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Showing records 1 to 25 of 505. [First] Page: 1 2 3 4 5 Last
Graphene Nanoplatelets Suspended in Different Basefluids Based Solar Collector: An Experimental and Analytical Study
Omer A. Alawi, Haslinda Mohamed Kamar, Abdul Rahman Mallah, Hussein A. Mohammed, Mohd Aizad Sazrul Sabrudin, Omar A. Hussein, Salim Newaz Kazi, Gholamhassan Najafi
November 27, 2022 (v1)
Subject: Materials
Keywords: characterization and stability, collector efficiency, flat plate solar collector (FPSC), GNPs
A flat plate solar collector (FPSC) was analytically studied, with functionalized graphene nanoplatelets (f-GNPs) as its working fluid. Four samples (wt % nanofluids) were prepared in different base fluids such as ethylene glycol (EG), distilled water (DW):EG (70:30), and DW:EG (50:50). Experimental results (via DW) were used to verify the effectiveness of the analytical model. Some of the operating conditions were taken into account in this research, including temperatures, power, and mass flow rates. Experimental techniques were used to elucidate the modified nanofluids’ physicochemical properties, such as its particle sizes, stability, and morphology, involving electron microscopes (EMs), UV−VIS, and X-ray techniques. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were applied to test the thermal analysis. The findings confirmed that the use of f-GNPs nanofluids enhanced the performance of the FPSC relative to the use of base fluids for all testing cond... [more]
Simultaneous Removal of Al, Cu and Zn Ions from Aqueous Solutions Using Ion and Precipitate Flotation Methods
Piotr Rybarczyk, Bożenna Kawalec-Pietrenko
November 27, 2022 (v1)
Subject: Materials
Keywords: aluminum, collector, copper, ion flotation, metal ions, precipitate flotation, zinc
This paper presents the results of investigations concerning the simultaneous removal of Al(III), Cu(II), and Zn(II) from dilute aqueous solutions using ion and precipitate flotation methods. The effects of initial solution pH, surface active substance concentration, and the gas velocity on the flotations’ efficiency and course are studied. Experimental results are discussed in terms of physicochemical aspects related to aqueous solutions of metal salts. The results indicate that satisfying simultaneous flotations of aluminum, copper and zinc species are observed if the pH value ranges between 7.0 and 9.0. It was found that an increase in collector concentration results in a decrease in the flotation rate constants. An increase in the gas velocity results in an increase in the ion and precipitate flotation rates.
Permeability Evolution of Naturally Fractured Coal Injected with High-Temperature Nitrogen: Experimental Observations
Shengcheng Wang, Haijian Li, Lanying Huang
November 7, 2022 (v1)
Subject: Materials
Keywords: coal permeability, cycle number, N2 injection pressure, N2 temperature, triaxial test
The permeability of more than 70% of coal seams in China is less than 1 mD, creating difficulties in recovering underground coal methane. Therefore, a new technology of high-temperature nitrogen (HTN2) injection into the coal seam was proposed to improve the coal permeability and gas extraction rate. In this paper, the effects of the N2 temperature, injection pressure and cycle number on the permeability of naturally fractured coking coal has been investigated. When HTN2 was injected into coal samples, the results indicated that the permeability decreased over time in the beginning, suddenly increased to a large value, and was subsequently maintained in a relatively stable range. The maximum permeability ratio increased with the rise of the N2 temperature and injection pressure. An analysis indicated that the increase of coal permeability was the result of the increase of the global coal strain caused by thermal expansion and the adsorption-induced expansion. The maximum permeability r... [more]
A Study of Catechin Photostability Using Photolytic Processing
Jeu-Ming P. Yuann, Shwu-Yuan Lee, Meei-Ju Yang, Shiuh-Tsuen Huang, Chien-Wei Cheng, Ji-Yuan Liang
November 7, 2022 (v1)
Subject: Materials
Keywords: aluminum, catechin, light, proanthocyanidin, tea
