- A fibrous adsorbent selectively recovers high-purity gold from waste - Dramatically reduces the cost and time of the recovery process and enables material to be mass-produced and repeatedly recycled Korea relies on imports for most of its metal resources, and in recent years, due to resource depletion and rising raw material prices, 'circular resources' that recycle waste metal resources have emerged. In response, SK hynix has established a mid- to long-term plan to increase the percentage of copper, gold, etc. recovered and reused from waste generated in the semiconductor manufacturing process to more than 30% by 2030, and Samsung Electronics is running a collection program for used mobile phones in cooperation with E-circulation Governance, a non-profit corporation. The global circular economy market is expected to more than double in size from approximately $338 billion in 2022 to approximately $712 billion in 2026. In this context, a team led by Dr. Jae-Woo Choi of the Water Resource Cycle Research Center at the Korea Institute of Science and Technology (KIST) announced that they have developed a technology that can selectively recover high-purity gold from electrical and electronic waste containing various metals using textile materials. Adsorbents for metal recovery are generally granular in shape to increase adsorption efficiency based on high specific surface area, but they are difficult to control underwater, resulting in low recovery rates and even secondary environmental pollution. On the other hand, fiber-like materials are easy to control underwater and can be made into various shapes through the weaving process, so they have high potential for industrial application. However, due to their thin thickness and low strength, they are easily broken when gold recovery is applied to the support. KIST researchers have chemically immobilized alkaline molecules on the surface of polyacrylonitrile (PANF) fibers to improve both molecular gold recovery performance and structural stability. The amine-containing polymer fiber has a dramatically larger surface area, which can improve the adsorption performance of gold ions (Au) in waste by up to 2.5 times (from 576 mg/g to 1,462 mg/g) compared to the team's previously developed granular gold adsorption material. The developed fibrous adsorbent not only showed a gold recovery efficiency of more than 99.9% in solutions obtained by leaching real CPUs, but also achieved a gold recovery efficiency close to 100% in a wide range of pH 1-4, which includes most waste liquids. It is particularly noteworthy that only gold ions can be recovered with a high purity of over 99.9%, even in the presence of 14 other metal ions coexisting in the solution. Furthermore, the gold recovery rate was maintained at 91% even after 10 uses, demonstrating excellent reusability. "By enabling efficient and eco-friendly metal resource recovery, the fiber-type adsorbent developed by KIST can reduce Korea's dependence on resource imports and prepare for the risk of rising raw material prices," said Dr. Jae-Woo Choi. "We plan to expand the scope of future research to selectively recover various target metals in addition to gold, said Dr. Youngkyun Jung." [Figure 1] Preparation and physicochemical characteristics of the aminated polyacrylonitrile fibers (PANFs). [Figure 2] Au recovery performance of the ALPF. [Figure 3] Applicability of the ALPF adsorbent for Au recovery processes. ### KIST was established in 1966 as the first government-funded research institute in Korea. KIST now strives to solve national and social challenges and secure growth engines through leading and innovative research. For more information, please visit KIST’s website at https://eng.kist.re.kr/ The research, which was funded by the Ministry of Science and ICT (Minister Jong-ho Lee) through the Leading Materials Innovation Project (2020M3H4A3106366) and the KIST Air Environment Complex Response Research Project (2E33081), was published in the international journal Chemical Engineering Journal.

