happen as well, so that we overall just reduce contaminant loads to the urban water cycle. Also, I think what needs to happen is in you know, as we're becoming more urbanized, and you know, looking to expand, or I guess, shrink our more rural suburban landscapes to more urbanized landscapes going to be very cognizant of the water infrastructure in place and how, you know, if we need to build new water infrastructure, say we need to build a new wastewater treatment plant for this growing city that's emerging in the Midwest, we need to think about ways to ensure maximized lifetime of that infrastructure, but also start to get creative with respect to these kind of modular units that could be used, you know, as I described, to tackle certain problems with respect to contaminant loads, and the kind of lasting contaminants that are hard to degrade. That also, of course, includes stormwater management. So, for example, cities built after the 1900s. They all have separate storm and sewer drains, so the sewage from your house and your businesses go to a wastewater treatment plant. The stormwater that flows over all of those engineered surfaces just gets directly discharged to a body of water. So, you've bypassed any opportunity for treatment in that case. So, if you're going to be you know, expanding a city or you know, building a new city, then you can think really creatively about how we manage these different water streams to ultimately reduce contaminant loads.
Paolo 29:55
And indeed, we need more people like yourself developing technologies for this, right? And thinking about the the problem in in a holistic way. And I'm glad to see that there are people around and obviously the future might look a bit brighter. So, as we get to the end of our chat, there's there's always that question that I like to ask for, for closing the interview. Which is, you know, what will be your piece of advice that you would pass on to someone just starting in their scientific career?
Dr. Jessica R. Ray 30:29
That's a great question. So, advice I would give to young folks, young students who are thinking about research is to just try you never know until you try. And also, to try a lot of different research experiences, I was lucky in that the first one I did, I really fell in love with that particular track and continued down that pathway. But I know a lot of folks who have dabbled in, you know, research where you would go out into the field and collect samples and do some analysis in the lab, or you would study air pollution, or soil quality. So, there's, there's so many options that you have available to you. And it really just starts with a simple email or phone call or conversation. So, to just try research as early as possible, because if it's something that you really enjoy, starting earlier is going to be really beneficial for you later on. So that's one advice, one piece of advice I would give. And then as a follow up to, you know, look to your local, you know, state universities, there are, you know, faculty who are looking always looking for, you know, young, talented, fresh minds to help out with projects that they have currently, you know, going on in their research. So, look to your local institutions there are also a lot of programs for you know, K through 12. Or, you know, elementary level, junior, you know, middle school level, but also high school students to go out and not only do research in their hometown and in their state, but to travel to other universities to do a summer research experience, for example. So, look out for those opportunities, they are absolutely out there you need to search.
Paolo 32:24
That was Dr. Jessica Ray, Assistant Professor of Civil and Environmental Engineering at the University of Washington, and one of our Chemical and Engineering News' Talented 12. Thanks for joining us for the season two episode of Bringing Chemistry to Life and keep an ear out for more. If you enjoyed this conversation, you're sure to enjoy the Dr. Ray's book, video, podcast, and other content recommendations. Look in the Episode Notes for the URL where you can access these recommendations and register for a free bringing chemistry to life T-shirt or simply visit thermofisher.com/BCTL This episode was produced by Matt Ferris, Matthew Stock and Emma-jean Weinstein.