Catechin exhibits numerous physiological characteristics. In this study, we determined the photosensitivity of catechin to various lights under alkaline conditions, and the mechanisms by which catechin generates free radical species and polymerizes via a photoreaction. In addition to this, the application of catechin photolysis was investigated. A solution of catechin is transparent, but turns yellowish under blue light illumination (BLI) in neutral or weak alkaline solutions. When catechin is subjected to BLI, a dimeric catechin (proanthocyanidin) and a superoxide anion radical (O2•−) are generated in a photolytic reaction. When ascorbic acid or gallic acid is added to catechin and the mixture is subjected to BLI at alkaline pH, fewer catechin dimers and less O2•− are produced, because both acids inhibit the photosensitive oxidation of catechin. When AlCl3 is added to catechin and the mixture is subjected to BLI at pH 8, a photolytic reaction is suppressed by AlCl3, and AlCl3 acts as... [more]
Making Concentrated Pterostilbene Highly Bioavailable in Pressure Processed Phospholipid Nanoemulsion
Fu-Min Sun, Yu-Jou Chou, Qingrong Huang, Jing-Yu Hu, Yuwen Ting
November 7, 2022 (v1)
Subject: Materials
Keywords: bioavailability, encapsulation, lecithin, nanoemulsion, pterostilbene
Pterostilbene, a dimethylether analog of resveratrol, has been found to have potent biological activity. However, the bioavailability of pterostilbene in the biological system is limited due to its poor solubility in an aqueous environment. A nanoemulsion system was designed for this purpose. Lecithin-based nanoemulsion was formed after 3 cycles through a high-pressure homogenizer at 500 psi. The rheological properties and particle size were measured using dynamic light scattering and a viscometer. The storage stabilities of the prepared formulation were determined based on its ability to maintain its particle size and loading concentration. According to the experimental results, the lecithin-based nanoemulsion system contained approximately 9.5% of pterostilbene. Over the 28-day stability test, the particle size, zeta potential, and encapsulation of pterostilbene in the nanoemulsion did not change significantly, indicating good storage stability. The positive effect of the prepared na... [more]
Extraction of Type I Collagen from Tilapia Scales Using Acetic Acid and Ultrafine Bubbles
Junko Kuwahara
November 6, 2022 (v1)
Subject: Materials
Keywords: circular dichroism, collagen, Sirius Red, tilapia scales, ultrafine bubbles
Type I collagen is commonly used in medical materials and cosmetics. While it can be extracted from the skin and bones of mammals, marine collagen has attracted attention recently, since the use of mammalian collagen could result in zoonosis, and products containing mammalian collagen are avoided due to some religious beliefs. Chemical extractions using strong acids and alkalis, thermal extractions, and other nonconventional methods have been used for collagen extraction. However, there are few reports on environmentally friendly methods. Although heat extractions provide higher yields of collagen, they often cause collagen denaturation. Therefore, dilute acetic acid and ultrafine bubbles of oxygen, carbon dioxide, and ozone were used to extract type I collagen from tilapia scales. The extraction performance of the different conditions employed was qualitatively analyzed by SDS-PAGE electrophoresis, and the collagen concentration was quantified using circular dichroism spectroscopy by... [more]
Separation and Rectification of Chloroacetyl Chloride from TiCl4
Fuxing Zhu, Liang Li, Dafu Zhang, Shangrun Ma, Zhanshan Ma, Kehui Qiu
November 6, 2022 (v1)
Subject: Materials
Keywords: chloroacetyl chloride (CAC), Fourier transform infrared (FTIR) spectroscopy, orthogonal design, removal efficiency, separation behavior, TiCl4 solution
