Heterostructured Bi2O2CO3/rGO/PDA photocatalysts with superior activity for organic pollutant degradation: Structural characterization, reaction mechanism and economic assessment

Enhanced photocatalytic performance of Bi2O2CO3/Bi4O5Br2/reduced graphene oxide Z-schemehe terojunction via a one-pot room-temperature synthesis

Bi2O2CO3(BOC)/Bi4O5Br2(BOB)/reduced graphene oxide (rGO) Z-scheme heterojunction with promising photocatalytic properties was synthesized via a facile one-pot room-temperature method. Ultra-thin nanosheets of BOC and BOB were grown in situ on rGO. The formed 2D/2D direct Z-scheme heterojunction of BOC/BOB with oxygen vacancies (OVs) effectively leads to lower negative electron reduction potential of BOB as well as higher positive hole oxidation potential of BOC, showing improved reduction/oxidation ability. Particularly, rGO is an acceptor of the electrons from the conduction band of BOC. Its dual roles significantly improve the transfer performance of photo-induced charge carriers and accelerate their separation. With layered nanosheet structure, rich OVs, high specific surface area, and increased utilization efficiency of visible light, the multiple synergistic effects of BOC/BOB/rGO can achieve effective generation and separation of the electron-holes, thereby generating more •O2- and h+. The photocatalytic reduction efficiency of CO2 to CO (12.91 µmol/(g·hr)) is three times higher than that of BOC (4.18 µmol/(g·hr)). Moreover, it also achieved almost 100% removal of Rhodamine B and cyanobacterial cells within 2 hours.

MgO-La2O3 mixed metal oxides heterostructure catalysts for photodegradation of dyes pollutant: synthesis, characterization and artificial intelligence modelling

In the present work, we prepared MgO-La₂O₃-mixed-metal oxides (MMO) as efficient photocatalysts for degradation of organic pollutants. First, a series of MgAl-%La-CO₃-layered double hydroxide (LDH) precursors with different contents of La (5, 10, and 20 wt%) were synthesized by the co-precipitation process and then calcined at 600 °C. The prepared materials were characterized by XRD, SEM-EDX, FTIR, TGA, ICP, and UV-vis diffuse reflectance spectroscopy. XRD indicated that MgO, La₂O₃, and MgAl₂O₄ phases were found to coexist in the calcined materials. Also, XRD confirms the orthorhombic-tetragonal phases of MgO-La₂O₃. The samples exhibited a small band gap of 3.0-3.22 eV based on DRS. The photocatalytic activity of the catalysts was assessed for the degradation of two dyes, namely, tartrazine (TZ) and patent blue (PB) as model organic pollutants in aqueous mediums under UV-visible light. Detailed photocatalytic tests that focused on the impacts of dopant amount of La, catalyst dose, initial pH of the solution, irradiation time, dye concentration, and reuse were carried out and discussed in this research. The experimental findings reveal that the highest photocatalytic activity was achieved with the MgO-La₂O₃-10% MMO with photocatalysts with a degradation efficiency of 97.4% and 93.87% for TZ and PB, respectively, within 150 min of irradiation. The addition of La to the sample was responsible for its highest photocatalytic activity. Response surface methodology (RSM) and gradient boosting regressor (GBR), as artificial intelligence techniques, were employed to assess individual and interactive influences of initial dye concentration, catalyst dose, initial pH, and irradiation time on the degradation performance. The GBR technique predicts the degradation efficiency results with R² = 0.98 for both TZ and PB. Moreover, ANOVA analysis employing CCD-RSM reveals a high agreement between the quadratic model predictions and the experimental results for TZ and PB (R² = 0.9327 and Adj-R² = 0.8699, R² = 0.9574 and Adj-R² = 0.8704, respectively). Optimization outcomes indicated that maximum degradation efficiency was attained under the following optimum conditions: catalyst dose 0.3 g/L, initial dye concentration 20 mg/L, pH 4, and reaction time 150 min. On the whole, this study confirms that the proposed artificial intelligence (AI) techniques constituted reliable and robust computer techniques for monitoring and modeling the photodegradation of organic pollutants from aqueous mediums by MgO-La₂O₃-MMO heterostructure catalysts.

Nanocomposite of Ag nanoparticles and deep eutectic solvent-derived carbon dots with oxidase mimicking activity as synergistic bactericidal agent

A new type of nitrogen and chloride co-doped carbon dots (N/Cl-CDs) based on choline chloride-urea-glycine ternary deep eutectic solvents (DESs) was synthesized using a one-step hydrothermal method. The prepared N/Cl-CDs exhibited oxidase-like activity and excellent antibacterial activity against Escherichia coli, Staphylococcus aureus, and methicillin-resistant staphylococcus aureus (MRSA). The addition of silver nanoparticles (Ag NPs) (i.e., N/Cl-CDs + Ag NPs) to the N/Cl-CDs also significantly enhanced the oxidase and antibacterial activity. The nanocomposite (1.8 mg ml^-1 ) completely inactivated 10⁵ CFU ml^-1 of MRSA in 90 min. E. coli and S. aureus were labeled with the N/Cl-CDs, enabling multicolor fluorescence imaging at different excitation wavelengths. The nanocomposites have high antibacterial efficiency as a new bactericidal agent, as well as application potential with good biocompatibility and low toxicity.

