Synthesis of mesoporous silica from geothermal water

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.

The Synthesis and Characterisation of Nano-Structured Calcium Silicate

<p>Nano-structured calcium silicate consists of randomly stacked nano-sized platelets that make up an open framework structure of macropores that resembles a house of cards. This structure affords the material the desirable physical properties of a large pore volume and a highly accessible surface area that exceed many other silicas and silicates. The material is possibly related to other disordered calcium silicate hydrates at an atomic level, although it is the macro-structure and the potential of performing chemistry upon its surface that is of great interest. Due to the novelty of nano-structured calcium silicate, little was known about it before this work. The focus of this study has therefore been placed upon characterising the material and determining the conditions that allow the pore volume and surface area to be maximised. The material is prepared through an initial precipitation from the reaction of a calcium salt with monomeric silica, followed subsequently by self-ordering on both an atomic-scale and on a macro-scale to develop the porous framework. The framework of the material has been found to collapse due to forces created from surface tension during the removal of water from the pores upon drying. The result of this collapse is a substantial reduction in both the surface area and pore volume of the material. Three different methods have been developed to maintain the structure with each modification producing a material that is suitable for different applications. A reinforcing process following the development of the open framework whereby additional silica is polymerised upon the structure strengthens the material so that the forces resulting from the removal pore water are unable to cause collapse of the framework. This material is therefore able to be repeatedly re-wet and dried without any detrimental effect to the pore volume or surface area of the material. The replacement of water within the pores with 2-ethoxyethanol, that has a low surface tension, and by modifying the material through treatment with acid have also been found to prevent collapse of the structure. Through the knowledge gained of the development of the nano-structured calcium silicate and of the reaction conditions required for the optimisation of the surface area and pore volume, a semi-continuous process has been devised that has allowed for production of the material on a larger scale. This work also contains details on the formation of nano-structured calcium silicate by using geothermal water from an electricity generation plant as the source of monomeric silica rather than using sodium silicate. Currently, the formation of a scale from supersaturated geothermal water is problematic for the industries that use the fluid and limits the use of the resource. The removal of monomeric silica from geothermal water as a result of producing nanostructured calcium silicate prevents the formation of the scale and therefore allows a greater proportion of the thermal energy in the fluid to be potentially utilised.</p>

The Synthesis and Characterisation of Nano-Structured Calcium Silicate

<p>Nano-structured calcium silicate consists of randomly stacked nano-sized platelets that make up an open framework structure of macropores that resembles a house of cards. This structure affords the material the desirable physical properties of a large pore volume and a highly accessible surface area that exceed many other silicas and silicates. The material is possibly related to other disordered calcium silicate hydrates at an atomic level, although it is the macro-structure and the potential of performing chemistry upon its surface that is of great interest. Due to the novelty of nano-structured calcium silicate, little was known about it before this work. The focus of this study has therefore been placed upon characterising the material and determining the conditions that allow the pore volume and surface area to be maximised. The material is prepared through an initial precipitation from the reaction of a calcium salt with monomeric silica, followed subsequently by self-ordering on both an atomic-scale and on a macro-scale to develop the porous framework. The framework of the material has been found to collapse due to forces created from surface tension during the removal of water from the pores upon drying. The result of this collapse is a substantial reduction in both the surface area and pore volume of the material. Three different methods have been developed to maintain the structure with each modification producing a material that is suitable for different applications. A reinforcing process following the development of the open framework whereby additional silica is polymerised upon the structure strengthens the material so that the forces resulting from the removal pore water are unable to cause collapse of the framework. This material is therefore able to be repeatedly re-wet and dried without any detrimental effect to the pore volume or surface area of the material. The replacement of water within the pores with 2-ethoxyethanol, that has a low surface tension, and by modifying the material through treatment with acid have also been found to prevent collapse of the structure. Through the knowledge gained of the development of the nano-structured calcium silicate and of the reaction conditions required for the optimisation of the surface area and pore volume, a semi-continuous process has been devised that has allowed for production of the material on a larger scale. This work also contains details on the formation of nano-structured calcium silicate by using geothermal water from an electricity generation plant as the source of monomeric silica rather than using sodium silicate. Currently, the formation of a scale from supersaturated geothermal water is problematic for the industries that use the fluid and limits the use of the resource. The removal of monomeric silica from geothermal water as a result of producing nanostructured calcium silicate prevents the formation of the scale and therefore allows a greater proportion of the thermal energy in the fluid to be potentially utilised.</p>

Effects on C-phycocyanin content of Arthrospira (Spirulina) platensis of culture medium containing geothermal water.

This research aimed to compare effects on product quality and algal growth of inoculation ratio of Arthrospira platensis in the culture medium containing 20% geothermal water. A. platensis was inoculated at the ratio of 1/6, 1/10, and 1/20 of nutrient medium volume (2500 mL). The experiment medium was prepared with 20% geothermal water and 80% distilled water. Schlösser medium, 100% geothermal water medium, and 100% distilled water were used as the control group. At the end of the experiment, Spirulina biomass was obtained by filtration through 80-micron plankton cloth and freeze-dried at -60 °C. Increasing inoculation density shortened the culture time and increased the growth rate compared to the other groups. The best growth among the experimental groups was obtained in a 1/6 ratio inoculated Spirulina group in a 20% geothermal water medium. Among the experimental groups, dry biomass was obtained in the Spirulina group inoculated at 1/6 in only 20% geothermal water medium. The optical density value was 0.989 (A750), and the biomass yield was 0.476 g/L in the experimental group, the highest among the Schlösser groups was 1.259 (A750), and the biomass yield was 0.928 g/L. The most efficient growth and phycocyanin content was determined in the 1/6 inoculated groups. The phycocyanin content in the experimental group was found in 22.49%, and the purity rate was 2.24. In control groups, 3.73 purity and 28.62% phycocyanin were determined in the Schlösser medium. While 48.42% protein was detected in the geothermal water group, 61.64% was obtained with the Schlösser medium.

Thermal Protection Technology for Acoustic–Magnetic Device in a Geothermal Water Anti-Scaling System

This article presents the results of the design of acoustic–magnetic device thermal protection technology based on simulation. The acoustic–magnetic device (AMD) was installed in the heat supply system of a greenhouse complex with a geothermal heat source, developed and patented by the authors of this paper. Simulation was performed to investigate the possibility of maintaining the acoustic transmitter temperature of the acoustic–magnetic device in its operating range. The QuickField Student Edition v 6.4 simulation environment was used for this purpose. Based on the results of the simulation, the optimum thermal mode of the acoustic–magnetic device was developed and implemented. The optimum temporal operating mode of the acoustic–magnetic device is necessary for the optimization of the non-reagent treatment of geothermal water in a heat supply system of a greenhouse complex. It allows for a considerable reduction in the intensity of scale formation in the heat exchanger and equipment of a geothermal heating system. As demonstrated by the simulation thermal modes, the acoustic–magnetic device provides conditions for the work maintenance of the AMD acoustic transmitter at the resonance frequency, reduces the power expenses, and increases the efficiency of the acoustic influence on the scale formed in the heat supply system of a greenhouse complex. The results of the simulation were implemented in the greenhouse complex of JSC “Raduga.” The thermal protection technology was realized by installing two acoustic–magnetic devices and automation systems in the geothermal heating system a greenhouse complex.