Hasil untuk "Chemical engineering"

A. Chaves, Javad G. Azadani, Hussain Alsalman et al.

Lijian Leng, Qin-pan Xiong, Lihong Yang et al.

Surface area and porosity are important physical properties of biochar, playing a crucial role in many biochar applications, such as wastewater treatment and soil remediation. The production of engineered biochar with highly porous structure and large surface area has received extensive attention. This paper comprehensively reviewed the effects of biomass and pyrolysis parameters on the surface area and porosity of biochar. The composition of biomass feedstock and pyrolysis temperature are the major influencing factors. It is suggested that the lignocellulosic biomass is an outstanding candidate, wood and woody biomass in particular. Besides, moderate temperatures (400-700 °C) are suitable for the development of the pore structure. Further improvement can be implemented by additional treatments. Activation is the most widely used and effective way to promote biochar surface area and porosity, especially the chemical activation. Enhancement can also be achieved by using other treatment methods, such as carbonaceous materials coating, ball milling, and templating. Future research should focus on upgrading or developing treatment technology to achieve enhanced functionality and porous structure of biochar simultaneously.

Y. S. Zhang, A. Khademhosseini

A. Sukhanova, S. Bozrova, P. Sokolov et al.

Studies on the methods of nanoparticle (NP) synthesis, analysis of their characteristics, and exploration of new fields of their applications are at the forefront of modern nanotechnology. The possibility of engineering water-soluble NPs has paved the way to their use in various basic and applied biomedical researches. At present, NPs are used in diagnosis for imaging of numerous molecular markers of genetic and autoimmune diseases, malignant tumors, and many other disorders. NPs are also used for targeted delivery of drugs to tissues and organs, with controllable parameters of drug release and accumulation. In addition, there are examples of the use of NPs as active components, e.g., photosensitizers in photodynamic therapy and in hyperthermic tumor destruction through NP incorporation and heating. However, a high toxicity of NPs for living organisms is a strong limiting factor that hinders their use in vivo. Current studies on toxic effects of NPs aimed at identifying the targets and mechanisms of their harmful effects are carried out in cell culture models; studies on the patterns of NP transport, accumulation, degradation, and elimination, in animal models. This review systematizes and summarizes available data on how the mechanisms of NP toxicity for living systems are related to their physical and chemical properties.

D. Christianson

The year 2017 marks the twentieth anniversary of terpenoid cyclase structural biology: a trio of terpenoid cyclase structures reported together in 1997 were the first to set the foundation for understanding the enzymes largely responsible for the exquisite chemodiversity of more than 80000 terpenoid natural products. Terpenoid cyclases catalyze the most complex chemical reactions in biology, in that more than half of the substrate carbon atoms undergo changes in bonding and hybridization during a single enzyme-catalyzed cyclization reaction. The past two decades have witnessed structural, functional, and computational studies illuminating the modes of substrate activation that initiate the cyclization cascade, the management and manipulation of high-energy carbocation intermediates that propagate the cyclization cascade, and the chemical strategies that terminate the cyclization cascade. The role of the terpenoid cyclase as a template for catalysis is paramount to its function, and protein engineering can be used to reprogram the cyclization cascade to generate alternative and commercially important products. Here, I review key advances in terpenoid cyclase structural and chemical biology, focusing mainly on terpenoid cyclases and related prenyltransferases for which X-ray crystal structures have informed and advanced our understanding of enzyme structure and function.

S. Walas

G. Tchobanoglous, F. L. Burton, Metcalf et al.

A. I. Stankiewicz

R. Sinnott

Chenguang Ouyang, Tian Tu, Haojie Yu et al.

Abstract Janus hydrogels have promising applications in tendon healing and anti‐peritendinous adhesions. However, their complicated preparation methods, weak mechanical properties, and unstable adhesion interfaces have severely limited their application in suture‐free and high‐quality tendon healing. In this work, by controlling the interfacial distribution of free ‐COOH groups and cationic‐π structures on both sides of the hydrogels, a series of PZBA‐EGCG‐ALC Janus hydrogels with varying degrees of asymmetric properties are successfully prepared using a simple and efficient one‐step synthesis method. The tensile strength and elongation at the break of the Janus hydrogel are as high as 0.51 ± 0.04 MPa and 922.89 ± 28.59%. In addition, the Janus hydrogel can achieve a high difference in adhesion strength (nearly 20‐fold) while maintaining a strong adhesion strength on their bottom sides (up to 524.8 ± 33.1 J m−2). In the spatial dimension, its excellent mechanical compliance and one‐sided adhesion behavior can provide effective mechanical support and physical barriers for the injured Achilles tendons. More importantly, the Janus hydrogel can also minimize early inflammation generation in the time dimension via its ROS‐responsive PZBA‐EGCG prodrug macromolecules. This study provided a more effective and convenient suture‐free strategy for constructing Janus hydrogels to promote high‐quality tendon healing.

