Green and Fast Extraction of Chitin from Waste Shrimp Shells: Characterization and Application in the Removal of Congo Red Dye

Due to their detrimental and carcinogenic effects, synthetic organic dyes pose significant environmental and health risks. Consequently, addressing the bioremediation of industrial wastewater containing these organic dyes has become an urgent environmental concern. The adsorption using low-cost and green materials is one of the best alternative techniques for the removal of dyes. This study aims to investigate the use of chitin to eliminate Congo red (CR), an anionic dye, from wastewater. The chitin was produced from shrimp shell in a quick and environmentally friendly manner by utilizing a co-solvent (glycerol/citric acid (GLC)). The resulting adsorbent was characterized through various techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), and FT-IR spectroscopy. The effectiveness of CR removal with chitin was studied with respect to contact time, adsorbent dose, initial pH, equilibrium isotherms, and kinetic and thermodynamic parameters. It was observed that variations in the dye concentration and pH significantly influenced the removal of CR with chitin. Under optimal operating conditions (pH = 7, contact time = 130 min, temperature = 50 °C), the adsorption capacity reached 29.69 ± 0.2 mg/g. The experimental data revealed that CR adsorption onto a chitin adsorbent is better represented by a Langmuir isotherm

Synthesis of Polytetrahydrofuran Using Protonated Kaolin as A Solid Acid Catalyst

In this work, a non-toxic protonated kaolin clay exchanged with protons, was successfully applied as a solid acid catalyst for the polymerization of tetrahydrofuran (poly(THF)) at room temperature in the presence of acetic anhydride. Prior to using the kaolin as a catalyst, it was treated with HCl (0.1 M) and characterized using various analytical techniques. The amounts of catalyst and reaction time on the conversion of THF were investigated. Characterizations of nuclear magnetic Resonance of proton (1H-NMR), Fourier Transform Infrared spectroscopy (FT-IR), X-ray Diffraction (XRD), Optical Microscopy (OM), and Differential Scanning Calorimetry (DSC) techniques were used to examine the resulting polymer. X-ray characterization and DSC data indicated that the obtained poly(THF) is a highly crystalline substance. The results showed that protonated kaolin (kaolin–H+) has a high catalytic activity for the polymerization of THF with a conversion rate of 50.02% after 20 hours. Copyright © 2019 BCREC Group. All rights reserved

Removal of Malachite Green Dye from Aqueous Solution by Catalytic Wet Oxidation Technique Using Ni/Kaolin as Catalyst

In this study, natural Algerian kaolin was used as a support and impregnated with nickel at different loading amounts (2 wt.%, 5 wt.%, and 7 wt.%) in order to prepare a supported catalyst. The wet impregnation technique was used in this preparation; nickel oxide (NiO) was the active phase precursor of the catalyst, and the catalysts were designated as follows: 2%, 5%, and 7% Ni/kaolin. These catalysts were put to the test in catalytic wet peroxide oxidation (CWPO) for degrading the organic contaminant malachite green dye (MG). Analytical techniques such as FTIR spectroscopy, X-ray diffraction, BET, and X-fluorescence were used to examine the structure, morphology, and chemical composition of the support and the produced catalysts. Several parameters, including temperature, catalytic dose, metal loading, hydrogen peroxide volume, and kinetic model were systematically investigated. The combination of improved parameters resulted in a significant increase in the catalytic activity, achieving a high removal rate of MG dye of 98.87%

A DFT-D4 investigation of the complexation phenomenon between pentachlorophenol and β-cyclodextrin

Density functional theory (DFT) calculations based on the BLYP-D4 and PBEh-3c composite methods were performed for investigating the encapsulation mode of pentachlorophenol (PCP) inside the cavity of β-cyclodextrin (β-CD). Different quantum chemical parameters such as HOMO, LUMO, and HOMO–LUMO gap were calculated. Complexation energies were computed at the molecular level to provide insight into the inclusion of PCP inside the β-CD cavity. The Independent gradient model (IGM) approach was applied to characterize the non-covalent interactions that occurred during the complex (PCP@β-CD) formation. Two modes of inclusion were considered in this work (modes A and B). Calculated complexation energies as well as the changes in enthalpy, entropy, and free Gibbs energy exhibit negative values for both modes A and B, indicating a thermodynamically favorable process. Weak Van der Waals interactions and one strong intermolecular hydrogen bond act as the main driving forces behind the stabilization of the formed most stable complex. This study was carried out to explore the potential use of the β-CD as a host macrocycle for sensing and capturing pentachlorophenol

Synthesis of Two Novel Copper (II) Complexes as Potential Inhibitors of HIV-1 Protease Enzyme: Experimental and Theoretical Investigations

