For the very first time all ESRs met in person from November 10 to 12 at the Autumn School 2021 at Eindhoven University of Technology in the Netherlands. The first two days were entirely dedicated to soft skill development. From the Japanese philosophy of Ikigai to the expansion of your personal potential and eventually analytic storytelling a lot of important aspects were covered. Of course networking did not come off badly.
The last day was dedicated to the science. Instead of presenting the latest results individually the ESRs prepared group presentation within their workpackage, thereby emphasizing the connections between their projects and maybe even uncover a few new ones.
From 25th to 28th November 2021 interested people can enjoy four days of science and culture under the guiding theme “Let’s imagine the future!” during the Sorbonne University Science and Culture Festival.
Also we as Pioneer project participate in the festival to discuss the question “How can we recycle CO2?“. If you are in Paris we would like to invite you! (Sunday, Salle polyvalente, 3.45pm-4.45pm. Registration required.)
Carbon dioxide is demonstrated as the main component of the Carbon Cycle on Earth – a series of processes that transfer carbon in various forms throughout our ecosystem. Volcanic outgassing and wildfires are two major natural sources of CO2 that should be named firstly. Respiration, the process by which organisms get energy from their food, produces carbon dioxide. Human activities, combustion engines or in the industry, all produce CO2. As this would be, CO2 is a very important part of the earth. It is a major greenhouse gas that aids in the trapping of heat in our atmosphere, our world would be inhospitably cold without it. However, when the CO2 concentration grows, it contributes to global warming, thereby threatening to change our planet’s climate as average world temperatures rise. After industrial revolutions, CO2 was thrown into the air, causing serious climate change and human issues.
CO2 concentrations had risen sharply from pre-industrial levels of around 280 parts per million to over 410.5 parts per million by the start of 2019 [1]. Lately, the world was hit by a global pandemic known as coronavirus (COVID-19), which has spread to hundreds of countries worldwide, it spread quickly over the first few months across the world, infecting countries and territories, resulting in about 25 million confirmed cases and nearly 837000 fatalities. As of October 2021, the numbers are 235 million and approximately 4.9 million, respectively (recently updated data can be found in [2]). The entire Coronavirus Pandemic database may be reviewed here [3].
Lockdown orders had become the most important defensive front-line we’d ever had, with facemasks and hand sanitizer as our weaponry. Lockdown cities, school closures, transportation restrictions, industrial closures, company downsizing, and institutions, to name a few examples, have all been imposed by governments to regulate human activity in times of crisis. The spread of the COVID-19 was slowed as a result of these huge measures. At the same time, global climate data had changed dramatically for the first time in recorded history.
According to investigations conducted during the lockdown, CO2 levels have already decreased by nearly a fifth of all time, Fig.1, a huge number not seen since World War II.
Figure 1. Global CO2 emission from 1960 till May 2020 [4].
Based on the fact that CO2 levels fell by 17 percent in April 2020 compared to that of 2019, the first prediction anticipated that the CO2 level would fall between 4.2 and 7.5 percent from last year. The amount of CO2 in the atmosphere seems to have dropped as a consequence of enhanced social distance, which has led to the reduction of product consumption and manufacturing activities. Likewise, a decline in transportation operations contributed to the global fall in carbon emissions. Global aircraft traffic decreased by 60% during the closure, resulting in a short drop in CO2 emissions relative to pre-crisis levels. According to CNBC [5], the United States led the way with a reduction of 12 percent in carbon dioxide emissions, followed by the European Union with an 11 percent lower. India experienced a 9 percent decrease, while China saw a 1.7 percent share. Scientists estimate that this cut may have saved at least 77,000 lives.
Simultaneously, analyzing the northern ozone hole reveals the smallest ozone hole ever seen in history, shrinking from 6.3 million square miles annually to less than 3.9 million square miles at the beginning of 2020. Fig.2. Previously, the Montreal Protocol, which limited the manufacture of ozone-depleting chemicals and was approved internationally in 1987, was mainly credited in major part for ozone recovery (Because the use of CFCs has already damaged the ozone layer). During the Crisis, according to NASA experts, ozone concentrations above Arctic parts of the planet dropped by around 240 Dobson Units (The Dobson Unit -DU is a unit of measurement of the amount of a trace gas in a vertical column through the Earth’s atmosphere) on March 12, 2020, compared to March 12, 2019.
The pandemic’s impact appears to have aided the ozone layer’s recovery since the urge to heal has accelerated the process.