Ncamisile Nondumiso Maseko, Dirk Enke, Pius Adewale Owolawi et al.

Viktoria Falkowski, Wilhelm Pfleging

Changing the topography of electrodes by ultrafast laser ablation has shown great potential in enhancing electrochemical performance in lithium-ion batteries. The generation of microstructured channels within the electrodes creates shorter pathways for lithium-ion diffusion and mitigates strain from volume expansion during electrochemical cycling. The topography modification enables faster charging, improved rate capability, and the potential to combine high-power and high-energy properties. In this study, we present a preliminary exploration of this approach for sodium-ion battery technology, focusing on the impact of laser-generated channels on hard carbon electrodes in sodium-metal half-cells. The performance was analyzed by employing different conditions, including different electrolytes, separators, and electrodes with varying compaction degrees. To identify key factors contributing to rate capability improvements, we conducted a comparative analysis of laser-structured and unstructured electrodes using methods including scanning electron microscopy, laser-induced breakdown spectroscopy, and electrochemical cycling. Despite being based on a limited sample size, the data reveal promising trends and serve as a basis for further optimization. Our findings suggest that laser structuring can enhance rate capability, particularly under conditions of limited electrolyte wetting or increased electrode density. This highlights the potential of laser structuring to optimize electrode design for next-generation sodium-ion batteries and other post-lithium technologies.

Thomas McKean, Courtney Wilmoth, S. Ranil Wickramasinghe et al.

Heavy metal ions are notoriously difficult to remove from water systems without the infrastructure present at a drinking water treatment plant. This work aimed to develop membrane adsorbers capable of capturing heavy metals at low pressure to avoid the need for extensive infrastructure. Removal of copper as a representative heavy metal was investigated. Membrane adsorbers were fabricated by using photo-initiated radical polymerization to graft glycidyl methacrylate (GMA) from the surface of polyethersulfone microfiltration membranes. The GMA modified membrane was sulfonated through an epoxide ring opening reaction to introduce sulfonic acid groups. The effect of grafting time and temperature on the degree of grafting and membrane performance (permeability and adsorption capacity) were determined. The reactions conditions that provided best performance were 4 min UV exposure at 35 °C. Under these conditions, the degree of grafting was 9% while maintaining a low operating pressure of 0.1 bar. Five and 6 min of UV exposure time increased the DOG to 19% and 41%, respectively, but compromised low pressure operation. Membrane surface properties were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. Membrane performance was investigated by determining membrane permeability and static and dynamic capacity. The dynamic binding capacity was 64.05 ± 0.6 mg Cu/g grafted weight. Using membranes in series demonstrated linear scaleup. Further at a flux of 135 Lm−2h−1 the feed pressure was under 0.15 bar ensuring low pressure operation. These results highlight the potential of membrane adsorbers for low pressure removal of heavy metals.

M. Tallawi, E. Rosellini, N. Barbani et al.

Jeong Han Lee, Min Ju O, Yong-Mook Kang et al.

Petroleum pitch (PP) is a by-product generated during the petroleum refining process, characterized by its high carbon content, tunable structure, and cost-effectiveness. These attributes have spurred extensive research into its potential as a carbon material. In this study, we prepared both untreated PP and oxidative stabilized PP (sPP) to explore the influence of pitch structural modifications on physical and electrochemical properties following carbonization and activation. Stabilizing the pitch above its softening point introduced oxygen functional groups on the surface, reaching levels of up to 19.6 at.%. These structural changes concurrently reduced aromaticity while increasing the coking value. Two types of activated carbons suitable for supercapacitors were derived from these distinct pitches, and their energy storage capacities were correlated with precursor pitch structural properties. The sPP-derived activated carbon exhibited a remarkable gravimetric specific capacitance of 39.6 F g−1, owing to its high specific surface area of 2508 m2 g−1. Conversely, PP-derived activated carbon exhibited a relatively lower specific surface area of 1122 m2 g−1. However, it demonstrated an increased electrode density and shallow ion intercalation within its graphitic structure, resulting in a notable volumetric capacitance of 26.0 F cc−1. This research not only sheds light on the electrochemical effects of pitch stabilization but also provides a foundation for the development of high-performance activated carbon materials through tailored modifications to the PP structure.

