High performance of N-doped TiO2-magnetic activated carbon composites under visible light illumination: Synthesis and application in three-dimensional photoelectrochemical process

Photocatalytic Reduction of CO2 with N-Doped TiO2-Based Photocatalysts Obtained in One-Pot Supercritical Synthesis

The objective of this work was to analyze the effect of carbon support on the activity and selectivity of N-doped TiO₂ nanoparticles. Thus, N-doped TiO₂ and two types of composites, N-doped TiO₂/CNT and N-doped TiO₂/rGO, were prepared by a new environmentally friendly one-pot method. CNT and rGO were used as supports, triethylamine and urea as N doping agents, and titanium (IV) tetraisopropoxide and ethanol as Ti precursor and hydrolysis agent, respectively. The as-prepared photocatalysts exhibited enhanced photocatalytic performance compared to TiO₂ P25 commercial catalyst during the photoreduction of CO₂ with water vapor. It was imputed to the synergistic effect of N doping (reduction of semiconductor band gap energy) and carbon support (enlarging e⁻-h⁺ recombination time). The activity and selectivity of catalysts varied depending on the investigated material. Thus, whereas N-doped TiO₂ nanoparticles led to a gaseous mixture, where CH₄ formed the majority compared to CO, N-doped TiO₂/CNT and N-doped TiO₂/rGO composites almost exclusively generated CO. Regarding the activity of the catalysts, the highest production rates of CO (8 µmol/gTiO₂/h) and CH₄ (4 µmol/gTiO₂/h) were achieved with composite N¹/TiO₂/rGO and N¹/TiO₂ nanoparticles, respectively, where superscript represents the ratio mg N/g TiO₂. These rates are four times and almost forty times higher than the CO and CH₄ production rates observed with commercial TiO₂ P25.

Research on dynamics and mechanism of treatment on phenol simulated wastewater by the ultrasound cooperated electro-assisted micro-electrolysis

In the research, the ultrasound was introduced to the electric-assisted micro-electrolysis system to improve the treatment efficiency of phenol simulated wastewater. The results showed that the phenol removal efficiency was significantly enhanced by the electric-assisted micro-electrolysis method in the presence of ultrasound, which could reach 88.61% under the initial value of pH 4, an iron dosage of 50 g/L, a mass ratio of iron/carbon of 1:1, and the initial phenol concentration of 100 mg/L. The degradation kinetics of phenol was in accordance with a second-order kinetic model. The synergistic effect of the ultrasonic and electric-assisted micro-electrolysis method was obvious with a synergistic factor at 98.02%. The degradation mechanism of phenol was that the treatment could effectively destroy the benzene ring structure of phenol in the liquid phase with ring-opening reaction and small molecules substances generated. PRACTITIONER POINTS: The article was the pretreatment of coking wastewater. First, the synergistic effects between ultrasound and electrochemical method through the removal ratio of phenol were found. Second, it was showed that the initial pH and applied intensity of voltage had the effects on removal ratio of phenol by the UEME method. Third, the synergy factor (S_yn ) between ultrasonic and electrochemical method was 98.02%. Finally, the mechanism of the UEME degradation of phenol was researched. The technology could effectively improve the biodegradability of coking wastewater and provide conditions for subsequent biochemical treatment. So, we thought this article was suitable for the journal.

Enhanced optical properties and photocatalytic activity of TiO2 nanotubes by using magnetic activated carbon: evaluating photocatalytic reduction of Cr(VI)

