Synthesis and characterization of [Zn–Al] LDH: Study of the effect of calcination on the photocatalytic activity

• Synthesis of [Zn–Al] LDH by the coprecipitation method
• Characterization of [Zn–Al] LDH and its derived forms obtained after calcination
• Photocatalytic application for the decolorization of methylene blue
• Effect of calcination and effect of operating parameters
• Kinetic study

The photocatalytic decolorization of methylene blue (MB) was performed using [Zn–Al] layered double hydroxides (LDH) either as such or calcined. The prepared photocatalysts were characterized by XRD, ICP, TEM, nitrogen physisorption at − 196 °C and DRS. Photocatalytic study showed that [Zn–Al] LDH without any treatment presented the best photocatalytic activity which was even better than that of commercial ZnO nanoparticles. It provided a decolorization percentage of 90% after 1 h irradiation time.The influence of dye concentration, solution pH, photocatalyst dose and some inorganic anions on the photodecolorization of MB was investigated. Results showed that an acidic pH reduced the effectiveness of the photocatalytic process however an alkaline pH slightly improved the reaction. The presence of Cl−, NO3− and CO32 − leads to a decrease in the decolorization rate of the dye contrary to SO42 − which improved the reaction. The optimum mass of photocatalyst corresponded to 0.49 mmol of Zn.The decolorization reaction followed a Langmuir–Hinshelwood model only at low concentrations of MB.