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Photocatalytic degradation of reactive dyes over Ni[sbnd]Al layered double hydroxide

Due to the uncontrolled discharge of textile effluents, the extent of reactive dyes in wastewater is rising. Due to their toxicity, efficient removal becomes quite essential. In this report, NiAl layered double hydroxide (LDH) has been prepared using the coprecipitation methodology for the photocatalytic degradation of reactive dyes. The as-prepared materials were characterized by different techniques, such as DRS, XRD, FESEM, HRTEM, and XPS etc. The XRD pattern of the LDH confirms the formation of the rhombohedral (R3m) phase. The FESEM analysis reveals the irregular hexagon-like shape of the prepared LDH. The NiAl LDH has 98(1) and 87(1)% photodegradation efficiencies towards the removal of reactive blue 19 and reactive Red 120, respectively. The control experiments in the presence of different scavengers confirm that hydroxyl radicals and superoxide anions participate in photocatalytic degradation. The HRMS studies confirm the formation of different smaller fragments, thereby providing a deeper insight into the photodegradation mechanism. Moreover, the demineralization efficiency (88.9%) is quite close to the degradation efficiency for reactive blue 19, signifying practically complete demineralization of the pollutants. The recyclability studies ascertain the high stability of the photocatalyst. Therefore, the as-prepared NiAl LDHs can be considered a promising photocatalyst for the removal of reactive dyes from wastewater.

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Synergistic enhancement of visible light Photocatalysis: Tailoring dual Z-scheme Fe2O3/C3N4/NH2-MIL-125 ternary composites for organic pollutant degradation

In this study, Fe2O3/C3N4/NH2-MIL-125 ternary composite photocatalysts were synthesized. Their amino groups provided close bonding between these materials, facilitating the effective separation of electrons and holes. Besides, each component of Fe2O3/C3N4/NH2-MIL-125 plays a crucial role. NH2-MIL-125 provided a high surface area, C3N4 contributed to the primary photocatalytic activity, and Fe2O3 aided in enhancing light absorption, generating additional potential to produce hydroxyl radicals, thereby further enhancing photocatalytic activity. Moreover, the proportion of loaded Fe2O3 and C3N4 in the ternary material was investigated. It was found that Fe2O3/C3N4/NH2-MIL-125 with a 1:1 ratio of Fe2O3 and C3N4 (FeCN1:1/NM125) exhibited excellent photocatalytic performance, in which RhB degradation reached 100% under visible light irradiation, conforming to first-order kinetics analysis with a reaction rate constant k of 0.0164 min−1. Its efficiency was twice that of the binary catalyst C3N4/NH2-MIL-125 or Fe2O3/NH2-MIL-125, seven times that of the pristine catalyst C3N4, and ten times that of the pristine catalyst NH2-MIL-125. Scavenger experiments showed that the degradation efficiencies were 52.57%, 55.51%, and 63.41%, respectively, indicating that three active species, namely superoxide radicals, holes, and hydroxyl radicals, made significant contributions to photocatalysis.

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