Effective coupling of phenol adsorption and photodegradation at the surface of micro-and mesoporous TiO2-activated carbon materials

Bamboo-derived nitrogen-doping magnetic porous hydrochar coactivated by K2FeO4 and CaCO3 for phenol removal: Governing factors and mechanisms

In this study, a novel nitrogen-doped magnetic Fe-Ca codoped biochar for phenol removal was successfully fabricated via a hydrothermal and coactivation pyrolysis method. A series of adsorption process parameters (K₂FeO₄ to CaCO₃ ratio, initial phenol concentration, pH value, adsorption time, adsorbent dosage and ion strength) and adsorption models (kinetic models, isotherms and thermodynamic models) were determined using batch experiments and various analysis techniques (XRD, BET, SEM-EDX, Raman spectroscopy, VSM, FTIR and XPS) to investigate the adsorption mechanism and metal-nitrogen-carbon interaction. The biochar with a ratio of Biochar: K₂FeO₄: CaCO₃ = 3:1:1 exhibited superior properties for adsorption of phenol and had a maximum adsorption capacity of 211.73 mg/g at 298 K, C₀ = 200 mg/L, pH = 6.0 and t = 480 min. These excellent adsorption properties were due to superior physicomechanical properties (a large specific surface area (610.53 m²/g) and pore volume (0.3950 cm³/g), a well-developed pore structure (hierarchical), a high graphitization degree (I_D/I_G = 2.02), the presence of O/N-rich functional groups and Fe-Ox,Ca-Ox, N-doping, as well as synergistic activation by K₂FeO₄ and CaCO₃). The Freundlich and pseudo-second-order models effectively fit the adsorption data, indicating multilayer physicochemical adsorption. Pore filling and π-π interactions were the predominant mechanisms for phenol removal, and H-bonding interactions, Lewis-acid-base interactions, and metal complexation played an important role in enhancing phenol removal. A simple, feasible approach with application potential to organic contaminant/pollutant removal was developed in this study.

Hydrogen Production through Glycerol Photoreforming on TiO2/Mesoporous Carbon: Influence of the Synthetic Method

This article explores the effect of the synthetic method of titanium dioxide (TiO₂)/C composites (physical mixture and the water-assisted/unassisted sol-gel method) on their photocatalytic activity for hydrogen production through glycerol photoreforming. The article demonstrates that, apart from a high surface area of carbon and the previous activation of its surface to favor titania incorporation, the appropriate control of titania formation is crucial. In this sense, even though the amount of incorporated titania was limited by the saturation of carbon surface groups (in our case, ca. 10 wt.% TiO₂), the sol-gel process without water addition seemed to be the best method, ensuring the formation of small homogeneously-distributed anatase crystals on mesoporous carbon. In this way, a ca. 110-fold increase in catalyst activity compared to Evonik P25 (expressed as hydrogen micromole per grams of titania) was achieved.

Degradation of Meropenem by Heterogeneous Photocatalysis Using TiO2/Fiberglass Substrates

Meropenem (MER), a carbapenem, is considered a last-resort antibiotic. Its presence in water bodies, together with other antibiotics, has brought about environmental problems related to the destruction of natural microorganisms and the development of antibiotic-resistant bacteria. Herein, the degradation of MER by heterogeneous photocatalysis using TiO2 immobilized on fiberglass substrates is reported. Morphological characterization of the substrates was performed by Scanning Electron Microscopy (SEM). Three pH values (4.0, 5.7, and 7.9) were tested for the treatment of MER solutions (100 mg/L). The best rate constants and MER removals were obtained at pH 4.0 (0.032 min−1; 83.79%) and 5.7 (0.032 min−1; 83.48%). Chemical Oxygen Demand (COD) and Total Organic Carbon (TOC) removals of 25.80% and 29.60% were achieved for the treatment at a pH value of 5.7. The reuse and regeneration of the plates were also tested. The activity of the substrates was maintained until the fourth cycle of reuse, nonetheless, a decrease in MER removal was observed for the 5th cycle. After the fourth cycle of reuse, the activity of the substrates was recovered by a regeneration procedure involving a wash stage of the substrates with a 1% H2O2 solution in an ultrasonic bath.

Effect of calcination on structure and photocatalytic property of N-TiO2/g-C3N4@diatomite hybrid photocatalyst for improving reduction of Cr(Ⅵ)

The N-TiO₂/g-C₃N₄@diatomite (NTCD) composite has been prepared through a simple impregnation method, using titanium tetrachloride as precursor and urea as nitrogen-carbon source. Then the effects of calcination temperature on structure, surface property and photocatalytic activity of the catalysts were investigated. And XRD, TEM, XPS, FTIR and UV-vis diffuse adsorption spectroscopy were used to characterize the obtained powders. The photocatalytic activity of the NTCD was evaluated through the reduction of aqueous Cr (VI) under visible light irradiation (λ > 400 nm). The results demonstrated that the nano-TiO₂ particles ranging from 15 to 30 nm in the crystal of anatase are well deposited on the surface of diatomite in the NTCD-500 which calcined at 500 °C for 2 h. Furthermore, the g-C₃N₄ with the lay thickness of 0.92 nm was attached to the surface of nano-TiO₂. The N-doped TiO₂ and g-C₃N₄ doped catalysts could co-enhance response in the visible light region and reduce band gap of NTCD-500 (Eg = 3.07 eV). And the NTCD-500 sample exhibited nearly 100% removal rate within 5 h for photocatalytic reduction of Cr (VI) which was higher activity than P25, crude TiO₂@diatomite and g-C₃N₄@diatomite.