Synthesis and characterization of Graphitic Carbon Nitride/Mesoporous Nano-Silica (g-C3N4/KCC-1) nanocomposite as a novel highly efficient and recyclable photocatalyst for degradation of antibiotic in aqueous solution

Fabrication of a CuS-cocatalyst-supported g-C3N4 nanosheet composite photocatalyst with improved performance in the photocatalytic reduction of CO2

Carbon dioxide (CO2) is not only a greenhouse gas but also an abundant carbon resource. By using solar energy to reduce CO2 into high-value hydrocarbons via photocatalysis, we can mitigate the greenhouse effect and enable energy recycling. In this paper, a two-step calcination process was employed to thermally exfoliate graphite-phase carbon nitride (g-C3N4) into ultrathin nanosheets, after which the CuS co-catalyst was loaded onto the g-C3N4 surface using a one-step hydrothermal method. The ultrathin nanosheet structure of g-C3N4 can increase the specific surface area of the composite material and improve the anchoring of active components and CO2 adsorption sites. CuS, acting as a co-catalyst, can capture photogenerated electrons from the g-C3N4 conduction band, thereby enhancing the separation and migration of photogenerated charges. Moreover, the interfacial charge transfer (IFCT) mechanism of CuS enhances the efficiency of separating photogenerated electrons and holes. The prepared 10CuS/g-C3N4 composite photocatalyst, loaded with 10 wt% CuS, has significantly improved CO2 photoreduction performance. The highest CO yield reached 15.34 μmol g-1. This work provides guidance for developing low-cost artificial photosynthesis to utilize CO2 as a resource.

Magnetic Fe-doped TiO2@Fe3O4 for metronidazole degradation in aqueous solutions: Characteristics and efficacy assessment

Antibiotics present in aquatic environments can contribute to the emergence of antibiotic-resistant bacterial strains, posing potential threats to public health. Therefore, efficient strategies to remove these compounds from water systems are essential to reduce both ecological and human health risks. This research aimed to assess the photocatalytic removal efficiency of metronidazole (MET) from an aqueous solution using a 15-W bare UVC lamp and magnetic nanocatalysts (Fe-doped TiO2@Fe3O4), which were synthesized using the sol-gel technique. Furthermore, scanning electron microscopy with integrated energy dispersive X-ray analysis (SEM/EDX), X-ray diffractometry (XRD), Differential reflectance spectroscopy (DRS), vibrating sample magnetometer (VSM), and Fourier transform infrared spectroscopy (FTIR) analysis were carried out to characterize the synthesized nanocatalysts. The influence of several factors, such as pH, initial MET, and nanocatalysts concentrations during reaction times of 15-120 min, was studied. The characterization results confirmed that Fe and Ti were successfully integrated into the Fe- doped TiO2@Fe3O4 nanocomposite. Highest MET degradation efficiency (99.37 %) was observed at a pH of 3, with an initial MET concentration of 60 mg/L, nanoparticle dosage of 800 mg/L, and a reaction time of 90 min. The stability of the nanocatalyst was acceptable. The results suggest that OH ions may play a crucial role in the degradation of MET demonstrating photocatalytic degradation can be an effective way to remove MET from water resources. This research sets a precedent for future endeavors aimed at harnessing photocatalysis for environmental remediation of pharmaceutical pollutants.

Dendritic mesoporous nanoparticles for the detection, adsorption, and degradation of hazardous substances in the environment: State-of-the-art and future prospects

Equipped with hierarchical pores and three-dimensional (3D) center-radial channels, dendritic mesoporous nanoparticles (DMNs) make their pore volumes extremely large, specific surface areas super-high, internal spaces especially accessible, and so on. Other entities (like organic moieties or nanoparticles) can be modified onto the interfaces or skeletons of DMNs, accomplishing their functionalization for desirable applications. This comprehensive review emphasizes on the design and construction of DMNs-based systems which serve as sensors, adsorbents and catalysts for the detection, adsorption, and degradation of hazardous substances, mainly including the construction procedures of brand-new DMNs-based materials and the involved hazardous substances (like industrial chemicals, chemical dyes, heavy metal ions, medicines, pesticides, and harmful gases). The sensitive, adsorptive, or catalytic performances of various DMNs have been compared; correspondingly, the reaction mechanisms have been revealed strictly. It is honestly anticipated that the profound discussion could offer scientists certain enlightenment to design novel DMNs-based systems towards the detection, adsorption, and degradation of hazardous substances, respectively or comprehensively.

