4-Nitrophenol (4-NP) is a high-priority industrial pollutant and is known to cause adverse effects to the human body. Owing to this, detoxification of water contaminated with 4-NP is highly essential. The photocatalytic degradation of 4-NP is considered an efficient method. However, for this purpose, mostly expensive reagents that can cause adverse effects on the environment are used. Therefore, for the treatment of 4-NP contaminated water, an eco-friendly method is considerably required. To meet this requirement, here, we have synthesized nitrogen-doped reduced graphene oxide (NrGO) covalently coupled with carbon modified porous graphitic carbon nitride/ sulfur-doped graphitic carbon nitride (g-C 3 N 4 /Sg-C 3 N 4 ) isotype heterojunction (g−g PSCN) nanocatalysts. The photocatalytic performance of the prepared NrGO/g−g PSCN nanocatalysts has been examined by the reductant-free reduction and H 2 O 2 -assisted degradation of 4-NP. The results of the photocatalytic performance suggest that the catalytic activity is strongly influenced by the presence of the NrGO content. For the 4NrGO/g−g PSCN nanocatalyst, the highest catalytic activity is observed, which is 12.25 and 2.92 times higher than that of g−g PSCN toward the reduction and degradation of 4-NP, respectively. The influence of various environmental factors such as solution pH, temperature, and the presence of competitive ions on the degradation rate of 4-NP have also been investigated. The reactive species involved during the reactions have also been explored, and a plausible mechanism has been proposed for both reactions. The durability and stability of the nanocatalysts have been examined, and the obtained results reveal that the nanocatalysts can endure the experimental conditions even after eight successive cycles. This approach opens up an avenue for the fabrication of graphitic carbon nitrite-based metal-free heterogeneous nanocatalysts with high catalytic performance.

Contamination of surface water by extremely poisonous arsenic (As) species due to indiscriminant disposal of industrial and mining waste is a serious concern worldwide. Considering the above apprehension, maghemite (γ-Fe2O3) and graphene oxide (GO) embedded in a polyacrylonitrile (PAN) polymer nanofiber matrix (PAN/GO/γ-Fe2O3) was successfully fabricated by electrospinning technique. Successful incorporation of γ-Fe2O3 and GO into the PAN polymer matrix via the electrospinning process was investigated by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and Raman analytical techniques. Magnetic and thermal properties of the prepared nanofibers were studied by vibrating sample magnetometer (VSM) and thermogravimetry–derivative thermogravimetry (TG-DTG) analysis. The specific surface area of the prepared adsorbent was found to be 30.24 m2/g, which was determined by Brunauer, Emmett, and Teller (BET) analysis. Batch adsorption experiments were conducted to study the effect of various parameters such as the effect of adsorbent dosage, pH, time, concentration, and coexisting ions during arsenate ion (As­(V)) adsorption. The kinetic and isotherm model indicates that the adsorption process follows the pseudo-second-order and Langmuir isotherm model, respectively, which reveals the chemisorption mechanism. From the Langmuir plot, the maximum adsorption capacity was found to be 36.1 mg/g, which is considerably greater than the earlier reported results. The stability and reusability of the membrane were demonstrated by five successive sorption–desorption cycles. After all, the As­(V) loaded PAN/GO/γ-Fe2O3 nanofiber membrane was analyzed by FTIR, TEM-EDAX, and X-ray photoelectron spectroscopy (XPS) analytical technique to elucidate the possible adsorption mechanism, which suggests electrostatic attraction and surface complexation are the main driving forces for As­(V) removal.

Designing a heterostructure photocatalyst material having high porosity with enhanced specific surface area and optoelectrical properties is one of the significant approaches toward the decontamination of hazardous organic contaminants and water-splitting reactions under visible light irradiation. In this study, a silver-nanoparticle-decorated g-C3N4 (ACN)/MIL-53­(Fe) photocatalyst was developed having an improved surface area by a facile solvothermal approach. The as-synthesized pure and composite materials are characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and photoluminescence analysis. It is observed that 15% of ACN-20 modified MIL-53 (MACN-15) exhibits improved charge separation between the photoinduced electron and hole pairs which eventually shows the highest photocatalytic applications in rhodamine B (RhB) degradation, photocatalytic Cr­(VI) reduction, and photocatalytic hydrogen evolution from water splitting. The optimal photocatalyst (MACN-15) shows 98% of RhB degradation and 95% of Cr­(VI) reduction efficiency within 60 min of visible light irradiation. The MACN-15 nanocomposite also exhibits a superior rate of H2 evolution (2.891 mmol g–1 h–1) with a specific conversion efficiency of 14.8%. A possible mechanism is also predicted for the MACN-15 nanocomposite in multimodal photocatalytic applications.

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