In recent years, photocatalytic reduction of Cr(VI) to Cr(III) by TiO₂ nanostructures, as a potent environmental technology has attracted a lot of attention. However, several defects including the large band gap energy of TiO₂, fast photogenerated charge recombination and re-oxidation of Cr(III) restrict their practical application. In this work, the incorporation of TiO₂ nanotubes (TNTs) with magnetic activated carbon (MAC) and photoreduction in the presence of a hole scavenger were studied as a preferable approach. The results revealed that coupling TNTs with 2 wt% MAC can boost the surface area from 89.54 to 307.87 m² g^-1 as well as decrease the band gap energy from 3.1 to 2.7 eV. As a consequence of the enhancement in textural features and optical properties, TNTs/MAC (2%) led to improvement of photoreduction efficiency (from 47% to 66%) in comparison with the TNTs. Meanwhile, the experiments demonstrated that using 0.2 g TNTs/MAC as an optimal dosage in acidic solution increases the photoreduction efficiency up to 81%. The hole scavenger investigation had a marvellous result. It was found that in the presence of oxalic acid, TNTs/MAC (2%) could reduce 97% of Cr(VI) which it was due to trapping oxidative species and charge-transfer-complex-mediated process. Furthermore, the kinetic study affirmed that the photoreduction follow first-order kinetics and the reaction rate constants by TNTs/MAC (2%) are 1.5 times as great as those of TNTs. Moreover, the reusability tests illustrated TNTs/MAC (2%) has good stability and is active even up to the six runs.

Synthesis of Ni-doped anatase TiO2 single crystals loaded on wood-based activated carbon for enhanced photodegradation of triphenylmethane dyes

In this work, the Ni-doped anatase TiO₂ single crystals loaded on activated carbon (Ni-T/AC) were synthesized by a sol-gel method. The chemical compositions and physical properties of as-prepared materials were analyzed by XRD, TEM, BET, FTIR, XPS, and PL characterizations. The obtained results implied that all of samples presented anatase phase with a clear mesoporous structure. The photocatalytic properties of nanocomposites were evaluated through photodegradation of crystal violet (CV), basic fuchsine (BF), and malachite green (MG). The results revealed that the catalyst Ni-T/AC-loaded AC exhibited an excellent photocatalytic activity compared with the original TiO₂, and the photodegradation efficiency for CV, BF, and MG is 99.00%, 94.85%, and 98.89% after 120 min of irradiation, respectively. This enhancement may be ascribed to the small crystallite size, large specific surface area, and pore volume of the photocatalysts. In addition, the possible degradation mechanism and pathway for triphenylmethane dyes (TPMs) were also well investigated. This work provides a new, low-cost, and effective route to improve the performance of TiO₂ for effective removing TPMs.

Single-step synthesis of eucalyptus sawdust magnetic activated carbon and its adsorption behavior for methylene blue

Eucalyptus wood-based magnetic activated carbon (MAC) was prepared by single-step carbonization activation magnetization with FeCl₃ and utilized for the adsorption of methylene blue (MB).

Treatment of coking wastewater by a novel electric assisted micro-electrolysis filter

A newly designed electric assisted micro-electrolysis filter (E-ME) was developed to investigate its degradation efficiency for coking wastewater and correlated characteristics. The performance of the E-ME system was compared with separate electrolysis (SE) and micro-electrolysis (ME) systems. The results showed a prominent synergistic effect on COD removal in E-ME systems. Gas chromatography/mass spectrometry (GC-MS) analysis confirmed that the applied electric field enhanced the degradation of phenolic compounds. Meanwhile, more biodegradable oxygen-bearing compounds were detected. SEM images of granular activated carbon (GAC) showed that inactivation and blocking were inhibited during the E-ME process. The effects of applied voltage and initial pH in E-ME systems were also studied. The best voltage value was 1V, but synergistic effects existed even with lower applied voltage. E-ME systems exhibited some pH buffering capacity and attained the best efficiency in neutral media, which means that there is no need to adjust pH prior to or during the treatment process. Therefore, E-ME systems were confirmed as a promising technology for treatment of coking wastewater and other refractory wastewater.

Recent progress in biochar-supported photocatalysts: synthesis, role of biochar, and applications

Incorporating photocatalytic nanoparticles with biochar templates can produce biochar-supported photocatalysts (BSPs) and combine the advantages of biochar with catalytic nanoparticles.