Electro polymerization for (N-Terminal tetrahydrophthalamic acid) for Anti-corrosion and Biological Activity Applications

The present work reports the electrochemical synthesis of poly N Terminal tetrahydrophthalamic acid on stainless steel 316 (S.S), which acts as a working electrode, using an electrochemical polymerization technique. Fourier Transform Infrared Spectroscopy (FT-IR), Atomic Force Microscope (AFM) and Scanning Electron Microscope (SEM) characterized the formed polymer film. Corrosion protection tests for coated and uncoated S.S with polymer film were studied in 0.2 M hydrochloric acid (HCl) solution by using electrochemical polarization technique. Kinetic and thermodynamic activation parameters (Ea, A, ΔH*, ΔS* and ΔG*) were calculated. The biological activity of the polymeric film was determined against Gram positive (Staphylococcus aureus; Staph.aure) and negative bacteria (Escherichia coli; E.coli).In addition, the polymer film was modified with nanomaterials(ZnOnnano and Graphene).

Towards Rational Computational Engineering of Psychrophilic Enzymes

Cold-adapted enzymes from psychrophilic species achieve their high catalytic efficiency at low temperature by a different partitioning of the activation free energy into its enthalpic and entropic components, compared to orthologous mesophilic enzymes. Their lower activation enthalpy, partly compensated by an increased entropic penalty, has been suggested to originate from changes in flexibility of the protein surface. Multiple sequence alignments of psychrophilic and mesophilic enzymes also show characteristic motifs located in surface loops of the protein. Here, we use computer simulations to examine the effects of a number of designed surface mutations of psychrophilic and mesophilic elastases on the temperature dependence of the catalyzed peptide cleavage reaction. For each of 14 mutant enzyme variants we report calculations of their thermodynamic activation parameters. The results show that substitution of psychrophilic loop residues into the mesophilic enzyme consistently changes both the activation parameters and loop flexibilities towards the former, and vice versa for opposite substitutions.

Comparative Evaluation of Anticorrosive Properties of Mahaleb Seed Extract on Carbon Steel in Two Acidic Solutions

Aqueous extract solution of Mahaleb seed (ASMS) was prepared using a simple and safe method. ASMS was tested to examine its potential to act as a green corrosion inhibitor for preventing the dissolution of Carbon steel in highly concentrated corrosive 2 M H2SO4 and 2 M H3PO4 using an electrochemical polarization Tafel plot and electrochemical impedance spectroscopy. ASMS provided a slight increase in the inhibition efficiency of H3PO4 (89%) compared with H2SO4 (86%). Fourier transform infrared spectroscopy (FTIR) and electronic scanning microscopy (SEM) were used to prove that adsorption of ASMS occurred on the metal surface. The thermodynamic adsorption and thermodynamic activation parameters were calculated at a range of concentrations and temperatures. The physisorption of ASMS followed the Langmuir adsorption isotherm (R2 = 0.98). Finally, the role of ASMS as a protection mechanism was discussed.

A kinetic study of Zn halide/TBAB-catalysed fixation of CO2 with styrene oxide in propylene carbonate

Synthesis of styrene carbonate (SC) via the fixation of CO2 with styrene oxide (SO) has been investigated using a combination of zinc bromide (ZnBr2) and tetrabutylammonium halides (TBAX) as acid-base binary homogeneous catalysts. The combination of ZnBr2 and TBAB had a synergistic effect, which led to about 6-fold enhancement in the rate of SC formation as compared to using TBAB alone as a catalyst. Propylene carbonate (PC) was chosen as a green solvent for a comprehensive study of reaction kinetics. The reaction followed a first-order kinetics with respect to SO, CO2, and TBAB, whereas a fractional order was observed for the ZnBr2 when used in combination with the TBAB. Arrhenius and Eyring’s expressions were applied to determine the kinetic and thermodynamic activation parameters, where activation energy (Ea) of 23.3 kJ mol−1 was obtained for the SC formation over the temperature range of 90-120°C. The thermodynamic analysis showed that positive values for enthalpy (ΔH‡ = 18.53 kJ mol−1), Gibbs free energy (ΔG‡ = 79.74 kJ mol−1), whereas a negative entropy (ΔS‡ = –162.88 J mol−1 K−1) was obtained. These thermodynamic parameters suggest that endergonic and kinetically controlled reactions were involved in the formation of SC from SO and CO2.

