2017 年 66 巻 6 号 p. 398-402
Zinc hydroxide nitrate (ZHN), which has layered structures including NO3- and H2O between the layers, is promising materials for application to an anion exchange. ZHN can be synthesized by direct precipitation adding sodium hydroxide solution to Zn(NO3)2 solution. ZHNs were synthesized at various synthesis conditions to use them as phosphorous removal agents. ZHN precipitates were obtained at pH6, 7 and 9 and aged at 25℃, 60℃, 90℃, 120℃ respectively under hydrothermal conditions. A small part of ZHN precipitates at pH6 and aged at 120℃ transformed to ZnO, however most of ZHN precipitated at pH7 and aged at over 90℃ transformed to ZnO. However, ZHN obtained at pH9 started to transform to ZnO on aging at 60℃ and most of ZHN precipitates transformed to ZnO at over 90℃. For phosphorus removal experiments, single ZHN phase precipitates could remove around 99% phosphate ions in a 100ppm phosphorous solution, and ZHNs containing a large amount of ZnO for the most part showed lower phosphorus removal ratio. Therefore, ZHNs prepared at lower pH and aged at lower temperatures including little ZnO showed high phosphorus removal capability.