Titanium tetrachloride (TiCl4) is an important intermediate material for the preparation of titanium products. The organic impurities in TiCl4 are easily accumulated during the production of titanium sponges due to the problems of imperfect detection methods and the lack of effective control methods, resulting in a poor quality of sponge titanium. Among all impurities, chloroacetyl chloride (CAC) is the most important in TiCl4. Herein, the determination of the CAC content in TiCl4 solution, with a low detection limit of 0.633 ppm, was established by the standard addition method using Fourier transform infrared (FTIR) spectrometry. This test method presented good repeatability, excellent accuracy, and moderate precision. Furthermore, the influencing factors of CAC separation in the continuous rectification process, including the heating power (the ratio of total heating power to feed rate), reflux temperature, top tower pressure, and feed temperature were optimized based on an orthogona... [more]
Optical Chemical Sensor Based on 2,2-Furildioxime in Sol-Gel Matrix for Determination of Ni2+ in Water
Suherman Suherman, Muh. Supwatul Hakim, Agus Kuncaka
November 6, 2022 (v1)
Subject: Materials
Keywords: furildioxime, Ni2+, optical sensor, sol-gel
A new optical chemical sensor was fabricated based on incorporation of 2,2-furildioxime as a sensitive reagent into the nanopore of a transparent glasslike material through the sol-gel method which was suitable for determination of Ni2+ ions in aqueous solutions. The prepared sensors were composed of tetraethoxysilane (TEOS), 2,2-furildioxime, methanol, hydrochloric acid and Triton X-100. The sensors were constructed by dip coating onto glass substrates. The optimum response of the sensor toward Ni2+ ions was reached at pH 8.5 and the contact time for the formation of the complex at 10 min. The linear concentration of the calibration curve was in the range of 1−5 mg L−1 with a detection limit of 0.111 mg L−1, and quantification limit of 0.337 mg L−1. In addition, the relative standard deviation (RSD) was less than 5% in determination of Ni2+ with ten slide sensor membranes. The developed sensor was tested on Ni2+ determination in real water samples which was confirmed by the atomic abs... [more]
Preparation and Tribological Properties of Graphene Lubricant Additives for Low-Sulfur Fuel by Dielectric Barrier Discharge Plasma-Assisted Ball Milling
Xianbin Hou, Yanjun Ma, Geetanj Bhandari, Zibin Yin, Leyang Dai, Haifeng Liao, Yukun Wei
October 31, 2022 (v1)
Subject: Materials
Keywords: dielectric barrier discharge plasma-assisted ball milling, graphene, low-sulfur fuel, lubricant additive, lubrication property, surface modification
Poor lubrication performance of low-sulfur fuel leads to increased wear of diesel engine components. In order to improve the lubrication properties of low-sulfur fuel, we successfully prepared graphene lubricant additives by dielectric barrier discharge plasma-assisted ball milling. The tribological properties of graphene lubricant additives in two types of 0# diesel oils with different sulfur content were evaluated by high-frequency reciprocating rig (HFRR). The results indicated that the expanded graphite was exfoliated and refined into graphene sheets with nine layers by the synergistic effect of the heat explosive effect of the discharge plasma, the impact of mechanical milling function, and the cavitation effect of 0# diesel oil. The organic functional groups of 0# diesel oil were successfully grafted on the surface of graphene sheets. The addition of 0.03 wt % graphene resulted in 20% reduction in the friction coefficient (COF) and 28% reduction in wear scar diameter (WSD) compar... [more]
Gd3+ Complexes Conjugated to Cyclodextrins: Hydroxyl Functions Influence the Relaxation Properties
Anais Biscotti, François Estour, Berthe-Sandra Sembo-Backonly, Sébastien Balieu, Michaël Bosco, Cécile Barbot, Agnès Pallier, Éva Tóth, Célia S. Bonnet, Géraldine Gouhier
October 31, 2022 (v1)
Subject: Materials
Keywords: contrast agent, cyclodextrin, gadolinium, magnetic resonance imaging, second hydration sphere
