Hasil untuk "Chemical engineering"

Fatemeh Ghadiminejad, Akbar Esmaeili, Manzarbanou Asnaashariisfahani

Abstract This research addresses the growing need for sustainable food packaging solutions by developing composite edible films that integrate Carum copticum extract into a matrix of chitosan, polyethylene, fish gelatin, gum arabic, and corn starch. The primary objective of this study is to investigate the impact of cold plasma treatment on enhancing the antioxidant and antimicrobial properties of these films. C. copticum extract is encapsulated in chitosan nanoparticles using a two-step emulsion and gelation method characterized by Field Emission Scanning Electron Microscopy (FESEM). Response surface methodology is employed to optimize polyethylene films, resulting in five variants that are evaluated for their microbial, antioxidant, and physical attributes, including tensile strength. Results indicate a significant improvement in tensile strength (Ts) with the inclusion of Ca C. copticum rum copticum extracts. The films exhibit substantial antioxidant activity (IC 50  = 1.48 mg mL⁻1) resulting from the integration of natural antioxidants and industrial antibacterial agents. Notably, cold plasma treatment enhances the antimicrobial efficacy of the polyethylene films compared to untreated controls. This study underscores the potential of combining natural extracts and cold plasma technology to advance the functional properties of edible films, thereby improving food safety and efficiency in food packaging applications through innovative hydrocolloid-based materials.

Consuelo Celesti, Daniela Iannazzo, Elpida Piperopoulos et al.

Jhony T. Teleken, Suélen M. Amorim, Sarah S. S. Rodrigues et al.

Shrimp is one of the most popular and widely consumed seafood products worldwide. It is highly perishable due to its high moisture content. Thus, dehydration is commonly used to extend its shelf life, mostly via air drying, leading to a temperature increase, moisture removal, and matrix shrinkage. In this study, a mathematical model was developed to describe the changes in moisture and temperature distribution in shrimp during hot-air drying. The model considered the heat and mass transfer in an irregular-shaped computational domain and was solved using the finite element method. Convective heat and mass transfer coefficients (57.0–62.9 W/m²∙K and 0.007–0.008 m/s, respectively) and the moisture effective diffusion coefficient (6.5 × 10⁻¹⁰–8.5 × 10⁻¹⁰ m²/s) were determined experimentally and numerically. The shrimp temperature and moisture numerical solution were validated using a cabinet dryer with a forced air circulation at 60 and 70 °C. The model predictions demonstrated close agreement with the experimental data (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msup><mrow><mi>R</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>≥</mo></mrow></semantics></math></inline-formula> 0.95 for all conditions) and revealed three distinct drying stages: initial warming up, constant drying rate, and falling drying rate at the end. Initially, the shrimp temperature increased from 25 °C to around 46 °C and 53 °C for the process at 60 °C and 70 °C. Thus, it presented a constant drying rate, around 0.04 kg/kg min at 60 °C and 0.05 kg/kg min at 70 °C. During this stage, the process is controlled by the heat transferred from the surroundings. Subsequently, the internal resistance to mass transfer becomes the dominant factor, leading to a decrease in the drying rate and an increase in temperatures. A numerical analysis indicated that considering the irregular shape of the shrimp provides more realistic moisture and temperature profiles compared to the simplified finite cylinder geometry. Furthermore, a sensitivity analysis was performed using the validated model to assess the impact of the mass and heat transfer parameters and relative humidity inside the cavity on the drying process. The proposed model accurately described the drying, allowing the further evaluation of the quality and safety aspects and optimizing the process.

Laura Nistor, Cătălin Lisa, Tsuyoshi Michinobu et al.

