Ultrasound-assisted catalytic activation of peroxydisulfate on Ti3GeC2 MAX phase for efficient removal of hazardous pollutants

Herein, Ti3GeC2 MAX phase was synthesized using the reactive sintering method and characterized via various techniques. The X-ray diffraction pattern confirmed the successful synthesis of the MAX phase in the hexagonal crystal structure with high purity. Based on the field-emission scanning electron microscopy and high-resolution transmission electron microscopy analysis, layered morphology with the compacted structure was observed. The catalytic activity of the MAX phase was evaluated for activation of peroxydisulfate (PDS) under ultrasound (US) irradiation. Ti3GeC2 MAX phase (0.2 g/L) with a bandgap of 1.72 eV demonstrated high capability to activate 0.15 mmol/L of PDS under US irradiation, resulting in 94.7% removal efficiency within 80 min of reaction time. The removal of diverse types of pollutants such as dimethyl phthalate, hydroxychloroquine, and mefenamic acid confirmed the high performance of the Ti3GeC2/PDS/US ternary system. The quenching tests indicated that both radical and non-radical pathways are involved in the degradation process, and O2•−, O•H, SO4•−, and O21 were recognized as critical species. In addition, a probable degradation mechanism was proposed. The results provide a promising perspective for the application of MAX phase-based materials in the ternary catalyst/oxidant/US systems for the efficient treatment of organic contaminants. To the best of our knowledge, the present work is the first effort to make use of the Ti3GeC2 MAX phase as a desirable catalyst for the removal of organic pollutants applying the catalyst/PDS/US ternary system. © 2022 Elsevier Lt

Carboxymethyl cellulose/polyethersulfone thin-film composite membranes for low-pressure desalination

Herein, we report the fabrication of carboxymethyl cellulose (CMC)/polyethersulfone (PES) thin-film composite nanofiltration membranes using a dip-coating method with glutaraldehyde (GA) as the crosslinking agent. The effects of crosslinking degree and the dip-coating parameters, including CMC concentration and dipping time, on the performance and morphology of the fabricated membranes were investigated. The properties of the prepared membranes were analyzed by ATR-FTIR, AFM, FE-SEM, and water contact angle analysis. The optimized membrane containing 0.2 wt% CMC, crosslinking degree of 20% by the dipping time of 10 min represented a rejection efficiency of 91.90%, 68.63%, and 45.90% towards the Na2SO4, MgSO4, and NaCl solutions (100 mg/L), respectively. The pure water flux of the optimal membrane was 47.90 ± 1.77 L/m2 h under a low transmembrane pressure of 0.4 MPa. The flux recovery ratio of the nanofiltration membrane was 63% higher than the PES support membrane, indicating an improvement in fouling resistance. © 2021 Elsevier B.V

Toxicity of Zn-Fe Layered Double Hydroxide to Different Organisms in the Aquatic Environment

The application of layered double hydroxide (LDH) nanomaterials as catalysts has attracted great interest due to their unique structural features. It also triggered the need to study their fate and behavior in the aquatic environment. In the present study, Zn-Fe nanolayered double hydroxides (Zn-Fe LDHs) were synthesized using a co-precipitation method and characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and nitrogen adsorption-desorption analyses. The toxicity of the home-made Zn-Fe LDHs catalyst was examined by employing a variety of aquatic organisms from different trophic levels, namely the marine photobacterium Vibrio fischeri, the freshwater microalga Pseudokirchneriella subcapitata, the freshwater crustacean Daphnia magna, and the duckweed Spirodela polyrhiza. From the experimental results, it was evident that the acute toxicity of the catalyst depended on the exposure time and type of selected test organism. Zn-Fe LDHs toxicity was also affected by its physical state in suspension, chemical composition, as well as interaction with the bioassay test medium

Improving photocatalytic activity of the ZnS QDs via lanthanide doping and photosensitizing with GO and g-C3N4 for degradation of an azo dye and bisphenol-A under visible light irradiation

