Biomass derived reduced-graphene-oxide supported α-Fe2O3/ZnO S-scheme heterostructure: Robust photocatalytic wastewater remediation

Ag-Cu2O Supported Biomass-Derived rGO for Catalyzing Suzuki-Miyaura Cross-Coupling

The search for cost-effective, efficient, and ecofriendly heterogeneous catalysts for the Suzuki-Miyaura reaction is crucial due to challenges with expensive, toxic homogeneous catalysts. This study centrally aims at crafting a pioneering green catalyst by adorning reduced graphene oxide (rGO), sourced from basil seeds (Ocimum basilicum L.), with an Ag-Cu2O composite structure. Comprehensive characterization of the Ag-Cu2O/rGO nanocomposite was conducted through FTIR, SEM, hHR-TEM, EDS, XPS, XRD, TGA, and N2 adsorption/desorption analyses. Results showed that nanosized Ag-Cu2O particles were partially integrated into rGO sheets derived from basil seeds, acting as active species for oxidative addition with aryl halides in the SMR. The catalytic efficacy of this robust nanocatalyst was assessed in Suzuki-Miyaura cross-coupling reactions, targeting the synthesis of biaryls employing various aryl halides and aryl boronic acids. The findings underscore that the Ag-Cu2O/rGO nanocatalyst manifests rapid reaction kinetics (15 min) alongside commendable yields (99%). The Ag-Cu2O/rGO demonstrates impressive recyclability, maintaining catalytic efficiency over four cycles. Utilizing it as a green substrate for metal loading highlights its potential, offering well-defined coordination sites. This approach facilitates stable heterogeneous catalyst fabrication, crucial for significant bond formations. Notable features include broad applicability, exceptional functional tolerance, scalability, and practicality. Moreover, it holds promise for automating safe processes and enabling efficient late-stage functionalization of complex molecules with moderate to high efficiency, presenting promising prospects for various applications in chemical synthesis.

Sustainable conversion of polyethylene plastic bottles into terephthalic acid, synthesis of coated MIL-101 metal-organic framework and catalytic degradation of pollutant dyes

Persistent environmental colored compounds, resistant to biodegradation, accumulate and harm eco-systems. Developing effective methods to break down these pollutants is crucial. This study introduces Ag-MIL-101 (Ag-MIL-101) as a composite and reusable catalyst that efficiently degrades specific colored organic pollutants (COPs) like Methylene blue (MB), 4-Nitrophenol (4-NP), and 4-Nitroaniline (4-NA) using sodium borohydride at room temperature. The MIL-101 was synthesized using Terephthalic acid (TPA) derived from the degradation of Polyethylene Terephthalate (PET) plastic waste, with the assistance of zinc chloride. To further investigation, the kinetics of degradation reaction was studied under optimized conditions in the presence of Ag-MIL-101 as catalyst. Our results demonstrated the remarkable efficiency of the degradation process, with over 93% degradation achieved within just 8 min. The catalyst was characterized using FTIR, XRD, FESEM, and TEM. In this study, the average particle size of Ag-MIL-101 was determined using SEM and XRD analysis. These methods allow us to accurately and precisely determine the particle size. We determined the reaction rate constants for the degradation of each COP using a pseudo first-order kinetic equation, with values of 0.585, 0.597 and 0.302 min-1 for MB, 4-NP, and 4-NA, respectively. We also evaluated the recyclability of the catalyst and found that it could be reused for up to three cycles with only a slight decrease in efficiency (10-15%). Overall, our findings highlight the promising application of Ag-MIL-101 as an effective catalyst for the degradation of COPs, emphasizing the importance of optimizing reaction conditions to achieve enhanced efficiency.

Recycled gold-reduced graphene oxide nanocomposite for efficient adsorption and photocatalytic degradation of crystal violet

In this study, gold-reduced graphene oxide (Au@rGO) nanocomposite has been synthesized by repurposing electronic waste and dry batteries. This innovative approach involved utilizing the graphite rod from dry batteries to produce reduced graphene oxide (rGO), which was subsequently modified through the incorporation of gold nanoparticles obtained from recycled electronic waste. This methodology marks a significant breakthrough in electronic waste recycling, presenting a cost-effective and sustainable means of creating novel nanocomposites for applications in photocatalysis and adsorption, particularly in the removal of crystal violet (CV) from aqueous media. The synthesized Au@rGO nanocomposite was characterized using X-ray diffraction, scanning electron microscopy, energy dispersed X-ray, and N2 adsorption/desorption. Parameters that affect the adsorption and photocatalytic degradation of CV dye have been studied in detail. The optimal conditions for CV adsorption and photocatalytic degradation were pH of 10, equilibrium time of 30 min, CV concentration of 10 mg/L and adsorbent dosage of 40 mg. Furthermore, the isotherm and kinetics of CV removal were also studied. The removal of CV dye using adsorption and photocatalytic degradation techniques reached 95% and 99%, respectively. Consequently, the results showed that photocatalytic degradation of CV dye onto the mesoporous Au@rGO nanocomposite is more proper way than the adsorption technique for removing the CV dye from aqueous media. The designed photocatalyst has high efficiency and it can be reused and activated several times so it can be used in real water treatment applications.

