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Endothermic reactions

Prajakta Rajaram Parab, K Alexander Heufer, Ravi Xavier Fernandes
Isopentanol is a potential next-generation biofuel for future applications to Homogeneous Charge Compression Ignition (HCCI) engine concepts. To provide insights into the combustion behavior of isopentanol, especially to its auto-ignition behavior which is linked both to efficiency and pollutant formation in real combustion systems, detailed quantum chemical studies for crucial reactions are desired. H-Abstraction reaction rates from fuel molecules are key initiation steps for chain branching required for auto-ignition...
March 13, 2018: Physical Chemistry Chemical Physics: PCCP
A M Nasir, P S Goh, A F Ismail
A novel hydrous iron-nickel-manganese (HINM) trimetal oxide was successfully fabricated using oxidation and coprecipitation method for metalloid arsenite removal. The atomic ratio of Fe:Ni:Mn for this adsorbent is 3:2:1. HINM adsorbent was identified as an amorphous nanosized adsorbent with particle size ranged from 30 nm to 60 nm meanwhile the total active surface area and pore diameter of HINM area of 195.78 m2 /g and 2.43 nm, respectively. Experimental data of arsenite adsorption is best fitted into pseudo-second order and Freundlich isotherm model...
February 23, 2018: Chemosphere
Farheen Khan, Rizwan Wahab, Mohamed Essam Hagar, Rua Alnoman, Mohd Rashid
The present work describes the synthesis of copper oxide nanoparticles (CuONPs) via a solution process with the aim of applying the nano-adsorbent for the reduction of methylene blue (MB) dye in alkaline media. These NPs were characterized via Field emission scanning electron microscopy (FE-SEM), X-ray diffraction, high-resolution Transmission electron microscopy (TEM), and ultra violet UV-visible spectroscopy to confirm their morphology and crystalline and optical properties in order to design an adsorption-degradation process...
February 27, 2018: Nanomaterials
Muhammad Mahmood-Ul-Hassan, Muhammad Yasin, Munazza Yousra, Rizwan Ahmad, Sair Sarwar
Lead (Pb), chromium (Cr), and cadmium (Cd) removal capacity of sawdust (Picea smithiana) from aqueous solution was investigated by conducting batch experiments. Thermodynamic parameters, like change in standard free energy (ΔGΘ ), enthalpy (ΔHΘ ) and entropy (ΔSΘ ) during bio-adsorption process were estimated using the Van't Hoff equation. The maximum metals adsorption was observed at pH 8, 20 g L-1 bio-adsorbent and at 60 min of contact time. The metal adsorption kinetics was examined by fitting the pseudo-first-order as well as four forms of pseudo-second-order kinetic models...
February 21, 2018: Environmental Science and Pollution Research International
Ingrid M Weiss, Christina Muth, Robert Drumm, Helmut O K Kirchner
Background: The pathways of thermal instability of amino acids have been unknown. New mass spectrometric data allow unequivocal quantitative identification of the decomposition products. Results: Calorimetry, thermogravimetry and mass spectrometry were used to follow the thermal decomposition of the eight amino acids G, C, D, N, E, Q, R and H between 185 °C and 280 °C. Endothermic heats of decomposition between 72 and 151 kJ/mol are needed to form 12 to 70% volatile products...
2018: BMC Biophysics
Liping Wang, Mingyu Zhang, Qizhong Huang, Chenxi Zhao, Kun Luo, Min Lei
ACF/GO/PEI (activated carbon fiber/graphene oxide/polyethyleneimine) composite was fabricated by crosslinking reaction and characterized with Scanning electron microscope (SEM), N2 physical adsorption and Fourier transform infrared spectroscopy (FTIR). Furthermore, the adsorption behavior of ACF/GO/PEI composite for methyl orange (MO) from aqueous solution was investigated. The experimental results showed that the specific surface area of ACF/GO/PEI composite is 1013.6 m2/g and almost the same as that of original ACFs...
March 1, 2018: Journal of Nanoscience and Nanotechnology
Sebastián Cuesta, Josefa Arias, Felipe Gallegos, Jans Alzate-Morales, Lorena Meneses
Lignin peroxidase (LiP) is an important enzyme for degrading aromatic hydrocarbons not only in nature but also in industry. In the presence of H₂O₂, this enzyme can easily decompose lignin and analogue compounds under mild conditions. In this reaction mechanism, LiP catalyzes the C-C cleavage of a propenyl side chain, being able to produce veratraldehyde (VAD) from 1-(3',4'-dimethoxyphenyl) propene (DMPP). One of the few and complete proposed mechanisms includes several non-enzymatic reactions. In this study, we performed a computational study to gain insight about the non-enzymatic steps involved in the reaction mechanism of VAD formation from DMPP using LiP as a catalyst...