In the search for improvement in the properties of gadolinium-based contrast agents, cyclodextrins (CDs) are interesting hydrophilic scaffolds with high molecular weight. The impact of the hydrophilicity of these systems on the MRI efficacy has been studied using five β-CDs substituted with DOTA or TTHA ligands which, respectively, allow for one (q = 1) or no water molecule (q = 0) in the inner coordination sphere of the Gd3+ ion. Original synthetic pathways were developed to immobilize the ligands at C-6 position of various hydroxylated and permethylated β-CDs via an amide bond. To describe the influence of alcohol and ether oxide functions of the CD macrocycle on the relaxation properties of the Gd3+ complexes, 1H Nuclear Magnetic Relaxation Dispersion (NMRD) profiles, and 17O transverse relaxation rates have been measured at various temperatures. The differences observed between the hydroxylated and permethylated β-CDs bearing non-hydrated GdTTHA complexes can be rationalized by a s... [more]
Visible Light-Driven Photocatalytic Rhodamine B Degradation Using CdS Nanorods
Haseeb Ullah, Eva Viglašová, Michal Galamboš
October 30, 2022 (v1)
Subject: Materials
Keywords: CdS, photocatalysis, pseudo-first order kinetics, rhodamine B
In this work, highly crystalline CdS nanorods (NRs) were successfully synthesized by a facile, one-step solvothermal method. The as-prepared CdS NRs powder was characterized by XRD, FESEM, Raman, PL, XPS, BET, and UV-visible techniques to evaluate the structural, morphological, and optical properties. The photocatalytic performance of the as-synthesized CdS NRs was investigated for the photodegradation of RhB dye under visible light irradiations. It has been found that CdS NRs show maximum RhB degradation efficiency of 88.4% in 120 min. The excellent photodegradation ability of the CdS NRs can be attributed to their rod-like structure together with their large surface area and surface state. The kinetic study indicated that the photodegradation process was best described by the pseudo-first-order kinetic model. The possible mechanism for the photodegradation of RhB dye over CdS NRs was proposed in this paper.
Low-Viscosity Ether-Functionalized Ionic Liquids as Solvents for the Enhancement of Lignocellulosic Biomass Dissolution
Asyraf Hanim Ab Rahim, Normawati M. Yunus, Wan Suzaini Wan Hamzah, Ariyanti Sarwono, Nawshad Muhammad
October 30, 2022 (v1)
Subject: Materials
Keywords: Biomass, dissolution, ionic liquids, Optimization, RSM, ultrasonic
Due to the substantial usage of fossil fuels, the utilization of lignocellulosic biomass as renewable sources for fuels and chemical production has been widely explored. The dissolution of lignocellulosic biomass in proper solvents is vital prior to the extraction of its important constituents, and ionic liquids (ILs) have been found to be efficient solvents for biomass dissolution. However, the high viscosity of ILs limits the dissolution process. Therefore, with the aim to enhance the dissolution of lignocellulosic biomass, a series of new ether-functionalized ILs with low viscosity values were synthesized and characterized. Their properties, such as density, viscosity and thermal stability, were analyzed and discussed in comparison with a common commercial IL, namely 1-butyl-3-methylimidazolium chloride (BMIMCl). The presence of the ether group in the new ILs reduces the viscosity of the ILs to some appreciable extent in comparison to BMIMCl. 1-2(methoxyethyl)-3-methylimidazolium ch... [more]
Influence of Metal Oxides and Their Precursors on the Composition of Final Products of Aquathermolysis of Raw Ashalchin Oil
Sergey M. Petrov, Aliya G. Safiulina, Natalya Yu. Bashkirtseva, Alfiya I. Lakhova, Galiya G. Islamova
October 25, 2022 (v1)
Subject: Materials
Keywords: aquathermolysis, carbonate, hydrothermal conversion of heavy oil, kaolin, metal oxides, mineral compounds, precursors
Experiments were conducted simulating hydrothermal conversion of heavy oil in the presence of carbonate, kaolin, Al2O3, Ni2+ and Cu2+, NiO mixed with poly-α-olefins, C6H8O7, C2H4O2 at 290−375 °C and 10−135 bar. Al2O3, carbonate at 375 °C and 135 bar, accelerated the resin degradation. Experiments with carbonate at 350 °C and 10 bar showed no significant composition changes. NiSO4, CuSO4, kaolin mineral, at 350 °C and 78 bar, accelerated decomposition of resins (from 35.6% to 32.5%). Al2O3 and carbonate at 290 °C and 14 bar led to the destruction of asphaltenes (from 6.5% to 4.7% by weight), which were adsorbed on the surface of carbonate. Al2O3, NiO, poly-α-olefins at 350 °C and 78 bar accelerated C−C bond cracking of high-boiling asphaltenes. C6H8O7, rock-forming carbonate, at 360 °C and 14 bar, contributed to the polymerization and polycondensation of hydrocarbons with the formation of additional resins. C2H4O2 and kaolin at 360 °C and 12 bar affected the reduction in the resin conte... [more]
