Enhanced photocatalytic reduction of 4‐nitrophenol over Ir/CeO₂ photocatalysts under UV irradiation

Abstract

BACKGROUND: Photoreduction of 4-nitrophenol (4-NP) photocatalytically to 4-aminophenol (4-AP) is considered a promising treatment of this recalcitrant pollutant. 4-aminophenol is widely applied as an intermediate in the pharmaceutical and agricultural industries. In this work, iridium/cerium dioxide (Ir/CeO 2 ) photocatalysts with different Ir contents (0.5, 1.0 and 2.0 wt%) were studied in the photoreduction of 4-NP using Na 2 SO 3 as hole scavengers under UV irradiation. In order to identify their physicochemical properties, the materials were studied by several techniques and photoactivity was monitored by UV-visible spectroscopy. RESULTS:The characterization results provided evidence that the modification of CeO 2 by impregnation of Ir causes a decrease in CeO 2 textural properties and its band gap energy. The photocatalytic reduction of 4-nitrophenol was enhanced by 26.1% using Ir/CeO 2 1.0 wt% in comparison with CeO 2 support. The phrase is related with the comparison between the photocatalytic behavior of Ir/CeO 2 1.0 wt% photocatalyst in regard the results evidenced with CeO 2 unmodified. An effect of the metal loading over photoactivity was observed and the optimal Ir content was 1.0 wt%. A reduction of 84% was obtained using 1.0 wt%Ir/CeO 2 , whereas for higher metal loading (2.0 wt%) 4-NP reduction decreased by 72%. CONCLUSION:The enhancement in the photocatalytic behavior of the Ir/CeO 2 series could be related to the presence of Ir + and Ir 0 species evidenced by X-ray photoelectron spectroscopy (XPS), thus, Ir + species could favor the adsorption of the pollutant and Ir 0 particles could act as trap of the photogenerated electrons that are responsible for reduction of the nitrocompound. The decrease in photoactivity when 2.0 wt% Ir/CeO 2 was used as photocatalyst could be associated with partial blockage of the surface active sites by increasing amounts of metal.

Animal bone affluence in environmental reclamation: Biodiesel production, petro‐diesel biodesulfurization and wastewater photo‐treatment

“…Egypt suffers from massive quantities of organic waste, exceeding approximately 70 million tons annually, and ABs are estimated to contribute about 1% of it 27 . Another environmental problem is that the industrial water effluents contain hazardous pollutants – for example, 4‐nitrophenol (4‐NP; C 6 H 5 NO 3 ), which is used in many industries like paper, drugs, dyes, fungicides, petrochemicals, and leather 28 . Nitrophenols are listed by the environmental protection agency (EPA) as being among the top 114 toxic hazardous substances from different industrial effluents 29 .…”

“…27 Another environmental problem is that the industrial water effluents contain hazardous pollutants -for example, 4-nitrophenol (4-NP; C 6 H 5 NO 3 ), which is used in many industries like paper, drugs, dyes, fungicides, petrochemicals, and leather. 28 Nitrophenols are listed by the environmental protection agency (EPA) as being among the top 114 toxic hazardous substances from different industrial effluents. 29 4-Nitrophenol is a toxic aromatic xenobiotic, known to cause skin and eye irritation.…”

Effective phosphated CeO2 materials in the photocatalytic degradation of phenol under UV irradiation

“…This characteristic promotes the effective separation of the charge carriers; thus Ce 4+ species may accept a photogenerated electron and easily transform to Ce 3+ . The Ce 3+ species can return back to the Ce 4+ state by releasing an electron by transferring it to the surrounding adsorbed substrate 30,31 . The signals observed in the solid 1.0PO 4 /CeO 2 shown a slight displacement to higher binding energy (Table 2).…”

“…The Ce 3+ species can return back to the Ce 4+ state by releasing an electron by transferring it to the surrounding adsorbed substrate. 30,31 The signals observed in the solid 1.0PO 4 /CeO 2 shown a slight displacement to higher binding energy (Table 2). However, the addition of a larger amount of phosphate anions on CeO 2 does not show a marked change in the spectra.…”

Catalytic activity of surface‐functionalized nanoscale nickel zinc multiferrites: potential vector for water purification

“…Several semiconductors such as ZnO, BiOCl, TiO 2 and SnO 2 have been shown to function as proficient photocatalysts for catalytic decomposition of recalcitrant contaminants and production of hydrogen gas owing to their sensitivity towards light, high catalytic activity, excellent chemical stability, non‐hazardous nature and low cost . However, these photocatalysts have wide band gap structures and can only absorb around the ultraviolet (UV) region (4% of solar light), which significantly restricts their practical applications . Therefore it becomes imperative to develop newer green visible‐light‐activated catalysts for wastewater purification and environmental remediation.…”