In this study, we report the synthesis of two new copper complexes: [Cu(C$_{11}$H$_{7}$O$_{2}$)(SCN)(C$_{10}$H$_{8}$N$_{2}$)], denoted as (C-1), and [Cu(C$_{11}$H$_{7}$O$_{2}$) (C$_{12}$H$_{8}$N$_{2}$) Cl]·H$_{2}$O, denoted as (C-2). They are based on 2,2′-bipyridine or 1,10-phenanthroline and 2-hydroxy-1-naphtaldehyde ligands. The obtained complexes were characterized by FT-IR, UV-visible spectroscopy, and single-crystal X-ray diffraction analysis. Molecular docking was employed to predict the binding mode involved in the interaction between the two synthetic copper (II) complexes and HIV-1 protease enzyme. The X-ray structural analysis revealed that the crystal structures of both complexes are mainly stabilized by several intra- and intermolecular hydrogen bonds. The fingerprint plots associated with the Hirshfeld surfaces of both complexes clearly show that H···H interactions provide the largest contributions. According to the docking results, the synthesized complexes exhibit promising features which enable them to be bound to the HIV-protease enzyme

DFT Analysis of Electronic and Bonding Properties in Face-Bridged inorganic Octahedral Clusters M 6 L 14

ABSTRACT Several theoretical studies shown that in face-bridged octahedral transition metal clusters M 6 L 14 (M = transition metal; L = π-Donor Ligand) the optimal metallic electron (ME) count is of 24 but for many clusters experimentally synthesized, the ME count can vary from 20 to 24 for early transition metals such as molybdenum, tungsten and rhenium, and from 24 to 48 for late transition metals such as cobalt and palladium without altering the architecture of the octahedral cluster core. Density Functional Theory (DFT) calculations were carried out on the species with 20 to 24 metallic electron count in order to rationalize their electronic structure and to explain the conservation of octahedral metallic core for all electron counts

Zwitterionic 1-{(E)-[(2-methylphenyl)iminiumyl]methyl}naphthalen-2-olate

The title Schiff base, C18H15NO, crystallizes in its zwitterionic form and an N—H...O hydrogen bond closes an S(6) ring. The dihedral angle between the aromatic ring systems is 36.91 (10)°. Weak aromatic π–π stacking occurs in the crystal [minimum centroid–centroid separation = 3.7771 (15) Å]

A Dispersion Corrected DFT Investigation of the Inclusion Complexation of Dexamethasone with β-Cyclodextrin and Molecular Docking Study of Its Potential Activity against COVID-19

The encapsulation mode of dexamethasone (Dex) into the cavity of β-cyclodextrin (β-CD), as well as its potential as an inhibitor of the COVID-19 main protease, were investigated using density functional theory with the recent dispersion corrections D4 and molecular docking calculations. Independent gradient model and natural bond orbital approaches allowed for the characterization of the host–guest interactions in the studied systems. Structural and energetic computation results revealed that hydrogen bonds and van der Waals interactions played significant roles in the stabilization of the formed Dex@β-CD complex. The complexation energy significantly decreased from −179.50 kJ/mol in the gas phase to −74.14 kJ/mol in the aqueous phase. A molecular docking study was performed to investigate the inhibitory activity of dexamethasone against the COVID-19 target protein (PDB ID: 6LU7). The dexamethasone showed potential therapeutic activity as a SARS CoV-2 main protease inhibitor due to its strong binding to the active sites of the protein target, with predicted free energy of binding values of −29.97 and −32.19 kJ/mol as calculated from AutoDock4 and AutoDock Vina, respectively. This study was intended to explore the potential use of the Dex@β-CD complex in drug delivery to enhance dexamethasone dissolution, thus improving its bioavailability and reducing its side effects

Removal of Malachite Green Dye from Aqueous Solution by Catalytic Wet Oxidation Technique Using Ni/Kaolin as Catalyst

In this study, natural Algerian kaolin was used as a support and impregnated with nickel at different loading amounts (2 wt.%, 5 wt.%, and 7 wt.%) in order to prepare a supported catalyst. The wet impregnation technique was used in this preparation; nickel oxide (NiO) was the active phase precursor of the catalyst, and the catalysts were designated as follows: 2%, 5%, and 7% Ni/kaolin. These catalysts were put to the test in catalytic wet peroxide oxidation (CWPO) for degrading the organic contaminant malachite green dye (MG). Analytical techniques such as FTIR spectroscopy, X-ray diffraction, BET, and X-fluorescence were used to examine the structure, morphology, and chemical composition of the support and the produced catalysts. Several parameters, including temperature, catalytic dose, metal loading, hydrogen peroxide volume, and kinetic model were systematically investigated. The combination of improved parameters resulted in a significant increase in the catalytic activity, achieving a high removal rate of MG dye of 98.87%