Experimental Study and Correlation Models of the Density and Viscosity of 2-Methoxy-2-methylpropane with n-propanol

Densities (r) and viscosities (h) of the binary systems 2-Methoxy-2-methylpropane with n-propanol were measured at temperatures 288.15, 293.15, 298.15, 303.15 and 308.15 K and atmospheric pressure, over the whole composition range. Belda, Herraez, Emmerling et al. and Gonzalez-Olmos-Iglesias models were used to correlate the densities of binary mixtures. The Mchaweh-Nasrifar-Mashfeghian, Hankinson-Thomson, Yamada-Gunn and Reid et al. models were used to estimate the liquid density of the binary mixtures. Viscosity results were fitted to the equations of Grunberg-Nissan, Heric-Brewer, Jouyban-Acree and McAllister. The thermodynamic activation parameters, free energy, DG�, enthalpy, DH� and entropy, DS� for viscous flow have been estimated and their variations with compositions have been discussed.

Surface Functionalization of Cellulose Fibers Extracted from Juncus Acutus L Plant: Application for the Adsorption of Anionic Dyes from Wastewaters

New amine-functionalized adsorbent was prepared by chemical modification of cellulose fibers extracted from Juncus acutus L (Smar) plants in order to be used as chelating support for the removal of copper ions (Cu (II)). Evidence of grafting DiEthyleneTriamine (DET) onto the raw Smar fibers was provided by nitrogen analysis and Fourier Transform Infrared (FTIR) spectra study. The ability of the binary system [Cu(II)/DET-Smar] for binding Acid Blue 25 (AB25) was then investigated in batch process. Equilibrium data were analyzed by Langmuir, Freundlich and Jossens models. The obtained results reveal that the adsorption of AB25 onto [Cu (II)/DET-Smar] complex show good compliance with the Jossens isotherm. Various thermodynamic activation parameters were estimated and it was found that the adsorption was spontaneous and follows an exothermic process.

Kinetics of multi-step processes of thermal degradation of Co(II) complex with N-benzyloxycarbonylglycinato ligand. Deconvolution of DTG curves

Thermal decomposition of Co(II) complex with N-benzyloxycarbonylglycinato ligand, [Co(N-Boc-gly)2(H2O)4]?2H2O, in non-isothermal conditions occurs in three complex steps. In order to investigate detail kinetics of first two steps, dehydration and ligand degradation, DTG curves were deconvoluted using product of Gaussian and Lorentzian function. It was shown that process of complex dehydration consists of three, while process of ligand fragmentation consist of five elementary steps. For elementary steps the kinetic triplet (Ea, Z and f(?)) was determinated. Kinetic parameters were obtained by application of IKP method. On the basis of M?lek?s criteria and Sest?k-Berggren's method, Sest?k-Berggren's model, f(?)=?M(1-?)N was suggested for all elementary steps, while Master plot method and Perez- Maqueda criteria confirmed suggested reaction models. The thermodynamic activation parameters were calculated for process of complex dehydration, and lifetime for first elementary step of the dehydration and ligand degradation processes was estimated.

Adsorption Characteristics of Four Acid Dyes on Reaming Functionalized Mesoporous Material

The present paper is aimed to investigate and develop renewable adsorption methods for four dyes removal from wastewater using pore-expanding mesoporous material. The sorption kinetics, sorption thermodynamic and the renewable adsorption test were evaluated. The adsorption process attained equilibrium within 60min, which show that the adsorbent can remove of the dye in a short time. It was shown that the process best described by the pseudo-second-order equation. Various thermodynamic activation parameters such as enthalpy of sorption △H, Gibbs energy change △G and entropy △S were estimated. The negative values of △G indicate that adsorption of dye with the adsorbent was spontaneous, while positive △H values indicative of endothermic nature of the adsorption. The negative △S values for the adsorbents show decreased randomness at the solid solution interface during the adsorption of dye. The adsorbent, washed by NaOH, can be reused by regeneration decolorizing process.