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Endothermic reactions

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
Yingju Yang, Jing Liu, Feng Liu, Zhen Wang, Sen Miao
Natural pyrite (FeS2) has been regarded as a kind of potential sorbents to control mercury emission from coal-fired power plants because of its low cost and high affinity between mercury and FeS2. Theoretical investigations based on density functional theory (DFT) were carried out to discern mercury adsorption, reaction and desorption mechanisms over pyrite surface. DFT calculation results indicate that Hg(0) adsorption on FeS2(100) and FeS2(110) surfaces is dominated by physisorption and chemisorption mechanisms, respectively...
October 7, 2017: Journal of Hazardous Materials
Chan Li, Xuejing Wang, Duye Meng, Li Zhou
Magnetic biosorbents derived from renewable resource are emerging as a new class of adsorbing material for environmental cleanup because of their eco-friendly characteristic, easy availability and low cost. Herein, a novel magnetic peach gum bead (MPGB) biosorbent was successfully fabricated by a simple one-step reaction based on the simultaneous formation of magnetic nanoparticles and cross-linking of natural peach gum polysaccharide. Benefiting from the combined merits of peach gum and magnetic nanoparticles, the MPGB not only showed excellent adsorption performance for cationic dyes but also exhibited convenient magnetic separation capability...
October 12, 2017: International Journal of Biological Macromolecules
M T Amin, A A Alazba, M Shafiq
Adsorption of the hazardous dye malachite green (MG) by Acacia nilotica (AN) waste was investigated. Batch process variables for the adsorption of MG by AN were optimized. The mechanisms involved in the adsorption of MG by AN were explored using isotherms and kinetic models. The thermodynamic parameters were calculated to determine the spontaneity and thermal nature of the MG adsorption reaction. The maximum equilibrium adsorption capacity of AN was found to be 113.26 mg/g at 30 °C. The MG adsorption data revealed that AN adsorbs MG by multilayer adsorption, as shown by the better fit of the data to the Freundlich and Halsey models (R(2) = 0...
October 2017: Water Science and Technology: a Journal of the International Association on Water Pollution Research
Fande Meng, Guodong Yuan, Steven L Larson, John H Ballard, Charles A Waggoner, Zikri Arslan, Fengxiang X Han
The occurrence of uranium (U) and depleted uranium (DU)-contaminated wastes from anthropogenic activities is an important environmental problem. Insoluble humic acid derived from leonardite (L-HA) was investigated as a potential adsorbent for immobilizing U in the environment. The effect of initial pH, contact time, U concentration, and temperature on U(VI) adsorption onto L-HA was assessed. The U(VI) adsorption was pH-dependent and achieved equilibrium in 2 h. It could be well described with pseudo-second-order model, indicating that U(VI) adsorption onto L-HA involved chemisorption...
September 29, 2017: Journal of Environmental Radioactivity
Jianfeng Liang, Jianrong Xia, Jianyou Long
The ability of Sargassum hemiphyllum to remove methylene blue (MB) from aqueous solution was evaluated. Batch experiments were conducted to examine the effects of parameters such as initial pH, contact time, biomass dose and initial dye concentration on adsorption capacity. S. hemiphyllum before and after MB adsorption was characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The Langmuir isotherm model provided the best correlation with experimental data, and the monolayer biosorption capacity was 729...
September 2017: Water Science and Technology: a Journal of the International Association on Water Pollution Research
Jun Liu, Siying Xia, Xiaomeng Lü, Hongxiang Shen
Phosphorus flame retardant tricresyl phosphate (TCP) adsorption on graphene nanomaterials from aqueous solutions was explored using batch and column modes. Comparative studies were performed regarding the kinetics and equilibrium of TCP adsorption on graphene oxide (GO) and graphene (G) in batch mode. The adsorption kinetics exhibited a rapid TCP uptake, and experimental data were well described by the pseudo-second-order kinetic model. Adsorption isotherm data of TCP on the two adsorbents displayed an improved TCP removal performance with increasing temperature at pH 5, while experimental data were well described by the Langmuir isotherm model with a maximum adsorption capacity of 87...
September 2017: Water Science and Technology: a Journal of the International Association on Water Pollution Research
Justin P Wiens, Oscar Martinez, Shaun G Ard, Brendan C Sweeny, Albert A Viggiano, Nicholas S Shuman
Reactions of the cations Ar(+), O2(+), CO2(+), and CF3(+) with the C2 radicals C2H5, H2C2F3, C2F3, and C2F5 were investigated using the variable electron and neutral density attachment mass spectrometry technique in a flowing afterglow-Langmuir probe apparatus at room temperature. Rate coefficients for observed product channels for these 16 reactions are reported as well as rate coefficients and product branching fractions for the 16 reactions of the same cations with each of the stable neutrals used as radical precursors (the species RI, where R is the radical studied)...