In-situ synthesis of biochar modified PbMoO4: An efficient visible light-driven photocatalyst for tetracycline removal

For highly efficient photocatalytic remediation of organic pollutants, broad-spectrum light response and effective charge separation are two key goals. To achieve these goals, a novel biochar (BC) modified PbMoO₄ composite catalyst was successfully synthesized in situ by combining coprecipitation with pyrolysis treatment of poplar sawdust and the technical feasibility of degradation of tetracycline (TC) with compound photocatalyst prepared from recovered agricultural and forestry residues was preliminarily demonstrated. The characterization demonstrated that the presence of BC narrowed the bandgap, enhanced visible light absorption as well as facilitated charge separation. Three composites (with the mass ratio of PbMoO₄ to BC = 1:4; 1:1; and 4:1, respectively) displayed higher activity than pure PbMoO₄. The results showed that the composite with the PbMoO₄ to BC ratio of 1:4 exhibited the best photocatalytic activity, for 150 mg L^-1 TC the removal rate was 61.0%, and the rate constant was 8.1 × 10^-3 min^-1, while the photocatalytic activity of PbMoO₄ was 26.0% and 3.9 × 10^-3 min^-1. The reactions in the presence of radical quenchers indicated that holes (h⁺) and superoxide radicals (O₂^-) were the dominant active species for photodegradation. In different water matrices, for 150 mg L^-1 TC solution the photocatalytic activity of optimal photocatalyst decreased as follows: ultrapure water > artificial sewage > farm sewage > municipal sewage. Moreover, the catalyst exhibited good stability over five cycles. Therefore, BC doped PbMoO₄ provides a useful strategy for improving the photocatalytic ability of PbMoO₄-based photocatalysts and offers a promising method for water purification.

Oxygen-rich bismuth oxybromide nanosheets coupled with Ag2O as Z-scheme nano-heterostructured plasmonic photocatalyst: Solar light-activated photodegradation of dye pollutants

In this research to enhance the photocatalytic activity of Bi₂₄O₃₁Br₁₀, precipitation fabrication of the Z-scheme heterojunction with Ag-Ag₂O has been investigated. The characterizations were carried out by XRD, FESEM, TEM, EDX, BET-BJH, DRS and pH_pzc analyzes. The Ag-Ag₂O/Bi₂₄O₃₁Br₁₀ Z-scheme heterojunction nanophotocatalyst with weighted ratio of 3:1 exhibited the wide absorption in the visible light region and displayed the high photocatalytic activity for the photodegradation of acid orange 7 (96.5%, 94.1% and 90% for 10, 20 and 60 mg/L, respectively after 120 min) and eosin yellow (for 10 mg/L: 81.5%) compared to the other composites and pure Bi₂₄O₃₁Br₁₀ and Ag-Ag₂O samples. The highly enhanced photocatalytic activity of Ag-Ag₂O/Bi₂₄O₃₁Br₁₀ (3:1) was assigned to the surface plasmon resonance effect of silver nanoparticles, high solar-light-response and the structure of Z-scheme heterojunction, which effectively reduces the recombination of the photogenerated charge carriers. Moreover Ag-Ag₂O/Bi₂₄O₃₁Br₁₀(3:1) Z-scheme heterojunction nanophotocatalyst exhibited the good photocatalytic activity even after 4 runs.

Photocatalytic Activity of S-Scheme Heterostructure for Hydrogen Production and Organic Pollutant Removal: A Mini-Review

Finding new technologies and materials that provide real alternatives to the environmental and energy-related issues represents a key point on the future sustainability of the industrial activities and society development. The water contamination represents an important problem considering that the quantity and complexity of organic pollutant (such as dyes, pesticides, pharmaceutical active compounds, etc.) molecules can not be efficiently addressed by the traditional wastewater treatments. The use of fossil fuels presents two major disadvantages: (1) environmental pollution and (2) limited stock, which inevitably causes the energy shortage in various countries. A possible answer to the above issues is represented by the photocatalytic technology based on S-scheme heterostructures characterized by the use of light energy in order to degrade organic pollutants or to split the water molecule into its components. The present mini-review aims to outline the most recent achievements in the production and optimization of S-scheme heterostructures for photocatalytic applications. The paper focuses on the influence of heterostructure components and photocatalytic parameters (photocatalyst dosage, light spectra and intensity, irradiation time) on the pollutant removal efficiency and hydrogen evolution rate. Additionally, based on the systematic evaluation of the reported results, several perspectives regarding the future of S-scheme heterostructures were included.

Enhanced norfloxacin degradation by visible-light-driven Mn3O4/γ-MnOOH photocatalysis under weak magnetic field

A valence-state heterojunction Mn₃O₄/γ-MnOOH was synthesized for norfloxacin (NOR) degradation under concurrent visible light and magnetic field. The charge carriers could transfer between the valence state components facilely, inhibiting recombination of photo-induced electron-holes significantly. Efficient NOR degradation by Mn₃O₄/γ-MnOOH was realized at 98.8% (rate constant of 0.0720 min^-1) within 60 min under magnetic field assisted visible light. In neutral media, the positively charged NOR and negatively charged Mn₃O₄/γ-MnOOH would arrange in an oriented manner in the presence of magnetic field, providing more active sites for NOR during photocatalysis. Moreover, the opposite Lorentz forces contributed to the attractive interactions between NOR and Mn₃O₄/γ-MnOOH, accelerating NOR degradation with lower active energy. Quenching experiment showed that ∙O₂^- and h⁺ played dominant roles in NOR degradation. Attractively, this study shed new lights on an innovative strategy of magnetic field assisted photocatalysis for refractory contaminants remediation from water.