Chenzi ZHAI, Xiaodong GUO, Wei WANG

In order to accurately predict the risk level of ancient timber structures under earthquake,22 evaluation indexes were selected, including hazard of disaster-causing factors, susceptibility assessment of disaster environment, and vulnerability of disaster-bearing body, combined with seismic damage characteristics and structural characteristics of ancient timber structures, and an earthquake risk assessment model was established by using the improved matter-element extension model. In this model, closeness degree is used instead of correlation degree, which improves the accuracy of evaluation results. This model was used to evaluate the risk of an ancient timber structure under different ground motion levels. The results show that the ancient timber structure is at moderate risk when the peak acceleration of ground motion is 0.05g, 0.10g, and 0.20g, and when it encounters earthquakes with peak ground accelerations of 0.40g, it becomes at a higher risk.

Wenwen Zhang, Xiaoyu Xu, Yongjun Yuan et al.

The global annual production of rice is over 750 million tons, and generates a huge amount of biomass waste, such as straw, husk, and bran, making rice waste an ideal feedstock for biomass conversion industries. This review focuses on the current progress in the transformation of rice waste into valuable products, including biochar, (liquid and gaseous) biofuels, valuable chemicals (sugars, furan derivatives, organic acids, and aromatic hydrocarbons), and carbon/silicon-based catalysts and catalyst supports. The challenges and future prospectives are highlighted to guide future studies in rice waste valorization for sustainable production of fuels and chemicals.

Yuqiao Guo, Kun Xu, Changzheng Wu et al.

Tadele Assefa Aragaw, Tadele Assefa Aragaw, Fekadu Mazengiaw Bogale et al.

Release of dye-containing textile wastewater into the environment causes severe pollution with serious consequences on aquatic life. Bioremediation of dyes using thermophilic microorganisms has recently attracted attention over conventional treatment techniques. Thermophiles have the natural ability to survive under extreme environmental conditions, including high dye concentration, because they possess stress response adaptation and regulation mechanisms. Therefore, dye detoxification by thermophiles could offer enormous opportunities for bioremediation at elevated temperatures. In addition, the processes of degradation generate reactive oxygen species (ROS) and subject cells to oxidative stress. However, thermophiles exhibit better adaptation to resist the effects of oxidative stress. Some of the major adaptation mechanisms of thermophiles include macromolecule repair system; enzymes such as superoxide dismutase, catalase, and glutathione peroxidase; and non-enzymatic antioxidants like extracellular polymeric substance (EPSs), polyhydroxyalkanoates (PHAs), etc. In addition, different bacteria also possess enzymes that are directly involved in dye degradation such as azoreductase, laccase, and peroxidase. Therefore, through these processes, dyes are first degraded into smaller intermediate products finally releasing products that are non-toxic or of low toxicity. In this review, we discuss the sources of oxidative stress in thermophiles, the adaptive response of thermophiles to redox stress and their roles in dye removal, and the regulation and crosstalk between responses to oxidative stress.

Hassan Idris Abdu, Hamouda Adam Hamouda, Hamouda Adam Hamouda et al.

In the presence of dry ice, a series of graphitic materials with carboxylated edges (ECGs) were synthesized by ball milling graphite for varied times (24, 36, and 46 h). The influence of carboxylation on the physiochemical characteristics and electrochemical performance as effective electrodes for supercapacitors were assessed and compared with pure graphite. Several characterization techniques were employed to investigate into the morphology, texture, microstructure, and modification of the materials. Due to its interconnected micro-mesoporous carbon network, which is vital for fast charge-discharge at high current densities, storing static charges, facilitating electrolyte transport and diffusion, and having excellent rate performance, the ECG-46 electrode among the investigated samples achieved the highest specific capacitance of 223 F g−1 at 0.25 A g−1 current density and an outstanding cycle stability, with capacitance retention of 90.8% for up to 10,000 cycles. Furthermore, the symmetric supercapacitor device based on the ECG-46 showed a high energy density of 19.20 W h kg−1 at 450.00 W kg−1 power density. With these unique features, ball milling of graphitic material in dry ice represents a promising approach to realize porous graphitic material with oxygen functionalities as active electrodes.