Background: 2-[4-(Dimethylamino)phenyl]-3-([4-(dimethylamino)phenyl]ethynyl)buta-1,3-diene-1,1,4,4-tetracarbonitrile (DDMEBT) is a thermally robust organic material of interest for applications requiring controlled volatility. Understanding its thermal stability, decomposition mechanism, and sublimation behavior is critical for optimizing deposition conditions in industrial processes. Methods: A comprehensive set of techniques was employed, including thermogravimetric analysis coupled with mass spectrometry and FTIR spectroscopy (TG/MS/FTIR), differential scanning calorimetry (DSC), ATR-FTIR spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), dynamic vapor sorption (DVS) analysis, polarized light microscopy (POM), and molecular modeling. Sublimation kinetics were investigated under isothermal conditions (130–150 °C) using anthracene as reference. Significant findings: DDMEBT exhibits a sequential three-step degradation mechanism, independent of heating rate, with high thermal stability (final residue ∼77 %) attributed to its nonplanar architecture and intermolecular π–π/dipole–dipole interactions. Thermal analysis revealed melting at ∼190 °C, structural rearrangements (196–230 °C), and an amorphous-to-crystalline transition at 270 °C. Sublimation proceeds via zero-order kinetics with low volatility (0.178 μg/min at 130 °C) and an activation energy of 66.5 kJ/mol. The determined vapor pressure (1998–4000 Pa) and transport coefficients confirm a thermally activated, hydrodynamically stable process. These findings establish a reliable basis for sublimation modeling and provide guidelines for optimizing material processing in high-temperature, low-volatility applications.

Lixia Feng, Qilong Bian, Shujun Wu et al.

Abstract Arsenic contaminants exist in different chemical forms with varying toxicity and mobility, making on-site analysis challenging. Here, a fluorogenic method is developed for the efficient detection of arsenite and arsenate ions using a portable platform directly in an aqueous phase. During sensing, the aggregation-induced emission (AIE) probe TPE-Cys/TPE-2Cys exhibits low fluorescence when dissolved, but reacts with the As(III) to form organic arsenic complexes with low solubility, inducing a turn-on fluorescence for quantitative analysis. Using a prior reduction strategy, the As(V) can be converted to As(III) and further analyzed in a sequential detection. Using a specialized laser-induced fluorescence instrument, this strategy allows on-site analysis of As(III) and As(V) species with sensitivity down to 0.14 ppb in environmental samples, showing that As(III) dominates while the As(V)/As(III) ratio varies in a constitutional equilibrium. The system has potential for the practical analysis of complex arsenic, revealing the dynamic arsenic transformations in the environment.

Silas M. Mbeche, Paul M. Wambua, David N. Githinji

Human hair (HH) is considered a waste material generated in salons and barbershops in most societies, especially highly populated cities, where it is produced in large quantities, thus rekindling the interests of academics. Several studies are ongoing on the possibility of utilizing it as a reinforcement in polymer composites, either in its raw form or as extracted keratin nanoparticles, due to its unique features and the current global emphasis on circular economy. The present review seeks to provide a synopsis of recent developments in the utilization of HH and keratin in polymer composites. Composites from different HH loading, length, and chemical treatments were made using hand lay-up and hot compression molding methods. HH has been investigated in diverse composite systems, encompassing HH/natural fiber composites, HH/synthetic fiber composites, and keratin-reinforced composites. Our study revealed that these innovative materials exhibit enhanced energy absorption capacity, mechanical strength, hardness, and thermal properties, positioning them as promising choices for a wide range of engineering applications. The review further revealed that keratin nano-particles can be extracted from waste HH using various methods such as reduction alkaline hydrolysis and can be used as reinforcement in polymer composites.

Xin Kong, Bin Liu, Zhongqiu Tong et al.

Abstract Metallic phthalocyanines are promising electrocatalysts for CO2 reduction reaction (CO2RR). However, their catalytic activity and stability (especially under high potential) are still unsatisfactory. Herein, we synthesized a covalent organic polymer (COP‐CoPc) by introducing charge‐switchable viologen ligands into cobalt phthalocyanine (CoPc). The COP‐CoPc exhibits great activity for CO2RR, including a high Faradaic efficiency over a wide potential window and the highest CO partial current density among all ligand‐tuned phthalocyanine catalysts reported in the H‐type cell. Particularly, COP‐CoPc also shows great potential for practical applications, for example, a FECO of >95% is realized at a large current density of 150 mA/cm2 in a two‐electrode membrane electrode assembly reactor. Ex situ and in situ X‐ray absorption fine structure spectroscopy measurements and theory calculations reveal that when the charge‐switchable viologen ligands switch to neutral‐state ones, they can act as electron donors to enrich the electron density of Co centers in COP‐CoPc and enhance the desorption of *CO, thus improving the CO selectivity. Moreover, the excellent reversible redox capability of viologen ligands and the increased Co–N bonding strength in the Co–N4 sites enable COP‐CoPc to possess outstanding stability under elevated potentials and currents, enriching the knowledge of charge‐switchable ligands tailored CO2RR performance.

