EP-4306486-B1 - PREPARATION METHOD OF POROUS HYDRATED CALCIUM SILICATE

Inventors

• YAN, FENG
• QU, Fan
• ZHANG, Zuotai
• LI, CHUNYAN
• SHEN, XUEHUA
• CHEN, Heijin

Dates

Publication Date

20260506

Application Date

20220513

Claims (6)

1. A preparation method of a porous calcium silicate hydrate, characterized in that the preparation method comprises the following steps: leaching: leaching fly ash with an alkali agent to obtain a silicate leaching solution; reaction: adding the silicate leaching solution dropwise to a calcium hydroxide suspension, and stirring and heating for reaction to obtain a calcium silicate hydrate gel, wherein the silicate leaching solution is dropped to the calcium hydroxide suspension at a uniform rate of 15-35 mL/h, the stirring is conducted at a rate of 450-550 rpm, the heating reaction is conducted for 2-12 h, and the reaction is conducted at 25-80 °C; and reaming: mixing the calcium silicate hydrate gel with an organic alcohol solvent, conducting azeotropic distillation, and then conducting separation, drying and calcination to obtain the porous calcium silicate hydrate, wherein the porous calcium silicate hydrate basically belongs to an amorphous form.
2. The preparation method according to claim 1, wherein in the step of leaching, the alkali agent is a sodium hydroxide aqueous solution, the sodium hydroxide aqueous solution and the fly ash are mixed and heated to undergo a hydrothermal reaction, followed by filtration and separation to obtain the silicate leaching solution and desilicified fly ash, the silicate leaching solution is a sodium silicate leaching solution, and the desilicified fly ash is used for recovering alumina; and in the step of leaching, the mass ratio of sodium hydroxide in the sodium hydroxide aqueous solution to the fly ash is 0.4:1 to 0.8:1, the sodium hydroxide aqueous solution has a concentration of 10-30 wt%, and the hydrothermal reaction is carried out at 105-115 °C for 0.4-0.6 h.
3. The preparation method according to claim 1, wherein the alkali agent is a sodium hydroxide aqueous solution; and in the step of reaction, stirring and a heating reaction are conducted, followed by filtration to obtain the calcium silicate hydrate gel and a sodium hydroxide byproduct, and the sodium hydroxide byproduct is used for recycling as the alkali agent.
4. The preparation method according to claim 1, wherein in the step of reaction, the molar ratio of a silicate in the silicate leaching solution to calcium hydroxide in the calcium hydroxide suspension is 0.9:1 to 1.1:1, and the silicate leaching solution has a concentration of 0.067-1.067 mol/L.
5. The preparation method according to any one of claims 1 to 4, wherein in the step of reaming, the organic alcohol solvent is at least one of ethanol, propanol or butanol, and the ratio of the mass of the calcium silicate hydrate gel to the volume of the organic alcohol solvent is 0.9 g: 15 mL to 1.1 g: 15 mL.
6. The preparation method according to any one of claims 1 to 4, wherein in the step of reaming, the azeotropic distillation comprises heating the calcium silicate hydrate gel and the organic alcohol solvent to a first temperature first, followed by distillation at constant temperature for 15-25 min, and then heating the same to a second temperature, followed by distillation at constant temperature for 35-45 min, wherein the first temperature is a boiling point temperature of a system formed by the organic alcohol solvent and water, and the second temperature is a boiling point temperature of the organic alcohol solvent; and the drying is conducted at 80-85 °C for 10-14 h, and the calcination is conducted at 400-600 °C for 4-4.5 h.