- Synergistic effect of nitrate on natural purification of groundwater discovered - New water quality management paradigm for Aquifer Storage Recovery (ASR) techniques to secure stable water resources In recent years, the world has been experiencing floods and droughts as extreme rainfall events have become more frequent due to climate change. For this reason, securing stable water resources throughout the year has become a national responsibility called 'water security', and 'Aquifer Storage Recovery (ASR)', which stores water in the form of groundwater in the ground when water resources are available and withdraws it when needed, is attracting attention as an effective water resource management technique. The Korea Institute of Science and Technology (KIST) announced that a team of Dr. Seunghak Lee, Jaeshik Chung, and Sang Hyun Kim from the Water Resources Cycle Research Center has discovered that the natural purification of groundwater is enhanced by nitrate, a known pollutant. In order to apply ASR techniques in practice, it is very important to predict and manage the quality of recharged water, and this research is expected to mark a turning point in the water quality management strategy of ASR systems. In addition to storing water resources, ASR techniques have the added benefit of improving water quality through various reactions in the ground. The organic pollutants in the recharged water are degraded by the interaction of microorganisms in the aquifer soil with the iron oxide minerals, and in general, the iron oxide minerals are gradually transformed and the effective surface area is reduced, causing the natural attenuation of organic pollutants to stop. The KIST researchers found that the coexistence of nitrate in the recharged water leads to the formation of a new type of iron oxide, which results in a much higher removal efficiency than the stoichiometrically predicted organic pollutant removal efficiency. The coexistence of nitrate increases the duration of natural attenuation because it creates new species of iron oxides that can sustain the degradation of organic contaminants. Furthermore, the researchers found that the pollutant nitrate is removed during the overall reaction. "This is the first study to confirm the positive role of nitrate in groundwater, which is known only as a water pollutant," said Dr. Seunghak Lee of KIST. "Based on this, we are promoting the development of ASR water quality management protocols that dramatically change the existing water quality management paradigm, such as introducing allowable standards for nitrate residue in the pretreatment process of the recharging water." [Fig 1] Aquifer Storage Recovery (ASR) Overview [Fig 2] Natural attenuation of organic pollutants by iron oxide reductive dissolution in aquifers during ASR [Fig 3] Increased removal efficiency of organic pollutants due to the generation of new type of iron oxide minerals in the presence of nitrate ### KIST was established in 1966 as the first government-funded research institute in Korea. KIST now strives to solve national and social challenges and secure growth engines through leading and innovative research. For more information, please visit KIST’s website at https://eng.kist.re.kr/ The results of the research, which was funded by the Ministry of Science and ICT (Minister Jong-ho Lee) through the Climate Change Impact Minimization Technology Development Project (2020M3H5A1080712) and the KIST K-Lab Program (2E33084), were published in the February issue of the international journal Water Research. Journal : Water Research Title : Synergetic effect of nitrate on dissolved organic carbon attenuation through dissimilatory iron reduction during aquifer storage and recovery Publication Date : 2024.02.01. DOI : https://doi.org/10.1016/j.watres.2023.120954

- Development of fiber-based adsorbent material to recover valuable metals from industrial wastewater - Minimize toxic chemicals and energy use by eliminating the need to replace and regenerate materials Technology to recover valuable metals from wastewater generated in various industries such as plating, semiconductors, automobiles, batteries, and renewable energy is important not only for environmental protection but also for economic reasons. In Korea, chemicals are mainly added to wastewater to precipitate heavy metal ions in the form of oxides, but accidents such as leakage of hazardous chemicals have occurred one after another, so it is necessary to develop more eco-friendly technologies. Against this backdrop, the Korea Institute of Science and Technology (KIST) announced that Dr. Jae-Woo Choi's team at the Water Resource Cycle Research Center has developed a fiber-like metal recovery material that can recover metal ions in water by adsorbing and crystallizing the metal, and the recovered metal crystals can desorb and regenerate themselves. KIST research team has developed a semi-permanent adsorption material by utilizing the phenomenon that metal ions in water crystallize when certain chemical functional groups are fixed on the surface of a fiber-like material and introducing a technology to remove the formed crystals. When tested with copper ions, the maximum adsorption amount of existing adsorbents is only about 1,060 mg/g, but by utilizing the developed material, near-infinite adsorption performance can be secured. In addition, existing high-performance adsorbents are in the form of small granules with diameters ranging from a few nanometers to tens of micrometers, making it difficult to utilize them underwater, but the metal recovery material developed by the KIST research team is in the form of fibers, making it easy to control underwater, making it easy to apply to actual metal recovery processes. “Since the developed material is based on acrylic fibers, it is not only possible to mass produce it through a wet spinning process, but also to utilize waste clothing,” said Dr. Jae-woo Choi of KIST. “The wastewater