Carbonaceous Adsorbents Derived from Agricultural Sources for the Removal of Pramipexole Pharmaceutical Model Compound from Synthetic Aqueous Solutions
Efstathios V. Liakos, Kyriazis Rekos, Dimitrios A. Giannakoudakis, Athanasios C. Mitropoulos, George Z. Kyzas
October 25, 2022 (v1)
Subject: Materials
Keywords: activated carbons, Adsorption, kiwi peels, orange peels, pharmaceuticals, sucrose, tea waste
The aim of the present study was to synthesize various samples of activated carbon (AC) from different agricultural sources as precursors, like orange peels, tea stalks, and kiwi peels, as well as sucrose. The synthesis of AC was achieved with chemical activation using H3PO4 and KOH. The produced AC samples were tested as adsorbents for the removal of a pharmaceutical model compound, pramipexole dihydrochloride (PRM), from synthetic aqueous synthetic solutions. The produced-from-sucrose AC presented the higher yield of synthesis (~58%). The physicochemical features of the materials were analyzed by FTIR spectroscopy, N2 physisorption, and SEM imaging. More specifically, the AC sample derived from sucrose (SG-AC) had the highest specific surface area (1977 m2/g) with the total pores volume, mesopores volume, and external surface area being 1.382 cm3/g, 0.819 cm3/g, and 751 m2/g, respectively. The effect of the initial pH and PRM concentration were studied, while the equilibrium results... [more]
The Effect of a Peptide Substrate Containing an Unnatural Branched Amino Acid on Chymotrypsin Activity
Yuuki Yamawaki, Tomoki Yufu, Tamaki Kato
October 18, 2022 (v1)
Subject: Materials
Keywords: 7-amino-4-methylcoumarin, chymotrypsin, fluorescent probe, peptide, specificity, unnatural amino acid
7-Amino-4-methylcoumarin (AMC) is a low molecular weight fluorescent probe that can be attached to a peptide to enable the detection of specific proteases, such as chymotrypsin, expressed in certain diseases. Because this detection depends on the specificity of the protease toward the peptidyl AMC, the development of specific substrates is required. To investigate the specificity of chymotrypsin, peptidyl AMC compounds incorporating four different amino acid residues were prepared by liquid-phase synthesis. Two unnatural amino acids, 2-amino-4-ethylhexanoic acid (AEH) and cyclohexylalanine (Cha), were used to investigate the substrate specificity as these amino acids have structures different from natural amino acids. AEH was synthesized using diethyl acetamidemalonate as a starting material. The substrate containing Cha had high hydrophobicity and showed a high reaction velocity with chymotrypsin. Although the AEH substrate with a branched side chain had high hydrophobicity, it showed... [more]
Liquid-Phase Removal of Methylene Blue as Organic Pollutant by Mesoporous Activated Carbon Prepared from Water Caltrop Husk Using Carbon Dioxide Activation
Yu-Quan Lin, Wen-Tien Tsai
October 13, 2022 (v1)
Subject: Materials
Keywords: adsorptive removal, CO2 activation, kinetic modeling, mesoporous activated carbon, methylene blue, water caltrop husk
In this work, a mesoporous activated carbon (AC) was prepared from a unique lignocellulosic biomass (water caltrop husk) in triplicate using a single-step physical activation process at lower temperature (i.e., 750 °C) and longer holding time (i.e., 90 min). Based on the pore properties and adsorption properties for removal of methylene blue (MB) as organic pollutant, the results proved that the resulting AC possesses a mesoporous feature with the Brunauer−Emmett−Teller (BET) surface area of 810.5 m2/g and mesopore volume of about 0.13 cm3/g. Due to its fast adsorption rate and maximal adsorption capacity fitted (126.6 mg/g), the mesoporous carbon material could be used as an excellent adsorbent for liquid-phase removal of MB. In addition, the pseudo-second-order model is well suited for describing the adsorption system between the cationic adsorbate and the resulting AC with oxygen surface groups.
