Enhanced sunlight photocatalytic activity of Ag3PO4 decorated novel combustion synthesis derived TiO2 nanobelts for dye and bacterial degradation

Solar Photocatalysis for Emerging Micro-Pollutants Abatement and Water Disinfection: A Mini-Review

This mini-review article discusses the critical factors that are likely to affect the performance of solar photocatalysis for environmental applications and, in particular, for the simultaneous degradation of emerging micro-pollutants and the inactivation of microbial pathogens in aqueous matrices. Special emphasis is placed on the control of specific operating factors like the type and the form of catalysts used throughout those processes, the intriguing role of the water matrix, and the composition of the microbial load of the sample in each case. The interplay among the visible responsive catalyst, the target pollutants/pathogens, including various types of microorganisms and the non-target water matrix species, dictates performance in an unpredictable and case-specific way. Case studies referring to lab and pilot-scale applications are presented to highlight such peculiarities. Moreover, current trends regarding the elimination of antibiotic-resistant bacteria and resistance genes by means of solar photocatalysis are discussed. The antibiotic resistance dispersion into the aquatic environment and how advanced photocatalytic processes can eliminate antibiotic resistance genes in microbial populations are documented, with a view to investigate the prospect of using those purification methods for the control-resistant microbial populations found in the environment. Understanding the interactions of the various water components (both inherent and target species) is key to the successful operation of a treatment process and its scaling up.

Agro-waste extracted cellulose supported silver phosphate nanostructures as a green photocatalyst for improved photodegradation of RhB dye and industrial fertilizer effluents

The efficiency and reusability of photocatalysts are the dominant factors for their pragmatic use. The visible light induced semiconductor silver phosphate is a superior photocatalyst effective under visible light but its stability is still an undiscussed issue. To overcome this stability issue in this present manuscript, eco-friendly agro-waste extracted cellulose supported silver phosphate nanostructures have been designed for the first time through a simple chemical process. At first, silver phosphate nanostructures were synthesized by the co-precipitation method. Then, different weights of cellulose were added to the silver nitrate solution to form cellulose supported silver phosphate nanostructures. The photodegradation efficiency for each weight ratio was examined in which the photocatalyst Ag-8 nanostructures showed a high rate (0.024 min^-1) for degradation of Rhodamine B (RhB) using a low intensity tungsten bulb. Real sample analysis has also been carried out using this photocatalyst for the degradation of industrial fertilizer effluents. The degradation rate of all the nanostructures was found to be high in comparison to pristine silver phosphate as well as the extracted bare cellulose. The photocatalytic activity is enhanced because of the participation of cellulose as a support which makes an interface for silver phosphate and assists it in delaying the charge recombination period under visible light. To understand the photochemical reaction of electrons and holes, scavenger studies were also performed.

Valorization of phosphate waste rocks to Ag3PO4/hydroxyapatite for photocatalytic degradation of Rhodamine B under visible light irradiation

A silver phosphate/hydroxyapatite (Ag₃PO₄/HA) composite was produced from phosphate waste rocks, firstly by the valorization of these wastes to HA and then by the treatment of this prepared HA with a silver nitrate solution. A type of response surface methodology, Box-Behnken experimental design, was used to find optimum synthesis parameters (silver to HA weight ratios, calcination temperature and calcination time). The visible light photodegradation of Rhodamine B in aqueous solution was used as the experimental response. The analysis of variance for the results showed that silver weight ratio is the most influential parameter on photoactivity of the synthesized photocatalyst. The optimum conditions were predicted to give an RhB degradation yield of 98.609%/4 hours under visible light conditions. In this context, a Ag/HA weight ratio of 14%, a calcination temperature of 300 °C, and a calcination time of 30 min were found to be the optimum conditions. Samples synthesized under the optimum condition were characterized by the use of X-ray diffraction, X-ray fluorescence spectrometer, Fourier transform infrared spectrum analysis, scanning electron microscopy, transmission electron microscopy and ultraviolet-visible diffuse reflection spectroscopy. By comparison with pure HA, the characterization results clearly showed the successful synthesis of the Ag₃PO₄/HA composite.

Fabrication of a magnetic ternary ZnFe2O4/TiO2/RGO Z-scheme system with efficient photocatalytic activity and easy recyclability

A magnetic composite based on TiO2 nanosheets, ZnFe2O4 and reduced graphene oxide (RGO) was synthesized by a one-step hydrothermal synthesis method, which possessed the band structure of a Z-scheme photocatalytic system. The properties and structures of the samples were characterized by XRD, UV-Vis DRS, Raman spectroscopy, SEM, EDS, XPS and PL spectroscopy. Compared with TiO2 nanosheets and the TiO2/RGO composite, the obtained ternary composite with 3 wt% RGO exhibited a significant enhancement in photocatalytic activities, attributed to the efficient charge separation induced by the fabricated Z-scheme system. About 99.7% of p-nitrophenol (p-NP) degraded within 60 min under simulated solar irradiation. Trapping experiments showed that superoxide anions (˙O2 -) and hydroxyl radicals (˙OH) were the main active species in the p-NP photocatalytic degradation. Finally, a possible photocatalytic mechanism of Z-scheme ZnFe2O4/TiO2/RGO was proposed based on the results of trapping experiments and the energy bands of TiO2 and ZnFe2O4.