October 13, 2017: Journal of Physical Chemistry. A
Shibin Wang, Linna Cong, Chengcheng Zhao, Yiting Li, Yaoqi Pang, Yonghui Zhao, Shenggang Li, Yuhan Sun
Periodic density functional theory calculations were performed to study the surface structures and stabilities of the La2O3 catalyst in CO2 and O2 environments, relevant to the conditions of the oxidative coupling of methane (OCM) reaction. Thermodynamic stabilities of the clean surfaces were predicted to follow the order of (001) ≥ (011) ≫ (110) > (111) > (101) > (100), with their direct band gaps at the Γ point following the similar order of (001) > (011) > (110) > (111) > (100) > (101)...
October 11, 2017: Physical Chemistry Chemical Physics: PCCP
Rama Mohana Rao Dumpala, Neetika Rawat, Anil Boda, Sk Musharaf Ali, B S Tomar
The mononuclear complexes formed by Eu(III) with three isomeric pyridine monocarboxylate-N-oxides namely picolinic acid-N-oxide (PANO), nicotinic acid-N-oxide (NANO) and isonicotinic acid-N-oxide (IANO) in aqueous solutions were studied by potentiometry, luminescence spectroscopy and isothermal titration calorimetry (ITC) to determine the speciation, coordination, luminescence properties and thermodynamic parameters of the complexes formed during the course of the reaction. More stable six membered chelate complexes with stoichiometry (MLi, i=1-4) are formed by Eu(III) with PANO while non chelating ML and ML2 complexes are formed by NANO and IANO...
September 9, 2017: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
Xiaojuan Li, Zhongmin Wang, Haijun Liang, Jingliang Ning, Guiyin Li, Zhide Zhou
Lead (Pb) pollution has triggered a great threat to ecological system as well as public health due to its highly toxic and mutagenic properties. In this study, chitosan surface modified persimmon tannin (PT-CS) biomass composite as an environmental friendly bioadsorbent for highly efficient removal of Pb(II) from aqueous solutions was investigated. FT-IR, XRD, SEM, BET, XPS and Zeta potential were used to elucidate the adsorption mechanism. Combining of oxidation reaction, electrostatic interaction and chelation reaction, PT-CS exhibited fine adsorption performance to Pb(II)...
September 15, 2017: Environmental Technology
Zongtang Fang, Michael A Outlaw, David A Dixon
Group 8 (RuO2)n (n = 1-4) nanoclusters, their anions, and the hydrolysis reactions of the neutral clusters have been studied with the density functional theory (DFT) as well as coupled cluster CCSD(T) theory. The ground state is predicted to be a singlet and a doublet for the neutral RuO2 clusters and anionic clusters, respectively. The CCSD(T) method is required to predict the correct ground state. The calculated singlet-triplet gaps (<15 kcal/mol) and fluoride affinities (<95 kcal/mol) are smaller than those of the group 4 (MO2)n and group 6 (MO3)n metal oxide clusters...
September 29, 2017: Journal of Physical Chemistry. A
Hongwei Guo, Lizhen Tang, Bingji Yan, Kang Wan, Peng Li
In this paper, high value added NaA zeolite material was prepared from blast furnace (BF) slag by hydrothermal method and its adsorption behavior on the removal of ammonium ion was investigated. It was found out that the synthetic NaA cubic zeolite with smaller crystal size obtained at nSiO2/nAl2O3 = 2 and nH2O/nNaOH = 20 showed better adsorption performance. The kinetics of the adsorption of ammonium ion by synthesized NaA zeolite was fitted by the pseudo-second-order kinetic model. The intra-particle diffusion modeling reveals that two mixed rate-controlling mechanisms were involved in the adsorption process...
September 2017: Water Science and Technology: a Journal of the International Association on Water Pollution Research
Harry W Green
Frictional failure is not possible at depth in Earth, hence earthquakes deeper than 30-50 km cannot initiate by overcoming dry friction. Moreover, the frequency distribution of earthquakes with depth is bimodal, suggesting another change of mechanism at about 350 km. Here I suggest that the change at 30-50 km is from overcoming dry friction to reduction of effective stress by dehydration embrittlement and that the change at 350 km is due to desiccation of slabs and initiation by phase-transformation-induced faulting...
September 28, 2017: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
Xiuzhen Yang, Tengzhi Zhou, Bozhi Ren, Zhou Shi, Andrew Hursthouse
A magnetic Fe3O4/GO composite with potential for rapid solid-liquid separation through a magnetic field was synthesized using GO (graphene oxide) and Fe3O4 (ferriferous oxide). Characterization of Fe3O4/GO used scanning electron microscope (SEM), X-ray diffractometer (XRD), Fourier transform infrared spectrometer (FT-IR), and Vibrating Sample Magnetometer (VSM). A number of factors such as pH and coexisting ions on adsorbent dose were tested in a series of batch experiments. The results showed that GO and Fe3O4 are strongly integrated...
2017: Journal of Analytical Methods in Chemistry
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