Haoyu Zhang, Shuang Gao, Haitao Guan et al.

<p>Photocatalytic CO₂ reduction to valuable chemical compounds could be a promising approach for carbon-neutral practice. In this work, a simple and robust thermal decomposition process was developed with ammonium carbonate ((NH₄)₂CO₃) as both precipitation agent and sacrificial template to produce fine Nb₂O₅ nanoparticles with the rich existence of surface hydroxyl (–OH) groups. It was found by density functional theory (DFT) calculations and experiments that the rich existence of the surface –OH groups enhanced the adsorption of both reactants (CO₂ and H₂O molecules) for the photocatalytic CO₂ reduction on these fine Nb₂O₅ nanoparticles, and the highly selective conversion of CO₂ to the high-value chemical compound of ethylene (C₂H₄, ~68 μmol·g⁻¹·h⁻¹ with ~100% product selectivity) was achieved under simulated solar illumination without usage of any sacrificial agents or noble metal cocatalysts. This synthesis process may also be readily applied as a surface engineering method to enrich the existence of the surface –OH groups on various metal oxide-based photocatalysts for a broad range of technical applications.</p>

Xujing Zhang, Songsong Tang, Zhaokun Wu et al.

Silver nanowires (AgNWs) have received much attention and application in transparent electrodes, wearable electronic devices, and sensors. The hope is for these nanowires to eventually replace the most commonly used transparent electrode material—indium tin oxide (ITO). However, electrospinning used for the preparation of AgNWs on a large scale is limited by its low productivity and high electric field, while the alcohol-thermal method is limited to mixing by-product silver nanoparticles in silver nanowires. We demonstrate a novel and simple centrifugal spinning approach in order to successfully fabricate ultra-long silver microfibers based on AgNO₃ and polyvinyl pyrrolidone (PVP). The centrifugal-spun precursor fiber and silver fiber can be prepared to as thin as 390 and 310 nm, respectively. Annealed fibers show typical nanostructures with grains down to a minimum size of 51 nm. Combinations of different parameters, including concentrations of PVP, needle size, and annealing temperature are also investigated, in order to optimize the spinning process of ultra-long silver microfibers. The feasibility of preparing silver microfibers by centrifugal spinning is preliminarily verified, examining prospects for mass production. Furthermore, numerous strategies related to assisting the creation of silver nanofibers using centrifugal spinning are presented as possibilities in future development.

Sareh Farahani, Abbas Akhavanesepahi, Sayed abbas Shojaosadati et al.

Introduction: Due to the increasing trend of industrial development and also the industrial production, the presence of heavy metals along with industrial wastewater is undeniable. Despite the various ways to remove heavy metals, choosing biological methods can be the best way to control them. Using bacteria in this field can be very useful and inexpensive with less harm. Materials and Methods: In the present study, various aquatic environments including rivers, ponds, industrial effluents, and activated sludge were sampled. Bacteria were identified based on the growth in iron-specific culture medium in terms of shape and 16S rRNA gene. These bacteria were cultured in specific culture media for iron-oxidizing bacteria, Luria-Bertoni (LB) and PHG II, containing 2 ppm of mercury chloride and cadmium chloride. The samples were then examined for the reduction or non-change of mercury and cadmium concentrations by atomic absorption spectrometry. Results: The results of the present study showed that the isolated bacteria were rod-shaped and chemoorganotrophic belonging to the genus Bacillus. The average percentages of mercury and cadmium removal by the isolated bacteria were about 95% and 40%, respectively.  The highest percentage of the removal of both heavy metals was observed in the effluent sample of iron factory wastewater. Discussion and Conclusion: Iron oxidizing bacteria were identified as reducing agents of heavy metals in the laboratory environment. These bacteria grew in both LB medium and iron-specific culture medium. The highest percentage of the removal of both heavy metals was observed in the effluent sample of the iron processing plant. Based on the results, it can be said that the bacteria of each environment have adapted to the compounds of that place and are the best option to remove compounds such as heavy metals.