recycling technology will help reduce the industry's dependence on overseas sources of valuable metals that are in high demand.” [Fig 1] Structure and concept of SRF (a) Schematic illustration of fabricating PAN/PMMA fibers using a dry-jet wet spinning machine. The diameter of the PAN/PMMA fiber was readily controlled by regulating the injection rate and rolling speed. Information on the diameter of the fibers is summarized in table S1. Illustrations representing the physicochemical structure of (b) the PAN/PMMA fiber and (c) the SRF. (d) A series of courses for self-regeneration in which crystal layers are repetitively formed-detached on an SRF surface. The heavy metal ions and counter-anions induced nuclei for crystal growth, resulting in the formation of crystal layers. The crystal layers are self-detached from the SRF surfacevia collisions with each other, non-sticky surfaces, and the curvature of the fiber, and new crystals grow on the SRF surface in which the crystal layers are detached. (e) SEM image of the SRFs immersed in 1,000 ppm copper nitrate solution for 1 h. The three self-detachment aspects of the copper crystal layer, i.e., collision between the crystal layers, a non-sticky surface, and curvature of the SRF, were observed. Scale bar: 100 μm (f) Snapshot images show the course of self-detachment of crystal layers from an SRF via (g) non-sticky surface formation, (h) collision, and (i) surfacecurvatureduring an elapsed time of 55 min (Ci of 100 ppm and no pH adjustment). Scale bar: 200 μm. [Fig 2] Analysis of the self-detachment of crystal layers on the SRF surface. (a) Defect regions, which are negligibly narrow compared to the size of the crystal layers, cause the non-sticky SRF surface. (b) It also accelerates the detachment of the crystal layers by an elastic restoring force against the curvature of the SRF. (c) The dominant detachment phenomenon of crystal layers around the critical defect area is a collision between the crystal layers, accompanied by divergence or convergence depending on their angle and position. (d) When the defect region is larger than the size of the crystal layers, the growth of the crystal layers is terminated. FEG-SEM images show the self-detaching phenomena of the copper crystal layers from the SRF surface. (e) Self-detachment by the non-sticky surface, (f) the curvature of fiber, (g) and the divergence (inset scale bar: 1 μm) and (h) the convergence of crystal layers. (i) Termination of crystal growth. The purple region expressed on the fiber to distinguish it from the heavy metal crystal layer formed on the SRF surface represents wide defect regions where the crystal layer is not formed. Commonly, new crystals grow on the SRF surface after the existing crystal layer is self-detached. Scale bar: 50 μm. (j) XRD pattern of the SRF including crystals grown from the adsorbed Cu2+. It is matched well with that of a Cu2(NO3)(OH)3 polycrystal (ICDD No.01-075-1779). (k) SEM image of the Cu2+ crystal layers separated from the SRF surface exhibits a form similar to the curved surface of SRF. Scalebar: 200μm. (l) HR-TEM image of the Cu2+ crystal layer displays d-spacing values that match well with the XRD pattern. Scalebar: 10nm. [Fig 3] A heavy metal recovery module packed with the SRF. (a) Representative illustration of the module packed with the SRF for continuous recovery of heavy metals. The recovery module includes an upper part, in which the SRF is filled and is connected to the inlet and outlet pipes of the heavy metal solution, and a lower space, in which crystals of the heavy metal resources self-detached from the SRF surface can be concentrated by a density difference. (b) Actual photographs of the module packed with the SRF. (c) The heavy metal ions are crystallized on the surface of the SRF fiber. Scale bar: 500 μm. (d) Actual photographs of the module packed with the SRF during the injection of copper nitrate solution for 5h. (e) The heavy-metal crystal layers are self-detached and gathered at the bottom of the module. Scale bar: 200 μm. (f) A constant weight of crystal layers for heavy metals could be recovered during continuous injection of 100 L of copper nitrate solution with 100 ppm concentration into the module, packed with 5 g of SRF at a flow rate of 0.2 L/min. (g) Deconvoluted XPS peaks of N 1s on the SRF with different immersing times in the copper nitrate solution: 0, 1, 5, 10, 20, and 50 h. ### KIST was established in 1966 as the first government-funded research institute in Korea. KIST now strives to solve national and social challenges and secure growth engines through leading and innovative research. For more information, please visit KIST’s website at https://eng.kist.re.kr/ The research, funded by the Ministry of Science and ICT (Minister Jong-ho Lee) through the Leading Project for Material Innovation (2020M3H4A3106366), Sejong Science Fellowship (RS-2023-00209565), and KIST Institutional Unique Project (2E32442), was published on October 16, 2023 in the international journal Advanced Fiber Materials. Journal : Advanced Fiber Materials Title : A Self-Regenerable Fiber Sloughing Its Heavy Metal Skin for Ultra-High Separation Capability Publication Date : 2023.10.16. DOI : https://doi.org/10.1007/s42765-023-00333-0