In this research, insertion of Gd ions (2 wt%) into the crystalline lattice of the ZnS QDs enhanced the photocatalytic activity of the QDs. In addition, the influence of graphene oxide (GO) and graphitic carbon nitride (g-C3N4) was assessed on the photocatalytic activity of the ZnS QDs through degradation of acid red 14 (AR14) and bisphenol-A (BA) under visible light. Higher photocatalytic degradation efficiency (97.1% for AR14 and 67.4% for BA within 180 min) and higher total organic carbon (TOC) removal (67.1% for AR14 and 59.2% for BA within 5 h) was achieved in the presence of ZnS QDs/g-C3N4 compared with ZnS QDs/GO nanocomposite. Finally, the Gd-doped ZnS QDs were hybridized with g-C3N4 as optimal support to fabricate a potent visible-light-driven photocatalyst for the decomposition of organic contaminants. The maximum photocatalytic degradation of 99.1% and 80.5% were achieved for AR14 and BA, respectively, in the presence of Gd-doped ZnS QDs/g-C3N4 nanocomposite. The photosensitization mechanism was suggested for the improved photocatalytic activity of the ZnS QDs/GO, ZnS QDs/g-C3N4, and Gd-doped ZnS QDs/g-C3N4 nanocomposites under visible light. © 2022 Elsevier Lt

Toxicity of Zn-Fe Layered Double Hydroxide to Different Organisms in the Aquatic Environment

The application of layered double hydroxide (LDH) nanomaterials as catalysts has attracted great interest due to their unique structural features. It also triggered the need to study their fate and behavior in the aquatic environment. In the present study, Zn-Fe nanolayered double hydroxides (Zn-Fe LDHs) were synthesized using a co-precipitation method and characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and nitrogen adsorption-desorption analyses. The toxicity of the home-made Zn-Fe LDHs catalyst was examined by employing a variety of aquatic organisms from different trophic levels, namely the marine photobacterium Vibrio fischeri, the freshwater microalga Pseudokirchneriella subcapitata, the freshwater crustacean Daphnia magna, and the duckweed Spirodela polyrhiza. From the experimental results, it was evident that the acute toxicity of the catalyst depended on the exposure time and type of selected test organism. Zn-Fe LDHs toxicity was also affected by its physical state in suspension, chemical composition, as well as interaction with the bioassay test medium

Modeling Preparation Condition and Composition–Activity Relationship of Perovskite-Type La_<i>x</i>Sr_1–<i>x</i>Fe_<i>y</i>Co_1–<i>y</i>O₃ Nano Catalyst

In this paper, an artificial neural network (ANN) is first applied to perovskite catalyst design. A series of perovskite-type oxides with the La_<i>x</i>Sr_1–<i>x</i>Fe_<i>y</i>Co_1–<i>y</i>O₃ general formula were prepared with a sol–gel autocombustion method under different preparation conditions. A three-layer perceptron neural network was used for modeling and optimization of the catalytic combustion of toluene. A high <i>R</i>² value was obtained for training and test sets of data: 0.99 and 0.976, respectively. Due to the presence of full active catalysts, there was no necessity to use an optimizer algorithm. The optimum catalysts were La_0.9Sr_0.1Fe_0.5Co_0.5O₃ (<i>T</i>_c = 700 and 800 °C and [citric acid/nitrate] = 0.750), La_0.9Sr_0.1Fe_0.82Co_0.18O₃ (<i>T</i>_c = 700 °C, [citric acid/nitrate] = 0.750), and La_0.8Sr_0.2Fe_0.66Co_0.34O₃ (<i>T</i>_c = 650 °C, [citric acid/nitrate] = 0.525) exhibiting 100% conversion for toluene. More evaluation of the obtained model revealed the relative importance and criticality of preparation parameters of optimum catalysts. The structure, morphology, reducibility, and specific surface area of catalysts were investigated with XRD, SEM, TPR, and BET, respectively