Biocatalytic Approach for Novel Functional Oligoesters of ε-Caprolactone and Malic Acid
Diana Maria Dreavă, Ioana Cristina Benea, Ioan Bîtcan, Anamaria Todea, Eugen Șișu, Maria Puiu, Francisc Peter
October 13, 2022 (v1)
Subject: Materials
Keywords: biobased monomers, enzymatic polymerization, green polymers, lipase, malic acid, oligoesters, ε-caprolactone
Biocatalysis has developed in the last decades as a major tool for green polymer synthesis. The particular ability of lipases to catalyze the synthesis of novel polymeric materials has been demonstrated for a large range of substrates. In this work, novel functional oligoesters were synthesized from ε-caprolactone and D,L/L-malic acid by a green and sustainable route, using two commercially available immobilized lipases as catalysts. The reactions were carried out at different molar ratios of the comonomers in organic solvents, but the best results were obtained in solvent-free systems. Linear and cyclic oligomeric products with average molecular weights of about 1500 Da were synthesized, and the formed oligoesters were identified by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) analysis. The oligoester synthesis was not enantioselective in the studied reaction conditions. The operational stability of both biocatalysts (Novozyme 435 and GF-... [more]
Bimetallic Pt-Co Nanoparticle Deposited on Alumina for Simultaneous CO and Toluene Oxidation in the Presence of Moisture
Peng Peng, Jun Li, Shengpeng Mo, Qi Zhang, Taiming Shen, Qinglin Xie
October 13, 2022 (v1)
Subject: Materials
Keywords: bimetallic alloy, catalytic oxidation, moisture, Pt-based catalysts, Toluene
Carbon monoxide (CO) and hydrocarbons (HCs) generally have competitive adsorption on the active site of noble-metal nano-catalysts, thus developing an effective way to reduce the passivation of competitive reaction with each other is an urgent problem. In this study, we successfully synthesized transition metal-noble metal (Pt-M) alloys via introducing inexpensive metal elements (M = Ni, Co and Cu) into Pt particles and then deposited on alumina support to form Pt-based catalysts. Subsequently, we choose CO and toluene as polluting gases to evaluate the catalytic activities of Pt-M/Al2O3 catalysts. Introducing inexpensive metal elements (M = Ni, Co, and Cu) significantly changed the physicochemical properties and catalytic activities of these Pt-based catalysts. It can be found that the Pt-Co/Al2O3 catalyst exhibited outstanding catalytic activity for CO and toluene oxidation under mixed gas atmosphere, compared with other Pt-based catalysts, which is due to the higher dispersity, more... [more]
Recovery of Raw Materials from Ceramic Waste Materials for the Refractory Industry
Severin Seifert, Sebastian Dittrich, Jürgen Bach
October 13, 2022 (v1)
Subject: Materials
Keywords: electrodynamic fragmentation, innovative process, recycling, refractory, regenerate
Products of the refractory industry are key for the production of heavy industry goods such as steel and iron, cement, aluminum and glass. Corresponding industries are dependent on thermal processes to manufacture their products, which in turn would not be possible if there were no refractory materials, such as refractory bricks or refractory mixes. For the production of refractory materials, primary raw materials or semi-finished products such as corundum, bauxite or zircon are used. Industrial recycling of refractory raw materials would reduce dependencies, conserve resources and reduce global CO2 emissions. Today, only a small quantity of the refractory materials used can be recycled because raw materials (regenerates) obtained from end-of-life materials are of insufficient quality. In this study, regenerates from different refractory waste products could be obtained using the innovative processing method of electrodynamic fragmentation. It was shown that these regenerates have a hi... [more]
Sequential Abatement of FeII and CrVI Water Pollution by Use of Walnut Shell-Based Adsorbents
Marius Gheju, Ionel Balcu