Description

FIELD OF TECHNOLOGY The present application relates to the technical field of resource utilization of industrial solid wastes, and in particular to a porous calcium silicate hydrate, a preparation method thereof and an adsorbent. BACKGROUND A calcium silicate hydrate is a porous material, and has been widely used in various fields. At present, an expensive template agent is usually required to add for adjusting a pore structure of the calcium silicate hydrate when the calcium silicate hydrate is prepared, resulting in high preparation cost. In addition, the calcium silicate hydrate prepared by adding the template agent for adjustment has some bottlenecks in pore size and volume, which are difficult to increase greatly, so that application of the calcium silicate hydrate is greatly limited, and industrial application and popularization are also difficult. CN103708479B discloses a process to prepare calcium silica hydrate. SUMMARY The present application provides a porous calcium silicate hydrate, a preparation method thereof and an adsorbent, so as to solve the problems that existing preparation methods of calcium silicate hydrates have high cost, the pore size and volume of the calcium silicate hydrates prepared are difficult to increase greatly and industrial application is limited. In a first aspect, the present application provides a preparation method of a porous calcium silicate hydrate. The preparation method includes the following steps: leaching: leaching fly ash with an alkali agent to obtain a silicate leaching solution;reaction: adding the silicate leaching solution dropwise to a calcium hydroxide suspension, and stirring and heating for reaction to obtain a calcium silicate hydrate gel, wherein the silicate leaching solution is dropped to the calcium hydroxide suspension at a uniform rate of 15-35 mL/h, the stirring is conducted at a rate of 450-550 rpm, the heating reaction is conducted for 2-12 h, and the reaction is conducted at 25-80 °C; andreaming: mixing the calcium silicate hydrate gel with an organic alcohol solvent, conducting azeotropic distillation, and then conducting separation, drying and calcination to obtain the porous calcium silicate hydrate, where the porous calcium silicate hydrate basically belongs to an amorphous form. Further, in the step of leaching, the alkali agent is a sodium hydroxide aqueous solution, the sodium hydroxide aqueous solution and the fly ash are mixed and heated to undergo a hydrothermal reaction, followed by filtration and separation to obtain the silicate leaching solution and desilicified fly ash, the silicate leaching solution is a sodium silicate leaching solution, and the desilicified fly ash is used for recovering alumina. Further, in the step of leaching, the alkali agent is a sodium hydroxide aqueous solution, the mass ratio of sodium hydroxide in the sodium hydroxide aqueous solution to the fly ash is 0.4:1 to 0.8:1, the sodium hydroxide aqueous solution has a concentration of 10-30 wt%, and the hydrothermal reaction is carried out at 105-115 °C for 0.4-0.6 h. Further, the alkali agent is a sodium hydroxide aqueous solution; and in the step of reaction, stirring and a heating reaction are conducted, followed by filtration to obtain the calcium silicate hydrate gel and a sodium hydroxide byproduct, and the sodium hydroxide byproduct is used for recycling as the alkali agent. Further, in the step of reaction, the molar ratio of a silicate in the silicate leaching solution to calcium hydroxide in the calcium hydroxide suspension is 0.9:1 to 1.1:1, and the silicate leaching solution has a concentration of 0.067-1.067 mol/L. Further, in the step of reaming, the organic alcohol solvent is at least one of ethanol, propanol or butanol, and the ratio of the mass of the calcium silicate hydrate gel to the volume of the organic alcohol solvent is 0.9 g: 15 mL to 1.1 g: 15 mL. Further, in the step of reaming, the azeotropic distillation includes heating the calcium silicate hydrate gel and the organic alcohol solvent to a first temperature first, followed by distillation at constant temperature for 15-25 min, and then heating the same to a second temperature, followed by distillation at constant temperature for 35-45 min, where the first temperature is a boiling point temperature of a system formed by the organic alcohol solvent and water, and the second temperature is a boiling point temperature of the organic alcohol solvent; and the drying is conducted at 80-85 °C for 10-14 h, and the calcination is conducted at 400-600 °C for 4-4.5 h. Compared with the prior art, the present application has the following beneficial effects. According to the preparation method provided in an embodiment of the present application, a porous calcium silicate hydrate with larger pore volume and a better pore structure can be obtained without the use of a template agent, so that the porous calcium silicate hydrate can be used as a carrier of an adsorbent and has excellent ad