抄録
This paper reports on the formation of gypsum dihydrate by hydration of II-anhydrous gypsum using sulfuric acid formed of sulfur oxidizing bacteria. The gypsum dihydrate formed by hydrating II-anhydrous gypsum in the medium including sulfur oxidizing bacteria.
pH of the medium decreased with progress of the days and was about 1 after 15 days. Number of bacteria multiplied to about 30 times in 15 days. The concentration of sulfuric acid formed by sulfur oxidizing bacteria was approximately 0.12 mol·dm-3. In addition, it tended to be equal to the S6 medium using the sodium thiosulfate-ammonia system medium.
In the case of adding II-anhydrous gypsum in the S6 medium, the hydration of II-anhydrous gypsum was slow until around 10 days, but was suddenly worse in after 12 days. The change in the average particle size of formed gypsum dihydrate was a tendency similar to relationship time and formation ratio of gypsum dihydrate, maximum particle size was approximately 85μm. The shape of formed gypsum dihydrate was plate-like or needle-like crystal. The hydration of II-anhydrous gypsum in sodium thiosulfate system medium was equal to that of the S6 medium.
