[article-cris] Kemian tekniikan korkeakoulu / CHEM

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    Through-Drop Imaging of Liquid-Solid Interfaces : From Contact Angle Variations Along the Droplet Perimeter to Mapping of Contact Angles Across a Surface
    (American Chemical Society, 2024) Vieira, Arthur; Jokinen, Ville; Lepikko, Sakari; Ras, Robin H.A.; Zhou, Quan; Department of Electrical Engineering and Automation; Department of Chemistry and Materials Science; Department of Applied Physics; Soft Matter and Wetting; Robotic Instruments; Center of Excellence in Life-Inspired Hybrid Materials, LIBER
    When a droplet interacts with a water-repellent surface, its triple-phase contact line typically exhibits varying contact angles, which can vary from point-to-point across the surface. Consequently, measuring the contact angles along the contact line would provide a better representation of the wetting properties of the surface than a single average contact angle. However, an effective method for estimating the local contact angle along the contact line on opaque hydrophobic surfaces is currently lacking. Here we present a method that combines through-drop imaging of the wetting interface during a sliding experiment with Finite Element Modeling of the droplet to estimate contact angle values along the contact line. Using this method, the mean advancing and receding contact angles were measured on four types of hydrophobic samples with contact angles between 99 and 178.9°. The method was further used to produce detailed advancing and receding contact angle maps of surfaces with wetting patterns with an unprecedented resolution of 3 μm.
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    Analogical environmental cost assessment of silicon flows used in solar panels by the US and China
    (Nature Publishing Group, 2024-04-25) Rahimpour Golroudbary, Saeed; Lundström, Mari; Wilson, Benjamin P.; Department of Chemical and Metallurgical Engineering; Hydrometallurgy and Corrosion
    Achieving carbon neutrality requires deployment of large-scale renewable energy technologies like solar photovoltaic (PV) panels. Nevertheless, methods to ascertain the overall environmental impacts PVs and further improve their sustainability are under-investigated. In an effort to provide more understanding of this crucial topic, this research focuses on silicon flows—a key element for manufacturing crystalline silicon PVs. Using system dynamics modeling, we conduct a comprehensive environmental cost assessment of the silicon flows used in PVs based on a comparative analysis between the United States and China as the leading global PV manufacturers. Despite the advancement in wafer quality, material usage reductions and overall price decreases achieved in recent decades, our results project a substantial increase in energy and water consumption in China related to Metallurgical Grade Si (MG-Si), Solar Grade Si (SoG-Si) and cell manufacturing by 2030. An approximate 6.5 times increase of energy and water consumption is observed for c-Si cell manufacturing in China between 2010 and 2020. In 2030, increases of 70% in energy consumption and 69% in water use are estimated for Chinese MG-Si and SoG-Si production. The most significant environmental impact is observed in silicon cell and module manufacturing in both countries, particularly concerning GHG, SOx and NOx emissions. This study provides valuable insights into the environmental impacts of these two major solar panel manufacturing countries by examining the silicon life cycle, from production to end-of-life.
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    Distinct structure-activity relationship and reaction mechanism over BaCoO3/CeO2 catalysts for NO direct decomposition
    (Elsevier BV, 2024-08-05) Kang, Running; Wang, Xuehai; Huang, Junqin; An, Sufeng; Wang, Lu; Wang, Gang; Chen, Hong; Zhang, Cuijuan; Bin, Feng; Li, Yongdan; Department of Chemical and Metallurgical Engineering; Industrial chemistry; Sinopec Ltd; CAS - Institute of Mechanics; Tianjin University
    The dependency on morphology is crucial for achieving highly efficient direct decomposition of NO. Herein, a BaCoO3/CeO2 catalyst is synthesized using CeO2 small particles (p), spheres (s) and rods (r) as supports. The NO conversion to N2 (NTN2) at 800 °C follows the order BaCoO3/CeO2-r (78.8 %) > BaCoO3/CeO2-s (75.9 %) > BaCoO3/CeO2-p (56.9 %) > BaCoO3 (8.6 %) at a space velocity 1 g s/cm3. BaCoO3/CeO2-r exhibts high tolerance to O2 and stability with conversion decreasing from 78.8 % to 74.6 %, 60.0 % and 50.0 % at 800 °C with 1, 5 and 10 vol% O2, respectively. The high redox activity, higher active oxygen mobility and NO adsorption capability ensures its superior performance, while the high surface area (31.29 m2/g) and uniform distribution of active sites on the surface further promote the activity. The mechanism of NO direct decomposition is elucidated by in situ Diffuse reflectance infrared Fourier transform spectroscopy, 18O2 isotopic transient exchange experiments and density functional theory (DFT) calculation.