Biosynthesis of MnFe2O4@TiO2 magnetic nanocomposite using oleaster tree bark for efficient photocatalytic degradation of humic acid in aqueous solutions

The presence of humic acid compounds in water resources, as one of the precursors of Trihalomethanes and Holoacetic acids, causes health problems for many communities. The aim of this research study was to investigate the photocatalytic degradation efficiency of humic acid using MnFe₂O₄@TiO₂ nanoparticles which produced by green synthesis method. The synthesis of metal nanoparticles using plant extracts and the study of their catalytic performance is a relatively new topic. Many chemical techniques have been proposed for the synthesis of MnFe₂O₄@TiO₂ nanoparticles, but green synthesis has received much attention due to its availability, simplicity, and non-toxicity. The properties of synthesized nanoparticles were determined by SEM, FT-IR, XRD, EDS, and DLS analysis. The results of the study showed that under optimal experimental conditions (pH = 3, nanocomposite dose = 0.03 g/L, humic acid initial concentration = 2 mg/L, and contact time = 20 min), it is possible to achieve maximum degradation of humic acid. Therefore; MnFe₂O₄@TiO₂ nanoparticles have high efficiency for removing of humic acid from aqueous solutions under UV light.

MIL-100(Fe)/g-C3N4 composites with enhanced photocatalytic activity for UO22+ reduction under visible light

As a clean energy source, nuclear energy can gradually replace traditional fossil energy sources, and is an important means to achieve the "double carbon goal". Uranium-containing wastewater is inevitable in the development of nuclear energy. The composites MIL/CNx of MOF material MIL-100(Fe) and carbon nitride (CN) were obtained by a simple solvo-thermal method using iron nitrate, homophthalic acid and CN. The material MIL-100(Fe) with high specific surface area was compounded with CN to increase the in-plane adsorption sites, which could adsorb 30% of uranium in solution during the dark reaction. The close interfacial contact of the two materials effectively inhibited the complexation of photo-generated electrons and holes and promotes electron migration. These two synergistic effects improved their overall photocatalytic reduction capacity, which could reduce 97% of UO₂²⁺ in solution in 20 min. The UO₂²⁺ removal efficiency of MIL/CN_0.1 was 2.3 and 1.6 times higher than that of CN and MIL-100(Fe), respectively. In addition, MIL/CN_0.1 was stable in reducing uranium during the five cycles of the experiment.

Synthesis and characterization of g-C3N4-CoFe2O4-ZnO magnetic nanocomposites for enhancing photocatalytic activity with visible light for degradation of penicillin G antibiotic

Nowadays, antibiotic water pollution is an increasingly dangerous environmental threat. Thus, water treatment is essential for their reduction and removal. In recent decades, photocatalysts have attracted much attention due to their influential role in solving this issue. The photocatalytic process, which is one of the green processes and part of advanced oxidation processes, can be a good choice for treating contaminated water containing non-degradable organic matter. However, the design of high-performance photocatalysts under free sunlight can be challenging. In this study, g-C₃N₄-Ca, Mg codoped CoFe₂O₄-ZnO (gCN-CFO-ZnO) nanocomposite photocatalyst was applied in removing penicillin G (PENG) from drug effluents. Also, the effects of contaminant concentration, initial pH, irradiation time, and zinc oxide ratio in the nanocomposites were investigated. The hydrothermal method was carried out to prepare the appropriate composites. Then, the obtained products were characterized by powder X-Ray diffraction (PXRD), Fourier-transform infrared spectroscopy (FT-IR), Raman, field-emission scanning and transmission electron microscope (FE-SEM&TEM), energy dispersive X-Ray (EDX), diffuse reflectance spectroscopy (DRS), vibrating sample magnetometer (VSM) and Photoluminescence (PL) techniques. According to the findings, the degradation of PENG in an acidic environment occurred remarkably; under the same conditions, with decreasing pH from 9 to 5 in the gCN-CFO-ZnO (33.33%) nanocomposite, the degradation efficiency grew from 47% to 74%. Also, the degradation rate of PENG in gCN-CFO-ZnO (16.66%) and gCN-CFO-ZnO (50%) nanocomposites under optimal conditions (pH = 5, PENG the concentration of 10 ppm, and irradiation time of 120 min) was achieved 52% and 60%, respectively. Further, gCN-CFO-ZnO (33.33%) nanocomposite showed higher efficiency in PENG degradation compared to the other two nanocomposites.

