In the present work, a theoretical study of five bipyrazolic-type organic compounds, 4-{bis[(3,5-dimethyl-1H-pyrazolyl-1-yl)methyl]-amino}phenol (1), N1,N1-bis[(3,5-dimethyl-1H-pyrazol-1-yl)methyl}]-N4,N4-dimethyl-1,4-benzenediamine (2), N,N-bis[(3,5-dimethyl-1H-pyrazol-1-yl)methyl]aniline (3), 4-[bis(3,5-dimethyl pyrazol-1-yl-methyl)-amino]butan-1-ol (4) and ethyl4-[bis(3,5-dimethyl-1H-pyrazol-1-yl-methyl) aminobenzoate] (5), has been performed using density functional theory (DFT) at the B3LYP/6-31G(d) level in order to elucidate the different inhibition efficiencies and reactive sites of these compounds as corrosion inhibitors. The efficiencies of corrosion inhibitors and the global chemical reactivity relate to some parameters, such as EHOMO, ELUMO, gap energy (DeltaE) and other parameters, including electronegativity (chi), global hardness (eta) and the fraction of electrons transferred from the inhibitor molecule to the metallic atom (DeltaN). The calculated results are in agreement with the experimental data on the whole. In addition, the local reactivity has been analyzed through the Fukui function and condensed softness indices.
Removal of pharmaceutically active compounds (PhACs) is of great importance in wastewater reclamation due to their potent negative impacts on human health. Typical polyamide nanofiltration (NF) membranes are negatively charged, which compromises their rejection rate of positively charged PhACs. Herein, we propose to rationally design a novel thin-film nanocomposite (TFN) NF membrane featuring a dually charged metal organic framework (MOF) to effectively remove both positively and negatively charged PhACs. Ethylenediamine (ED) was grafted to the coordinately unsaturated metal sites inside the MIL-101(Cr). The resulting ED-MIL-101(Cr) contained both strong positively charged amine groups inside its channels and negatively charged carboxyl groups at its surface. This dually charged nature of the MOF nanoparticles enabled the ED-MIL-101(Cr)-containing TFN membrane to achieve high rejection rates (mostly >90%) for both positively (terbutaline, atenolol, fluoxetine) and negatively charged PhACs (ketoprofen, diclofenac, bezafibrate). At the same time, the ED-MIL-101(Cr) TFN membrane had greatly improved water permeance (140% over the control membrane with MOF loading). Calculations based on density functional theory further confirmed the large energy barrier for the migration of both negatively and positively charged PhACs across the nanochannels of ED-MIL-101(Cr). This study highlights a promising potential of dually charged MOF-TFN membranes for efficient removal of trace organic contaminants in wastewater reclamation.
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