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    Toward vanishing droplet friction on repellent surfaces
    (National Academy of Sciences, 2024-04-15) Backholm, Matilda; Kärki, Tytti; Nurmi, Heikki; Vuckovac, Maja; Turkki, Valtteri; Lepikko, Sakari; Jokinen, Ville; Quéré, David; Timonen, Jaakko; Ras, Robin; Department of Applied Physics; Department of Chemistry and Materials Science; Living Matter; Active Matter; Soft Matter and Wetting; Center of Excellence in Life-Inspired Hybrid Materials, LIBER; ESPCI
    Superhydrophobic surfaces are often seen as frictionless materials, on which water is highly mobile. Understanding the nature of friction for such water-repellent systems is central to further minimize resistance to motion and energy loss in applications. For slowly moving drops, contact-line friction has been generally considered dominant on slippery superhydrophobic surfaces. Here, we show that this general rule applies only at very low speed. Using a micropipette force sensor in an oscillating mode, we measure the friction of water drops approaching or even equaling zero contact-line friction. We evidence that dissipation then mainly stems from the viscous shearing of the air film (plastron) trapped under the liquid. Because this force is velocity dependent, it can become a serious drag on surfaces that look highly slippery from quasi-static tests. The plastron thickness is found to be the key parameter that enables the control of this special friction, which is useful information for designing the next generation of ultraslippery water-repellent coatings.
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    Improving the flame retardancy of furfurylated wood by introducing DOPO
    (Springer, 2024-01) Dong, Youming; Fu, Zhenyu; Yan, Yutao; Shi, Jingbo; Hughes, Mark; Zhan, Xianxu; Li, Jianzhang; Department of Bioproducts and Biosystems; Wood Material Technology; Nanjing Forestry University; Zhejiang Agriculture and Forestry University; Dehua Tubao New Decoration Material Co., Ltd
    Poor dimensional stability, sensitivity to microorganisms, and flammability restrict the application of wood in certain areas where these properties are critical. Although furfurylation can improve the physical and mechanical properties of wood, the heat and smoke release of furfurylated wood during combustion are dramatic and need to be addressed. As a kind of halogen-free phosphorus flame retardant, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and its derivatives exhibit excellent performance in polymer composites. In this study, DOPO was dissolved in furfuryl alcohol (FA) and used to modify wood. The effect of DOPO on the thermal stability, combustion behavior, and physical and mechanical properties of furfurylated wood was investigated. The chemical structure, morphology, and char residue after combustion were also characterized. The studies show that DOPO can react with the FA polymer and is incorporated and homogeneously dispersed in the wood structure. Compared to untreated wood, furfurylated wood has a much higher heat and smoke release during combustion. The addition of DOPO remarkably reduces the heat release of furfurylated wood, and this effect increases as the amount of DOPO increases. When the amount of introduced DOPO of furfurylated wood is 7%, its total heat release is reduced by 37.4% and becomes comparable to the untreated wood. However, DOPO does not suppress smoke production effectively. DOPO improves the thermal stability of furfurylated wood by promoting char formation and inhibiting the diffusion of oxygen and the escape of pyrolysis products. The addition of DOPO has little effect on the physical and mechanical properties of furfurylated wood. The results indicate that the combination of DOPO and furfurylation could be an efficient way to prepare highly stable and fire-resistant wood materials.