Photocatalytic Reduction of Hexavalent Chromium Using Cu3.21Bi4.79S9/g-C3N4 Nanocomposite

The photocatalytic reduction of hexavalent chromium, Cr(VI), to the trivalent species, Cr(III), has continued to inspire the synthesis of novel photocatalysts that are capable of achieving the task of converting Cr(VI) to the less toxic and more useful species. In this study, a novel functionalized graphitic carbon nitride (Cu3.21Bi4.79S9/gC3N4) was synthesized and characterized by using X-ray diffraction (XRD), thermogravimetry analysis (TGA), energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), transmission electron microscope (TEM), and scanning electron microscope (SEM). The composite was used for the photocatalytic reduction of hexavalent chromium, Cr(VI), under visible light irradiation. A 92.77% efficiency of the reduction was achieved at pH 2, using about 10 mg of the photocatalyst and 10 mg/L of the Cr(VI) solution. A pseudo-first-order kinetic study indicated 0.0076 min−1, 0.0286 min−1, and 0.0393 min−1 rate constants for the nanoparticles, pristine gC3N4, and the nanocomposite, respectively. This indicated an enhancement in the rate of reduction by the functionalized gC3N4 by 1.37- and 5.17-fold compared to the pristine gC3N4 and Cu3.21Bi4.79S9, respectively. A study of how the presence of other contaminants including dye (bisphenol A) and heavy-metal ions (Ag(I) and Pb(II)) in the system affects the photocatalytic process showed a reduction in the rate from 0.0393 min−1 to 0.0019 min−1 and 0.0039 min−1, respectively. Finally, the radical scavenging experiments showed that the main active species for the photocatalytic reduction of Cr(VI) are electrons (e−), hydroxyl radicals (·OH−), and superoxide (·O2−). This study shows the potential of functionalized gC3N4 as sustainable materials in the removal of hexavalent Cr from an aqueous solution.

Technological trends in nanosilica synthesis and utilization in advanced treatment of water and wastewater

Water and wastewater treatment applications stand to benefit immensely from the design and development of new materials based on silica nanoparticles and their derivatives. Nanosilica possesses unique properties, including low toxicity, chemical inertness, and excellent biocompatibility, and can be developed from a variety of sustainable precursor materials. Herein, we provide an account of the recent advances in the synthesis and utilization of nanosilica for wastewater treatment. This review covers key physicochemical aspects of several nanosilica materials and a variety of nanotechnology-enabled wastewater treatment techniques such as adsorption, separation membranes, and antimicrobial applications. It also discusses the prospective design and tuning options for nanosilica production, such as size control, morphological tuning, and surface functionalization. Informative discussions on nanosilica production from agricultural wastes have been offered, with a focus on the synthesis methodologies and pretreatment requirements for biomass precursors. The characterization of the different physicochemical features of nanosilica materials using critical surface analysis methods is discussed. Bio-hybrid nanosilica materials have also been highlighted to emphasize the critical relevance of environmental sustainability in wastewater treatment. To guarantee the thoroughness of the review, insights into nanosilica regeneration and reuse are provided. Overall, it is envisaged that this work's insights and views will inspire unique and efficient nanosilica material design and development with robust properties for water and wastewater treatment applications.

g-C3N4: Properties, Pore Modifications, and Photocatalytic Applications

Graphitic carbon nitride (g-C3N4), as a polymeric semiconductor, is promising for ecological and economical photocatalytic applications because of its suitable electronic structures, together with the low cost, facile preparation, and metal-free feature. By modifying porous g-C3N4, its photoelectric behaviors could be facilitated with transport channels for photogenerated carriers, reactive substances, and abundant active sites for redox reactions, thus further improving photocatalytic performance. There are three types of methods to modify the pore structure of g-C3N4: hard-template method, soft-template method, and template-free method. Among them, the hard-template method may produce uniform and tunable pores, but requires toxic and environmentally hazardous chemicals to remove the template. In comparison, the soft templates could be removed at high temperatures during the preparation process without any additional steps. However, the soft-template method cannot strictly control the size and morphology of the pores, so prepared samples are not as orderly as the hard-template method. The template-free method does not involve any template, and the pore structure can be formed by designing precursors and exfoliation from bulk g-C3N4 (BCN). Without template support, there was no significant improvement in specific surface area (SSA). In this review, we first demonstrate the impact of pore structure on photoelectric performance. We then discuss pore modification methods, emphasizing comparison of their advantages and disadvantages. Each method's changing trend and development direction is also summarized in combination with the commonly used functional modification methods. Furthermore, we introduce the application prospects of porous g-C3N4 in the subsequent studies. Overall, porous g-C3N4 as an excellent photocatalyst has a huge development space in photocatalysis in the future.