Ultrasonic impregnation assisted in-situ photoreduction deposition synthesis of Ag/TiO2/rGO ternary composites with synergistic enhanced photocatalytic activity

Advances in photocatalytic degradation of tetracycline using graphene-based composites in water: a systematic review and future directions

In this study, a comprehensive systematic review was conducted to better recognize the applicability of graphene-based photocatalytic processes for the degradation of tetracycline (TC) from water. A broad search strategy was developed for English language articles available in PubMed, Scopus, and Web of Science. The effect of parameters such as pH, TC concentration, photocatalyst dose, radiation source intensity, and the effect of graphene on the process, kinetics, and reuse of the photocatalyst were investigated. A total of 63 out of a possible 3498 retrieved records met inclusion criteria. The results showed that most related studies have increased since 2019. About 46.7% of the articles showed 90-100% TC removal efficiency and 59.52% of the studies had optimal pH equal to 5 and 6. Also, the widespread use of visible light had a significant trend. The effect of the dose of graphene in the catalyst was one of the most important and effective factors on the process; hence, the difference in efficiency with and without graphene was completely evident. This review indicated that the presence of graphene has been able to have a positive effect on increasing the efficiency of oxidation processes, and it can be used for environmental pollutants remediation.

Plasmonic effect of metal nanoparticles on the photocatalytic properties of TiO2/rGO composite

A comparative study of the plasmon effect of Ag and Au nanoparticles on TiO2/rGO nanocomposite was carried out. The synthesis of Au and Ag nanoparticles was carried out by laser ablation. The morphology and structure of the nanocomposites were studied by EDA, HRTEM, XRD and Raman spectroscopy. It was shown that the absorption capacity of the nanocomposite material was increased in the visible range of the spectrum when Ag and Au nanoparticles were added to TiO2/rGO. This leads to an increase in their photocatalytic activity. The photocurrent generated by NC/Au 10-11films is in 3.8 times and NC/Ag 10-12is in 2 times higher compared to pure TiO2/rGO film. Similar results were obtained from experimental data on the dyes photodegradation. In the presence of plasmon nanoparticles a significant enhancement in the electrical properties of the TiO2/rGO nanocomposite was recorded. The charge carrier transfer resistance in nanocomposites was decreased by almost ∼7 times for NC/Au,10-11and ∼4 times for NC/Ag,10-12films compared to pure TiO2/rGO. In addition, for nanocomposites with Ag or Au nanoparticles, a decrease in the effective electron lifetime was observed. The data obtained allow us to conclude that plasmonic NPs have a synergistic effect in TiO2/rGO nanocomposites, which consists in modifying both their light-harvesting properties and charge-transport characteristics. The results obtained can be used for the design of materials with improved photocatalytic and optoelectronic characteristics.

Insight into the photocatalytic reduction of hexavalent chromium using photodeposited metal nanoparticle-TiO2 photocatalysis

Hexavalent chromium (Cr(VI)) is carcinogenic to organisms. It is widely used in several industries. In this work, we investigated the Cr(VI) photocatalytic reaction with a scavenger on Pt and Cu-TiO2 photocatalysts. Metal-deposited TiO2 was successfully synthesized by a photodeposition method. TEM-EDX, XRD, and UV-DR were analyzed to study the changes in morphology, crystallinity, and the electronic properties of photocatalysts. The rate of charge recombination during reduction and photoluminescence (PL) spectroscopy was used to examine the catalysts in depth. Cu-TiO2 demonstrates the highest photocatalytic activity for 63.74% of Cr(VI) removal. To understand the photoreduction of Cr(VI), the fate transformation of Cr species during the adsorption and reaction was investigated using in situ XANES. The results demonstrated that the Cr(III) was noticeably main component adsorbed over the catalyst, particularly in Cu-TiO2. The presence of humic acid can boost the Cr(VI) removal efficiency and enhanced the Cr(VI) reduction to Cr(III). We believe that the extensive research on Cr(VI) photoreduction on metal-TiO2 heterojunction will provide a comprehensive understanding of catalytic behaviors, paving the way for rationally designed novel Cr reduction catalysts.

The CO2 photoconversion over reduced graphene oxide based on Ag/TiO2 photocatalyst in an advanced meso-scale continuous-flow photochemical reactor

This study aims at examining the use of an advanced meso-scale continuous-flow photochemical reactor for the photocatalytic conversion of CO₂ with water into fuel over TiO₂ (P25), Ag/TiO₂, and Ag/TiO₂/RGO catalysts. The silver loaded photocatalysts were prepared by one-step process via hydrothermal method. The prepared photocatalysts were characterized by various characterization techniques in order to identify the morphological, chemical, physical, and optical properties. The photocatalytic activity of the as-prepared catalysts was firstly examined by the photoelectrochemical (PEC) measurements and secondly by the photocatalytic reduction of CO₂ in the proposed setup. Liquid products were analyzed using gas chromatography-mass spectrometry (GC-MS) and total organic carbon (TOC) techniques. It was found that the ternary composite revealed an outstanding performance towards CO₂ photocatalytic reduction, where its selectivity was directed towards methanol production. The incorporation of graphene nanosheets enhanced the photocatalytic reduction of CO₂ by 3.3 and 9.4 times compared with Ag/TiO₂ and bare TiO₂, respectively, using the proposed photochemical reactor in a continuous mode. This study sheds the light on a novel type of a photocatalytic reactor where CO₂ conversion over Ag/TiO₂/RGO ternary composite was evaluated. A meso-scale continuous-flow photochemical reactor.

Application of graphene-based materials for removal of tetracyclines using adsorption and photocatalytic-degradation: A review

Tetracyclines are extensively used to treat human and animal infectious diseases due to its effective antimicrobial activities. About 70-90% of its parent materials are released into the environment through urine and feces, implying they are the most frequently detected antibiotics in the environment with high ecological risks. Adsorption and photocatalysis have been promising techniques for the removal of tetracyclines due to effectiveness and efficiency. Graphene-based materials provide promising platforms for adsorptive and photocatalytic removal of tetracyclines from aqueous environment owning to distinctive remarkable physicochemical, optical, and electrical characteristics. Herein, we intensively reviewed the available literatures in order to provide comprehensive insight about the applications and mechanisms of graphene-based materials for removal of tetracyclines via adsorption and phototocatalysis. The synthesis methods of graphene-based materials, the tetracycline adsorption and photocatalytic-degradation conditions, and removal mechanisms have been extensively discussed. Finally concluding remarks and future perspectives have been deduced and recommended to stimulate further researches in the subject. The review study can be used as theoretical guideline for further researchers to improve the current approaches of material synthesis and application towards tetracyclines removal.