Photocatalytic silver recovery using ZnO nanopowders synthesized by modified glycine-nitrate process

Zinc oxide (ZnO) powders were synthesized by the modified glycine-nitrate process (MGNP) with various oxidants and fuels. Single-phase ZnO powders were easily obtained regardless of oxidants and fuels. The particle size and shape of ZnO powders were dependent on the types of fuels. The ZnO powder synthesized using Zn(OH)(2) and glycine as an oxidant and a fuel, at a fuel/oxidant ratio of 0.8, showed the best powder characteristics, such as an average grain size of 30 nm and the specific surface area of 120 m(2)/g. The removal of silver ions from the waste-development solution was tried to confirm photocatalytic activities of the synthesized ZnO powder. The silver ions were completely removed within 15 min. This silver recovery rate is three times higher than that of commercial state-of-the-art TiO2. The photoluminescence (PL) measurement also showed the PL intensity at ultraviolet (UV) of the synthesized ZnO powder is almost three times higher than that of commercial state-of-the-art TiO2. The synthesized ZnO nanopowder absorbed more UV than any other powders, including commercial state-of-the-art TiO2 and ZnO powders. This means the high UV absorption efficiency leads to the generation of more electrons that are involved in the reduction of silver ions.