Preparation method of silicon dioxide and graphene gel composite adsorbent

Abstract

The invention discloses a preparation method of a silicon dioxide and graphene gel composite adsorbent, which comprises the following steps: fully absorbing N, N-dimethylacetamide by using hydrophobic porous silicon dioxide powder, so that the hydrophobic porous silicon dioxide temporarily has certain hydrophilicity; n, N-dimethylacetamide is taken as a raw material, the N, N-dimethylacetamide and a graphene oxide solution are fully stirred in an aqueous solution, hydro-thermal treatment is performed to obtain the silicon dioxide and graphene gel composite adsorbent, and hydrophobic porous silicon dioxide and hydrophilic graphene oxide can be smoothly compounded by utilizing the hydrophilic and oleophylic characteristics of N, N-dimethylacetamide. The method does not need violent mechanical stirring and ultrasonic treatment, and is beneficial to protecting the integrity of silicon dioxide holes. The method does not need special instruments and equipment, and is favorable for controlling the production cost.

Description

Technical Field

[0001] This invention relates to the field of liquid separation, and more specifically, to a method for preparing an adsorbent for adsorbing and separating petroleum components from water, particularly a method for preparing a silica and graphene gel composite adsorbent. Background Technology

[0002] Leaks of crude oil and its components cause severe water pollution, which can be absorbed and eliminated from the water using highly hydrophobic and oleophilic adsorbent materials. Specially treated silica possesses a highly hydrophobic porous structure and an oil absorption value of up to 3.24 mL g. -1 (Gu Shan. Preparation and carbon footprint analysis of high-performance nano-silica based on rice husk [D]. Zhejiang University, 2015.), is an ideal crude oil adsorption material. In order to accelerate the adsorption of crude oil by hydrophobic porous silica and improve its adsorption capacity for small molecule aromatic compounds, it can be combined with graphene materials. Such composite materials have been shown to have good application prospects for treating crude oil pollution (Wang X, Liu Z, Liu X, et al. Ultralight and multifunctional PVDF / SiO2@GO nanofibrous aerogel for efficient harshenvironmental oil-water separation and crude oil absorption [J]. Carbon: An International Journal Sponsored by the American Carbon Society, 2022(193-):193.DOI:10.1016 / j.carbon.2022.03.028.).

[0003] The preparation of graphene oxide via chemical oxidation (Hummers method) offers advantages such as considerable yield, low cost, and stable quality, making it a relatively economical approach to preparing graphene composites. However, specially treated porous silica exhibits strong hydrophobicity, while graphene oxide is highly hydrophilic, making it difficult to composite the two in a single solvent. Furthermore, combining the two in an aqueous solution through vigorous mechanical stirring or ultrasound (refer to Chinese Patent CN202011604078.6) significantly damages the structure of the porous silica, weakening its ability to adsorb crude oil. Summary of the Invention

[0004] To address the difficulty in combining hydrophobic porous silica and hydrophilic graphene oxide in a single solvent, this invention provides a method for preparing a silica-graphene gel composite adsorbent.

[0005] This method utilizes the simultaneous oleophilic and hydrophilic properties of DMAC. First, DMAC is used to fill the pores of hydrophobic porous silica, temporarily imparting a degree of hydrophilicity to the silica. After the hydrophobic porous silica and graphene oxide are combined in water, the DMAC is then removed. This method also leverages the stability of DMAC; it does not participate in the reaction, therefore its modification of the hydrophobic porous silica is temporary. This differs from N,N-dimethylformamide (DMF) under the same conditions, which decomposes during hydrothermal processes and generates highly hydrophilic nitrogen-doped graphene quantum dots (N-GQDs) on the silica surface (Saisree S, Nair JSA, Sandhya KY. Variant solvothermal synthesis of N-GQD for colour tuning emissions and naked eye reversible shadetweaking pH sensing ability[J]. Chemical papers, 2022.DOI:10.1007 / s11696-022-02376-w.). DMF cannot be used in this reaction.

[0006] The technical solution provided by this invention is: a method for preparing a silica-graphene gel composite adsorbent, wherein hydrophobic porous silica powder fully absorbs N,N-dimethylacetamide, temporarily giving the hydrophobic porous silica a certain degree of hydrophilicity. After thorough stirring with a graphene oxide solution in an aqueous solution, hydrothermal treatment is performed to obtain the silica-graphene gel composite adsorbent. This method utilizes the simultaneous hydrophilic and oleophilic properties of N,N-dimethylacetamide, enabling the successful composite of hydrophobic porous silica and hydrophilic graphene oxide. The method includes the following steps: (1) Prepare an aqueous solution of graphene oxide.

[0007] (2) Add hydrophobic porous silica powder into N,N-dimethylacetamide (DMAC) to fill the pores of the hydrophobic porous silica with DMAC; use filter paper to remove excess DMAC.

[0008] (3) The hydrophobic porous silica saturated with DMAC obtained in step (2) is added to the aqueous solution of graphene oxide obtained in step (1) and stirred to obtain the composite precursor.

[0009] (4) The composite precursor obtained in step (3) is loaded into a hydrothermal reactor and reacted at 180°C for 1 h.

[0010] (5) Soak the complex in hot water to desorb DMAC.

[0011] Advantages of this invention: (1) This method does not require vigorous mechanical stirring and ultrasound, which helps to protect the integrity of the silica pores.

