2022 年 69 巻 5 号 p. 208-216
This study investigated the conditions for zeolite synthesis from waste concrete powder (WCP) using the hydrothermal synthesis method. The WCP was prepared by milling the waste concrete using pot mill equipment. The synthesis conditions, i.e., the heating time, heating temperature, and NaOH solution concentration were varied. Furthermore, hydrochloric acid-treated WCP (WCP-HCl), which is removed the calcium component, was prepared to examine the effectiveness of acid treatment in the zeolite synthesis. The zeolite synthesis was investigated using X ray diffraction (XRD) and scanning electron microscopy (SEM). Analcime-type zeolite was synthesized using WCP and WCP-HCl. The requirements of synthesis conditions for analcime were as follows: heating time above 12 h, heating temperature above 433 K, and NaOH solution concentration above 2 mol/L. With a progressive increase in the concentration of the NaOH solution from 5 to 7 mol/L, analcime could be synthesized at NaOH concentrations below 4 mol/L, while cancrinite was synthesized at NaOH concentrations exceeding 5 mol/L. The peak intensity of analcime and cancrinite of WCP-HCl showed high value in comparison to the WCP. Thus, the effectiveness of the HCl treatment of WCP was confirmed from the XRD patterns.