Enhanced synergistic system for the persulfate activation under visible light using novel N-ZnO photocatalyst supported on Lantana camara-based biochar

Herein, a novel nitrogen-doped ZnO photocatalyst supported on biochar (N-ZnO@LBC) was synthesized using the Lantana camera as a green source of biochar. The synthesized photocatalyst was applied as an activator of persulfate (PS) for the photodegradation of methylene blue (MB) under visible light irradiation. The properties of the synthesized photocatalyst were explored before and after photocatalysis using different characterization analyses. The results revealed that the nitrogen doping of ZnO@LBC could reduce the band gap energy from 2.83 eV to 2.78 eV resulting in higher activity under visible light. The synergetic effect of the N-ZnO@LBC/PS/visible process was investigated under various reaction conditions. Surprisingly, about 95.7% of MB photodegradation could be achieved using N-ZnO@LBC/PS/visible process under optimal conditions. Moreover, a prediction model with an excellent correlation between the actual and predicted data (R2 = 0.9844) was established to forecast MB removal. Interestingly, the scavenging tests exhibited that various reactive species could induce MB degradation in an order of O2-• > h+ > SO4-• >•OH with the highest contribution of O2-•. Additionally, the presence of functional hydroxyl groups in the N-ZnO@LBC structure could lead to the generation of additional radicals as confirmed by FT-IR analysis after photocatalysis. The reusability test showed that the photocatalyst could be reused for up to five cycles without a significant loss in the photocatalytic activity indicating its high stability. The cost of wastewater treatment by N-ZnO@LBC/PS/Visible process was estimated to be US$ 9.79/m3 based on an economic analysis. It worth mentioning that the proposed process was investigated for the degradation of other dyes including Congo red (CR) and methyl orange (MO) and the efficiencies were 65.41% and 59.23% for CR and MO, respectively. Overall, the proposed process could be a promising and cost-effective approach for the degradation of various dyes in real applications.

Magnetic Carbon Quantum Dots/Iron Oxide Composite Based on Waste Rice Noodle and Iron Oxide Scale: Preparation and Photocatalytic Capability

To provide an economical magnetic photocatalyst and introduce an innovative approach for efficiently utilizing discarded waste rice noodle (WRN) and iron oxide scale (IOS), we initially converted WRN into carbon quantum dots (CQDs) using a hydrothermal method, simultaneously calcining IOS to obtain iron oxide (FeOx). Subsequently, we successfully synthesized a cost-effective, magnetic CQDs/FeOx photocatalytic composite for the first time by combining the resulting CQDs and FeOx. Our findings demonstrated that calcining IOS in an air atmosphere enhanced the content of photocatalytically active α-Fe2O3, while incorporating WRN-based CQDs into FeOx improved the electron-hole pair separation, resulting in increased O2 reduction and H2O oxidation. Under optimized conditions (IOS calcination temperature: 300 °C; carbon loading: 11 wt%), the CQDs/FeOx composite, utilizing WRN and IOS as its foundation, exhibited exceptional and reusable capabilities in photodegrading methylene blue and tetracycline. Remarkably, for methylene blue, it achieved an impressive degradation rate of 99.30% within 480 min, accompanied by a high degradation rate constant of 5.26 × 10-3 min-1. This composite demonstrated reusability potential for up to ten photocatalytic cycles without a significant reduction in the degradation efficiency, surpassing the performance of IOS and FeOx without CQDs. Notably, the composite exhibited strong magnetism with a saturation magnetization strength of 34.7 emu/g, which enables efficient and convenient recovery in photocatalytic applications. This characteristic is highly advantageous for the large-scale industrial utilization of photocatalytic water purification.

Antibiotics oxytetracycline removal by photocatalyst titanium dioxide and graphitic carbon nitride in aquaculture wastewater

The surge in the use of antibiotics, especially in aquaculture, has led to development of antibiotic resistance genes, which will harm environmental and public health. One of the most commonly used antibiotics in aquaculture is oxytetracycline (OTC). Employing photocatalysis, this study compared OTC degradation efficiency of two different types of common photocatalysts, TiO₂ and graphitic carbon nitride (GCN) in terms of their photochemical properties and underlying photocatalytic mechanism. For reference purpose, self-synthesized GCN from urea precursor (GCN-Urea) and commercial GCN (GCN-Commercial) were both examined. OTC adsorption-photocatalysis removal rates in pure OTC solution by TiO₂, GCN-Urea and GCN-Commercial were attained at 95%, 60% and 40% respectively. Photochemical properties evaluated included light absorption, band gap, valence and conduction band positions, photoluminescence, cyclic voltammetry, BET surface area and adsorption capability of the photocatalysts. Through the evaluations, this study provides novel insights towards current state-of-the-art heterogeneous photocatalytic processes. The electron-hole recombination examined by photoluminescence is not the key factor influencing the photocatalytic efficacies as commonly discussed. On the contrary, the dominating factors governing the higher OTC degradation efficiency of TiO₂ compared to GCN are the high mobility of electrons that leads to high redox capability and the high pollutant-photocatalyst affinity. These claims are proven by 86% and 40% more intense anodic and cathodic cyclic voltammetry curve peaks of TiO₂ as compared to both GCNs. OTC also demonstrated 1.7 and 2.3 times higher affinity towards TiO₂ than GCN-Urea and GCN-Commercial. OTC removal by TiO₂ in real aquaculture wastewater only achieved 50%, due to significant inhibition effect by dissolved solids, dissolved organic matters and high ionic contents in the wastewater.