February 14, 2018: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Yang Si, Jichuan Huo, Yin Hengbo, Aili Wang
Porous hydroxyapatite (HAP) nanoparticles with the specific surface area of 76.1 m2 g-1 were facilely prepared using calcium nitrate and phosphoric acid as the starting materials and ammonia aqueous solution as the pH regulator by a hybrid precipitation and hydrothermal method at lower reaction temperatures of 35 and 110 °C. The adsorption of Cr(III), Pb(II), and Cu(II) ions on HAP nanoparticles was well simulated by the pseudo-second-order adsorption kinetics and Langmuir adsorption isotherm. The maximum adsorption capacities of HAP nanoparticles for Cr(III), Pb(II), and Cu(II) ions were 96...
May 1, 2018: Journal of Nanoscience and Nanotechnology
Gan Qiu, Danfeng Wang, Xiaoyong Song, Yun Deng, Yanyun Zhao
We investigated the types, degradation kinetics, and antioxidant capacities of anthocyanins in purple potato slices subjected to air-impingement jet drying (AIJD) at different drying temperatures (50, 65, and 80°C). Petunidin-3-p-coumaroylrutinoside-5-glucoside was the predominant anthocyanin in AIJD-treated purple potato and was positively correlated with antioxidant capacity. Anthocyanin concentration decreased with drying time, and anthocyanin degradation followed first-order reaction kinetics. At high drying temperatures, anthocyanin degradation had higher degradation rates and shorter half-life than at low drying temperatures...
March 2018: Food Research International
Y T Chan, Y T Liu, Y M Tzou, W H Kuan, R R Chang, M K Wang
Inappropriate treatments for the effluents from semiconductor plants might cause the releases and wide distributions of selenium (Se) into the ecosystems. In this study, Al/Si and Fe/Si coprecipitates were selected as model adsorbents as they often formed during the wastewater coagulation process, and the removal efficiency of selenite (SeO3) and selenate (SeO4) onto the coprecipitates were systematically examined. The removal efficiency of SeO3 and SeO4 was highly related to surface properties of Al/Si and Fe/Si coprecipitates...
January 29, 2018: Chemosphere
Elena A Buvaylo, Vladimir N Kokozay, Nataliia Yu Strutynska, Olga Yu Vassilyeva, Brian W Skelton
Guanidine is the functional group on the side chain of arginine, one of the fundamental building blocks of life. In recent years, a number of compounds based on the aminoguanidine (AG) moiety have been described as presenting high anticancer activities. The product of condensation between two molecules of AG and one molecule of formaldehyde was isolated in the protonated form as the dinitrate salt (systematic name: 2,8-diamino-1,3,4,6,7,9-hexaazanona-1,8-diene-1,9-diium dinitrate), C3H14N82+·2NO3-, (I). The cation lacks crystallographically imposed symmetry and comprises two terminal planar guanidinium groups, which share an N-C-N unit...
February 1, 2018: Acta Crystallographica. Section C, Structural Chemistry
Dipak J Garole, Bharat C Choudhary, Debajyoti Paul, Amulrao U Borse
In this study, Lagerstroemia speciosa biomass modified by polyethylenimine (PEI-LS) was developed as a potential biosorbent for sorption and recovery of platinum(II) from platinum bearing waste solutions. Batch experiments were conducted to study the effect of various parameters on the sorption and recovery of platinum(II) using PEI-LS. The equilibrium time for platinum(II) sorption process was found to be 6 h. Both the sorption kinetics and sorption isotherm data fits pseudo second-order kinetic model and Langmuir isotherm, respectively...
February 3, 2018: Environmental Science and Pollution Research International
Małgorzata Krasowska, Holger F Bettinger
Borirane is isoelectronic to the cyclopropyl cation, but is stable toward electrocyclic ring opening to 2-bora-propa-1,3-diyl A, the boron analogue of the allyl cation. A computational investigation using density functional theory (B3LYP) in combination with highly correlated electronic structure theory methods of the coupled-cluster [CCSD(T)] and multireference configuration interaction (MRCI) type in conjunction with basis sets of up to quadruple-ζ quality reveal that formation of A is endothermic by roughly 15 kcal mol-1 and that A collapses almost without barrier (0...
January 31, 2018: Journal of Organic Chemistry
Divine Angela G Sumalinog, Sergio C Capareda, Mark Daniel G de Luna
The adsorption potential and governing mechanisms of emerging contaminants, i.e. acetaminophen or acetyl-para-aminophenol (APAP) and methylene blue (MB) dye, on activated carbon derived from municipal solid waste were investigated in this work. Results showed that MB adsorption was significantly more effective, with a maximum removal of 99.9%, than APAP adsorption (%Rmax = 63.7%). MB adsorption was found to be unaffected by pH change, while the adsorption capacity of APAP drastically dropped by about 89% when the pH was adjusted from pH 2 to 12...