[0012] (2) This method does not require special instruments and equipment, which is conducive to controlling production costs. Attached Figure Description

[0013] Figure 1 A composite effect diagram of Example 1 and the prior art. Detailed Implementation

[0014] The present invention will be further illustrated below with reference to specific embodiments. Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods. Unless otherwise specified, the materials and reagents used in the following embodiments are commercially available. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0015] Example 1 A silica-graphene gel composite adsorbent was prepared, wherein the ratio of silica to graphene oxide was 2:1, comprising: (1) Preparation of graphene oxide solution: Add 40 mL of pure water and 0.20 g of graphene oxide powder to a 100 mL beaker, stir magnetically at 1500 rpm for 30 minutes, and sonicate for 30 minutes. (2) Fill hydrophobic porous silica with DMAC: Place 0.40 g of hydrophobic porous silica in a 50 mL beaker, add 10 mL of DMAC, gently shake the beaker and let it stand for 30 min. The DMAC will gradually fill the hydrophobic porous silica, turning it from white to transparent. Use filter paper to absorb the excess DMAC from the surface of the beaker. (3) Material composite: The hydrophobic porous silica completely wetted by DMAC obtained in step (2) was transferred to the graphene oxide solution obtained in step (1) using a plastic spatula. The solution was magnetically stirred at 500 rpm for 30 min until it turned into a viscous black fluid. Stirring was then stopped. (4) Solvothermal reaction: The black fluid obtained in step (3) was sealed in a hydrothermal reactor and reacted at 180°C for 1 hour; the product was a graphene gel loaded with hydrophobic porous silica particles. (5) Desorption of DMAC The graphene gel obtained in step (4) was transferred to a 400 mL beaker, 200 mL of pure water was added, and the mixture was kept at 50 °C for 24 h. DMAC, which is miscible with hot water, was desorbed from the graphene gel. Excess water was removed to obtain a silica and graphene gel composite adsorbent.

[0016] Figure 1 The left figure shows the effect of combining hydrophobic porous silica and graphene oxide according to the method of Chinese patent CN202011604078.6. Due to the non-wetting nature of hydrophobic porous silica, it floats on the water surface (appearing white) and is clearly separated from the graphene oxide dispersed in the water (appearing black), making it impossible to obtain the ideal composite.

[0017] Figure 1 The figure on the right shows the composite effect of the silica and graphene gel composite adsorbent prepared by the method of the present invention, in which the hydrophobic porous silica particles and the graphene gel achieve a uniform composite.

[0018] The above embodiments are merely examples to clearly illustrate the present invention and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a silica and graphene gel composite adsorbent, characterized in that, Hydrophobic porous silica powder is used to fully absorb N,N-dimethylacetamide, temporarily imparting a certain degree of hydrophilicity to the hydrophobic porous silica. This is followed by hydrothermal treatment with a graphene oxide solution in an aqueous solution to obtain a silica-graphene gel composite adsorbent. This utilizes the simultaneous hydrophilic and oleophilic properties of N,N-dimethylacetamide, enabling the successful composite of hydrophobic porous silica and hydrophilic graphene oxide. The process includes the following steps: (1) Prepare an aqueous solution of graphene oxide; (2) Add hydrophobic porous silica powder into N,N-dimethylacetamide (DMAC) to fill the pores of the hydrophobic porous silica powder with DMAC; (3) The hydrophobic porous silica powder and graphene oxide that have absorbed N,N-dimethylacetamide were thoroughly mixed in water, with the ratio of silica to graphene oxide being 2:

1. (4) The mixture obtained in hydrothermal treatment step (3); (5) N,N-dimethylacetamide was removed by solvent exchange to obtain a hydrophobic porous silica powder and graphene gel composite adsorbent.

2. The preparation method of the silica and graphene gel composite adsorbent according to claim 1, characterized in that, Includes the following steps: (1) Preparation of graphene oxide solution: Add 40 mL of pure water and 0.20 g of graphene oxide powder to a 100 mL beaker, stir magnetically at 1500 rpm for 30 minutes, and sonicate for 30 minutes. (2) Fill hydrophobic porous silica with DMAC: Place 0.40 g of hydrophobic porous silica in a 50 mL beaker, add 10 mL of DMAC, gently shake the beaker and let it stand for 30 min. The DMAC will gradually fill the hydrophobic porous silica, turning it from white to transparent. Use filter paper to absorb the excess DMAC from the surface of the beaker. (3) Material composite: The hydrophobic porous silica completely wetted by DMAC obtained in step (2) was transferred to the graphene oxide solution obtained in step (1) using a plastic spatula. The solution was magnetically stirred at 500 rpm for 30 min until it turned into a viscous black fluid. Stirring was then stopped. (4) Solvothermal reaction: The black fluid obtained in step (3) was sealed in a hydrothermal reactor and reacted at 180°C for 1 hour. The product was a graphene gel loaded with hydrophobic porous silica particles. (5) Desorption of DMAC: The graphene gel obtained in step (4) was transferred to a 400 mL beaker, 200 mL of pure water was added, and the mixture was kept at 50 °C for 24 h. The DMAC, which is miscible with hot water, was desorbed from the composite gel. The excess water was removed to obtain the silica and graphene gel composite adsorbent.

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