Figure 2. Arctic Ozone hole areas (million km2) measured from 1980 to 2019.
In another development, the ozone hole over Antarctica rapidly expanded starting in mid-August and peaked at around 24.8 million square kilometers in September 2020, covering the whole continent with ozone layer depths as low as 94 DU. As temperatures rise high in the atmosphere in late spring, ozone depletion diminishes, the polar vortex weakens, eventually breaks down, and ozone levels recover to near-zero by the end of December. Since the time that the ozone layer was started monitoring 40 years ago, it was the longest-lasting and one of the biggest and deepest holes [6].
These are all promising information, nevertheless, might be far away from reality because it was projected based on all indications during a shelter-in-place order, and circumstances will alter afterward, particularly when tight limitations have been relaxed. Researchers anticipate that emissions will rebound at the end of 2021 and the beginning of 2022, and they urge governments to include renewable energy and climate policy in their economic recovery strategies.
The fact that CO2 emissions globally decreased by 1.4-1.5 percent during the Financial Crisis in 2009, but followed by a huge increase of over 5% [7] only a year after. The Washington Post [8] also reported that COVID-19 might stabilize the global CO2 emission rate, but we shouldn’t be too relieved as evidence of the financial crisis. There is no surprise that CO2 could be emitted in excess of it after this situation.
Back into 2017, the CO2 emitted 2017 had an average concentration of 404 parts per million and keep reaching higher over the years. In 2019, it reached 410.5 parts per million, up 2.6 parts per million from 2018, and higher than the 10-year average. Although the carbon emissions decreased by 17 percent at their peak due to the lockdowns in late 2019-2020, the total effect on concentrations was extremely minor.
Figure 3. Data Comparison of CO2 release during 12 months of years from 2017 – June 2021. (Source: Global Monitoring Laboratory [4]).
CO2 recorded data keep growing in the second half of the year, following the prior pattern (Fig.3), notwithstanding the earlier effects of the crisis. The CO2 emitted steadily rises, with statistics showing that the average CO2 in August 2021 was 414.47 ppm, whereas it was 412.78 ppm in August 2020, with no signs of slowing down anytime soon.
The situation, as the evaluation of the National Oceanic and Atmospheric Administration, is still complex. CO2 Global emissions fell in 2020, has minimal impact on overall carbon emissions due to seasonal and natural fluctuations. Wildfires burning through forests released carbon dioxide even as emissions fell, potentially at a rate equal to the modest fall in emissions owing to the pandemic’s diminishing effect on the global financial system.
So, did the epidemic demonstrate that we had already begun to cut carbon emissions?
Temporarily, the answer is “Sort of, but not much”. When emissions fall below a certain level, global warming draws to a standstill, and COVID-19 doesn’t appear to have changed much.
From Tuesday 29th of June until 1st of July 2021 the ESRs attended the Liverpool Summer School organized by Xin Tu and Timo Gans. The training focused not only on plasma catalysis with lectures like Plasma catalytic experiment design, data analysis & energy efficiency by Xin Tu and Olivier Guaitella but also on the development of soft skills e.g. Communication skills by Dr. Dale Heywood or on commercialization issues like Understand IP by Howard Read and Richard Bray. This diversity was very much appreciated by the students. The only to make the school even better would have been to meet in person rather than online. We are looking forward for the next event…
We would like to thank the Sorbonne University Library service for providing our ESRs with a cycle of workshops about Open Access and bibliographic Search and Watch on May 5th and 6th, 2021 . It was very useful and informative, looking forward to use the tips learned for our future publications within the PIONEER consortium.
On March 17, 2021 Brigitte Attal-Tretout (member of the advisory board) and Richard Engeln were joined by quite a few ESRs as well as supervisors to discuss in situ analysis of trace species in plasma by Raman and LIF (Laser induced fluorescence ) diagnostics while enjoying a cup of coffee. This really shined light on the possible challenges.
In the last sixty years, the freshwater demand has more than doubled and as many as 3.5 billion people could experience water scarcity by 2025. Agriculture is the largest global user of freshwater and its consumption has increased by a 100 % in the last century while industrial water demand has more than tripled, due to an increasing requirement of electricity, fuel and water-intensive goods like textiles. During the same period, domestic water use has quickly risen by 600 %1. As the world population is still growing fast, finding suitable technologies to achieve a smarter water reuse and reduce our water footprint is urgent and of vital importance.