October 13, 2022 (v1)
Subject: Materials
Keywords: acid mine drainage, heavy metals, hexavalent chromium, innovative adsorbent, sustainable water treatment, water treatment residuals
In this study walnut shells, an inexpensive and readily available waste, were used as carbonaceous precursor for preparation of an innovative adsorbent (walnut-shell powder (WSP)) which was successfully tested for the removal of FeII from synthetic acid mine drainage (AMD). Then, the exhausted iron-contaminated adsorbent (WSP-FeII) was recovered and treated with sodium borohydride for the reduction of adsorbed FeII to Fe0. The resulting material (WSP-Fe0) was subsequently tested for the removal of CrVI from aqueous solutions. Treatability batch experiments were employed for both FeII and CrVI-contaminated solutions, and the influence of some important experimental parameters was studied. In addition, the experimental data was interpreted by applying three kinetic models and the mechanism of heavy metal removal was discussed. The overall data presented in this study indicated that fresh WSP and WSP-Fe0 can be considered as promising materials for the removal of FeII and CrVI, respective... [more]
Preparation and Characterization of the Sulfur-Impregnated Natural Zeolite Clinoptilolite for Hg(II) Removal from Aqueous Solutions
Marin Ugrina, Martin Gaberšek, Aleksandra Daković, Ivona Nuić
October 13, 2022 (v1)
Subject: Materials
Keywords: chemical modification, leaching, mercury sorption, natural zeolite clinoptilolite, sulfur impregnation
Sulfur-impregnated zeolite has been obtained from the natural zeolite clinoptilolite by chemical modification with Na2S at 150 °C. The purpose of zeolite impregnation was to enhance the sorption of Hg(II) from aqueous solutions. Chemical analysis, acid and basic properties determined by Bohem’s method, chemical behavior at different pHo values, zeta potential, cation-exchange capacity (CEC), specific surface area, X-ray powder diffraction (XRPD), scanning electron microscopy with energy-dispersive X-ray analysis (SEM-EDS), Fourier transform infrared spectroscopy (FTIR), as well as thermogravimetry with derivative thermogravimetry (TG-DTG) were used for detailed comparative mineralogical and physico-chemical characterization of natural and sulfur-impregnated zeolites. Results revealed that the surface of the natural zeolite was successfully impregnated with sulfur species in the form of FeS and CaS. Chemical modification caused an increase in basicity and the net negative surface charge... [more]
A Novel Method to Investigate the Activity Tests of Fresh FCC Catalysts: An Experimental and Prediction Process from Lab Scale to Commercial Scale
Yanqing Ma, Yitao Liao, Yi Su, Dong Ji, Hongwei Li, Yong Yang
October 12, 2022 (v1)
Subject: Materials
Keywords: commercial equilibrium catalyst, deactivation, FCC catalyst, industrial evaluation, yield distribution
The issues of feedstocks, product markets, and environmental emissions have continuously proposed a number of challenges for industrial evaluation of fresh fluid catalytic cracking (FCC) catalyst before its application in commercial units. In this work, a convenient method was proposed by comparing with the existing commercial equilibrium catalyst. A series of laboratory experiments for steam treatments and microactivity tests were established to collect reliable data, and the standalone catalyst or co-catalysts were assessed to show the evaluation process and the predicted unit performance. The results had deviation, but a consistent yield distribution than that of a commercial equilibrium catalyst. These evaluations and predictions would provide us with not only the view of hydrothermal stability and yield distribution at the unit level, but also the economic potential for fresh catalyst based on the existing industrial catalyst, which will provide refiners with industrial basis for... [more]
Methyl Orange Photo-Degradation by TiO2 in a Pilot Unit under Different Chemical, Physical, and Hydraulic Conditions
