Adsorption kinetics and photocatalytic degradation of malachite green (MG) via Cu/ZnO nanocomposites

Abstract

Cu/ZnO composites were synthesized via a simple sol-gel method catalyzed by 2.3.dihydroxysuccinic acid and annealed at different temperatures (TC). The obtained nanomaterials were characterized by means of several analytical techniques. Photocatalytic performances of nanomaterials were evaluated by adsorption and degradation of malachite green (MG) solutions (300ppm high concentration) under UV light irradiation. The results show a wurtzite phase for Cu/ZnO nanoparticles with a crystallite size of 15.86 to 24.25nm, depending on the annealing temperature. A mesoporous structure of type IV with hysteresis type H3 was obtained for all synthesized nanomaterials, with mean pore diameter from 24.63 to 52.88nm and surface area in the range of 35.1 to 8.66m2/g. Adsorption and degradation results showed the effect of copper doping on the ZnO. At the same TA (550°C), 14.49 and 23.55% MG were adsorbed on pure ZnO and Cu/ZnO, respectively. The adsorption isotherm of Cu/ZnO composite was fast, and it agreed well with the Langmuir model with a capacity of 1539mg/g. The MG degradation rate constant of Cu/ZnO reaches 10×10−3min−1 when the initial concentration of MG was 300ppm, about 8 times higher than that of pure ZnO (1.28×10−3min−1). The optimal annealing temperature was at 550°C for Cu/ZnO nanoparticles with 92.62×10−3 and 10×10−3min−1 as adsorption and degradation rate constant, respectively. This makes the nanocomposite Cu/ZnO a promising and good candidate for wastewater treatment at high dye concentrations.