Synthesis of mesoporous silica from geothermal water

Yujiro Watanabe,Naoki Amitani,Yoshiji Odashima,Shigeko Unami,Minoru Kusakabe,Takushi Yokoyama,Akira Ueda

doi:10.1038/s41598-021-03133-x

Yujiro Watanabe, Naoki Amitani + Show 5 more

Open Access

https://doi.org/10.1038/s41598-021-03133-x

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Abstract

Mesoporous silica was successfully synthesized for the first time using geothermal water from the Onuma Geothermal Power Plant, Akita Prefecture, Japan. Cetyltrimethylammonium bromide (CTAB) was used as an organic template for the synthesis. CTAB with a concentration of 2.4 × 10–4 mol/L was reacted for 30 min with geothermal water at a temperature of 90 °C, which had a total silicic acid concentration of 475 mg/L (SiO2), at pH 7.0, pH 8.2 (raw water) and pH 9.0. By calcination of the resulting precipitate at 550 °C, mesoporous silica with a pore size of about 2.8 nm and a specific surface area of > 800 m2/g was formed. The total silicic acid concentration in the solution after formation of the mesoporous precipitates was reduced to < 280 mg/L, indicating efficient recovery of supersaturated silicic acid from geothermal water. The monosilicic acid in geothermal water plays an important role in the formation of mesoporous silica. Production of mesoporous silica by our method will contribute not only to prevention of silica scale formation in the piping systems of geothermal power plants but also to its use as an industrial resource.

Highlights

Mesoporous silica was successfully synthesized for the first time using geothermal water from the Onuma Geothermal Power Plant, Akita Prefecture, Japan
We investigated the possibility of direct synthesis of mesoporous silica from supersaturated silicic acid dissolved in high-temperature geothermal water
Since monosilicic acid needs to be combined with Cetyltrimethylammonium bromide (CTAB) at the initial stage of mesoporous silica formation, the geothermal fluid used in this study is suitable for the formation of mesoporous silica

Summary

Introduction

Mesoporous silica was successfully synthesized for the first time using geothermal water from the Onuma Geothermal Power Plant, Akita Prefecture, Japan. Silicic acids precipitate as silica scale inside the pipes of the reinjection wells and the channels in geological formations around the reinjection wells. This results in a reduction of the efficiency of water reinjection, widely known as clogging problems[4,5,6,7,8]. We investigated the possibility of direct synthesis of mesoporous silica from supersaturated silicic acid dissolved in high-temperature geothermal water. Kitsuki et al.[30] described the selective removal of polysilicic acid from geothermal water at the Hatchobaru Geothermal Power Plant, Oita, Japan, by using CTAB, and indicated that dissolved silica in geothermal fluids can be effectively recovered. We examined the properties of precipitates that were recovered from the geothermal water at different pH conditions

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