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    Accelerated thermostabilization through electron-beam irradiation for the preparation of cellulose-derived carbon fibers
    (Elsevier Ltd, 2024-01-31) Jang, Minjeong; Fliri, Lukas; Trogen, Mikaela; Choi, Dongcheon; Han, Jeong Heum; Kim, Jungwon; Kim, Sung Kon; Lee, Sungho; Kim, Sung Soo; Hummel, Michael; Department of Bioproducts and Biosystems; Biopolymer Chemistry and Engineering; Korea Institute of Science and Technology; Jeonbuk National University
    The potential of biobased materials like regenerated celluloses as precursors for carbon fibers (CFs) is long known. However, owing to an intrinsic two pathway pyrolysis mechanism of cellulose its carbonization is accompanied with side reactions under generation of volatiles. In practice, this leads to a reduced char yield, results in inferior mechanical properties of the CFs, and requires time-consuming thermostabilization procedures or wet-chemical pretreatments during production. Thus, their market share currently remains low. In ambitions to circumvent these issues, the potential of electron beam irradiation (EBI) as a dry chemical pretreatment for cellulosic CFs was investigated in this study. The conducted chemical analyses showed that high radiation dosages (2 MGy) lead to a strong depolymerization of the cellulose chains down to oligomers, while the fibrous macrostructure was preserved. Minor oxidation reactions were also evident. Thorough thermostabilization experiments under air in the temperature range from 100 °C to 250 °C revealed that reactions caused by EBI treatment alone were insufficient to increase the char yield. Only when the EBI treated precursor fibers are subjected to heating between 200 and 250 °C the char yield increased significantly to 34.4 % compared to 12.1 % for the untreated fiber. Furthermore, the EBI treatment strongly accelerated the reactions during thermostabilization allowing to collect CFs at heating rates of 2 °C/min compared to 0.5 °C/min needed for pristine fibers. Additionally, cellulose-lignin composite fibers were subjected to EBI treatment, proving that this strategy can also be applied to these emerging biobased CF precursors.
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    Quantifying droplet–solid friction using an atomic force microscope
    (John Wiley & Sons, 2024-04) Koh, Xue Qi; Thenarianto, Calvin; Jokinen, Ville; Daniel, Dan; Department of Chemistry and Materials Science; Agency for Science, Technology and Research
    Controlling the wetting and spreading of microdroplets is key to technologies such as microfluidics, ink-jet printing, and surface coating. Contact angle goniometry is commonly used to characterize surface wetting by droplets, but the technique is ill-suited for high contact angles close to (Formula presented.). Here, we attach a micrometric-sized droplet to an atomic force microscope cantilever to directly quantify droplet–solid friction on different surfaces (superhydrophobic and underwater superoleophobic) with sub-nanonewton force resolutions. We demonstrate the versatility of our approach by performing friction measurements using different liquids (water and oil droplets) and under different ambient environments (in air and underwater). Finally, we show that underwater superoleophobic surfaces can be qualitatively different from superhydrophobic surfaces: droplet–solid friction is highly sensitive to droplet speeds for the former but not for the latter surface.
