Effect of pH and aging temperature on the phosphorus removal properties of layered hydroxide synthesized from zinc acetate

Zinc hydroxide acetate (ZHA) is a promising material for anion exchange applications because it has a layered structure with intercalating CH3COO− and H2O. ZHA can be synthesized through a direct precipitation method by adding sodium hydroxide solution to a Zn(OCOCH3)2 solution. In this study, ZHAs were synthesized under various conditions and tested as phosphorous removal agents. The ZHA precipitates were obtained at pH 6, 7, and 9. They were then aged at 25°C, 60°C, 90°C, and 120°C under hydrothermal conditions. At pH 6, nearly pure single-phase ZHAs were obtained regardless of the aging temperature. On the other hand, most of the ZHAs that were prepared at higher pH and aged at higher temperature were transformed to ZnO. For the phosphorous removal experiments, the single-phase ZHA precipitates removed approximately 99% of the phosphate ions in a 100 mg L−1 phosphorous solution, and the phosphorus removal efficiency decreased with increasing amounts of ZnO. Therefore, ZHAs that were prepared at lower pH and aged at lower temperatures contained little to no ZnO, thereby showing high phosphorous removal capabilities