Facile fabrication of g-C3N4/precipitated silica composite with enhanced visible-light photoactivity for the degradation of rhodamine B and Congo red

Multiaperture g-C3N4@SiO2 to activate peroxydisulfate via visible light for efficient Rhodamine B removal

The sulfate radical-based advanced oxidation process (SR-AOPs) has been verified as a promising method to handle the persistent organic compounds in water using peroxydisulfate (PDS) as oxidant. A Fenton-like process was constructed and showed great potential to remove organic pollutants using visible-light-assisted PDS activation. The g-C₃N₄@SiO₂ was synthesized via thermo-polymerization, and characterized using powder X-ray diffraction (XRD), scanning electron microscope equipped with an energy-dispersive X-ray (SEM-EDX), X-ray photoelectron spectroscopy (XPS), N₂ adsorption-desorption, Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH) method, photoluminescence (PL), transient photocurrent, and electrochemical impedance. Photocatalytic performance was demonstrated using the removal rate of Rhodamine B (RhB), and 96.08% RhB was removed from the solution within 50 min (10 mg/L in 200 mL, g-C₃N₄@SiO₂ = 0.25 g/L, pH = 6.3, PDS = 1 mmol/L). The free radical capture experiment proved that HO^•, h⁺, [Formula: see text] and [Formula: see text] were generated and removed RhB. The cyclic stability of g-C₃N₄@SiO₂ has also been studied, and the result shows no noticeable difference in the six cycles. The system of visible-light-assisted PDS activation might provide a novel strategy for wastewater treatment and must be an environment-friendly catalyst.

Construction of novel g-C3N4 coupled efficient Bi2O3 nanoparticles for improved Z-scheme photocatalytic removal of environmental wastewater contaminant: Insight mechanism

Recently, the major environmental pollution produced by the release of wastewater in liquid type is one of the most extensive forms of foremost pollution in water ecosystems. In this article, the Bi₂O₃/g-C₃N₄ nanocomposite with a direct Z-scheme was effectively obtained by a facile hydrothermal system. The crystal structures, surface morphology, chemical composition, and the optical belongings of the as-obtained composite catalysts were examined by Power XRD, FT-IR spectra, High-resolution XPS spectra, FE-SEM images with EDX spectra, High-resolution TEM images, UV-Vis DRS, and PL spectra respectively. Furthermore, the photocatalytic performance was assessed by the degradation of aqueous Rhodamine B (Rh B) dye under visible-light exposure. The Bi₂O₃/g-C₃N₄ composite photocatalysts (PCs) showed the maximum photo-degradation efficiency through a rate constant value of 0.0149 min^-1, which is 4.9 and 5.3 folds superior to Bi₂O₃, and GCN, respectively. The better GBO2 nanocomposite PCs showed a superior photocatalytic degradation performance (>82%) of aqueous Rh B dye after five successive recycles. Moreover, based on these outcomes of the radical scavenging test, a direct and effective Z-scheme photocatalytic charger transfer mechanism was also projected. Finally, the reusability of the as-obtained Bi₂O₃/g-C₃N₄ nanocomposite has better stability and reusability, which was a favourable applicant for wastewater handling.

Facile fabrication of three-dimensional nanofibrous foams of cellulose@g-C3N4@Cu2O with superior visible-light photocatalytic performance

In this work, a unique three-dimensional nanofibrous foam of cellulose@g-C₃N₄@Cu₂O was prepared via electrospinning followed by a foaming process. A cellulose solution in DMAc/LiCl containing g-C₃N₄ and CuSO₄ was applied for electrospinning, while aqueous alkali was used as the coagulation bath. The solidification of electrospun cellulose/g-C₃N₄ nanofibers would be accompanied with in-situ formation of Cu(OH)₂ nanoparticles. Interestingly, the hydrogen gas (H₂) generated from NaBH₄ could transform the two-dimensional membrane into a three-dimensional foam, leading to the increased specific surface area and porosity of the material. Meanwhile, the Cu(OH)₂ nanoparticles attached on the electrospun nanofibers were reduced to Cu₂O to form a p-n heterostructure between Cu₂O and g-C₃N₄. The as-prepared cellulose@g-C₃N₄@Cu₂O foam exhibited a high degradation efficiency (99.5 %) for the dye of Congo Red under visible light radiation. And ·O^2- was discovered to be the dominant reactive species responsive for dye degradation. Moreover, the cellulose@g-C₃N₄@Cu₂O could maintain its initial degradation efficiency even after seven cycles of reuse, suggesting the excellent stability and cycling performance.

Natural coal gangue as a stable catalyst to activate persulfate: tetracycline hydrochloride degradation and its explored mechanism

The surface-bonded hydroxyl groups on CG play the dominant role in PS activation and TC removal.

Adsorption of metals from oil sands process water (OSPW) under natural pH by sludge-based Biochar/Chitosan composite

Some metals in oil sands process water (OSPW) are potential threats to human health and the environment. Hence, the removal of excess metals from OSPW is of great significance. In this study, anaerobic sludge waste from a wastewater treatment plant, was reused to prepare sludge-based biochar. A Biochar/Chitosan (Biochar/CS) adsorbent with excellent removal efficiency for metals (Cr, Cu, Se and Pb) in real OSPW was prepared through a facile hydrothermal method. The structural properties of the synthesized Biochar/CS composite were characterized via X-ray diffraction (XRD), scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) method. This study reports for the first time the removal of metals from OSPW under natural pH using Biochar/CS adsorbent. The composite exhibited a higher removal efficiency towards Cr (83.9%), Cu (97.5%), Se (87.9%) and Pb (94.3%) when the initial concentrations of Cr, Cu, Se and Pb were 0.02914, 0.06185, 0.00800 and 0.00516 mg/L, respectively, at a dosage of 0.5 g/L, compared with biochar or chitosan alone. The possible adsorption mechanism was proposed, and the enhanced removal ability was due to the improved specific surface area and pore volume, which increased by about 20 and 14 times as compared with chitosan. Functional groups in the composite, such as -NH₂, -OH and some oxygen containing groups, were also responsible for the enhanced removal ability, which also might be the reason for the better performance of the composite than biochar alone due to the lack of functional groups on the biochar. Moreover, the adsorption process was best modelled by the Freundlich model, pseudo second order and intraparticle diffusion kinetic models. The results indicated that chemical adsorption might play the dominant role in the removal process. Overall, the Biochar/CS composite would be a promising and effective adsorbent for metals removal, owing to its advantages of being cost-effective and environmentally friendly.