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    Trainable bioinspired magnetic sensitivity adaptation using ferromagnetic colloidal assemblies
    (Elsevier, 2024-04-17) Liu, Xianhu; Tan, Hongwei; Stråka, Emil; Hu, Xichen; Chen, Min; van Dijken, Sebastiaan; Scacchi, Alberto; Sammalkorpi, Maria; Ikkala, Olli; Peng, Bo; Department of Applied Physics; Department of Chemistry and Materials Science; Department of Bioproducts and Biosystems; Molecular Materials; Nanomagnetism and Spintronics; Soft Materials Modelling; Biomolecular Materials; Center of Excellence in Life-Inspired Hybrid Materials, LIBER; Department of Chemistry and Materials Science; Fudan University
    Nature has already suggested bioinspired functions. Beyond them, adaptive and trainable functions could be the inspiration for novel responsive soft matter beyond the state-of-the-art classic static bioinspired, stimulus-responsive, and shape-memory materials. Here, we describe magnetic assembly/disassembly of electrically conducting soft ferromagnetic nickel colloidal particles into surface topographical pillars for bistable electrical trainable memories. They allow magnetic sensing with adaptable and rescalable sensitivity ranges, enabled by bistable memories and kinetic concepts inspired by biological sensory adaptations. Based on the soft ferromagnetism of the nanogranular composition and the resulting rough particle surfaces prepared via a solvothermal synthesis, triggerable structural memory is achieved by the magnetic field-driven particle assembly and disassembly, promoted by interparticle jamming. Electrical conversion from current to frequency for electrical spikes facilitates rescalable and trainable frequency-based sensitivity on magnetic fields. This work suggests an avenue for designing trainable and adaptable life-inspired materials, for example, for soft robotics and interactive autonomous devices.
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    Deaggregation of cellulose macrofibrils and its effect on bound water
    (Elsevier Science Ltd., 2023-11-01) Maloney, Thaddeus; Phiri, Josphat; Zitting, Aleksi; Paajanen, Antti; Penttilä, Paavo; Ceccherini, Sara; Department of Bioproducts and Biosystems; Bio-based Materials; Wood Material Science; VTT Technical Research Centre of Finland
    The purpose of this study was to determine how to control and measure the hierarchical swelling in pulp fibers via electrostatic interactions and localized osmotic pressure. A eutectic solvent system was used to systematically increase phosphate groups in the cell wall. Increase in fiber charge led to an increase in swelling properties, as expected. At a charge value around 180–200 μmol/g the macrofibrils were found to deaggregate. This led to a large jump in mesoscale swelling, from 0.9 to 2.5 mL/g, and surface area, from 400 to 1000 m2/g. This deaggregation was confirmed with X-ray scattering and solute exclusion. A novel thermoporosimetry method was used in the study. This involved splitting the nonfreezing water into two subfractions, thus allowing a more complete analysis of pore structure and surface area. The hydrated surface area for the samples was in the range 1200–1400 m2/g, which agreed well with simulations of aggregated microfibrils. Adding charge to the pulp fibers had a nonlinear effect on handsheet strength properties. This suggests that hierarchical control of fiber swelling may be a useful approach to improve important property pairs such as strength/density in packaging and other commercially important fiber products.
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    In Vitro and In Vivo Degradation of Photo-Crosslinked Poly(Trimethylene Carbonate-co-ε-Caprolactone) Networks
    (Wiley-VCH Verlag, 2024-03) van Bochove, Bas; Rongen, Jan J.; Hannink, Gerjon; Seppälä, Jukka V.; Poot, André A.; Grijpma, Dirk W.; Department of Chemical and Metallurgical Engineering; Polymer technology; Radboud University Nijmegen; University of Twente
    Three-armed poly(trimethylene carbonate) (PTMC) and poly(trimethylene carbonate-co-Ɛ-caprolactone) (P(TMC-co-ε-CL)) macromers with molecular weights of approximately 30 kg mol−1 are synthesized by ring-opening polymerization and subsequent functionalization with methacrylic anhydride. Networks are then prepared by photo-crosslinking. To investigate the in vitro and in vivo degradation properties of these photo-crosslinked networks and assess the effect of ε-caprolactone content on the degradation properties, PTMC networks, and copolymer networks with two different TMC:ε-CL ratios are prepared. PTMC networks degraded slowly, via an enzymatic surface erosion process, both in vitro and in vivo. Networks prepared from P(TMC-co-ε-CL) macromers with a 74:26 ratio are found to degrade slowly as well, via a surface erosion process, albeit at a higher rate compared to PTMC networks. Increasing the ε-CL content to a ratio of 52:48, resulted in a faster degradation. These networks lost their mechanical properties much sooner than the other networks. Thus, PTMC and P(TMC-co-ε-CL) networks are interesting networks for tissue engineering purposes and the exact degradation properties can be tuned by varying the TMC:ε-CL ratio, providing researchers with a tool to obtain copolymer networks with the desired degradation rate depending on the intended application.