- East Asian and North American cold snap anomalies are caused by mid-latitude ocean fronts, not sea ice - Important predictor fornear-term climate change on a decadal time scale If the world is warming, why are our winters getting colder? Indeed, East Asia and North America have experienced frequent extreme weather events since the 2000s that defy average climate change projections. Many experts have blamed Arctic warming and a weakening jet stream due to declining Arctic sea ice, but climate model experiments have not adequately demonstrated their validity. The massive power outage in Texas in February 2021 was caused by an unusual cold snap, and climate models are needed to accurately predict the risk of extreme weather events in order to prevent massive socioeconomic damage. In particular, climate technology leaders have recently set the ability to predict the climate of the next decade or so as an important goal. The Korea Institute of Science and Technology (KIST) announced that senior researcher Mi-Kyung Sung of the Sustainable Environment Research Center and professor Soon-Il An of the Center for Irreversible Climate Change at Yonsei University (President Seung-hwan Seo) have jointly discovered the role of mid-latitude oceans as a source of anomalous waves that are particularly frequent in East Asia and North America, paving the way for a mid- to long-term response to winter climate change. Ocean currents have a major impact on the weather and climate of neighboring countries as they transport not only suspended and dissolved matter but also heat energy. In particular, regions where temperatures change rapidly in a narrow latitudinal band, such as the Gulf Stream in the Atlantic Ocean and the downstream region of the Kuroshio Current in the Pacific Ocean, are called "ocean fronts," and the KIST-Yonsei joint research team attributes the atmospheric wave response to the excessive accumulation of heat in these ocean fronts as the cause of the increase in extreme cold waves. From the early 2000s until recently, anomalous cold trend in East Asia coincided with the accumulation of heat near the Gulf Stream in the North Atlantic, and that in North America coincided with the intensification of heat accumulation near the Kuroshio Current. The oceanic frontal region acts as a thermostat to control the frequency of winter cold waves and anomalous high temperatures. The process of heat accumulation in oceanic frontal regions lasts from years to decades. During this time, a warming hiatus can occur in the continental regions that bucks the global warming trend. Conversely, during decades of ocean frontal cooling, continental regions appear to experience a sharp acceleration of warming. This suggests that the recent decadal cooling trend is essentially reinforced by temporary natural variability in the global climate system, and that we can expect unseasonably warm winter weather to become more prevalent as the heat buildup in the ocean front is relieved. These results are also evident in climate model experiments that vary the amount of heat accumulation near ocean fronts, showing that observations and climate model experiments are consistent in their conclusions, in contrast to conventional sea ice theory. This highlights the importance of accurately simulating ocean front variability in climate models to improve our ability to predict medium- and long-term climate change over the next decade. As global warming intensifies in the future and changes the structure of the ocean, these regional climate variations could change dramatically. Climate model experiments with increased greenhouse gases have shown that North America is likely to experience shorter and fewer warming hiatus, while East Asia is likely to experience more frequent intersections between warming hiatus and acceleration. These different continental responses are driven by the different oceanic responses of the Kuroshio Current and the Gulf Stream to global warming. "Applying the effects of ocean fronts revealed in this research to global warming climate models can improve climate change forecasts for the near future," said Dr. Mi-Kyung Sung of KIST. "It will provide important references for long-term forecasts of winter energy demand and the construction of climate change response infrastructure to prevent climate disasters such as the 2021 Texas power outage." [Fig 1] Winter temperature trend - Observed temperature trends during the winters (Dec-Feb) of 1995/96-2021/22. [Fig 2] Atlantic & Pacific ocean fronts - Ocean fronts near the Gulf Stream and Kuroshio Currents that represent narrow regions where sea surface temperature sharply decreases northward. [Fig 3(Attachment notes)] Gulf stream & East Asia covariability - Decadal cooling in East Asia accompanied by Gulf Stream warming (climate model simulation) ### KIST was established in 1966 as the first government-funded research institute in Korea. KIST now strives to solve national and social challenges and secure growth engines through leading and innovative research. For more information, please visit KIST’s website at https://eng.kist.re.kr/ The research, which was funded by the Ministry of Science and ICT (Minister Jong-ho Lee) through the Mid-Career Researcher Support Project (2021R1A2C1003934), the Leading Research Center Support Project (2018R1A5A1024958), and the Ultra-High Performance Computing Utilization Advancement Project (2022M3K3A1094114), was published on November 27 in the international journal Nature Communications Journal : Nature Communications Title : Ocean fronts as decadal thermostats modulating continental warming hiatus Publication Date : 2023.11.27. DOI : https://doi.org/10.1038/s41467-023-43686-1

The global consumption of pharmaceuticals is growing rapidly every year, reaching 4 billion doses in 2020. As more and more pharmaceuticals are metabolized by the human body and enter sewage and wastewater treatment plants, the amount and types of trace substances found in them are also increasing. When these trace substances enter rivers and oceans and are used as water sources, they can have harmful effects on the environment and human health, including carcinogenesis and endocrine disruption. Therefore, technologies are needed to quickly and accurately predict the properties and behavior of these trace substances, but analyzing unknown trace substances requires expensive equipment, skilled experts, and a long time. The Korea Institute of Science and Technology (KIST) announced that a team led by Hong Seok-won, head of the Water Resources and Cycle Research Center, and Son Moon, a senior researcher, has developed a technology to classify emerging trace substances