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Abstract The Nickel oxide nanoparticles (NiO NPs) and Nickel oxide/Nanoclay nanocomposite (NiO/Nc NC) were synthesized by chemical reduction method and used for the photodegradation of Orange II dyes in aqueous solution. The synthesized samples were characterized through SEM, EDX, FTIR and TGA. The SEM analysis presented that the NiO NPs are spherical with irregular shapes and sizes. The size of particles is in the range of 100–400 nm. It was also observed that the NiO NPs are deposited on the surface of Nanoclay. The EDX study confirmed the formation of metal NPs and verify and purity. The FT-IR spectra of NiO and NiO/Nc NC presented peaks at 432 cm−1 and 504 cm−1, which correspond to NiO while peak at 1090–940 cm−1 is due to Si–O stretching vibration of orthosilicate anions and Si–O–Al groups. The photodegradation study illustrated that the NiO NPs and NiO/Nc NC degraded about 93 and 96% Orange II in aqueous medium, respectively within 20 min. The effect of various parameters like initial concentration of dyes, pH, recycled catalysts, and catalyst dosage were also studied.

Abstract The bromophenol blue dye in aqueous medium was photodegraded (under UV irradiation) by graphene nanoplates-supported titanium oxide (TiO2/GNP). The determination of various elements (percentage) and morphological study was performed using energy-dispersive X-rays and scanning electron microscopy, while the photodegradation study of dye was done by UV–visible spectrophotometer. The morphological study showed that the TiO2 particles were dispersed well on the surface of GNP. The sizes of TiO2 particles were below 500 nm. The photodegradation study was performed as function of time, and it was found that the photodegradation of dye in aqueous medium was increased as the time duration of UV irradiation increased. It was found that about 86% of dye was degraded within 8 h. The degradation of bromophenol blue is pH-dependent, and the photodegradation rate was increased as the pH of solution increased. The increase in dye degradation might be due to the formation of more hydroxyl radical at higher pH. The degradation of dye at pH 2, 4, 6 and 8 was about 70, 79, 90 and 95%, respectively.