Combustion synthesis of ZnAl2O4 powders with tuned surface area

Zinc aluminate powders with tuned surface area were prepared by solution combustion synthesis, using different oxidizer-fuel ratios. As the amount of urea increased, standard heat of reaction and standard Gibbs free energy decreased, whilst adiabatic temperature increased. The larger amount of energy released during combustion facilitated grain growth and sintering, causing the decrease of specific surface area from 156 to 27 m2 g−1. The particle size estimated from TEM increased from 8 to 40 nm. The adsorption capacity of zinc aluminate powders with respect to methyl orange was highly dependent on the specific surface area. For an adsorbent dose of 3 g L−1 the removal efficiency of methyl orange was much larger (86 versus 18%) in the case of the sample with larger surface area. The adsorption kinetics followed a pseudo-second-order model and the equilibrium data were correlated with the Freundlich isotherm.