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    Phase equilibrium study of the CaO–SiO2–CrOx system at 1600°C in reducing atmospheres
    (Wiley-Blackwell, 2024-05) Chen, Min; Taskinen, Pekka; Sukhomlinov, Dmitry; Lindberg, Daniel; Michallik, Radoslaw; Jokilaakso, Ari; Department of Chemical and Metallurgical Engineering; Metallurgy (MTG); Metallurgical Thermodynamics and Modelling; Geological Survey of Finland
    Phase equilibria in the CaO–SiO2–CrOx system were experimentally investigated at 1600°C and pO2 of 10−10 to 10−11 atm using the high-temperature isothermal equilibration/drop quenching/electron probe X-ray microanalysis technique. The constrained isothermal sections of the CaO–SiO2–CrOx system were constructed at 1600°C and pO2 of 10−10 to 10−11 atm based on the experimental results. The primary phase fields including cristobalite (SiO2), larnite (Ca2SiO4), (Ca,Cr)Cr2O4, and corundum (Cr2O3) were determined. Simulations by thermodynamic software MTDATA, FactSage, and Thermo-Calc were compared with the present experimental results.
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    A facile coprecipitation approach for synthesizing LaNi0.5Co0.5O3 as the cathode for a molten-salt lithium–oxygen battery
    (Royal Society of Chemistry, 2024-01-01) Qiu, Qianyuan; Wang, Jiaqi; Yao, Penghui; Li, Yongdan; Department of Chemical and Metallurgical Engineering; Industrial chemistry
    The cathode of a lithium–oxygen battery (LOB) should be well designed to deliver high catalytic activity and long stability, and to provide sufficient space for accommodating the discharge product. Herein, a facile coprecipitation approach is employed to synthesize LaNi0.5Co0.5O3 (LNCO) perovskite oxide with a low annealing temperature. The assembled LOB exhibits superior electrochemical performance with a low charge overpotential of 0.03–0.05 V in the current density range of 0.1–0.5 mA cm−2. The battery ran stably for 119 cycles at a high coulombic efficiency. The superior performance is ascribed to (i) the high catalytic activity of LNCO towards oxygen reduction/evolution reactions; (ii) the increased temperature enabling fast kinetics; and (iii) the LiNO3–KNO3 molten salt enhancing the stability of the LOB operating at high temperature.
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    Towards Tailored Dialdehyde Cellulose Derivatives: A Strategy for Tuning the Glass Transition Temperature
    (Wiley-VCH Verlag, 2024-03-08) Simon, Jonas; Schlapp-Hackl, Inge; Sapkota, Janak; Ristolainen, Matti; Rosenau, Thomas; Potthast, Antje; Department of Bioproducts and Biosystems; Biopolymer Chemistry and Engineering; UPM Research Center; University of Natural Resources and Life Sciences, Vienna
    The derivatization of dialdehyde cellulose (DAC) has received increasing attention in the development of sustainable thermoplastics. In this study, a series of dialcohol celluloses were generated by borohydride reduction, which exhibited glass transition temperature (Tg) values ranging from 23 to 109 °C, depending on the initial degree of oxidation (DO) of the DAC intermediate. However, the DAC derivatives did not exhibit thermoplastic behavior when the DO of the modified DAC was below 26 %. The influence of introduced side chains was highlighted by comparing DAC-based thermoplastic materials obtained by either oximation or borohydride reduction. Our results provide insights into the generation of DAC-based thermoplastics and highlight a strategy for tailoring the Tg by adjusting the DO during the periodate oxidation step and selecting appropriate substituents in subsequent modifications.