Solar Light-Irradiated Photocatalytic Degradation of Model Dyes and Industrial Dyes by a Magnetic CoFe2O4-gC3N4 S-Scheme Heterojunction Photocatalyst

Magnetic CoFe₂O₄-gC₃N₄ nanocomposites were successfully synthesized, and their photocatalytic activities toward the decomposition of model synthetic dyes (e.g., methylene blue, methyl orange, and Congo red) in the presence of H₂O₂ were evaluated under simulated solar light irradiation. The 50CoFe₂O₄-50gC₃N₄ nanocomposite exhibited the highest catalytic activity. The catalytic activity of 50CoFe₂O₄-50gC₃N₄ toward the photodegradation of some industrially used dyes (such as Drimaren Turquoise CL-B p, Drimaren Yellow CL-2R p, and Drimaren Red CL-5B p) was also examined, and the catalyst exhibited its capability to decompose the industrial dyes completely. An aqueous mixture of these dyes was prepared to mimic the dye-containing wastewater, which was fully photodegraded within 30 min. 50CoFe₂O₄-50gC₃N₄ also exhibited facile magnetic separability from the reaction mixture after the accomplishment of photocatalysis reaction and stable performance after five cycles. The high photocatalytic efficiency to degrade several dyes, including dyes used in textile industries, under solar light irradiation makes 50CoFe₂O₄-50gC₃N₄ a promising photocatalyst for the treatment of dye-containing wastewater discharged from industries.

Synthesis of Novel Kaolin-Supported g-C3N4/CeO2 Composites with Enhanced Photocatalytic Removal of Ciprofloxacin

Herein, novel ternary kaolin/CeO₂/g-C₃N₄ composite was prepared by sol-gel method followed by hydrothermal treatment. The self-assembled 3D “sandwich” structure consisting of kaolin, CeO₂ and g-C₃N₄ nanosheets, was systematically characterized by appropriate techniques to assess its physicochemical properties. In the prerequisite of visible-light irradiation, the removal efficiency of ciprofloxacin (CIP) over the kaolin/CeO₂/g-C₃N₄ composite was about 90% within 150 min, 2-folds higher than those of pristine CeO₂ and g-C₃N₄. The enhanced photocatalytic activity was attributed to the improved photo-induced charge separation efficiency and the large specific surface area, which was determined by electrochemical measurements and N₂ physisorption methods, respectively. The synergistic effect between the kaolin and CeO₂/g-C₃N₄ heterostructure improved the photocatalytic performance of the final solid. The trapping and electron paramagnetic resonance (EPR) experiments demonstrated that the hole (h⁺) and superoxide radicals (•O₂⁻) played an important role in the photocatalytic process. The photocatalytic mechanism for CIP degradation was also proposed based on experimental results. The obtained results revealed that the kaolin/CeO₂/g-C₃N₄ composite is a promising solid catalyst for environmental remediation.

Fabrication of Novel Cyanuric Acid Modified g-C3N4/Kaolinite Composite with Enhanced Visible Light-Driven Photocatalytic Activity

A novel kind of cyanuric-acid-modified graphitic carbon nitride (g-C3N4)/kaolinite (m-CN/KA) composite with enhanced visible light-driven photocatalytic performance was fabricated through a facile two-step process. Rhodamine B (RhB) was taken as the target pollutant to study the photocatalytic performance of the synthesized catalysts. It is indicated that the cyanuric acid modification significantly enhanced photocatalytic activity under visible light illumination in comparison with the other reference samples. The apparent rate constant of m-CN/KA is almost 1.9 times and 4.0 times those of g-C3N4/kaolinite and bare g-C3N4, respectively. The superior photocatalytic performance of m-CN/KA could be ascribed, not only to the generation of abundant pore structure and reactive sites, but also to the efficient separation of the photogenerated electron-hole pairs. Furthermore, the possible photocatalytic degradation mechanism of m-CN/KA was also presented in this paper. It could be anticipated that this novel and efficient, metal-free, mineral-based photocatalytic composite has great application prospects in organic pollutant degradation.

Conversion of post consumer waste polystyrene into a high value adsorbent and its sorptive properties for Congo Red removal from aqueous solution

Using post-consumer waste polystyrene (WPS), a conjugated microporous polymer (CMP) was synthesised and activated into a sulphonic-group carrying resin (SCMP). The surface chemistry of the materials showed a decline in both the aromatic CH and aliphatic CH₂ stretching vibrations confirming successful crosslinking. The synthesised polymers were thermally stable with decomposition temperatures above 300 °C, had surface heterogeneity, and BET surface areas of 752 and 510 m²/g, respectively. A distribution of pores ranging from meso- to micro-pores was comparable to other CMPs. The materials had maximum adsorption capacities of 500 and 357 mg/g for Congo Red (CR) on CMP and SCMP, respectively. Converting waste polystyrene to an adsorbent is a cost effective way of handling waste and simultaneously providing material for wastewater remediation.