Mochou Liao, Xiao Ji, Yongjie Cao et al.

It is challenging to prepare electrolyte that could achieve wide electrochemical window, broad working temperature, non-inflammability, and fast ion transport simultaneously. Here the authors report a rocking-chair proton battery utilizing a solvent-free protic liquid electrolyte, which could operate in a broad temperature range from 0 to 250 celsius degree.

Jacob D. Crowe, Pengchao Hao, Sivakumar Pattathil et al.

Plant biomass represents an abundant and increasingly important natural resource and it mainly consists of a number of cell types that have undergone extensive secondary cell wall (SCW) formation. These cell types are abundant in the stems of Arabidopsis, a well-studied model system for hardwood, the wood of eudicot plants. The main constituents of hardwood include cellulose, lignin, and xylan, the latter in the form of glucuronoxylan (GX). The binding of GX to cellulose in the eudicot SCW represents one of the best-understood molecular interactions within plant cell walls. The evenly spaced acetylation and 4-O-methyl glucuronic acid (MeGlcA) substitutions of the xylan polymer backbone facilitates binding in a linear two-fold screw conformation to the hydrophilic side of cellulose and signifies a high level of molecular specificity. However, the wider implications of GX–cellulose interactions for cellulose network formation and SCW architecture have remained less explored. In this study, we seek to expand our knowledge on this by characterizing the cellulose microfibril organization in three well-characterized GX mutants. The selected mutants display a range of GX deficiency from mild to severe, with findings indicating even the weakest mutant having significant perturbations of the cellulose network, as visualized by both scanning electron microscopy (SEM) and atomic force microscopy (AFM). We show by image analysis that microfibril width is increased by as much as three times in the severe mutants compared to the wild type and that the degree of directional dispersion of the fibrils is approximately doubled in all the three mutants. Further, we find that these changes correlate with both altered nanomechanical properties of the SCW, as observed by AFM, and with increases in enzymatic hydrolysis. Results from this study indicate the critical role that normal GX composition has on cellulose bundle formation and cellulose organization as a whole within the SCWs.

Yimei Xi, Song Xue, Xupeng Cao et al.

Abstract Accumulation of β-carotene in Dunaliella salina is highly dependent on light exposure intensity and duration, but quantitative analysis on photon numbers received per cell for triggering β-carotene accumulation is not available so far. In this study, experiment results showed that significant β-carotene accumulation occurred after at least 8 h illumination at 400 µmol photons·m−2·s−1. To quantify the average number of photons received per cell, correlations of light attenuation with light path, biomass concentration, and β-carotene content were, respectively, established using both Lambert–Beer and Cornet models, and the latter provided better simulation. Using Cornet model, average number of photons received per cell (APRPC) was calculated and proposed as a parameter for β-carotene accumulation, and constant APRPC was maintained by adjusting average irradiance based on cell concentration and carotenoids content changes during the whole induction period. It was found that once APRPC reached 0.7 µmol photons cell−1, β-carotene accumulation was triggered, and it was saturated at 9.9 µmol photons cell−1. This study showed that APRPC can be used as an important parameter to precisely simulate and control β-carotene production by D. salina. Graphic Abstract