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    Co-sputtering of A Thin Film Broadband Absorber Based on Self-Organized Plasmonic Cu Nanoparticles
    (Wiley-VCH Verlag, 2024-02) Drewes, Jonas; Perdana, Nanda; Rogall, Kevin; Hartig, Torge; Elis, Marie; Schürmann, Ulrich; Pohl, Felix; Abdelaziz, Moheb; Strunskus, Thomas; Kienle, Lorenz; Elbahri, Mady; Faupel, Franz; Rockstuhl, Carsten; Vahl, Alexander; Department of Chemistry and Materials Science; Nanochemistry and Nanoengineering; Kiel University; Karlsruhe Institute of Technology
    The efficient conversion of solar energy to heat is a prime challenge for solar thermal absorbers, and various material classes and device concepts are discussed. One exciting class of solar thermal absorbers are plasmonic broadband absorbers that rely on light absorption thanks to plasmonic resonances sustained in metallic nanoparticles. This work focuses on Cu/Al2O3 plasmonic absorbers, which consist of a thin film stack of a metallic Cu-mirror, a dielectric Al2O3 spacer, and an Al2O3/Cu-nanoparticle nanocomposite. This work explores two preparation routes for the Al2O3/Cu-nanoparticle nanocomposite, which rely on the self-organization of Cu nanoparticles from sputtered atoms, either in the gas phase (i.e., via gas aggregation source) or on the thin film surface (i.e., via simultaneous co-sputtering). While in either case, Cu-Al2O3-Al2O3/Cu absorbers with a low reflectivity over a broad wavelength regime are obtained, the simultaneous co-sputtering approach enabled better control over the film roughness and showed excellent agreement with dedicated simulations of the optical properties of the plasmonic absorber using a multi-scale modeling approach. Upon variation of the thickness and filling factor of the Al2O3/Cu nanocomposite layer, the optical properties of the plasmonic absorbers are tailored, reaching an integrated reflectance down to 0.17 (from 250 to 1600 nm).
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    Microstructure and thermal properties of dissimilar M300–CuCr1Zr alloys by multi-material laser-based powder bed fusion
    (University of Science and Technology Beijing, 2024-01) Li, Xiaoshuang; Sukhomlinov, Dmitry; Que, Zaiqing; Department of Chemical and Metallurgical Engineering; Metallurgy (MTG); Aerosint SA; VTT Technical Research Centre of Finland
    Multi-material laser-based powder bed fusion (PBF-LB) allows manufacturing of parts with 3-dimensional gradient and additional functionality in a single step. This research focuses on the combination of thermally-conductive CuCr1Zr with hard M300 tool steel. Two interface configurations of M300 on CuCr1Zr and CuCr1Zr on M300 were investigated. Ultra-fine grains form at the interface due to the low mutual solubility of Cu and steel. The material mixing zone size is dependent on the configurations and tunable in the range of 0.1–0.3 mm by introducing a separate set of parameters for the interface layers. Microcracks and pores mainly occur in the transition zone. Regardless of these defects, the thermal diffusivity of bimetallic parts with 50vol% of CuCr1Zr significantly increases by 70%–150% compared to pure M300. The thermal diffusivity of CuCr1Zr and the hardness of M300 steel can be enhanced simultaneously by applying the aging heat treatment.
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    Enhancing 360° virtual laboratory safety training with linear learning pathway design: Insights from student experiences
    (Elsevier Science Inc., 2024-04) Girmay, Samuel; Yliniemi, Kirsi; Nieminen, Minna; Linnera, Jarno; Karttunen, Antti J.; Department of Chemistry and Materials Science; Inorganic Materials Modelling
    This paper investigates the role of learning pathway design in a web-based 360° virtual laboratory safety training. A linearly structured virtual laboratory safety training was designed and implemented. Student experiences with the linear learning pathway were compared with a previously implemented non-linear learning pathway. In the linear pathway, students complete the virtual laboratory tour in a predetermined order, while in a non-linear pathway the students can complete the virtual laboratory tour in any order. Student feedback was collected from over 900 students and the experiences from the linearly structured virtual laboratory were highly positive. Compared to the previously implemented non-linear learning pathway, the student feedback related to the learning experience improved significantly. The feedback also showed a difference between preferred learning styles, highlighting the importance of choosing the learning pathway based on the intended learning outcomes and offering different types of learning materials for different learners. Overall, the findings of this study indicate that the linearly structured virtual laboratory offers an effective and motivating learning environment for laboratory safety training.
