Dispersion effect of sodium hexametaphosphate on the photocatalytic efficiency of a solution-combusted ZnO nanopowder

Abstract

ZnO nanopowder was synthesized by using a unique method combusting a mixed water solution that contained an oxidant and a fuel. Zn(OH)2 powder was used as an oxidant (source material). Three kinds of fuels, glycine, carbohydrazide and urea, were respectively used to synthesize the ZnO nanopowder. Sodium hexametaphosphate was used as a dispersant to avoid aggregation of the ZnO nanoparticles in the solution. The zeta potential and the ion mobility of the dispersed ZnO nanoparticles were measured to evaluate the dispersion properties. The ZnO nanopowder synthesized with glycine showed highest zeta potential and ion mobility. A photocatalytic reaction was performed to evaluate the photocatalytic efficiency. The dispersion of the ZnO nanoparticles in waste water enhanced the Cu++ ion removal from the waste water. The Cu++ ions were completely removed in 15 h with dispersion. Without dispersion, however, they were not completely removed, not even in 35 h. This means that the dispersant changed even the extreme performance limit of the photocatalyst.