Photocatalytic degradation of methylene blue dye by zinc oxide nanoparticles obtained from precipitation and sol-gel methods

Abstract

Zinc oxide (ZnO) nanoparticles were synthesized by precipitation and sol-gel methods. The aim of this study was to understand how different synthetic methods can affect the photocatalytic activity of ZnO nanoparticles. As-synthesized ZnO nanoparticles were characterized by X-ray diffraction (XRD) and UV-Visible spectroscopic techniques. XRD patterns of ZnO powders synthesized by precipitation and sol-gel methods revealed their hexagonal wurtzite structure with crystallite sizes of 30 and 28 nm, respectively. Their photocatalytic activities were evaluated by photocatalytic degradation of methylene blue, a common water pollutant, under UV radiation. The effects of operational parameters such as photocatalyst load and initial concentration of the dye on photocatalytic degradation of methylene blue were investigated. While the degradation of dye decreased over the studied dye concentration range of 20 to 100 mg/L, an optimum photocatalyst load of 250 mg/L was needed to achieve dye degradation as high as 81 and 92.5 % for ZnO prepared by precipitation and sol-gel methods, respectively. Assuming pseudo first-order reaction kinetics, this corresponded to rate constants of 8.4 × 10 and 12.4 × 10 min, respectively. Hence, sol-gel method is preferred over precipitation method in order to achieve higher photocatalytic activity of ZnO nanostructures. Photocatalytic activity is further augmented by better choice of capping ligand for colloidal stabilization, starch being more effective than polyethylene glycol (PEG).

Titania/gum tragacanth nanohydrogel for methylene blue dye removal from textile wastewater using response surface methodology

“…According to the removal experiments at run orders of 1, 13, 15, 16, 23, 24 and 30 (the center of variables), standard deviation is 1.7% of dye removal efficiency. It is noteworthy that photocatalysis of methylene blue is typically investigated at low concentrations . To statistically analyze the results and evaluate the adequacy and validity of the developed model, analysis of variance (ANOVA) and R 2 (coefficient of determination) statistic were employed.…”

“…It is noteworthy that photocatalysis of methylene blue is typically investigated at low concentrations. 18,19 To statistically analyze the results and evaluate the adequacy and validity of the developed model, analysis of variance (ANOVA) and R 2 (coefficient of determination) statistic were employed. To accept the mathematical model by RSM, its ANOVA should reach high statistical significance in terms of P values below 0.05 at a confidence level of 95%.…”

Investigating Methylene Blue Adsorption and Photocatalytic Activity of ZnO/CNC Nanohybrids

“…After absorbing excited energy, photogenerated electron-hole pairs would be produced and migrated to the surface of ZnO nanoparticles (Equation (7)). Then, these eand h + can react with O 2 and H 2 O absorbed on its surface to generate active radical OH ⋅ (Equation (8)) and O 2 -(Equation (9)), which could participate in dye degradation by direct oxidation [11,22,28].…”

Structural, optical and photocatalytic properties of zinc oxides obtained from spent alkaline batteries

“…In order to obtain high-quality zinc oxide powders with fine particle size, narrow size distribution and special morphology, different techniques for preparing ZnO have been investigated such as sol-gel process, chemical coprecipitation, thermal decomposition, precipitation, microemulsion, etc. [3][4][5]. The different preparation methods are analyzed to create vacancies and defects, which are important parameters for electronic and optoelectronic applications.…”