Guoliang Dai

Isotherm, thermodynamic, kinetics and adsorption mechanism studies of methyl orange by surfactant modified silkworm exuviae

This paper reports on the development of organo-modified silkworm exuviae (MSE) adsorbent prepared by using hexadecyltrimethylammonium bromide (HDTMAB) for removing methyl orange (MO), a model anionic dye, from aqueous solution. The natural and modified samples were characterized by scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and Fourier transform infrared spectroscopy (FT-IR). Batch adsorption experiments were carried out to remove MO from its aqueous solutions using SE and MSE. It was observed that the adsorption capacity of MSE is 5-6 times of SE. The different parameters effecting on the adsorption capacity such as pH of the solution, initial dye concentration, temperature and contact time have been investigated. Analysis of adsorption results obtained at different temperatures showed that the adsorption pattern on the MSE can be described perfectly with Langmuir isotherm model compared with Freundlich and Dubinin-Radushkevich (D-R) isotherm models, and the characteristic parameters for each adsorption isotherm were also determined. The adsorption process has been found exothermic in nature and thermodynamic parameters have been calculated. The adsorption kinetic followed the pseudo-second order kinetic model. The results of FT-IR, EDS and desorption studies all suggest that methyl orange adsorption onto the MSE should be mainly controlled by the hydrophobic interaction mechanism, along with a considerable contribution of the anionic exchange mechanism. The results indicate that HDTMAB-modified silkworm exuviae could be employed as low-cost material for the removal of methyl orange anionic dye from wastewater.

Silkworm exuviae—A new non-conventional and low-cost adsorbent for removal of methylene blue from aqueous solutions

In this paper, silkworm exuviae (SE) waste, an agricultural waste available in large quantity in China, was utilized as low-cost adsorbent to remove basic dye (methylene blue, MB) from aqueous solution by adsorption. Kinetic data and sorption equilibrium isotherms were carried out in batch process. The adsorption kinetic experiments revealed that MB adsorption onto SE for different initial dye concentrations all followed pseudo-second order kinetics and were mainly controlled by the film diffusion mechanism. Batch equilibrium results at different temperatures suggest that MB adsorption onto SE can be described perfectly with Freundlich isotherm model compared with Langmuir and D-R isotherm models, and the characteristic parameters for each adsorption isotherm were also determined. Thermodynamic parameters calculated show the adsorption process has been found to be endothermic in nature. The analysis for the values of the mean free energies of adsorption (E(a)), the Gibbs free energy (ΔG(0)) and the effect of ionic strength all demonstrate that the whole adsorption process is mainly dominated by ion-exchange mechanism, which has also been verified by variations in FT-IR spectra and pH value before and after adsorption and desorption studies. The results reveal that SE can be employed as a low-cost alternative to other adsorbents for MB adsorption.

Novel fluorescent 1,8-naphthalimide derivatives containing thiophene and pyrazole moieties: synthesis by direct C-H arylation and evaluation of photophysical and electrochemical properties.

A series of novel 1,8-naphthalimide derivatives containing thiophene and pyrazole moities were synthesized by direct Pd-catalyzed C-H arylation and then characterized by (1)H NMR, (13)C NMR, MALDI-HRMS, and elementary analysis. The photophysical and electrochemical properties of the derivatives were also investigated. All compounds have green emission both in diluted CH2Cl2 solution and solid film. The cyclic voltammetry (CV) measurements showed that the target compounds had a lowest unoccupied molecular orbital (LUMO) range from -3.49 eV to -3.29 eV and a highest occupied molecular orbital (HOMO) range from -6.04 eV to -5.81 eV. Quantum chemical calculations were performed to obtain the optimized ground-state geometry as well as the spatial distributions of the HOMO, LUMO levels of the compounds.

Synthesis, crystal structure, and DNA-binding of a 3-D netlike supramolecular manganese picrate complex with 2,6-bis(benzimidazol-2-yl)pyridine

Manganese picrate with 2,6-bis(benzimidazol-2-yl)pyridine (L) has been prepared and characterized by elemental analysis, IR spectroscopy, and single-crystal X-ray diffraction. The complex crystallizes in the triclinic system, space group P–1 with a = 14.234(3) Å, b = 14.324(2) Å, c = 15.242(2) Å, α = 77.569(2)°, β = 63.350(3)°, γ = 82.130(2)°, and Z = 2. Interaction of the complex with calf-thymus DNA (CT-DNA) has been investigated with diverse spectroscopic techniques and viscosity measurements, and the binding constant is 1.76 × 105 mol−1. Results suggest that the complex bind to CT-DNA via intercalation.