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    Synergistic adsorption of methylene blue with carrageenan/hydrochar-derived activated carbon hydrogel composites: Insights and optimization strategies
    (Elsevier, 2024-04) Akbari, Ali; Abbasi, Habib; Shafiee, Mojtaba; Baniasadi, Hossein; Department of Chemical and Metallurgical Engineering; Polymer Synthesis Technology; Jundi-Shapur University of Technology
    The study explores the use of hydrochar-derived activated carbon (AC) to improve the adsorption capacity and mechanical properties of carrageenan (CAR) hydrogel beads. Four distinct samples, with carrageenan to activated carbon ratios of 1:0 (CAR), 2:1 (CAC2), 4:1 (CAC4), and 10:1 (CAC10), were prepared. These polymeric beads underwent comprehensive evaluation for their methylene blue (MB) adsorption capacity, gel content (GC), and swelling ratio (SR). Increasing activated carbon content up to 50 % of carrageenan mass significantly enhanced GC and SR by 20.57 % and 429.24 %, respectively. Various analytical techniques were employed to characterize the composites, including FTIR, XRD, Raman Spectroscopy, BET, SEM, and EDS-Mapping. Batch adsorption tests investigated the effects of pH, contact time, dye concentration, and temperature on MB adsorption. Maximum adsorption capacities for CAR, CAC10, CAC4, and CAC2 were 475.48, 558.54, 635.93, and 552.35 mg/g, respectively, under optimal conditions. Kinetic models (Elovich and pseudo-second-order) and isotherm models (Temkin for CAR and Freundlich for CAC10, CAC4, and CAC2) fitted well with the experimental data. Thermodynamic analysis showed spontaneous, exothermic MB adsorption. Primary mechanisms include electrostatic attraction, hydrogen bonding, n-π, and π-π stacking. The study highlights enhanced adsorption capacity of carrageenan hydrogel via carrageenan/activated carbon composites, providing cost-effective wastewater treatment.
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    Quantifying the degree of selectivity in a Flocculation-Flotation process of LiCoO2 and graphite using scanning electron microscopy and image processing analysis
    (Elsevier Ltd, 2024-04) Rinne, Tommi; Saeed, Mohazzam; Serna-Guerrero, Rodrigo; Department of Chemical and Metallurgical Engineering; Mineral Processing and Recycling
    This research article studies selective flocculation as a means for improving flotation of lithium-ion battery active materials using mixtures of pure LiCoO2 (LCO) and graphite. Scanning electron microscopy (SEM) combined with image analysis via density-based spatial clustering of applications with noise (DBSCAN) is presented as a novel method to quantitatively determine the degree of selectivity in a process that applies selective flocculation as a conditioning stage for froth flotation. SEM was shown to provide visual proof of flocculated particles, even in dried froth samples. Under optimal flocculant concentration of 10 g/t only a few flocs were detected in the froth concentrate, suggesting that heteroflocculation of LCO and graphite was minimized under said conditions. Using a flocculant concentration in excess (50 g/t) resulted in multiple flocculated LCO particles within the froth, indicating loss of flocculation selectivity. These results were corroborated by batch flotation experiments, which showed that treating the pulp with 10 g/t flocculant concentration yielded a graphite froth product at a grade of 98.2 %, compared to 98.1 % recovered from a non-flocculated pulp. An excess flocculant concentration led to a drastic reduction in graphite grade. Similar graphite recoveries were observed in all flotation experiments, indicating that the reduced graphite grade with excess flocculant was a result of hydrophobic heteroflocs carrying entrapped LCO to the froth. Proper pH control throughout the experiment prevented a negative influence of flocculation on the kinetics of graphite recovery, which had been reported in earlier research. The results suggest that selective flocculation is a potential method for improving the separation efficiency of graphite from Li-ion battery waste, and that SEM/DBSCAN can be applied for characterization of selectivity in combined flocculation-flotation processes.
