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Endothermic reactions

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
Zongtang Fang, Edward B Garner, David A Dixon, Yu Gong, Lester Andrews, Benjamin K Liebov
Laser-ablated U atoms react with (CN)2 in excess argon and neon during co-deposition at 4 K to form UNC, U(NC)2, and U(NC)4 as the major uranium bearing products, which are identified from their matrix infrared spectra using cyanogen substituted with 13C and 15N and from quantum chemical calculations. The 12/13CN and C14/15N isotopic frequency ratios computed for the U(NC)1,2,4 molecules agree better with the observed values than those calculated for the U(CN)1,2,4 isomers. Multiplets using mixed isotopic cyanogens reveal the stoichiometries of these products, and the band positions and quantum chemical calculations confirm the isocyanide bonding arrangements, which are 14 and 51 kJ/mol more stable than the cyanide isomers for UNC and U(NC)2, respectively, and 62 kJ/mol for U(NC)4 in the isolated gas phase at the CCSD(T)/CBS level...
December 20, 2017: Journal of Physical Chemistry. A
Hala Atallah, Mahmoud ELcheikh Mahmoud, Abdinoor Jelle, Alan Lough, Mohamad Hmadeh
A new porous indium metal organic framework namely (AUBM-1) was successfully synthesized via a solvothermal reaction of pyromellitic acid and indium chloride. Single crystal X-ray analysis revealed the formation of a 3D framework with a pts topology. The resulting MOF structure showed high chemical stability at different pH values. Thus, the activated indium MOF was applied for As removal from water for the first time and showed a high arsenate uptake capacity of 103.1 mg g-1 at neutral pH, which is higher than the commercial adsorbents (usually less than 100 mg g-1 at neutral pH)...
December 18, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
Adam R Luxon, Natalie Orms, René P F Kanters, Anna I Krylov, Carol A Parish
The Bergman cyclization is an important reaction in which an enediyne cyclizes to produce a highly reactive diradical species, p-benzyne. Enediyne motifs are found in natural antitumor antibiotic compounds, such as calicheammicin and dynemicin. Understanding the energetics of cyclization is required in order to better control the initiation of the cyclization, which induces cell death. We computed the singlet and triplet potential energy surfaces for the Bergman cyclization of (Z)-hex-3-ene-1,5-diyne using the CCSD and EOM-SF-CCSD methods...
December 11, 2017: Journal of Physical Chemistry. A
P B Armentrout, Maria Demireva, Kirk A Peterson
Previous work has shown that atomic samarium cations react with carbonyl sulfide to form SmS+ + CO in an exothermic and barrierless process. To characterize this reaction further, the bond energy of SmS+ is determined in the present study using guided ion beam tandem mass spectrometry. Reactions of SmS+ with Xe, CO, and O2 are examined. Results for collision-induced dissociation processes with all three molecules along with the endothermicity of the SmS+ + CO → Sm+ + COS exchange reaction are combined to yield D0(Sm+-S) = 3...
December 7, 2017: Journal of Chemical Physics
Eric M Karp, Todd R Eaton, Violeta Sànchez I Nogué, Vassili Vorotnikov, Mary J Biddy, Eric C D Tan, David G Brandner, Robin M Cywar, Rongming Liu, Lorenz P Manker, William E Michener, Michelle Gilhespy, Zinovia Skoufa, Michael J Watson, O Stanley Fruchey, Derek R Vardon, Ryan T Gill, Adam D Bratis, Gregg T Beckham
Acrylonitrile (ACN) is a petroleum-derived compound used in resins, polymers, acrylics, and carbon fiber. We present a process for renewable ACN production using 3-hydroxypropionic acid (3-HP), which can be produced microbially from sugars. The process achieves ACN molar yields exceeding 90% from ethyl 3-hydroxypropanoate (ethyl 3-HP) via dehydration and nitrilation with ammonia over an inexpensive titanium dioxide solid acid catalyst. We further describe an integrated process modeled at scale that is based on this chemistry and achieves near-quantitative ACN yields (98 ± 2%) from ethyl acrylate...
