Pb doped ZnO nanoparticles for the sorption of Reactive Black 5 textile azo dye.

In this study, Pb doped ZnO nanoparticles were synthesized by a sol-gel technique for the sorption of Reactive Black 5 (RB5) textile dye in aqueous solution. The ZnO:Pb (2 and 4%) nanoparticles have been characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and cryogenic nitrogen adsorption method. The average size of the synthesized nanoparticles was less than 100 nm and the surface areas were 18.8 and 20.8 m2/g, respectively for ZnO:Pb 2% and ZnO:Pb 4%. Batch sorption experiments were performed for color removal of RB5 dye at ambient temperature and 30 mg/L dye concentration. The central composite design with response surface methodology was used to study the effect of sorption condition (pH, nanoparticles dose and contact time). The significance of independent variables and their interactions was tested by analysis of variance. The optimum conditions of color removal were pH = 7, 2 g/L dose of nanoparticles and a contact time of 79 min. The color removal performance was 79.4 and 98.1% for ZnO:Pb 2 and 4% respectively. The pseudo-second-order model described well the removal rates while the Langmuir model fitted well the adsorption isotherms.