Efficient Photocatalytic Degradation of Methylene Blue Dye from Aqueous Solution with Cerium Oxide Nanoparticles and Graphene Oxide-Doped Polyacrylamide

Abstract

A cerium oxide nanoparticles (CeO2-NPs)/graphene oxide (GO)/polyacrylamide (PAM) ternary composite was synthesized through free-radical polymerization of acrylamide in the presence of CeO2 nanoparticles and GO in an aqueous system. The synthesized composite material was characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) spectroscopy techniques and applied for the photocatalytic degradation of methylene blue (MB) dye from an aqueous solution. Tauc’s model for direct transition was used to model for the optical band gap. The key operating parameters such as the amounts of CeO2-NPs and GO, pH, initial MB concentration, type of light irradiation, and contact time have been optimized to achieve the highest MB degradation percentage. The photocatalysis process was pH-dependent, and the optimum pH value was found to be 12.0. Under UV-A light, 90% dye degradation occurred in 90 min. The degradation of MB was also specified in terms of total organic carbon (TOC) and chemical oxygen demand (COD). Free-radical capture experiments were also performed to determine the role of radical species during the photocatalytic oxidation process. The photocatalytic process showed that the equilibrium data is in good agreement with the Langmuir–Hinshelwood kinetic model. A rate constant of 0.0259 min–1 was obtained. The hydrogel was also tested to assess its reusability, which is an important key factor in practical wastewater treatment. The photocatalytic activity only decreased to 75% after nine uses.

CuAs2O4: Design, Hydrothermal Synthesis, Crystal Structure, Photocatalytic Dye Degradation, Hydrogen Evolution Reaction, Knoevenagel Condensation Reaction, and Thermal Studies

“…After photocatalysis, a decrease of stretching frequency of ∼69% and ∼75% T was observed at 751 and 507 cm –1 for Cu–O bond, however, a decrease of ∼15% T falls for As–O bond at 903 and 955 cm –1 , which signifies that the responsible units participated in the dye degradation. The FTIR spectrum of the catalyst confirms that the position of stretching frequencies of the corresponding bonds remains the same both before and after the photocatalytic dye degradation, although the intensities are dropped for the responsible bonds for the dye degradation ,,− …”

“…Photocatalysts undergo redox reactions by absorbing photons of UV light or visible light. 10 The light absorption on the surface of catalyst produced electron−hole (e − /h + ). 6 The photocatalyst has a charged surface that breaks organic pollutants into simple, nontoxic fragments.…”

“…Photocatalytic dye degradation is the process of removing toxic effluent from contaminated water. Photocatalysts undergo redox reactions by absorbing photons of UV light or visible light . The light absorption on the surface of catalyst produced electron–hole (e – /h + ) .…”

A deeper insight into the evaluation of water-in-oil amicroemulsion templated samarium sulfide nanospheres: exploring its role in pickering emulsion formulation for photocatalytic dye degradation and synthesis of PANI@Sm2S3 nanocomposites

“…The electrons in Sm 2 S 3 absorb photons, which causes the formation of hole pair inside the nanoparticles. 34,59,60 SmF 3 + hυ(UV) → SmF 3 *(e CB − + h υB + )here, SmF 3 * is the excited state of the SmF 3 , e CB − is the photoexcited electron present in the conduction band, and h υB + represents the photogenerated holes persisting in the valence band.…”

“…Superoxide ions (˙O 2 − ) and unstable hydroxyl radicals (˙OH) are produced when these molecules (O 2 and H 2 O) interact with photoexcited electrons (e CB − ) and electron–hole pairs (h υB + ), respectively (eqn (4) and (5)). 34,59 The CV is then oxidised into inorganic compounds by interacting with these ionic or radical species (eqn (6) and (7)). h υB + + CV → CV + → oxidation of CVorO 2 + e CB − → ˙O 2 − H 2 O + h υB + → ˙OH + H + and˙O 2 − + CV dye → CO 2 +H 2 O˙OH + CV dye → CO 2 +H 2 O…”