Utilization of Zinc Oxide Nanopowder for Photocatalytic Removal of Pb Ions from Aqueous Wastewater.

Nanometer-sized zinc oxide powders were prepared with a "solution-combustion method (SCM)." This method used zinc oxide nanopowder as a semiconductor oxide catalyst to initiate light-induced redox reactivity in the presence of 150 ppm aqueous lead-ethylenediaminetetraacetic acid solution (Pb-EDTA) for photocatalysis under UV illumination. Removal rates of lead ions in the aqueous Pb-EDTA solution using SCM ZnO powder were compared with those of two other titanium dioxide photocatalysts, P-25 TiO₂-powder (Degussa) and rutile TiO₂ powder, prepared via a homogeneous precipitation process at low temperature (HPPLT). Using SCM ZnO nanopowder, complete removal of lead ions from the aqueous Pb-EDTA solution was observed within 25 min after UV irradiation. However, HPPLT TiO₂ powder and P25 TiO₂ powder took almost 45 and 65 minutes to completely remove the lead ions, respectively. Thus, lead ions removal efficiency of SCM ZnO nanopowder is at least twice higher than the efficiency of the other two titanium dioxide photocatalysts investigated.