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    Side-stream lignins: Potential antioxidant and antimicrobial agents in milk
    (Elsevier Ltd, 2024-03) Marangon, Crisiane A.; Otoni, Caio G.; Bertuso, Paula C.; Rossi, Patrícia F.; dos Santos, Danilo M.; Lourençon, Tainise V.; Martins, Virginia C.A.; Plepis, Ana Maria G.; Mattoso, Luiz H.C.; Nitschke, Marcia; Department of Bioproducts and Biosystems; Wood Material Science; Nanotechnology National Laboratory for Agriculture; Universidade Federal de São Carlos; Universidade de São Paulo; Universidade Federal de Minas Gerais
    In recent years, lignin has drawn increasing attention due to its intrinsic antibacterial and antioxidant activities, biodegradability, and biocompatibility. Yet, like several other biogenic structures, its compositional heterogeneity represents a challenge to overcome. In addition, there are few studies regarding food applications of lignin. Herein, we evaluate the antimicrobial and antioxidant effects of lignin from two different sources. These lignins were characterized by attenuated total reflectance Fourier-transform infrared (ATR-FTIR) and hydrogen nuclear magnetic resonance (1H NMR) spectroscopies. Their antibacterial and antioxidant capacities (DPPH and Folin-Ciocalteu methods) were also investigated. Susceptibility tests were performed with the minimal inhibitory (MIC) and bactericidal (MBC) concentrations using the micro-broth dilution technique. Kraft lignin presented higher radical-scavenging and antibacterial activities than alkali lignin, indicating the dependence of antioxidant and antibacterial activities on the precursor biomass. Scanning electron microscopy shows morphologic changes in the bacteria after exposure to lignin, while confocal microscopy suggests that kraft lignin has affinity towards bacterial surfaces and the ability to cause cell membrane destabilization. Lignin inhibited the growth of Staphylococcus aureus and Salmonella Enteritidis in skimmed milk, herein taken as food model. Our results suggest that lignins are promising candidates for green additives to improve quality and safety within the food chain.
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    Construction of hydrophilic-hydrophobic domains in Bi2O3/nitrogen-doped carbon electrode to boost CO2-to-formate conversion
    (Elsevier, 2024-04) Shi, Junjie; Han, Nana; Jin, Benjin; Suominen, Milla; Lahtinen, Jouko; Miikki, Kim; Wilson, Benjamin P.; Kallio, Tanja; Department of Chemistry and Materials Science; Department of Applied Physics; School common, CHEM; Department of Chemical and Metallurgical Engineering; Electrochemical Energy Conversion; Surface Science; Hydrometallurgy and Corrosion
    Bi has drawn attention in catalyzing the electrochemical CO2-to-formate conversion due to promising selectivity and low cost, but the process suffers from low activity. Herein, we introduce nitrogen-doped carbon (NC) support with hydrophobicity modification to enhance the activity of a binder-free Bi2O3 electrode. Formate partial current on the NC supported Bi2O3 electrode almost doubles compared to Bi2O3 on unmodified support. Furthermore, the hydrophobicity modification with polytetrafluoroethylene (PTFE) significantly extends the stability of NC supported Bi2O3 by diminishing flooding. It also maintains >90% formate selectivity at a broad potential range from −0.87 to −1.27 V (vs. RHE) and shows a formate partial current density of −100 mA cm−2 at −1.37 V (vs. RHE) in 0.5 M KHCO3. The improvement is attributed to the synergetic effects of the hydrophilic active sites and the hydrophobic PTFE modified NC support. The unique structure promotes the reactants transport and thus maximizes the active site utilization at the triple-phase interface. This facile microenvironment regulation can be extended to other applications involving gaseous-aqueous phases.