CN114014307B

CN114014307B - Preparation method of few-layer aphanitic graphene

Info

Publication number: CN114014307B
Application number: CN202111487832.7A
Authority: CN
Inventors: 洪声安; 刘洪涛
Original assignee: Hunan Runzhong New Material Technology Co ltd
Current assignee: Hunan Runzhong New Material Technology Co ltd
Priority date: 2021-12-07
Filing date: 2021-12-07
Publication date: 2023-05-02
Anticipated expiration: 2041-12-07
Also published as: CN114014307A

Abstract

The invention provides a low-cost batch preparation method of few-layer aphanitic graphene, which is used for obtaining the few-layer aphanitic graphene with high carbon content through a brand new liquid phase stripping process.

Description

Preparation method of few-layer aphanitic graphene

Technical Field

The invention relates to a flotation method of a preparation method of few-layer aphanitic graphene, and belongs to the field of graphene preparation.

Background

Graphene (Graphene) is a kind of Graphene which is formed by sp ² The hybridized and connected carbon atoms are closely packed into the thinnest and the most rigid nano material with a single-layer two-dimensional honeycomb lattice structure, the nano material is almost completely transparent, only absorbs 2.3 percent of light, the acting force among the carbon atoms in the graphene is very strong, even if surrounding carbon atoms collide, the interference of electrons in the graphene is very small at normal temperature, the electron mobility of the graphene exceeds 15000cm < 2 >/V.s at normal temperature, the movement speed of electrons reaches 1/300 of the light speed, the carbon is higher than that of a nano tube or a silicon crystal, and the resistivity is only about 10 omega.cm and lower than copper and silver. Therefore, the graphene has excellent optical, electrical and mechanical properties, has important application prospects in the aspects of material science, micro-nano processing, energy sources, biomedicine, drug delivery and the like, and is considered as a revolutionary material in the future. Common production methods of graphene are a mechanical stripping method, an oxidation intercalation re-reduction method and a SiC epitaxial growth method, and thin film production methods are a chemical vapor deposition method, a liquid phase stripping method, a mechanical stripping method, a liquid phase mechanical stripping method and the like, wherein the chemical vapor deposition method can obtain high-quality graphene, but the yield is low, the requirement on a substrate is high, and great difficulty exists in transferring; the oxidation intercalation and re-reduction method can realize batch production of graphene, but the structure of graphene is destroyed in the oxidation process, so that a high-quality graphene product is difficult to obtain, a large amount of concentrated sulfuric acid is required for oxidation intercalation, and the waste acid is huge and difficult to treat; the liquid phase exfoliation method is to dissociate a graphite sheet layer using ultrasonic energy in a suitable solvent, however, the liquid phase exfoliation method has a problem that it is difficult to remove a residual solvent in preparing graphene, and the solvent exfoliation yield is generally low. In contrast, the liquid-phase mechanical physical stripping method is a reliable and easy method for preparing high-quality graphene at low cost. The intercalation agent is a stripping auxiliary agent commonly used in a liquid-phase mechanical physical stripping method, however, most of inorganic intercalation agents in the prior art are soluble salts or surfactants, and mainly play a role in regulating the surface tension of aqueous solution, so that the intercalation agent is easy to remain in graphene after the preparation process of graphene is finished, and the quality of the graphene is influenced.

The patent with publication number CN113443620A provides a method for adding expanded graphite and glycol into inorganic intercalation liquid to perform stirring pre-dispersion, high-speed shearing and high-pressure stripping to obtain a few-layer graphene nano dispersion liquid; the selected inorganic intercalation agent is one or more of nanometer fumed silica, superfine barium sulfate, nanometer calcium carbonate, nanometer titanium dioxide, nanometer ferric oxide, nanometer zirconium oxide, nanometer zinc oxide, spherical aluminum oxide, carbon black and carbon nano tube. However, the intercalating agent is difficult to separate when adsorbed in the aphanitic graphite, so that the quality of the final graphene is greatly affected, and the use of the organic dispersing agent affects the electric conductivity and the heat conductivity of the graphene, so that the application of the intercalating agent in a conductive material or a lead storage battery is affected.