Andrea Petrella, Danilo Spasiano, Pinalysa Cosma, Vito Rizzi, Marco Race, Maria Cristina Mascolo, Ezio Ranieri
October 12, 2022 (v1)
Subject: Materials
Keywords: azo dye, hydraulic and hydrodynamic parameters, kinetic study, photo-catalysis, TiO2
The photo-catalytic degradation of a textile azo-dye as Methyl Orange was studied in an innovative unit constituted by a channel over which a layer of titanium dioxide (TiO2) catalyst in anatase form was deposited and activated by UVB irradiation. The degradation kinetics were followed after variation of the chemical, physical, and hydraulic/hydrodynamic parameters of the system. For this purpose, the influence of the TiO2 dosage (g/cm3), dye concentration (mg/L), pH of the solution, flow-rate (L/s), hydraulic load (cm), and irradiation power (W) were evaluated on the degradation rates. It was observed that the maximum dosage of TiO2 was 0.79 g/cm3 while for higher dosage a reduction of homogeneity of the cement conglomerate occurred. The Langmuir−Hinshelwood (LH) kinetic model was followed up to a dye concentration around 1 mg/L. It was observed that with the increase of the flow rate, an increase of the degradation kinetics was obtained, while the further increase of the flow-rate as... [more]
Effects of Osmotic Dehydration on the Hot Air Drying of Apricot Halves: Drying Kinetics, Mass Transfer, and Shrinkage
Ivan Pavkov, Milivoj Radojčin, Zoran Stamenković, Krstan Kešelj, Urszula Tylewicz, Péter Sipos, Ondrej Ponjičan, Aleksandar Sedlar
October 12, 2022 (v1)
Subject: Materials
Keywords: apricot, drying, kinetics, mass transfer, Modelling, osmotic dehydration, shrinkage
This study aimed to determine the effects of osmotic dehydration on the kinetics of hot air drying of apricot halves under conditions that were similar to the industrial ones. The osmotic process was performed in a sucrose solution at 40 and 60 °C and concentrations of 50% and 65%. As expected increased temperatures and concentrations of the solution resulted in increased water loss, solid gain and shrinkage. The kinetics of osmotic dehydration were well described by the Peleg model. The effective diffusivity of water 5.50−7.387 × 10−9 m2/s and solute 8.315 × 10−10−1.113 × 10−9 m2/s was calculated for osmotic dehydration. Hot air drying was carried out at 40, 50, and 60 °C with air flow velocities of 1.0 m/s and 1.5 m/s. The drying time shortened with higher temperature and air velocity. The calculated effective diffusion of water was from 3.002 × 10−10 m2/s to 1.970 × 10−9 m2/s. The activation energy was sensitive to selected air temperatures, so greater air velocity resulted in great... [more]
Equilibrium and Kinetics of CO2 Adsorption by Coconut Shell Activated Carbon Impregnated with Sodium Hydroxide
Chaiyot Tangsathitkulchai, Suravit Naksusuk, Atichat Wongkoblap, Poomiwat Phadungbut, Prapassorn Borisut
October 12, 2022 (v1)
Subject: Materials
Keywords: activated carbon, adsorption isotherms, adsorption kinetics, alkali impregnation, carbon dioxide adsorption
The equilibrium and kinetics of CO2 adsorption at 273 K by coconut-shell activated carbon impregnated with sodium hydroxide (NaOH) was investigated. Based on nitrogen adsorption isotherms, porous properties of the tested activated carbons decreased with the increase of NaOH loading, with the decrease resulting primarily from the reduction of pore space available for nitrogen adsorption. Equilibrium isotherms of CO2 adsorption by activated carbons impregnated with NaOH at 273 K and the pressure up to 100 kPa displayed an initial part of Type I isotherm with most adsorption taking place in micropores in the range of 0.7−0.9 nm by pore-filling mechanisms. The amount of CO2 adsorbed increased with the increase of NaOH loading and passed through a maximum at the optimum NaOH loading of 180 mg/g. The CO2 isotherm data were best fitted with the three-parameter Sips equation, followed by Freundlich and Langmuir equations. The pore diffusion model, characterized by the effective pore diffusivit... [more]
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