Efficiency and mechanism of enhanced norfloxacin removal using amorphous TiO2-modified biochar

Inadequate treatment of antibiotic-contaminated wastewater, including compounds such as norfloxacin (NOR), poses a substantial treat to both ecological safety and human well-being. An innovative approach was devised to address NOR pollution using amorphous TiO2 modified biochar (A-TiO2/BC) prepared via sol-gel impregnation. The resultant had a commendably specific surface area of 131.8 m2/g-1, which was 1.91 times more than the original surface area of unmodified BC. A-TiO2/BC also exhibited abundant hydroxyl and oxygen-containing functional groups, thereby provided adequately active sites for NOR adsorption. R2 values obtained from NOR isotherm adsorption models descended in order of Freundlich < Temkin < Sips < Langmuir, which indicated that the NOR removal by A-TiO2/BC mainly complied with monolayer adsorption accompanied by heterogeneous surface adsorption. Under weakly acidic conditions, NOR adsorption benefits from the synergistic physicochemical interactions of A-TiO2 and BC. Notably, A-TiO2/BC demonstrated an impressive NOR adsorption capacity of up to 78.14 mg g-1, with a dosage of 20 mg L-1 at 25 °C under pH 6. Such A-TiO2 modified biochar thus presents a promising alternative for NOR removal.

3D ordered amorphous and porous TiO2 framework anode with low insertion barrier and fast kinetics for K-ion hybrid capacitors

TiO₂ is considered as a low cost, long-term stable, and safe anode for high power K-ion hybrid capacitors (KICs) due to its abundant reserve, small volume expansion rate, and sloping voltage plateau that avoids K-ion plating at high voltage polarization. However, the enhancement of its low capacity and sluggish kinetics caused by poor electroconductivity and high insertion barrier is still challenging to further develop high-performance KICs. Herein, the reduced graphene oxide (rGO) is embedded in the walls of 3D ordered macro-/mesoporous TiO₂ (termed as TiO₂@rGO framework) to create intimate TiO₂/rGO interfaces, ensuring the effectively electron transportation during potassiation/depotassiation of TiO₂ while maintaining rapid ions/electrolyte diffusion. Furthermore, the controlled amorphous TiO₂ framework can further lower the lattice insertion energies, contributing to a fast accommodation of K-ion. As expected, the amorphous TiO₂@rGO framework (TiO₂@rGO-1) exhibits a superior rate capability (148.8 mAh g^-1 at 5 A g^-1) and cycling stability (171.2 mAh g^-1 at 1 A g^-1 after 800 cycles). The assembled KICs can reach a high energy/power density of 125.2 Wh kg^-1/4267.4 W kg^-1 as well as a long-term lifespan. This tactic provides a reliable and general way to design a TiO₂-based anode with fast kinetics toward high-performance KICs.

Single-step fabrication of highly stable amorphous TiO2 nanotubes arrays (am-TNTA) for stimulating gas-phase photoreduction of CO2 to methane

This study investigates the facile fabrication of interfacial defects assisted amorphous TiO₂ nanotubes arrays (am-TNTA) for promoting gas-phase CO₂ photoreduction to methane. The am-TNTA catalyst was fabricated via a one-step synthesis, without heat treatment, by anodization of Titanium in Ethylene glycol-based electrolyte in a shorter anodizing time. The samples presented a TiO₂ nanostructured array with a nanotubular diameter of 100 ± 10 nm, a wall thickness of 26 ± 5 nm, and length of 3.7 ± 0.3 μm, resulting in a specific surface of 0.75 m² g. The am-TNTA presented prolonged chemical stability, a high exposed surface area, and a large number of surface traps that can reduce the recombination of the charge carriers. The am-TNTA showed promising photoactivity when tested in the CO₂ reduction reaction with water under UV irradiation with a methane production rate of 14.0 μmol g_cat^-1 h^-1 for a pure TiO₂ material without any modification procedure. This enhanced photocatalytic activity can be explained in terms of surface defects of the amorphous structure, mainly OH groups that can act as electron traps for increasing the electron lifetime. The CO₂ interacts directly with those traps, forming carbonate species, which favors the catalytic conversion to methane. The am-TNTA also exhibited a high stability during six reaction cycles. The photocatalytic activity, the significantly reduced time for synthesis, and high stability for continuous CH₄ production make this nanomaterial a potential candidate for a sustainable CO₂ reduction process and can be employed for other energy applications.

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).

The preparation of amorphous TiO2 doped with cationic S and its application to the degradation of DCFs under visible light irradiation

An amorphous S-doping TiO₂ catalyst [S-TiO₂ (300)] with visible light catalytic activity was successfully prepared via a sol-gel method with low-temperature calcination (300 °C) using thiourea as the sulfur source. The S-TiO₂ (300) catalyst showed great performance in degrading the recalcitrant pharmaceutical, diclofenac (DCF). 93% of the target pollutant DCF degraded in 4 h under visible light irradiation. Both the amorphous form of the catalyst and cationic S-doping (with a coordinated structure) contributed to narrowing the band gap. As a result, the photocatalytic activity of S-TiO₂ (300) was significantly enhanced under visible light irradiation. In addition, oxidative species such as photogenic cavitation (h+), OH and O₂^- were proved to participate in the photodegradation process, attacking COOH group and NH bond, degraded DCF into low molecule organic gradually.

Platinum-enhanced amorphous TiO2-filled mesoporous TiO2 crystals for the photocatalytic mineralization of tetracycline hydrochloride

The adsorption ability and photoactivity of a photocatalyst largely determine the mineralization efficiency of antibiotics. Herein, aiming to enhance the adsorption and mineralization of antibiotics, we constructed a hierarchical porous core-shell structure by filling amorphous TiO₂ in the pores of Pt-doped mesoporous TiO₂ crystals (MCs). The physical-chemical properties of the prepared samples were investigated by surface photovoltage spectroscopy, X-ray photoelectron spectroscope, etc. Adsorption and photocatalysis experiments were conducted with tetracycline hydrochloride as the model antibiotic. Pt nanoparticles doped at the interface of the rutile-amorphous homojunction remarkably enhanced the built-in electric field. The enhanced electric field increased the hole transfer to the catalyst surface, and the Pt doping treatment promoted the growth of amorphous TiO₂ into the mesopores of the MCs. The optimization increased the surface area of the catalyst without increasing the thickness of the amorphous TiO₂ shell, thereby reducing the charge migration distance from the core-shell interface to the catalyst surface. The adsorption amount and mineralization efficiency of tetracycline hydrochloride for the porous core-shell composite were 6.7 and 3.8 times of those for MCs, respectively.

Construction of amorphous TiO₂/BiOBr heterojunctions via facets coupling for enhanced photocatalytic activity

Facets coupled BiOBr with amorphous TiO2 composite photocatalysts are synthesized via an in situ direct growth approach under microwave irradiation. XRD, SEM and HRTEM characterizations indicate that the heterointerface between BiOBr and amorphous TiO2 occurs mainly on the {001} facets of BiOBr. BET and TEM verify that the heterojunctions possess higher specific surface areas and smaller amorphous TiO2 particle size than bare BiOBr and amorphous TiO2, exhibiting the inhibition function of BiOBr on the growth of TiO2 particles. XPS verifies the interaction between the two components. The degradation of methyl orange (MO) and phenol are used as the objective reaction to evaluate the photocatalytic activity of the as-prepared samples. The reaction rate constant of 15% TiO2/BiOBr composite is 3.4 times greater than that of pure BiOBr, which is attributed to its higher surface area, and efficient separation of photo-generated electron-hole pairs between BiOBr and amorphous TiO2.