Hard time for conventional water treatment processes
Figure 1: Aerial view of a wastewater facility in California, US. Photo by J. Cameron on Unsplash2.
According to the WHO, 500 million people die each year because of poisoning or disorders associated to water contamination by biological or chemical agents3. The need to tackle water scarcity together with health issues related to pollution calls for the introduction of treatment capability beyond conventional water treatments methods. Water contaminants may include organic and inorganic substances, which can be toxic, and pathogens. Conventional water treatment processes are not always very effective in their removal. For instance, coagulation, sedimentation and filtration units are unable to effectively remove trace organic compounds such as pharmaceuticals, personal care products and endocrine disrupting chemicals4. Moreover, chlorination can lead to the formation of by-products such as trihalomethanes (e.g. chloroform), haloacetic acids and chloramines, which can be even more toxic than the parental molecules and thus requiring further depuration steps5. In order to meet the modern requirements for water quality, a combination of reverse osmosis and advanced oxidation processes (AOPs) has been often proposed. Moreover, UV irradiation is typically added as an additional layer of protection against pathogens and some chemicals. However, treatment costs are typically higher than conventional methods6.
Advanced oxidation processes (AOPs)
AOPs refer to those processes that generate large amounts of OH radicals, which have proven to be effective in the decomposition of a wide range of organic contaminants, toxins and pathogens. Conventional AOPs generally involve the addition of chemical precursors on site as well as adequate infrastructure to accommodate storage. Therefore, treatment costs exceed that of conventional water treatment methods, making them less attractive for the commercial scale and poorly accessible to the underdeveloped regions of the world, where the water scarcity is more severe6.
Plasma is here to help
At this purpose, plasma technologies are attracting more and more interest as a source of advanced oxidation species. Plasma-liquid interactions can offer a number of features that conventional treatment cannot provide at all and conventional AOPs can only provide at high cost. In particular, Foster6 points out that plasma can be generated in regular air or in the liquid itself, without the requirement of consumables. Moreover, plasma can combine the effects of different reactive species simultaneously, leading to faster decomposition rates. In addition, its application is inherently modular and therefore can be easily suited in a conventional water treatment system to substitute and reduce the number of depuration steps6.
Plasma for organic contaminant reduction
The reliability of plasma treatment to decontaminate water from organic pollutants has been deeply investigated in the past years. Magureanu et al.7 reviewed numerous studies on the removal of harmful pollutants such as phenols, organic dyes, pharmaceuticals and pesticides. While the potential of plasma to remove these contaminants is widely accepted, many efforts are still required to improve the energy efficiency of their decomposition and mineralization. In this respect, reactor design stands out as a major critical point. Besides the intrinsic characteristics of the pollutants and the aqueous medium, faster and efficient removal rates depend on the mass transfer of reactive species from the plasma to the liquid. At this purpose, maximizing the contact area between the plasma and the treated solution is of crucial importance. This could be achieved by generating a foam on the liquid surface or spraying the solution through the discharge area7,8. Magureanu et al.7 also points out that the combination of plasma treatment with other AOPs can enhance the removal efficiency by the generation of additional OH radicals. This can be realized either by recycling the effluent gas from plasma, rich in ozone, or by adding a catalyst to promote Fenton oxidation with the plasma-generated hydrogen peroxide. Indeed, additional ozone gas bubbling could improve removal rate of alachlor, an aromatic pesticide, and energy cost by more than 50 %9. Nevertheless, as much efficient as it is considered compared to conventional processes, plasma is energy consuming. At this purpose, Jiang et al.10 suggested that biological treatment should be coupled with plasma into integrated technologies for water treatment. Here, the AOP treatment step should be minimize as much as possible in favor of the biological stage, which is almost energy free. Therefore, the role of plasma should be limited to the breakdown of non-biodegradable molecules into biodegradable byproducts, leaving the task of completing the decomposition and mineralization processes to the biological treatments.
Figure 2: AC discharge (a) and self-pulsing discharge (b) tested for the degradation of PFAS in water by Saleem et al.11 Taken by a master’s thesis12 published at the University of Padova, Italy. Reproduced with kind permission of the authors.