according to their physicochemical properties and predict their concentrations using clustering and prediction-based artificial intelligence technology. The researchers used self-organizing maps, an AI technique that clusters data into maps based on their similarities, to classify 29 known trace substances, including medicinal compounds and caffeine, based on information such as physicochemical properties, functional groups, and biological reaction mechanisms. Random forests, a machine learning technique that classifies data into subsets, were then further built to predict the properties and concentration changes of new trace substances. If a new trace substance belongs to a cluster in the self-organizing map, the properties of other substances in that cluster can be used to predict how the properties and concentration of the new trace substance will change. As a result of applying this clustering and prediction AI model (self-organizing map and random forest) to 13 new trace substances, the prediction accuracy of about 0.75 was excellent, far exceeding the prediction accuracy of 0.40 of existing AI techniques using biological information. Compared to traditional prediction methods based on formulas, the KIST research team's data-driven analysis model has the advantage of only inputting the physicochemical properties of trace substances and efficiently identifying how the concentration of new trace substances will change in the sewage treatment process through clustering with substances with similar data. In addition, the data-driven AI model can be used in the future to predict the concentration of new substances such as drugs that are of social concern. "It can be applied not only to actual wastewater treatment plants, but also to most water treatment-related facilities where new trace substances exist, and can provide quick and accurate data in the policy-making process for related regulations," said Dr. Seokwon Hong and Dr. Moon Son (co-corresponding authors) of KIST. “Since it utilizes machine learning technology, the accuracy of the prediction will improve as relevant data is accumulated.” [Fig 1] Machine learning approaches for predicting the behavior of new trace substances ### KIST was established in 1966 as the first government-funded research institute in Korea. KIST now strives to solve national and social challenges and secure growth engines through leading and innovative research. For more information, please visit KIST’s website at https://eng.kist.re.kr/ This study was supported by the Korea Environment Industry & Technology Institute through the "Project for developing innovative drinking water and wastewater technologies," funded by the Korea Ministry of Environment [Grant No. 2019002710010], and the National Research Foundation of Korea (NRF) grant, funded by the Korean government (MSIT) [No. 2021R1C1C2005643]. The results were published in the October issue of the npj Clean Water (IF: 11.4, top 1.5% in JCR Water Resources). Journal : npj Clean water Title : Clustering micropollutants and estimating rate constants of sorption and biodegradation using machine learning approaches Publication Date : 2023.10.28. DOI : https://doi.org/10.1038/s41545-023-00282-6

- Microplastics can be removed by 99% with flocculants alone, without any additional equipment, by irradiating them with sunlight. Plastic waste breaks down over time into microplastics (<0.1 μm). Microplastics smaller than 20 μm cannot be removed in currently operating water treatment plants and must be agglomerated to a larger size and then removed. Iron (Fe) or aluminum (Al) based flocculants are used for this purpose, but they are not the ultimate solution as they remain in the water and cause severe toxicity to humans, requiring a separate treatment process. Dr. Jae-Woo Choi of the Center for Water Cycle Research at the Korea Institute of Science and Technology (KIST) has developed an eco-friendly metal-organic skeleton-based solid flocculant that can effectively aggregate nanoplastics under visible light irradiation. Prussian blue, a metal-organic frameworks-based substance made by adding iron (III) chloride to a potassium ferrocyanide solution, is the first synthetic pigment used to dye jeans a deep blue color and has recently been used to adsorb cesium, a radioactive element, from Japanese nuclear plant wastewater. While conducting experiments on the removal of radioactive materials from water using Prussian blue, the KIST research team discovered that Prussian blue effectively aggregates microplastics under visible light irradiation. [Figure 1] NANOPLASTIC TREATMENT USING FEHCF NANOBOTS UNDER VISIBLE-LIGHT IRRADIATION The research team developed a material that can effectively remove microplastics by adjusting the crystal structure to maximize the aggregation efficiency of Prussian blue. When the developed material is irradiated with visible light, microplastics with a diameter of about 0.15 μm (150 nm), which are difficult to remove using conventional filtration technology, can be agglomerated to a size about 4,100 times larger, making them easier to remove. In experiments, the researchers found that they were able to remove up to 99% of microplastics from water. The developed material is also capable of flocculating microplastics more than three times its own weight, outperforming the flocculation efficiency of conventional flocculants using iron or aluminum by about 250 times. [Figure 2] Schematics of the preparation of the FeHCH nanobots and process for NP removal The material not only uses Prussian blue, which is harmless to the human body, but is also a solid flocculant, making it easy to recover residues in water. It also uses natural light as an energy source, enabling a low-energy process. "This technology has a high potential for commercialization as a candidate material that can be applied to general rivers, wastewater treatment facilities, and water purification plants," said Dr. Choi of