January 20, 2018: Journal of Environmental Management
Lianke Zhang, Xinyu Liu, Xuemin Huang, Weida Wang, Peng Sun, Yumei Li
This study evaluated the removal of Pb2+ in aqueous solution using Fe-Mn binary oxides-loaded biochar (BFMs). The characteristics of BFM were obtained using scanning electron microscopy(SEM), energy dispersive spectrometer(EDS), BET, X-ray diffraction(XRD), and X-ray photoelectron spectroscopy(XPS). The effects of pH, adsorbent dose, contact time, initial Pb2+ concentration, and temperature in the batch sorption experiments were investigated. Adsorption was evaluated by adsorption kinetics, isotherm models, and thermodynamics...
January 24, 2018: Environmental Technology
Balint Hajdu, Gabor Czako
We report a comprehensive high-level explicitly correlated ab initio study on the X- + NH2Y [X,Y = F, Cl, Br, I] reactions characterizing the stationary points of the SN2 (Y- + NH2X) and proton-transfer (HX + NHY-) pathways as well as the reaction enthalpies of various endothermic additional product channels such as H- + NHXY, XY- + NH2, XY + NH2-, and XHY- + NH. Benchmark structures and harmonic vibrational frequencies are obtained at the CCSD(T)-F12b/aug-cc-pVTZ(-PP) level of theory, followed by CCSD(T)-F12b/aug-cc-pVnZ(-PP) [n = Q and 5] and core correlation energy computations...
January 23, 2018: Journal of Physical Chemistry. A
Sean P Graham, Kevin T Fielman, Mary T Mendonça
Complement-an immune protein cascade involved in pathogen lysis-was discovered as a temperature-labile component of vertebrate plasma, yet since that time the thermal performance of complement has not received much attention from a comparative or ecological perspective. We investigated two thermal hypotheses involving the complement system of the cottonmouth snake (Agkistrodon piscivorus). We tested whether complement performance would conform to optimal thermal reaction norms commonly observed in ectotherm ecophysiological studies, predicting that complement efficiency would be maximal at or near the cottonmouth's field body temperatures...
July 2017: Journal of Experimental Zoology. Part A, Ecological and Integrative Physiology
Rong Song, Shengke Yang, Haiyang Xu, Zongzhou Wang, Yangyang Chen, Yanhua Wang
The adsorption behavior and mechanism for the uptake of fluoride ions by untreated and desugared reed residues (roots, stems and leaves) were studied through adsorption experiments, elemental analysis, infrared spectroscopy and surface area analysis. The results showed that the adsorption capacity of untreated and desugared reeds followed the order: desugared roots 2136 mg/kg > desugared leaves 1825 mg/kg > desugared stems 1551 mg/kg > untreated roots 191 mg/kg > untreated stems 175 mg/kg > untreated leaves 150 mg/kg, so adsorption capacity of desugared reeds was larger than that of the untreated reeds...
January 9, 2018: International Journal of Environmental Research and Public Health
Seo-Yun Lee, Hee-Jeong Choi
The aim of this study was to investigate heavy metal removal using waste biomass adsorbent, persimmon leaves, in an aqueous solution. Persimmon leaves, which are biomaterials, have a large number of hydroxyl groups and are highly suitable for removal of heavy metals. Therefore, in this study, we investigated the possibility of removal of Cu, Pb, and Cd in aqueous solution by using raw persimmon leaves (RPL) and dried persimmon leaves (DPL). Removal of heavy metals by RPL and DPL showed that DPL had a 10%-15% higher removal than RPL, and the order of removal efficiency was found to be Pb > Cu > Cd...
January 5, 2018: Journal of Environmental Management
Mina Oveisi, Mokhtar Alina Asli, Niyaz Mohammad Mahmoodi
Herein, 1,4-benzenedicarboxylate (BDC) and 2-amino-1,4-benzenedicarboxylate (NH2-BDC) as organic linkers and tetraisopropyl orthotitanate as a metal source were used to synthesize several metal-organic frameworks (MOFs) nanomaterials. Five Materials Institut Lavoisiers (MILs) as MOFs include MIL-125(Ti), NH2-MIL-125(Ti) and three MILs with different organic linkers molar ratios (BDC/NH2-BDC: 75/25, 50/50 and 25/75 denoted as MIL-X1, MIL-X2 and MIL-X3, respectively). The synthesized nanomaterials were used for ultrasound-aided adsorption of cationic dyes (Basic Red 46 (BR46), Basic Blue 41 (BB41) and Methylene Blue (MB)) from single and multicomponent (binary) systems...
December 26, 2017: Journal of Hazardous Materials
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