2018 年 67 巻 6 号 p. 593-597
As a research to explore the application of layered zinc hydroxide incorporated with ion exchangeable anions between layers as a phosphorus removal material, a layered zinc hydroxide containing sulfate ions between the layers was synthesized. Its chemical formula is Zn4SO4(OH)6・n H2O (ZHS). The effects of pH during the synthesis and of the aging temperature on crystal composition and phosphorus removal ability were investigated. From the XRD analysis, it was found that ZHSs with different numbers of crystal water were obtained depending on the pH during the synthesis and aging temperature. It was also found that zin oxide was more likely to be formed as the pH during the synthesis and the aging temperature were increased. The phosphorus removal capacity of each sample powder was evaluated by immersing each sample in a potassium dihydrogen phosphate aqueous solution adjusted to a phosphorus concentration of 100 ppm for 10 minutes. All samples showed phosphorus removal ratio of above 80%. Particularly, the ZHS powder synthesized at pH 6 showed the phosphorus removal ratio above 95% regardless of the aging temperature. In the case of ZHS synthesized at pH 7 or higher, zinc oxide was formed as the aging temperature increased, and thus, the phosphorus removal ratio decreased. However, for ZHS, the formation of zinc oxide by aging was extremely few compared with the layered zinc hydroxide containing nitrate ions between the layers, which was previously reported by the authors, and so the decrease in the phosphorus removal rate was also small.