Perfluoroalkyl substances: a new threat to water quality
Unfortunately, there are some extreme situations where most of the work cannot be delegated the biological treatment step and almost all the mineralization process needs to be completed beforehand. This is the case of perfluoroalkyl substances (PFAS), whose degradation byproducts are still harmful and non-biodegradable. PFAS are a group of more than 4700 chemicals and are used in a wide variety of consumer products and industrial applications because of their unique chemical and physical properties, including oil and water repellence, temperature and chemical resistance and surfactant properties. Those outstanding features are deriving from the fluoro-carbon bonds, which are extremely stable and thus unreactive. Their extraordinary characteristics turn out to be very undesirable when it comes to remove PFAS from water. The high hydrophobicity of the perfluorinated tails makes PFAS very prone to bioaccumulation and therefore potentially dangerous even at very low concentrations. On the other hand, their surfactant behavior and persistency bring those molecules far away from the source of contamination. Detection of PFAS in water is still very challenging and requires advanced analytical methods such as high-resolution mass spectrometry. To face this new challenge, water treatment plants are often equipped with activated carbon beds and ion exchange resins to adsorb PFAS. However, these techniques are affected by short breakthrough times and generate waste products, which require further treatments13. Moreover, most of the AOPs, based on oxidation by OH radicals, have proven to be inefficient against PFAS14. At this purpose, plasma technologies can be helpful to handle the issues related to the removal of these hazardous molecules by featuring a wide range of reactive species beyond OH radicals. Of particular interest are aqueous and free electrons, which are able to attack and remove fluorine from the long perfluorinated tails protruding from the solution surface into the gas phase. When the plasma feed gas is argon and a positive voltage polarity is applied, argon ions may also initiate reactions of charge transfer and trigger the decomposition of PFAS15. Moving from air to argon as feed gas can indeed improve the energy efficiency and lead to a faster mineralization without producing nitric acid and thus maintaining almost unaltered the characteristics of the aqueous medium11. Moreover, argon allows recirculation of argon through the reactor, reducing its consumption and eventually leading to decomposition of gaseous by-products which otherwise would be introduced in the atmosphere. Here, reactor design is extremely important and should focus on increasing the contact area between plasma and solution. In addition, bubbling should be introduced in order to increase the concentration of PFAS in the plasma-liquid interface11,15.
New challenges for plasma: micro- and nanoplastics
Figure 3: Collected plastic during Community Cleanup at the shoreline and harbourfront in Hamilton, Canada. Photo by J. Sessler on Unsplash16.
After disposal, up to 70 % of plastics is lost to the environment. Most of plastic materials are hardly degradable through weathering and ageing, thereby accumulating in the aquatic system for decades. Their slow degradation leads to the formation of plastic debris of different size. Particles with a diameter between 1 and 5 µm are defined microplastics (MPs), while particles with lower diameters are categorized as nanoplastics (NPs). Water and wastewater treatment plants are considered as an important pathway for the release of NPs/MPs since fragmentation and ageing of plastics can be accelerated by photo-oxidation by UV light, hydrolysis and mechanical fracture17. MPs are also contained in some commercial products such as face cleaners, drilling fluids, 3D printing products, pharmaceutical vectors and industrial abrasives and thus are directly introduced in the environment18. Detection of NPs/MPs is still very challenging and, due to their small particle size, only a few techniques can give a reliable quantification. Those techniques would be Raman and micro-Raman spectroscopy dynamic light scattering (DLS) and nanoparticles tracking analysis (NTA) which are quite expensive and sensitive to impurities in real water and wastewater samples17. AOPs, such as photo-degradation by UV light and chemical oxidation, have been proposed as suitable way to reduce the concentration of NPs/MPs in water but they are limited by long process periods, making them disadvantageous for scaling up18. However, ozonation led to formation of carbonyl groups on the surface of polystyrene plastic making its mineralization by microorganisms faster. Moreover, the generation of reactive oxygen species and strong UV irradiation in plasma systems could work together to induce the dissociation of C-C and C-H bonds in the PVC MPs19. In recent years, a few studies to simulate the artificially-accelerated aging of MPs have been carried out and those are reviewed by Liu et al.20 The aging potential of plasma treatment compared to the other processes tested is outstanding and very promising. However, no studies have been conducted on the possibility to decompose and/or make NPs/MPs more biodegradable by plasma treatment so far.
To conclude…
Plasma is a very promising and versatile tool, which can help to tackle water scarcity and reduce the disparity on the access to high quality drinking water. The wide range of reactive species produced can simultaneously decontaminate water by organic and inorganic compounds, pathogens and perhaps even by micro and nanoplastics, with a low energy demand and cost. Studies on the upscaling of such technologies must be prioritized as the stress on the water resources is constantly increasing.