KIST. "The developed material can be utilized not only for nanoplastics in water, but also to clean up radioactive cesium, thus providing safe water." Meanwhile, Dr. Youngkyun Jung, the first author of the paper, said, "The principle of this material can be utilized to remove not only microplastics, but also a variety of contaminants in water systems." ### KIST was established in 1966 as the first government-funded research institute in Korea. KIST now strives to solve national and social challenges and secure growth engines through leading and innovative research. For more information, please visit KIST’s website at https://eng.kist.re.kr/ The research, which was supported by the Ministry of Science and ICT (Minister Lee Jong-ho) through the Material Innovation Leading Project (2020M3H4A3106366) and the KIST Institutional Project (2E32442), was published on October 1 in the international journal Water Research*. Journal : Water Research Title : Visible-light-induced Self-propelled Nanobots Against Nanoplastics Publication Date : 1-October-2023 DOI :https://doi.org/10.1016/j.watres.2023.120543

- KIST's iron oxide-graphene oxide heterostructure improves removal efficiency of harmful volatile organic compounds by up to 15 times Volatile organic compounds (VOCs) in daily products such as paints, adhesives, furniture, cosmetics, and deodorants make our lives easier. However, constant exposure can cause serious health problems such as respiratory illness, headaches, dermatitis, and cancer. Natural ventilation is the most effective way to reduce VOCs in indoor air, but recently, air purifiers have become a common method to maintain indoor air quality due to the frequent extreme outdoor condition (e.g. high concentration of fine dust, heat waves, and extreme cold). Generally, air purifiers remove VOCs by adsorption using activated carbon, which has a non-polar carbon surface and a large specific surface area. This activated carbon can effectively remove non-polar substances such as toluene and benzene, but cannot remove polar substances such as ketones and aldehydes. The Korea Institute of Science and Technology (KIST, President Seok Jin Yoon) announced that Dr. Jiwon Lee and Dr. Youngtak Oh from the Center for Sustainable Environment Research have developed a new adsorbent technology that can efficiently adsorb amphiphilic VOCs, which have both hydrophilic and hydrophobic properties and are difficult to remove with existing activated carbon technology. [Figure 1] ADSORPTION MECHANISM AND ADSORPTION PERFORMANCE GRAPH OF IRON OXIDE GRAPHENE ADSORBENT FOR POLAR VOCS The KIST research team synthesized a graphene-iron oxide heterostructure by precisely controlling the surface oxidation of graphite and iron, resulting in a high adsorption capacity for amphiphilic VOCs due to the increase of oxygen functional groups and iron oxide on the surface. This unique adsorbent showed up to 15 times better adsorption efficiency for amphiphilic VOCs than conventional activated carbon adsorbents. They also found that precise oxygen functional groups and iron oxides control of the adsorbent can offer flexible surface optimization freedom for a desirable nature of the pollutant. By testing four different ketones that are difficult to control with activated carbon adsorbents, the researchers found the correlation between the length of carbon chains and the adsorption efficiency; by optimizing the content of oxygen functional groups and iron oxides in the adsorbent, they were able to bring the maximum removal efficiency for the ketones. The researchers also analyzed the sub-nanometer electron transfer phenomenon between the adsorbent and VOC molecules; they found a link between the geometric shape of the pollutant and its adsorption trend for the first time. This is expected to enable the development of customized detection and control technologies for various air pollutants in our environment. "Unlike previous studies that focused on mere improvement of the adsorption performance and regeneration efficiency of adsorbents, we succeeded in developing a breakthrough material that exceeds the limits of existing adsorbents using accessible materials such as graphite and iron, which have high commercialization potential," said Dr. Jiwon Lee. ### KIST was established in 1966 as the first government-funded research institute in Korea. KIST now strives to solve national and social challenges and secure growth engines through leading and innovative research. For more information, please visit KIST’s website at https://eng.kist.re.kr/ The research, which was conducted as a major project of KIST (Air Environment Research Program) with support from the Ministry of Science and ICT (Minister Jong-ho Lee), was published on October 1 in the Chemical Engineering Journal. Journal : Chemical Engineering Journal Title : Effect of adsorbate geometry and hydrogen bonding on the enhanced adsorption of VOCs by an interfacial Fe3O4?rGO heterostructure Publication Date : 9-August-2023 DOI : https://doi.org/10.1016/j.cej.2023.145346

- KIST developed an annealing activated carbon that improves the adsorption efficiency of nitrogen-containing odorous compounds by up to 38 times - The multidentate adsorption mechanism of nitrogen-containing odorous gases such as ammonia was revealed for the first time Odorous gases, which are unpleasant and strongly irritating to the eyes, nose, and respiratory tract, are ubiquitous in facilities such as septic tanks, sewage systems, livestock farms, and waste disposal plants. These gases exert a negative impact on the human body as well as the surrounding environment, thus numerous ways have been developed to eliminate them. Typical odor removal methods use activated carbon as an adsorbent. However, activated carbon has low recyclability, making it difficult to remove the sources of complex odorous gases for reuse. [Figure 1] ADSORPTION MECHANISMS OF HEAT-DRIED ACTIVATED CARBON AND ADSORPTION PERFORMANCE OF