F. S. Aghaei Maybodi, M. H. Heydari, F. M. Maalek Ghaeini et al.

Introduction Many mathematical formulations of physical phenomena contain integro-differential equations. These equations arise in fluid dynamics, biological models, chemical kinetics, ecology, control theory of financial mathematics, aerospace systems, industrial mathematics etc. It is worth mentioning that integro-differential equations are usually difficult to solve analytically, and so it is required to obtain an efficient approximate solution for them. Fractional calculus deals with derivatives and integrals of arbitrary real or complex orders.  This subject has attracted attention of many scientists in mathematics, physics and engineering. So, it has become a hot issue in recent years. Fractional integro-differential equations arise in the mathematical modelling of various physical phenomena, such as heat conduction in materials with memory. Moreover, these equations are encountered in combined conduction, convection and radiation problems. There are only a few techniques for the solution of fractional integro-differential equations, since it is relatively a new subject in mathematics. Some of these methods are Legendre spectral tau method, Adomian decomposition method, piecewise polynomial collocation methods, spline collocation method, hybrid collocation method, hybrid functions approximation by block-pulse functions and Bernoulli polynomials, Taylor expansion approach, differential transform method and wavelet methods. In recent years many problems in mathematics, physics and engineering have been numerically solved by radial basis functions (RBFs) methods.  In this paper, we focus on the Gaussian and inverse multiquardic RBFs as two of the most important tools in engineering and sciences to solve a class of fractional parabolic integro-differential equations. This class of equations describes some phenomena in compression of viscoelastic media and nuclear reactor dynamics. Material and methods In the proposed method, first the fractional derivative operator is transformed into a non-singular equivalent.  Then, the Gaussian and inverse multiquardic RBFs together with the collocation method and Gauss-Legendre quadrature formula are used to transform the problem under consideration into the corresponding system of linear algebraic equations, which can be simply solved to achieve an approximate solution of the problem. Results and discussion Some numerical examples are examined to demonstrate the efficiency and high accuracy of the present method. The obtained results demonstrate that there is a good agreement between the approximate solutions and the exact ones. Also we hope that the proposed method can provide numerical solutions with high accuracy for the problems under study for all fractional orders. Meanwhile, the best value for the shape parameter in the Gaussian and inverse multiquardic RBFs method can be obtained by employing an appropriate optimization method. Conclusion The following conclusions were extracted from this research. The established method transforms such problems into equivalent systems of algebraic equations by expanding the solution of the problem in terms of the RBFs and applying Gauss-Legendre integration formula. Only a few number of the RBFs is needed to obtain a high accurate numerical solution for such problems. The presented method can easily be developed for other classes of fractional partial integro-differential equations../files/site1/files/71/2.pdf

Hoofar Shokravi, Hooman Shokravi, Norhisham Bakhary et al.

Bridges are designed to withstand different types of loads, including dead, live, environmental, and occasional loads during their service period. Moving vehicles are the main source of the applied live load on bridges. The applied load to highway bridges depends on several traffic parameters such as weight of vehicles, axle load, configuration of axles, position of vehicles on the bridge, number of vehicles, direction, and vehicle’s speed. The estimation of traffic loadings on bridges are generally notional and, consequently, can be excessively conservative. Hence, accurate prediction of the in-service performance of a bridge structure is very desirable and great savings can be achieved through the accurate assessment of the applied traffic load in existing bridges. In this paper, a review is conducted on conventional vehicle-based health monitoring methods used for bridges. Vision-based, weigh in motion (WIM), bridge weigh in motion (BWIM), drive-by and vehicle bridge interaction (VBI)-based models are the methods that are generally used in the structural health monitoring (SHM) of bridges. The performance of vehicle-assisted methods is studied and suggestions for future work in this area are addressed, including alleviating the downsides of each approach to disentangle the complexities, and adopting intelligent and autonomous vehicle-assisted methods for health monitoring of bridges.

Vadim Fetisov, Vladimir Pshenin, Dmitrii Nagornov et al.

Emissions of volatile organic compounds into the atmosphere when loading oil or petroleum products into tankers are strong environmental pollutants. Given the increase in oil transport by sea and the development of Arctic routes, humanity faces the task of preserving the Arctic ecosystem. Vapor recovery units can limit the emissions of volatile organic compounds. However, it is necessary to estimate the emissions of oil and petroleum products vapors. This article offers two methods for estimating emissions of volatile organic compounds. In the analytical method, a mathematical model of evaporation dynamics and forecasting tank gas space pressure of the tanker is proposed. The model makes it possible to estimate the throughput capacity of existing gas phase discharge pipeline systems and is also suitable for designing new oil vapor recovery units. Creating an experimental laboratory stand is proposed in the experimental method, and its possible technological scheme is developed.