1World Resources Institute. (2021, March 9). Retrieved from https://www.wri.org/
2Aerial view of a wastewater facility in California, US [online]. Available at: [https://unsplash.com//][Accessed 11 March 2021]
3World Health Organization (WHO). (2018). Retrieved from http://www.who.int/
4Huerta-Fontela, M., Galceran, M. T., & Ventura, F. (2011). Occurrence and removal of pharmaceuticals and hormones through drinking water treatment. Water Research 45, 3, 1432-1442.
5Gopal, K., Tripathy, S. S., Bersillon, J. L., & Dubey, S. P. (2007). Chlorination byproducts, their toxicodynamics and removal from drinking water. Journal of Hazardous Materials 140, 1-6.
6Foster, J. E. (2017). Plasma-based water purification: Challenges and prospects for the future. Phys. Plasmas 24, 055501.
7Magureanu, M., Bradu, C., & Parvulescu, V. I. (2018). Plasma processes for the treatment of water contaminated with harmful organic compounds. J. Phys. D: Appl. Phys. 51, 313002 (23pp).
8Stratton, G. R., Bellona, C. L., Dai, F., Holsen, T. M., & Mededovic Thagard, S. (2015). Plasma-based water treatment: Conception and application of a new general principle for reactor design. Chemical Engineering Journal 273, 543-550.
9Wardenier, N., Gorbanev, Y., Van Moer, I., Nikiforov, A., Van Hulle, S. W., Surmont, P., . . . Vanraes, P. (2019). Removal of alachlor in water by non-thermal plasma: Reactive species and pathways in batch and continuous process. Water Research 161, 549-559.
10Jiang, B., Zheng, J., Qiu, S., Wu, M., Z. Q., Yan, Z., & Xue, Q. (2014). Review on electrical discharge plasma technology for wastewater remediation. Chemical Engineering Journal 236, 348-368.
11Saleem, M., Biondo, O., Sretenović, G., Tomei, G., Magarotto, M., Pavarin, D., . . . Paradisi, C. (2020). Comparative performance assessment of plasma reactors for the treatment of PFOA; reactor design, kinetics, mineralization and energy yield. Chemical Engineering Journal 382, 123031.
12Tomei, G. (2019). Plasma non-termico per la degradazione di acido perfluoroottanoico (PFOA) in acqua (Master’s thesis). Università degli studi di Padova, Italy.
13Woodard, S., Berry, J., & Newman, B. (2017). Ion exchange resin for PFAS removal and pilot test comparison to GAC. Remediation 27, 19-27.
14Trojanowicz, M., Bojanowska-Czajka, A., Bartosiewicz, I., & Kulisa, K. (2018). Advanced Oxidation/Reduction Processes treatment for aqueous perfluorooctanoate (PFOA) and perfluorooctanesulfonate (PFOS) – A review of recent advances. Chemical Engineering Journal 336, 170-199.
15Stratton, G. R., Dai, F., Bellona, C. L., Holsen, T. M., Dickenson, E. R., & Mededovic Thagard, S. (2017). Plasma-Based Water Treatment: Efficient Transformation of Perfluoroalkyl Substances in Prepared Solutions and Contaminated Groundwater. Environ. Sci. Technol. 51, 1643-1648.
16Collected plastic during Community Cleanup at the shoreline and harbourfront in Hamilton, Canada [online]. Available at: [https://unsplash.com//][Accessed 11 March 2021]
17Enfrin, M., Dumee, L. F., & Lee, J. (2019). Nano/microplastics in water and wastewater treatment processes – Origin, impact and potential solutions. Water Research 161, 621-638.
18Rodríguez-Narvaez, O. M., Goonetilleke, A., Perez, L., & Bandala, E. R. (2021). Engineered technologies for the separation and degradation of microplastics in water: A review. Chemical Engineering Journal, 128692.
19Zhou, L., Wang, T., Qu, G., Jia, H., & Zhu, L. (2020). Probing the aging processes and mechanisms of microplastic under simulated multiple actions generated by discharge plasma. Journal of Hazardous Materials 398, 122956.
20Liu, P., Shi, Y., Wu, X., Wang, H., Huang, H., Guo, X., & Gao, S. (2021). Review of the artificially-accelerated aging technology and ecological risk of microplastics. Science of the Total Environment 768, 144969.
From 25th to 28th November 2021 interested people can enjoy four days of science and culture under the guiding theme “Let’s imagine the future!” during the Sorbonne University Science and Culture Festival.