NITROGEN-CONTAINING ODOROUS COMPOUNDS A research team led by Dr. Jiwon Lee and Youngtak Oh of the Sustainable Environment Research Center at the Korea Institute of Science and Technology (KIST, President Seok-Yeol Yoon) announced that they developed an activated carbon manufacturing technology that dramatically improves the removal of four representative nitrogen-containing odorous compounds (NOCs) from air: ammonia, ethylamine, dimethylamine, and trimethylamine. Not only did the research team improve the adsorption efficiency of activated carbon for removing odor substances, but they have also discovered the adsorption mechanism between adsorbents and odorous gases, making it possible to develop a wider variety of adsorbents for complex odor substances. The research team was able to precisely control the degree of surface oxidation to increase the adsorption efficiency of NOCs through an thermal annealing process after oxidizing the activated carbon with nitric acid. They found that the most oxidized heat-treated activated carbon could increase the removal efficiency of odor substances by up to 38 times compared to conventional activated carbon. For the first time, the researchers revealed that the oxygen atoms on the surface of oxidized activated carbon form strong hydrogen bonds with the amines in nitrogen-containing odor molecules. This finding reflects the principle of optimizing the adsorption effect of NOCs by increasing the degree of oxidation so that more hydrogen bonds can be formed with amines on the surface of activated carbon. Furthermore, the research team also demonstrated that unlike typical gas reactions, the interaction between the adsorbent and odor substances was primarily influenced by the number of hydrogen bonds, rather than proton affinity. [Figure 2] DFT calculation result and nitrogen-containing odorous compound selectivity of heat-dried activated carbo Furthermore, thermally dried activated carbon(TDAC) was found increase selectivity for trimethylamine by more than 13 times. This result represents a substantial improvement, as trimethylamine has the lowest adsorption efficiency among conventional NOCs. Trimethylamine, a designated odor substance regulated by law in Korea, is a typical source of odors in agriculture, landfills, and sewage and waste water treatment plants. In particular, the heat-dried activated carbon has an average recyclability of 93.8% for trimethylamine, showing high economic efficiency compared to the 63% recyclability of conventional activated carbon. "By identifying the adsorption mechanism of odorous gases, we can develop materials that are specialized for removing specific gases, and heat-dried activated carbon, which undergoes an oxidation process, is relatively simple to produce and can be reused. Thus, it can be applied as a material for purification devices such as filters and masks,” claimed Dr. Jiwon Lee of KIST. ### KIST was established in 1966 as the first government-funded research institute in Korea. KIST now strives to solve national and social challenges and secure growth engines through leading and innovative research. For more information, please visit KIST’s website at https://eng.kist.re.kr/ This research was conducted through the KIST Major Projects supported by the Ministry of Science and ICT, and the results were published in the latest issue of the Journal of Cleaner Production (IF: 11.072, top 8.423% in JCR), an international journal in the environmental science field. Journal : Journal of Cleaner Production Title : Adsorption Enhancement of Hazardous Odor Gas using Controlled Thermal Oxidation of Activated Carbon Publication Date : 20-Mar-2023 DOI : https://doi.org/10.1016/j.jclepro.2023.136261 T

- KIST develops membrane distillation methods using hydrothermal and solar energy - The goal is to maximize system efficiency through customized membrane distillation technologies for regional climate characteristics Clean water is essential for human survival. However, less than 3% of fresh water can be used as drinking water. According to a report published by the World Meteorological Organization, there is scarcity of drinking water for approximately 1 billion people worldwide, which is expected to rise to 1.4 billion by 2050. Seawater desalination technology, which produces fresh water from seawater, could solve the problem of water scarcity. At the Korea Institute of Science and Technology (KIST, President: Seok-Jin Yoon), a research team led by Dr. Kyung Guen Song from the Center for Water Cycle Research, have developed a hybrid membrane distillation module that combines solar energy with hydrothermal heat pumps to reduce thermal energy consumption during the desalination process. Reverse osmosis and evaporation methods are relatively common seawater desalination processes; however, these methods can operate only at high pressures and temperatures. In comparison, the membrane distillation method produces fresh water by utilizing the vapor pressure generated by the temperature difference between the flowing raw water and treated water separated by a membrane. This approach has the advantage of low energy consumption, as fresh water can be generated at pressures of 0.2–0.8 bar, which is lower than atmospheric pressure, and temperatures of 50–60℃. However, large scale operation requires more thermal energy. Thus, research studies are required to reduce the use of thermal energy for commercial operation. The membrane distillation involves simultaneous mass and heat (energy) transfer. It is divided into a direct contact membrane distillation (DCMD) and an air gap membrane distillation (AGMD) based on the modes applied to the treated water side of membrane to generate vapor pressure differences, which are the driving force. For high energy supply, the mode of producing water by direct contact of raw water of high temperature and treated water of low temperature to the membrane surface (i.e., DCMD) is beneficial. In contrast, for