Khairul Khairul, Helentina Mariance Manullang

Perairan Belawan Pulau Sicanang merupakan kawasan yang rentan terhadap pencemaran logam berat, karena kawasan perairan ini berdekatan dengan kawasan industri, pelabuhan, dan permukiman. Logam berat sangat berbahaya bagi kehidupan hewan aquatik maupun bagi kesehatan manusia. Penelitian ini merupakan penelitian diskriptif eksploratif yang bertujuan untuk mengetahui kandungan logam berat berupa: Timbal (Pb), Cadmium (Cd), dan Merkuri (Hg) pada perairan ekositem mangrove Belawan Pulau Sicanang. Keberadaan ekosistem hutan mangrove di kawasan ini berfungsi sebagai penyangga kehidupan. Kandungan logam berat di perairan bisa diserap oleh tanaman mangrove sebagai fitoremediasi.Penentuan stasiun pengamatan berdasarkan purvosive sampling, dengan Stasiun 1 yang merupakan kawasan hutan mangrove alami dan Stasiun 2 yang merupakan kawasan perusahaan dan pabrik). Metode uji sampel air dengan Atomic Absorption Spectroscopy (AAS). Hasil analisis logam berat dari air sampel berupa: Pb (0,15 ppm) pada Stasiun 1 dan 0,33 ppm pada Stasiun 2, Cd (0,04 ppm) pada Stasiun 1 dan 0,11 ppm pada Stasiun 2, Sedangkan Hg (<0.1011 ppm) nilainya sama pada Stasiun 1 dan 2. Berdasarkan hasil analisis logam berat berupa: Pb, Cd dan Hg pada kedua perairan, dapat disimpulkan bahwa kawasan hutan magrove alami memiliki kandungan logam lebih rendah daripada kawasan industri. 

Ming-Yu Zhang, Ke Xu, Jian-Hong Xu et al.

A new microfluidic approach to preparing anisotropic colloidal photonic crystal microparticles is developed and the self-assembly kinetics of colloidal nanoparticles is discussed. Based on the “coffee ring” effect in the self-assembly process of colloidal silica particle in strong solvent extraction environment, we successfully prepared anisotropic photonic crystal microparticles with different shapes and improved optical properties. The shapes and optical properties of photonic crystal microparticles can be controlled by adjusting the droplet size and extraction rate. We studied the self-assembly mechanism of colloidal silica particles in strong solvent extraction environment, which has potential applications in a variety of fields including optical communication technology, environmental response, photo-catalysis and chromic material.

Wang Peng, Wang Siqi, Zhang Qian

To address the stability issue of coiled tubing operation,the stress and elongation of two kinds of hydraulic jet annulus sand delivery fracturing string have been analyzed in the whole process of operation in Daqing oilfield.The main research include:(1)Stress and deformation analysis of the coiled tubing hydraulic jet fracturing string in the whole operation,and the corresponding mathematical model;(2)Analysis on the two common packer K344 and Y211 during fracturing;processing methods of the boundary conditions at the bottom of the fracturing string during the setting of different packers;(3)Calculation of the deformation and stress of the coiled tubing fracturing string during fracturing operation of Well Gulongnan P,and comparison with the field measured data.Analysis results showed that the mechanical model results have a small deviation with the measured data.The research results could provide theoretical guidance for coiled tubing hydraulic jet fracturing operation design and construction.

M. Kumasaki, T. Shoji

The quality of hazard identification has a significant impact on the quality of overall risk assessment and occupational accident prevention in workplace. Currently accepted hazard identification approaches tend to rely on knowledge of previous accidents, experience of the task, and participants’ imagination, although hazard identification itself is most important for new tasks and novices who do not have experiences of the same or similar tasks. This paper outlines a logical hazard identification method based on a concept for object-based energy analysis as a tool that does not require experience, knowledge of tasks, or imagination. The method is derived from a physical principal and the analysis of occupational accidents. This method is expected to enable users to identify hazards effectively and easily, and contribute to successful risk assessment.