Transition metal co-doped TiO2 nanotubes decorated with Pt nanoparticles on optical fibers as an efficient photocatalyst for the decomposition of hazardous gaseous pollutants

Facile Sol-Gel Synthesis of C, N Codoped-TiO2 for Efficient Degradation of Palm Oil Mill Effluent

Wastewater treatment has been regarded as an effective solution in lowering the potential environmental hazards caused by palm oil mill effluent (POME). To ensure the efficient remediation of POME, the implementation of a promising strategy is necessary to overcome the limitations of conventional water treatment methods for the treatment of this pollutant. In this study, the synthesis of carbon, nitrogen codoped titanium dioxide nanoparticles (C, N-TiO2 NPs) was successfully performed by a sol-gel approach for the treatment of POME as a model pollutant under solar light irradiation. The synthesized C, N-TiO2 NPs displayed unique characteristics including an anatase phase with an average crystallite size of 11.35 nm and irregular spherical structures. Additionally, C, N-TiO2 possessed a lower band gap energy of 2.95 eV than 3.2 V of bulk anatase TiO2 and slower electron-hole (e--h+) pair recombination rate as evidenced by photoluminescence (PL) studies. The adsorption isotherm study of POME was most compatible with the Langmuir isotherm model, and the POME degradation kinetics proceeded according to first-order kinetics. Accordingly, the photocatalytic degradation of POME displayed a maximum degradation efficiency of 100% under the optimum condition of pH 7 in the presence of 0.12 g of the C, N-TiO2 photocatalyst within 150 min. The scavenging study showed that the superoxide radical (•O2 -) was the primary active species in the POME photodegradation. Finally, the reusability analysis confirmed that the C, N-TiO2 NPs could be reused for a maximum of five cycles, making them promising photocatalysts for wastewater treatment.

Novel Engineered Carbon Cloth-Based Self-Cleaning Membrane for High-Efficiency Oil-Water Separation

A novel engineered carbon cloth (CC)-based self-cleaning membrane containing a Cu:TiO2 and Ag coating has been created via hydrothermal and light deposition methods. The engineered membrane with chrysanthemum morphology has superhydrophilic and underwater superoleophilic performance. The cooperativity strategy of Cu doping and Ag coating to the TiO2 is found to be critical for engineering the separation efficiency and self-cleaning skill of the CC-based membrane under visible light due to the modulated bandgap structure and surface plasmon resonance. The CC-based membrane has excellent oil-water separation performance when Cu is fixed at 2.5 wt% and the Ag coating reaches a certain amount of 0.003 mol/L AgNO3. The contact angle of underwater oil and the separation efficiency are 156° and 99.76%, respectively. Furthermore, the membrane has such an outstanding self-cleaning ability that the above performance can be nearly completely restored after 30 min of visible light irradiation, and the separation efficiency can still reach 99.65% after 100 cycles. Notably, the membrane with exceptional wear resistance and durability can work in various oil-water mixtures and harsh environments, indicating its potential as a new platform of the industrial-level available membrane in dealing with oily wastewater.

Enhanced photocatalytic decomposition of phenol in wastewater by using La-TiO2 nanocomposite

In this work, La-TiO₂ nanocomposite was synthesized by loading lanthanum onto TiO₂ and used for improving photodegradation of phenol in wastewater. The characterizations of La-TiO₂ demonstrated that the loading of La onto TiO₂ not only increased its adsorption light zone up to 470 nm but also decreased the band gap energy from 3.1 to 2.64 eV. Photoluminescence spectra of La-TiO₂ confirmed the enhancing separation rate between electron and hole, leading to improve photodegradation efficiency of phenol. The removal rate of phenol was influenced by solution pH and alkaline conditions could bring better removal efficiency. In presence of light, the photodegradation efficiency of phenol by TiO₂ was 64.1%, while it increased up to 93.4% by La-TiO₂ photocatalyst. La-TiO₂ nanocomposite was tested for five cycles and it showed only 13.8% dropping in the photodegradation efficiency of phenol. Besides, over 82% of phenol was removed from the wastewater sample by modified TiO₂, demonstrating the potential of La-TiO₂ photocatalyst for water pollution control.

Role of Post-Hydrothermal Treatment on the Microstructures and Photocatalytic Activity of TiO2-Based Nanotubes

The present study demonstrates the thermal stability and photocatalytic activity of TiO2-based nanotubes with respect to post-hydrothermal treatment. Titanate nanotubes were synthesized by adapting an alkali hydrothermal method from TiO2 sol using NaOH as a catalyst. The effect of post-hydrothermal heating on the properties—such as structure, morphology, textural properties, and activity—of as-synthesized one-dimensional titania nanostructure is investigated in detail. The characterizations are carried out using SEM, EDX, TEM, XRD, and a BET surface area analyzer. When heated in the presence of water in an autoclave, the protonated titanate phase of the nanotubes converts to anatase phase. Meanwhile, the tubular morphology is gradually lost as the post-hydrothermal heating duration increases. The photocatalytic activity was assessed utilizing the photo-oxidation of an amaranth dye. It is discerned that the as-prepared nanotubes are photocatalytically inactive but become active after post-hydrothermal processing. The activity trend follows the formation of the active phase—the titanate phase crystallizes into a photocatalytically-active anatase phase during post-hydrothermal heating. The effect of experimental parameters, such as reaction pH, dye concentration, and amount of catalyst, on the dye removal is studied. The findings also highlight that the role of holes/OH• is more prominent as compared to conduction band electron/O2−• for the removal of the dye. In addition, the photocatalyst exhibited excellent stability and reusability.