Large-scale pattern fabrication of 3D rGO-Ag@Ag3PO4 hydrogel composite photocatalyst with the excellent synergistic effect of adsorption and photocatalysis degradation

Exploring the photocatalytic inactivation mechanism of Microcystis aeruginosa under visible light using Ag3PO4/g-C3N4

In this work, a series of Ag₃PO₄/g-C₃N₄ (AG) photocatalysts were synthesized. After characterizing the properties, the effects of mass ratio, light intensity, and material dosages on photodegradation were investigated. The material with a 1/2 mass ratio of Ag₃PO₄/g-C₃N₄ showed the highest photocatalytic activity under visible light, and the removal efficiency reached 90.22% for an initial suspended algae concentration of 2.7 × 10⁶ cells/mL, 0.1 g of AG, and 3 h of irradiation. These results showed that the conductivity was increased while the total protein and COD contents of the algae suspension were declined rapidly. In contrast, the variations in the malondialdehyde (MDA) level suggested that the algae cell wall was severely damaged and that selective permeability of the membrane was significantly affected. A possible photocatalytic mechanism was proposed and •O₂^- was shown to be the major reactive oxygen species in the photocatalysis. In summary, during the visible light photocatalytic process, the cell structure was destroyed, which caused the leakage of electrolyte, the inactivation of protein, and the inhibition of photosynthesis; finally, the cells died. This study provides a reference for photodegradation of algae pollution in water bodies.

Efficient adsorption and full spectrum photocatalytic degradation of low concentration PPCPs promoted by graphene/TiO2 nanowires hybrid structure in 3D hydrogel networks

The removal of low concentration PPCPs from water is a challenging issue. A graphene hydrogel with 3D networks shows great potential for accelerating eddy diffusion of low concentration PPCPs. Herein, to further promote its molecular diffusion, a graphene/TiO₂ nanowires (GNW) hybrid structure was implanted into graphene hydrogel. The as-prepared rGO/GNW hydrogel exhibited significantly enhanced adsorption–photocatalytic performance and excellent stability for low concentration ethenzamide, a typical pharmaceutical pollutant in water, under vacuum ultraviolet (VUV), ultraviolet (UV), visible and near-infrared light irradiation. When the initial ethenzamide concentration was 500 ppb and catalyst dosage was 10 mg/150 mL, ethenzamide was completely removed in 3 min and the corresponding photocatalytic apparent rate constant was 2.20 times that by GNW, 4.09 times that by rGO/P25 and 4.31 times that by rGO/NW under VUV irradiation, respectively, and its removal rate attained 99.0% in 120 min and the corresponding photocatalytic apparent rate constant was 2.06 times that by GNW, 3.34 times that by rGO/P25 and 17.42 times that by rGO/NW under UV irradiation, respectively. The GNW hybrid structure in the hydrogel played a vital role in overcoming the mass transfer resistance of low concentration PPCPs. The as-prepared rGO/GNW hydrogel exhibits significant potential for the removal of low concentration PPCPs from water.

A 3D rGO/GNW hydrogel exhibits efficient adsorption, full spectrum photocatalytic performance and significant potential for low concentration PPCP removal from water.

Mesoporous CuS nanospheres decorated rGO aerogel for high photocatalytic activity towards Cr(VI) and organic pollutants

Mesoporous CuS nanospheres (CuS-NS) decorated reduced graphene oxide (rGO) aerogel composite (3D CuS-NS/rGO) was prepared by chemical reduction process and used for the synergistic removal of Cr(VI) and cationic dyes. The porosity of the as prepared samples was determined by Bruner-Emmet-Teller (BET) surface Area. Structural and morphological properties were studied by Scanning electron microscopy (SEM) and Transmission electron microscope (TEM). These analysis revealed that the as obtained hybrid CuS-NS/rGO composite with three dimensional (3D) structure was composed of mesoporous CuS nanospheres clearly induced onto the interconnected network of rGO sheets. The photocatalytic performance of 3D CuS-NS/rGO composites was studied against the reduction of Cr(VI) and degradation of cationic dyes (MB and RhB) under visible light spectrum. Excellent photocatalytic performance was observed with 3D CuS/rGO hybrid composites as compared to the as prepared CuS nanospheres. This high photocatalytic activity was attributed to the efficient charge transfer from the mesoporous CuS nanospheres to nanosheets of rGO, which was confirmed by UV-Vis spectrometry (UV-Vis). Electrical conductivity of the prepared samples was also investigated using electrochemical impedance spectroscopy (EIS). Additionally, the as prepared hybrid composites was easy to recycle by using simple tweezers and can be a best candidate for industrial applications.