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Water pollution has becoming an increasingly serious issue, and it has attracted a significant amount of attention from scholars. Here, in order remove heavy metal hexavalent chromium (Cr (VI)) from wastewater, graphitic carbon nitride (g-C3N4) was modified with molybdenum disulfide (MoS2) at different mass ratios via an ultrasonic method to synthesize g-C3N4/MoS2 (CNM) nanocomposites as photocatalysts. The nanocomposites displayed efficient photocatalytic removal of toxic hexavalent chromium (Cr (VI)) from water under UV, solar, and visible light irradiation. The CNM composite with a 1:2 g-C3N4 to MoS2 ratio achieved optimal 91% Cr (VI) removal efficiency at an initial 20 mg/L Cr (VI) concentration and pH 3 after 120 min visible light irradiation. The results showed a high pH range and good recycling stability. The g-C3N4/MoS2 nanocomposites exhibited higher performance compared to pure g-C3N4 due to the narrowed band gap of the Z-scheme heterojunction structure and effective separation of photo-generated electron–hole pairs, as evidenced by structural and optical characterization. Overall, the ultrasonic synthesis of g-C3N4/MoS2 photocatalysts shows promise as an efficient technique for enhancing heavy metal wastewater remediation under solar and visible light. [ABSTRACT FROM AUTHOR]

Photocatalysis has emerged as a highly promising, green, and efficient technology for degrading pollutants in wastewater. Among the various photocatalysts, Bismuth tungstate (Bi2WO6) has gained significant attention in the research community due to its potential in environmental remediation and photocatalytic energy conversion. However, the limited light absorption ability and rapid recombination of photogenerated carriers hinder the further improvement of Bi2WO6's photocatalytic performance. This review aims to present recent advancements in the development of Bi2WO6-based photocatalysts. It delves into the photocatalytic mechanism of Bi2WO6 and summarizes the achieved photocatalytic characteristics by controlling its morphology, employing metal and non-metal doping, constructing semiconductor heterojunctions, and implementing defective engineering. Additionally, this review explores the practical applications of these modified Bi2WO6 photocatalysts in wastewater purification. Furthermore, this review addresses existing challenges and suggests prospects for the development of efficient Bi2WO6 photocatalysts. It is hoped that this comprehensive review will serve as a valuable reference and guide for researchers seeking to advance the field of Bi2WO6 photocatalysis. [ABSTRACT FROM AUTHOR]

Graphitic carbon nitride (g-C 3 N 4) exhibits remarkable thermal and chemical stability, enabling effective activation of molecular oxygen and generation of superoxide radicals for photocatalytic pollutant degradation. However, its low surface area and poor photocatalytic activity have limited its development, and the reaction mechanism of pollutant degradation remains unclear. In this study, we synthesized g-C 3 N 4 /BC/Fe 2 O 3 catalysts by combining g-C 3 N 4 , biochar (BC), and Fe 2 O 3 in intimate contact. The highest photocatalytic degradation efficiency of tetracycline (TC) reached 94.9 % in the g-C 3 N 4 /BC/Fe 2 O 3 -2/PDS system, which was 3.01, 1.53, and 2.35 times higher than that of pure g-C 3 N 4 , BC, and BC/Fe 2 O 3 , respectively. The addition of persulfate (PDS) accelerated the formation of reactive oxygen species (ROS), providing more active species and improving photocatalytic performance, thereby enhancing TC degradation. LC-MS analysis and density functional theory (DFT) calculations were used to elucidate possible TC degradation pathways in the g-C 3 N 4 /BC/Fe 2 O 3 -2/PDS system. Electron paramagnetic resonance (EPR) confirmed the generation of multiple ROS in the reaction system, including h+, •OH, SO 4 •−, •O 2 −, and 1O 2. This work provides mechanistic insights into TC degradation and offers a theoretical foundation for future studies on advanced oxidation processes for water treatment. [Display omitted] • Novel g-C 3 N 4 /BC/Fe 2 O 3 photocatalyst synthesized using coffee grounds as biochar precursor. • g-C 3 N 4 /BC/Fe 2 O 3 /PDS system achieved 94.9 % tetracycline removal under visible light. • 87.4 % TOC removal indicates effective mineralization of tetracycline. [ABSTRACT FROM AUTHOR]

The rapid progress of modern industry not only brings convenience to people's lives, but also brings negative effects. Industrial development produces a large amount of waste metal, which brings harm to the environment and human health. Carbon nitride (g-C3N4) was successfully prepared using the thermal-polymerization method and petal-like g-C3N4 (CA-g-C3N4) was impregnated with citric acid (CA). Compared with g-C3N4, CA-g-C3N4 showed extremely high photocatalytic activity because the petal-like g-C3N4 (CA-g-C3N4) had a larger specific surface area, which increased the active sites on the surface of the photocatalyst and improved the photocatalytic activity. After citric acid treatment, the removal of hexavalent chromium (Cr(VI)) by g-C3N4 increased from 48% to 93%. The photocatalytic materials were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET) and UV-vis diffuse reflectance spectra (UV-vis). In summary, this study confirmed that citric acid can improve the photocatalytic activity of g-C3N4 by increasing its specific surface area and the active site of the photocatalytic material so as to achieve the purpose of removing hexavalent chromium from water. [ABSTRACT FROM AUTHOR]