Olefin/paraffin separation is one of the most challenging processes in the gas separation field. Nowadays, membrane technology has emerged as a promising alternative for the current energy-intensive cryogenic distillation. Due to the demonstration of higher selectivity of glassy polymers, these polymers are preferred in this regard. Herein, polyethylene glycol (PEG), known as a plasticizer, was used to blend with glassy cellulose acetate (CA) and enhanced its permeability and separation factor over ethylene and propylene. The existence of all specific bands for CA and PEG was proved using Fourier transform infrared analysis. Changes in the glass-transition temperature (T g) of the membrane were investigated through differential scanning calorimetry analysis, which confirmed that a uniform blending was attained. With the addition of PEG up to 30 wt %, T g and crystallinity of the membranes also decreased. The scanning electron microscopy results indicated a uniform dense structure for the pristine membrane, which changed into a grooved structure upon addition of PEG due to the created intermolecular interaction. The gas separation test indicated that upon addition of different amounts of PEG to the polymer matrix at 2 bar pressure, the gas separation performance of all the blended membranes improved. Ethylene permeability showed 56% increase from 0.59 in neat CA to 0.92 Barrer in a CA/30 wt % PEG membrane. A similar enhancement was also seen in propylene permeability, which increased from 0.57 to 0.91 Barrer. Addition of PEG into the polymer matrix increased the selectivity of ethylene/ethane from 2.185 for the pristine membrane to 2.484 for the 30 wt % PEG membrane. Moreover, the selectivity of propylene/propane increased from 2.375 to 3.033. The gas separation performance of all the blended membranes also enhanced upon increasing the feed pressure in all membranes. The selectivity of ethylene/ethane enhanced from 2.48 to 2.57 and that of propylene/propane increased from 3.033 to 3.52 at a pressure of 10 bar.
In this study, a new solar light-driven magnetic heterogeneous photocatalyst, denoted as ZnO/NiFe2O4/Co3O4, is successfully prepared. FT-IR, XPS, XRD, VSM, DRS, FESEM, TEM, EDS, elemental mapping, and ICP analysis are accomplished for full characterization of this catalyst. FESEM and TEM analyses of the photocatalyt clearly affirm the formation of a hexagonal structure of ZnO (25–40 nm) and the cubic structure of NiFe2O4 and Co3O4 (10–25 nm). Furthermore, the HRTEM images of the photocatalyst verify some key lattice fringes related to the photocatalyt structure. These data are in very good agreement with XRD analysis results. According to the ICP analysis, the molar ratio of ZnO/NiFe2O4/Co3O4 composite is obtained to be 1:0.75:0.5. Moreover, magnetization measurements reveals that the ZnO/NiFe2O4/Co3O4 has a superparamagnetic behavior with saturation magnetization of 32.38 emu/g. UV-vis DRS analysis indicates that the photocatalyst has a boosted and strong light response. ZnO/NiFe2O4/Co3O4, with band gap energy of about 2.65 eV [estimated according to the Tauc plot of (αhν)2vs. hν], exhibits strong potential towards the efficacious degradation of tetracycline (TC) by natural solar light. It is supposed that the synergistic optical effects between ZnO, NiFe2O4, and Co3O4 species is responsible for the increased photocatalytic performance of this photocatalyst under the optimal conditions (photocatalyst dosage = 0.02 g L−1, TC concentration = 30 mg L−1, pH = 9, irradiation time = 20 min, and TC degradation efficiency = 98%). The kinetic study of this degradation process is evaluated and it is well-matched with the pseudo-first-order kinetics. Based on the radical quenching tests, it can be perceived that •O2− species and holes are the major contributors in such a process, whereas the •OH radicals identify to have no major participation. The application of this methodology is implemented in a facile and low-cost photocatalytic approach to easily degrade TC by using a very low amount of the photocatalyst under natural sunlight source in an air atmosphere. The convenient magnetic isolation and reuse of the photocatalyst, and almost complete mineralization of TC (based on TOC analysis), are surveyed too, which further highlights the operational application of the current method. Notably, this method has the preferred performance among the very few methods reported for the photocatalytic degradation of TC under natural sunlight. It is assumed that the achievements of this photocatalytic method have opened an avenue for sustainable environmental remediation of a broad range of contaminants.
In the present study, ZnCo2O4/g-C3N4/Cu is synthesized as a new and highly effectual solar-lightdriven heterogeneous photocatalyst. The prepared photocatalyst is characterized using FT-IR, XRD, XPS, DRS, FESEM, TEM, EDS, and elemental mapping techniques. The performance of ZnCo2O4/g-C3N4/Cu is studied towards the Metronidazole (MNZ) degradation under the solar light radiation. The kinetics of MNZ degradation and efficacy of the operational parameters comprising the initial MNZ amount (10-30 mg L -1 ), photocatalyst dosage (0.005-0.05 g L -1 ), pH (3-11), and contact time (5-30 min) on the MNZ degradation process are investigated. Surprisingly, the ZnCo2O4/g-C3N4/Cu nanocomposite present a privileged photocatalytic performance towards the MNZ degradation under solar light irradiation. The enhanced photocatalytic activity of this photocatalyst can be attributed to the synergistic optical effects between ZnCo2O4, g-C3N4, and Cu. The value of the band gap energy for ZnCo2O4/g-C3N4/Cu is estimated to be 2.3 eV based on the Tauc plot of (αhν) 2 vs. hν. The radical quenching experiments confirm that the superoxide radicals and holes are the principal active species in the photocatalytic degradation of MNZ, whereas the hydroxyl radicals have no major role in such a degredation. The as-prepared catalyst is simply isolated and recycled for at least eight runs without noticeable loss of efficiency. Using the natural sunlight source, applying very low amount of the photocatalyst, neutrality of the reaction medium, short reaction time, high efficiency of the degradation procedure, utilizing air as the oxidant, low operational costs and easy to recover and reuse of the catalyst are the significant highlights of the present method. It is supposed that this study can be a step forward in creating an effective photocatalytic system in the treatment of a wide range of contaminated aquatic environments.
A Corrigendum on Solar light induced photocatalytic degradation of tetracycline in the presence of ZnO/NiFe2O4/Co3O4 as a new and highly efficient magnetically separable photocatalyst
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