December 8, 2017: Science
Juan-Carlos Lizardo-Huerta, Baptiste Sirjean, Laurent Verdier, René Fournet, Pierre-Alexandre Glaude
Phosgene (COCl2) is a toxic compound used or formed in a wide range of applications. The understanding of its thermal decomposition for destruction processes or in the event of accidental fire of stored reserves is a major safety issue. In this study, a detailed chemical kinetic model for the thermal decomposition and combustion of phosgene and diphosgene is proposed for the first time. A large number of thermo-kinetic parameters were calculated using quantum chemistry and reaction rate theory. The model was validated against experimental pyrolysis data from the literature...
December 7, 2017: Journal of Physical Chemistry. A
Mohammad A Al-Ghouti, Mariam Khan
This study investigated the use of eggshell membrane (ESM) as a bio-sorbent and the effect of temperature, pH, and initial concentration on its efficiency. Furthermore, by altering the chemical composition, modified eggshell membrane (MESM) was prepared, and its efficiency was compared with the ESM. Results showed that the adsorption of boron preferred an acidic condition; pH 6 at 35 °C. In addition, the positive value of ΔH° suggested that the reaction favored endothermic pathway, while the negative value for ΔG° further suggested that the adsorption process was spontaneous...
November 27, 2017: Journal of Environmental Management
Yibo Liu, Juewen Liu
The interaction between lipids and metal ions is important for metal sensing, cellular signal transduction, and oxidative lipid damage. While most previous work overlooked the phosphate group of lipids for metal binding, we herein highlight its importance. Phosphocholine (PC) and its headgroup inversed choline phosphate (CP) lipids were respectively used to prepare liposomes. From dynamic light scattering (DLS), Zn2+ causes significant aggregation or fusion of the CP liposomes, but not PC liposomes. The size change induced by Zn2+ is not fully reversed by adding EDTA, implying liposome fusion induced by Zn2+...
November 27, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Nouf F El-Harby, Shaimaa M A Ibrahim, Nadia A Mohamed
Adsorption capacity of three antimicrobial terephthaloyl thiourea cross-linked chitosan hydrogels for Congo red dye removal from its aqueous solution has been investigated for the first time in this work. These hydrogels were prepared by reacting chitosan with various amounts of terephthaloyl diisothiocyanate cross-linker. The effect of the hydrogel structural variations and several dye adsorption processing parameters to achieve the best adsorption capacity were investigated. The hydrogels' structural variations were obtained by varying their terephthaloyl thiourea moieties content...
November 2017: Water Science and Technology: a Journal of the International Association on Water Pollution Research
Sudabeh Pourfadakari, Sahand Jorfi, Mehdi Ahmadi, Afshin Takdastan
The aim of this study was to evaluate the efficiency of nano-sized cellulose obtained from rice husk for Cr(VI) adsorption. The effect of operational parameters including initial pH (3-10), contact time (0-120 min), adsorbent dosage (0.2-1.5 g/L), and initial Cr(VI) concentration (5-50 mg/L) were investigated according to one factor at time method. The results showed, in pH=6, contact time=100 min, adsorbent dose=1.5 g/L and 30 mg/L initial chromium concentration, the adsorption efficiency reached to 92...
December 2017: Data in Brief
María Erans, Michal Jeremias, Vasilije Manovic, Edward J Anthony
Calcium looping (CaL) is a post-combustion CO2 capture technology that is suitable for retrofitting existing power plants. The CaL process uses limestone as a cheap and readily available CO2 sorbent. While the technology has been widely studied, there are a few available options that could be applied to make it more economically viable. One of these is to increase the oxygen concentration in the calciner to reduce or eliminate the amount of recycled gas (CO2, H2O and impurities); therefore, decreasing or removing the energy necessary to heat the recycled gas stream...