Theoretical study on the reactions of Zr+ and Zr with CO2 in gas phase

Density functional theory (DFT) calculations have been performed to explore the potential energy surfaces of C-O bond activation in CO2 molecule by gas-phase Zr+ cation and Zr atom, for better understanding the mechanism of second-row transition metal reacting with CO2. The minimum energy reaction path is found to involve the spin inversion in the different reaction steps. This potential energy curvecrossing dramatically affects reaction energetics. The present results show that the reaction mechanism is insertion-elimination mechanism along the C-O bond activation. All theoretical results not only support the existing conclusions inferred from early experiment, but also complement the pathway and mechanism for this reaction.

CARBON DIOXIDE ACTIVATION BY Y ATOM AND Y+ CATION IN THE GAS PHASE: A DENSITY FUNCTIONAL THEORETICAL STUDY

ABSTRACT The potential energy surfaces for the Y+CO 2 and Y + +CO 2 reactions have been investigated by using the DFT (B3LYP/ECP/6−311+G*) level of theory. Both ground and excited state potential energy surfaces are discussed. The present results show that the reaction mechanism is an insertion mechanism along the C−O bond activation branch. The reaction of Y atom with CO 2 was shown to occur preferentially on the doublet PES throughout the reaction process. As for the reaction between Y + cation with CO 2 , it involves potential energy curve-crossing which dramatically affects reaction mechanism. Due to the intersystem crossing existing in the reaction process of Y + with CO 2 , the intermediate (OY(η 2 CO)) + may not form. This mechanism is different from that of Y + CO 2 system. All our theoretical results not only support the existing conclusions inferred from early experiment, but also complement the pathway and mechanism for this reaction. Keywords: DFT theory, Potential energy surface, Intersystem, Yttrium

A novel azide copper complex: [[Azido{bis[2-(piperidin-1-ylmethyl)pyridine]}copper(II)]perchlorate] hydrate

Synthesis and single crystal X-ray diffraction study were carried for compound {[Cu(C11H16N4)2(N3)](ClO4)} · H2O (I). The structure is molecular, and the Cu2+ ion is in a five-coordinated compressed trigonal bipyramid environment. Copper ion is bound to five N atoms, in which four N atoms are from two chlelating ligands 2-(piperidin-1-ylmethyl)pyridine and the fifth N donor is from a monodentate azido ligand. The complex cations [Cu(C11H16N4)2(N3)]+, the perchlorate anions, and solvent water molecules are further joined into three dimensional supramolecular networks by rich hydrogen bonds including strong O-H…N between solvent water and azide ion and O-H…O between solvent water and perchlorate ion, and weak hydrogen bonds C-H…O, and weak bifurcated hydrogen bonds C-H/C-H…N in which N atom of azide ion serving as bifurcated acceptor and two C-H groups as donors.

Reaction of CH3CHO with Y+: A density functional theoretical study

The reaction mechanism of the Y+ cation with CH3CHO has been investigated with a DFT approach. All the stationary points are determined at the UB3LYP/ECP/6-311++G** level of the theory. Both ground and excited state potential energy surfaces are investigated in detail. The present results show that the title reaction start with the formation of a CH3CHO-metal complex followed by C-C, aldehyde C-H, methyl C-H and C-O activation. These reactions can lead to four different products (Y+CH4 + CO, Y+CO + CH4, Y+COCH2 + H2 and Y+O + C2H4). The minimum energy reaction path is found to involve the spin inversion in the different reaction steps, this potential energy curve-crossing dramatically affects reaction exothermic. The present results may be helpful in understanding the mechanism of the title reaction and further experimental investigation of the reaction.

Theoretical Investigation of the Reaction of Yttrium Cation with Acetone

Abstract The reaction mechanism of Y+ with CH3COCH3 has been investigated with a DFT method. All the stationary points are determined at the UB3LYP/ECP/6-311++G** level of the theory. Both the ground and the excited state potential energy surfaces are investigated in detail. The present results show that the title reaction starts with the formation of an O-attached complex (IM0) followed by C–O, C–H and C–C activation. The minimum energy reaction path is found to involve the spin inversion in the initial reaction step. The potential energy curve-crossing dramatically affects reaction exothermic. The present results may be helpful in understanding the mechanism of the title reaction and further experimental investigation of the reaction.

Theoretical survey of the reaction between osmium and acetaldehyde

The mechanism of the reaction of osmium atom with acetaldehyde has been investigated with a DFT approach. All the stationary points are determined at the UB3LYP/sdd/6-311++G** level of the theory. Both ground and excited state potential energy surfaces are investigated in detail. The present results show that the title reaction start with the formation of a CH3CHO-metal complex followed by C-C, aldehyde C-H, C-O, and methyl C-H activation. These reactions can lead to four different products (HOsCH3 + CO, OsCO + CH4, OsCOCH3 + H, and OsO + C2H4). The minimum energy reaction path is found to involve the spin inversion in the initial reaction step. This potential energy curve-crossing dramatically affects reaction exothermic. The present results may be helpful in understanding the mechanism of the title reaction and further experimental investigation of the reaction.