low energy supply, the efficiency is greater if the heat transmitted (heat loss) is reduced by air gaps, rather than direct contact between raw water and processed water (see Figure 1). Thus, the mode that generate water by condensing over a cold surface and which maintain air gaps between the membrane and the condensation surface (i.e., AGMD) are preferred. The KIST Research Team developed a hybrid desalination technology by conducting on-site tests for 1 month to compare the system performance and economy using solar energy and hydrothermal heat pumps. When the system operated in parallel with solar energy, production increased by 9.6% (see Figure 2) and energy usage was reduced by 30% (see Figure 3) compared to the membrane distillation method using only hydrothermal heat pumps. In addition, comparison of the consumption of thermal energy depending on the presence of solar energy showed that the efficiency of the membrane distillation plant process increased by up to 17.5% when solar energy was used as an additional heat source. According to Dr. Song, “The hybrid desalination technology we developed can be considered a method to supply water to some industrial complexes and island areas facing water scarcity as it can reduce the energy consumption required to generate fresh water. We expect this technology to be applied to significant water supply facilities in the Middle East and Southeast Asia where the annual solar radiation quantity is 1.5 times that in Korea." He added, “Membrane distillation is not significantly affected by raw water quality, so it will be possible to supply drinking water to areas where raw water quality became heavily contaminated due to water pollution and areas where heavy metal detection is high." Image [그림 1] Comparison of Production Volume and Efficiency for Different Membrane Distillation Compositions [그림 2] Comparison of Specific Energy Consumption (SEC) and Gain Output Ratio (GOR) with Weather in Hybrid Systems [그림 3] Photographs of (a) Solar Energy Collector, (b) Membrane Distillation System

- Excellent gold recovery performance even under the coexistence of metal ions and suspended solids - Significant reduction in cost and time of the recovery process, mass production of materials, and repeated recycling is possible In South Korea, which relies on imports for 99.3% of metal resources, the per capita consumption of metal resources is the highest in the OECD (Organization for Economic Co-operation and Development), and consumption of precious metals in various industries such as renewable energy, healthcare, and semiconductors is increasing. Among the different precious metals, gold is in demand in various fields such as batteries, electric vehicles, and renewable energy in the electric and electronic industries but always acts as a big variable in the industry due to its limited availability and high cost. Thus, research on ‘urban mining,’ which extracts precious metals from waste, is being actively conducted around the world. However, most of the technologies for extracting high-purity gold using waste resources require large amounts of chemicals and high operating temperatures; therefore, it has environmental regulations and efficiency problems. A Korean research team has developed a technology that can dramatically increase the recovery rate of precious metals from waste. The research team comprising Dr. Jae Woo Choi and Dr. Kyung-Won Jung from the Center for Water Cycle Research at the Korea Institute of Science and Technology (KIST, President Seok-Jin Yoon) reported that they developed a gold recovery process with the world’s highest recovery efficiency of 99.9 % by developing a capsule-type material in which a polymeric shell surrounds a multi-layered internal structure. The developed material has the advantage of high recovery efficiency compared to conventional adsorption materials since the material traps gold ions inside the capsule for recovery. The material also has the advantage of preventing the clogging of the internal porous structure since the polymeric shell allows gold ions to penetrate while being impermeable to suspended solids present with gold. By introducing functional groups that react only with gold ions in the multi-layered internal structure, gold that has passed through the polymeric shell could be stably recovered even with the coexistence of 14 types of ions and 3 types of suspended solids. Capsule-type material can be produced through a continuous process based on the solvent exchange method, and its efficiency and stability were demonstrated by maintaining a recovery performance of 99.9% or more even when the material was reused 10 times. Dr. Choi and Dr. Jung stated that, “The material developed through this research solves the problems of conventional materials developed for the recovery of precious metals. Moreover, it can be immediately applied to related industrial processes as they can be easily synthesized in large quantities". They also stated, “Through this study, it was evident that the chemical properties and morphology of the recovered material could also play a very important role in recovering metal resources from the water.” The lead author, Dr. Youngkyun Jung of KIST said that, “The results of this research are expected to serve as a basis for the development of the first eco-friendly process in Korea that can selectively recover and refine metal resources from waste and precious metal scraps generated in various industries, such as automobiles and petrochemicals.” Image Manufacturing process and the physical/chemical structures of gold recovery material Gold recovery concept of material (left) and its performance (right) (From left) gold-containing waste liquid, a capsule-type material wrapped in a circular polymeric shell (white) developed by KIST researchers to recover gold in an eco-friendly manner, gold extracted through the recovery process, and recovered gold refined into high-purity gold