October 25, 2017: Journal of Visualized Experiments: JoVE
Wayne Lin, Catherine J Murphy
Photothermal desorption of molecules from plasmonic nanoparticles is an example of a light-triggered molecular release due to heating of the system. However, this phenomenon ought to work only if the molecule-nanoparticle interaction is exothermic in nature. In this study, we compare protein adsorption behavior onto gold nanoparticles for both endothermic and exothermic complexation reactions, and demonstrate that Le Chatelier's principle can be applied to predict protein adsorption or desorption on nanomaterial surfaces...
October 25, 2017: ACS Central Science
J P Valle, B Gonzalez, J Schultz, D Salinas, D F Gonzalez, C Valdes, J M Cantu, T M Eubanks, J G Parsons
A Rancieite type material (K2Mn4O9) nanomaterial was synthesized and tested for the removal of chromium (III) and chromium (VI) from aqueous solutions. The synthesized nanomaterial was characterized using powder XRD and SEM. XRD showed weak diffraction peaks at only at the angles associated with K2Mn4O9. The SEM corroborated that the nanoparticles were present; however, the nanoparticles were clustered into larger aggregates. Batch studies were performed to determine the optimum pH, capacity, time dependency, interferences, and the thermodynamics of the binding...
July 2017: Microchemical Journal, Devoted to the Application of Microtechniques in All Branches of Science
Yu Jin, Chunying Teng, Sumei Yu, Tao Song, Liying Dong, Jinsong Liang, Xin Bai, Xuesheng Liu, Xiaojing Hu, Juanjuan Qu
To prevent the blockage in a continuous fix-bed system, Pleurotus Ostreatus spent substrate (POSS), a composite agricultural waste, was immobilized into granular adsorbents (IPOSS) with polymeric matrix, and used to remove Cd(II) from synthetic wastewater in batch experiment as well as in continuous fixed-bed column system. In batch experiment, higher pH, temperature and Cd(II) initial concentration were conducive to a higher biosorption capacity, and the maximum biosorption capacity reached up to 87.2 mg/g at Cd(II) initial concentration of 200 mg/L, pH 6 and 25 °C...
September 27, 2017: Chemosphere
Caiqin Chen, Dezhi Chen, Shasha Xie, Hongying Quan, Xubiao Luo, Lin Guo
Herein, we studied the adsorption behaviors of organic micropollutants, such as anticonvulsant carbamazepine (CBZ) and antibiotic tetracycline hydrochloride (TC), on zirconium metal-organic framework UiO-66 in water. The maximum adsorption capacities of CBZ and TC on the UiO-66 were 37.2 and 23.1 mg·g(-1) at 25 °C, respectively. The adsorption isotherms and kinetics of CBZ and TC were well described by using the Langmuir model and pseudo-second-order model, respectively, and the adsorptions on UiO-66 are endothermic reactions...
November 8, 2017: ACS Applied Materials & Interfaces
Daoyuan Zheng, Mingzhen Zhang, Guangjiu Zhao
Time-dependent density functional theory (TDDFT) and atoms in molecules (AIM) theory are combined to study the photoinduced excited state intramolecular proton transfer (ESIPT) dynamics for eight anthraquinones (AQs) derivatives in solution. The calculated absorption and emission spectra are consistent with the available experimental data, verifying the suitability of the theory selected. The systems with the excited-state exothermic proton transfer, such as 1-HAQ, 1,5-DHAQ and TFAQ, emit completely from transfer structure (T), while the reactions for those without ESIPT including 1,4-DHAQ and AAAQ appear to be endothermic...
October 23, 2017: Scientific Reports
Kai Li, Xin Song, Tingting Zhu, Chi Wang, Xin Sun, Ping Ning, Lihong Tang
The catalytic hydrolysis of carbonyl sulfide (COS) and the effect of small clusters of H2O and H2SO4 have been studied by theoretical calculations. The addition of H2SO4 could increase the enthalpy change (ΔH<0) and decrease relative energy of products (relative energy<0), resulting in hydrolysis reaction changed from an endothermic reaction to an exothermic reaction. Further, H2SO4 decreases the energy barrier by 5.25 kcal/mol, and it enhances the catalytic hydrolysis through the hydrogen transfer effect...
October 9, 2017: Environmental Pollution
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