Current Trends in the Application of Nanomaterials for the Removal of Emerging Micropollutants and Pathogens from Water

Water resources contamination has a worldwide impact and is a cause of global concern. The need for provision of clean water is becoming more and more demanding. Nanotechnology may support effective strategies for the treatment, use and reuse of water and the development of next-generation water supply systems. The excellent properties and effectiveness of nanomaterials make them particularly suitable for water/wastewater treatment. This review provides a comprehensive overview of the main categories of nanomaterials used in catalytic processes (carbon nanotubes/graphitic carbon nitride (CNT/g-C₃N₄) composites/graphene-based composites, metal oxides and composites, metal–organic framework and commercially available nanomaterials). These materials have found application in the removal of different categories of pollutants, including pharmaceutically active compounds, personal care products, organic micropollutants, as well as for the disinfection of bacterial, viral and protozoa microbial targets, in water and wastewater matrices. Apart from reviewing the characteristics and efficacy of the aforementioned nanoengineered materials for the removal of different pollutants, we have also recorded performance limitations issues (e.g., toxicity, operating conditions and reuse) for their practical application in water and wastewater treatment on large scale. Research efforts and continuous production are expected to support the development of eco-friendly, economic and efficient nanomaterials for real life applications in the near future.

Curcumin-Functionalized Ag/Ag2 O Nanocomposites: Efficient Visible-Light Z-scheme Photocatalysts

Curcumin-functionalized Ag/Ag₂ O (c-Ag/Ag₂ O) nanocomposites with varying proportions of curcumin and Ag/Ag₂ O were prepared by a simple one pot green synthesis protocol in aqueous medium. The plasmonic band undergoes slight redshift, broadening and decrease in intensity with increase in the proportion of Ag₂ O formed. These composite nanoparticles were found to be efficient visible-light photocatalysts for aerobic oxidation of methyl orange and rhodamine B (RhB). Functionalization by curcumin significantly enhanced the photocatalytic activity with good reusability. The photocatalytic oxidation rate showed super linear increase with light intensity because of localized surface plasmon resonance (LSPR)-induced strong near field. The trapping experiments confirmed that superoxide radicals were the main active species responsible for the degradation reaction. A plasmonic Z-scheme photocatalytic mechanism is proposed to explain the possible charge transfer and separation behavior of electron-hole pairs among Ag, Ag₂ O and curcumin under visible-light irradiation.

Efficient interfacial charge transfer through plasmon sensitized Ag@Bi2O3 hierarchical photoanodes for photoelectrocatalytic degradation of chlorinated phenols

Understanding the interfacial charge transfer behavior of plasmonically active Ag decorated hierarchical Bi₂O₃ photoanodes for the photo-electro-oxidation of chlorinated phenols.

Ternary semiconductor ZnxAg1−xS nanocomposites for efficient photocatalytic degradation of organophosphorus pesticides

Some approaches have been carried out for the degradation of organophosphorus pesticides using simple metal oxide nanostructures. This paper reports a comparison of the photocatalytic activity of ZnS and Ag₂S with that of ternary semiconductor Zn_0.5Ag_0.5S nanocomposites without any surfactant for the degradation of the pesticides MLT, MCP, and CPS under UV light for environmental safety.

Sequential ionic layer adsorption and reaction (SILAR) deposition of Bi4Ti3O12 on TiO2: an enhanced and stable photocatalytic system for water purification

A new method to produce bismuth titanate – titanium dioxide composites by modification of a TiO₂ film deposited on a variety of different glass substrates is reported.

Enhanced adsorbability and photocatalytic activity of TiO2-graphene composite for polycyclic aromatic hydrocarbons removal in aqueous phase

Photodegradation via titanium dioxide (TiO₂) has been used to remove polycyclic aromatic hydrocarbons (PAHs) from environmental media broadly. In this study, a series of TiO₂-graphene composites (P25-GR) with different GR weight ratios were synthesized via hydrothermal reaction of graphene oxide (GO) and P25. Their structures were characterized and the proprieties were tested in aqueous phase. Phenanthrene (PHE), fluoranthene (FLAN), and benzo[a]pyrene (BaP) were selected as models of PAHs. The experiment indicated that P25-2.5%GR exhibited enhancement in both adsorption and photodegradation, ∼80% of PAHs were removed after 2h photocatalysis. The influence of photodegradation rate was studied, including PAHs initial concentration and pH. Aromatic intermediates were identified during the reaction process and the degradation pathways were portrayed. This work explored the enhanced photocatalysis performance was attributed to the PAH-selective adsorbability and the strong electron transfer ability of the composite. The analysis of the degradation intermediates confirmed that the reaction proceeded with the formation of free radicals, leading to the gradual PAH mineralization.

Visible light driven efficient N and Cu co-doped ZnO for photoinactivation of Escherichia coli

N and Cu co-doped ZnO shows outstanding antibacterial activity for E. coli inactivation under visible light.

Construction of a multipurpose photochemical reactor with on-line spectrophotometric detection

A versatile photoreactor was constructed from commercially available parts, which is capable of recording high quality kinetic traces in homogeneous and heterogeneous photoreactions and also easily adaptable to flow-through operation.

Novel synergistic photocatalytic degradation of antibiotics and bacteria using V–N doped TiO2 under visible light: the state of nitrogen in V-doped TiO2

Interstitial and substitutional nitrogen co-doped in vanadium–TiO₂ for simultaneous photocatalytic antibiotic degradation and bacterial inactivation.