Clinoptilolite mediated activation of peroxymonosulfate through spherical dispersion and oriented array of NiFe2O4: Upgrading synergy and performance

Inspired by the features of both transition metal oxide and natural clinoptilolite (flaky structure with suitable pore diameter and open skeleton structure), we adopted a robust strategy by immobilization of nickel ferrite nanoparticles (NiFe₂O₄) on the clinoptilolite surface via typical citric acid combustion method. The hybrid catalyst exhibited enhanced peroxymonosulfate (PMS) activation efficiency and bisphenol A (BPA) degradation performance. Calculated by effective equivalent of NiFe₂O₄, it is found that the reaction rate constant (k) of NiFe₂O₄/clinoptilolite/PMS system (0.1859 min^-1) was 11.9 times higher than that of bare NiFe₂O₄/PMS system (0.0156 min^-1), which demonstrated that catalyst would be conjugated to PMS or contaminant efficiently and renders the rapid degradation and mineralization in the presence of clinoptilolite. After comprehensive characterization analysis and DFT simulations, natural mineral carrier effect (i.e. decreased crystalline size, increased oxygen vacancy content, etc.), abundant surface-bonded and structural hydroxyl groups as well as effective bonding with iron or nickel ions charged for the potential activation mechanism of PMS by NiFe₂O₄/clinoptilolite composite. And it is indicated that not only ^•OH and SO₄^•-, but also ¹O₂ was involved into series reactions. Overall, this study put forward a green and promising technology for high-toxic wastewater treatment.

Elbaite catalyze peroxymonosulfate for advanced oxidation of organic pollutants: Hydroxyl groups induced generation of reactive oxygen species

In this work, the abundant, low-cost, innocuous, and chemically stable elbaite (a type of tourmaline) was employed to catalyze peroxymonosulfate (PMS) for wastewater purification by using methylene blue (MB) as one of the target pollutants. The results revealed that PMS could be catalyzed by elbaite within broad pH range (i.e., 2.9-10.7) and with low activation energy (i.e., 18.6 kJ/mol). Complete MB degradation was obtained within 15 min under the optimized conditions: [elbaite]₀ = 1.00 g/L, [PMS]₀ = 0.50 g/L, initial solution pH = 2.9. MB degradation (%) sustained 99.9 % after five successive catalytic reactions, indicating good durability and long-term stability. In addition, the complete degradation of doxycycline hydrochloride (DOX) and bisphenol A (BPA) further confirmed the degradation activity of the PMS/elbaite system. PMS interacted with elbaite via replacing the surface-bonded and structural OH groups of elbaite with its OH groups to bond with ^YLi^YAl^YR and ^YLi^ZAl^ZR cations (R = Al, Li, Fe, Mg, Mn, Cr, V), which offered channels for electron transfer from negatively charged elbaite to PMS, leading to the activation of PMS. Thus, elbaite is found to be promising for catalyzing PMS to treat organic wastewater.

Synthesis of Novel Kaolin-Supported g-C3N4/CeO2 Composites with Enhanced Photocatalytic Removal of Ciprofloxacin

Herein, novel ternary kaolin/CeO₂/g-C₃N₄ composite was prepared by sol-gel method followed by hydrothermal treatment. The self-assembled 3D “sandwich” structure consisting of kaolin, CeO₂ and g-C₃N₄ nanosheets, was systematically characterized by appropriate techniques to assess its physicochemical properties. In the prerequisite of visible-light irradiation, the removal efficiency of ciprofloxacin (CIP) over the kaolin/CeO₂/g-C₃N₄ composite was about 90% within 150 min, 2-folds higher than those of pristine CeO₂ and g-C₃N₄. The enhanced photocatalytic activity was attributed to the improved photo-induced charge separation efficiency and the large specific surface area, which was determined by electrochemical measurements and N₂ physisorption methods, respectively. The synergistic effect between the kaolin and CeO₂/g-C₃N₄ heterostructure improved the photocatalytic performance of the final solid. The trapping and electron paramagnetic resonance (EPR) experiments demonstrated that the hole (h⁺) and superoxide radicals (•O₂⁻) played an important role in the photocatalytic process. The photocatalytic mechanism for CIP degradation was also proposed based on experimental results. The obtained results revealed that the kaolin/CeO₂/g-C₃N₄ composite is a promising solid catalyst for environmental remediation.

Multidimensional assembly of oxygen vacancy-rich amorphous TiO2-BiOBr-sepiolite composite for rapid elimination of formaldehyde and oxytetracycline under visible light

Herein, a novel oxygen vacancy-rich amorphous TiO₂-BiOBr-sepiolite composite was synthesized through a facile one-pot solvothermal method. Under visible light, it exhibited enhanced adsorption and photocatalytic removal activity towards gaseous formaldehyde, whose reaction rate constant is nearly 11.75, 3.44, 1.69, 2.18 and 6.27 times higher than those of amorphous TiO₂, BiOBr, TiO₂-BiOBr, oxygen vacancy-poor composite and P25, respectively. Moreover, it also displayed significantly improved photodegradation performance towards oxytetracycline under visible light. The improved photocatalytic activity is mainly ascribed to the synergy between the ternary heterogeneous structure and introduced oxygen vacancy, leading to the superior adsorption performance, extended visible-light adsorption scope and faster carriers' separation rate. The photogenerated holes are the dominant active species during the reaction process. Additionally, a plausible photocatalytic degradation pathway for oxytetracycline was also proposed. In general, this work provides a viable strategy of visible-light-driven photocatalyst for practical environmental remediation of indoor volatile organic compounds (VOCs) and pharmaceuticals and personal care products (PPCPs).