Disclosure of Invention

The first aim of the invention is to provide a preparation method of few-layer graphene. The method can prepare the low-layer aphanitic graphene with high carbon content at low cost.

A preparation method of a few-layer aphanitic graphene comprises the following steps:

s1, adding water into cryptocrystalline graphite powder with a particle size of 100-200 meshes and a fixed carbon content of 40-80% to prepare ore pulp with a concentration of 30wt%, adding an intercalation agent, and carrying out first-stage grinding to obtain slurry I;

s2, diluting the slurry I to 10wt%, adding a foaming agent, a collector, an inhibitor and an anionic surfactant, and performing first open-circuit flotation to obtain slurry II;

s3, concentrating the slurry II to 25wt%, adding an intercalation agent, and carrying out second-stage grinding; then diluting the slurry II to 23wt%, adding an intercalation agent, and carrying out third-stage grinding to obtain slurry III;

s4, diluting the slurry III to 8wt%, adding a foaming agent, a collector, an inhibitor and an anionic surfactant, and performing second open-circuit flotation to obtain slurry IV;

s5, concentrating the slurry IV to 21wt%, adding an intercalation agent, and carrying out fourth stage grinding; diluting the slurry IV to 19wt%, adding an intercalation agent, and carrying out fifth stage grinding to obtain a slurry V;

s6, diluting the slurry V to 8wt%, adding a foaming agent, a collector, an inhibitor and an anionic surfactant, and performing third open-circuit flotation to obtain slurry VI;

s7, concentrating the slurry IV to 17wt%, adding an intercalation agent and a grinding aid, and carrying out sixth-stage grinding; then diluting the slurry II to 15wt%, adding an intercalation agent, and carrying out seventh stage grinding to obtain a slurry VII;

s8, diluting the slurry VII to 6wt%, adding a foaming agent, a collector, an inhibitor and an anionic surfactant, performing fourth-path flotation, diluting the slurry III to 6wt%, adding the collector and the anionic surfactant, and performing fifth-path flotation to obtain slurry VIII;

s9, purifying the flotation concentrate obtained by press filtration and drying of the slurry VIII by an acid-base method to obtain few-layer graphene with carbon content higher than 99.5%;

the intercalating agent comprises sodium hydroxide or potassium hydroxide.

The method comprises the steps of S1, adding water into aphanitic graphite powder with a fixed carbon content of 40-80% and a material diameter of 100-200 meshes, pulping to obtain pulp with a concentration of 30wt%, adding 8kg of an intercalating agent into the pulp per ton of aphanitic graphite powder, grinding in a wet grinding machine, wherein the feeding speed of the pulp of the grinding machine is 28 liters/min, and the linear speed of the pulp of the grinding machine is 10 m/S, and grinding in a first stage to obtain pulp I;

and S2, diluting the slurry I to 10wt%, adding 1.5kg of foaming agent, 0.8kg of collecting agent, 5kg of inhibitor and anionic surfactant per ton of aphanitic graphite powder, and performing first open-circuit flotation to obtain slurry II.

The S3 is that 5kg of intercalation agent is added into ore pulp by per ton of aphanitic graphite powder after the ore pulp II is concentrated to 25wt%, ore grinding is carried out in a wet mill, the feeding speed of the ore pulp of the mill is 28 liters/min, the linear speed is 10 meters/sec, and third stage ore grinding is carried out to obtain slurry III;

and S4, diluting the slurry III to 8wt%, adding 1kg of foaming agent, 0.5kg of collector, 5kg of inhibitor and 2kg of anionic surfactant per ton of aphanitic graphite powder, and performing second open-circuit flotation to obtain slurry IV.

S5, after concentrating slurry IV to the concentration of 21wt% of ore pulp, adding 3kg of an intercalating agent into the ore pulp according to each ton of aphanitic graphite powder, grinding in a wet grinding machine, wherein the feeding speed of the ore pulp of the grinding machine is 28 liters/min, and the linear speed is 10 meters/second, and grinding in a fourth stage; and diluting the slurry IV to 19wt%, adding 1kg of an intercalating agent per ton of aphanitic graphite powder, and carrying out fifth-stage grinding to obtain a slurry V.

And S6, after the slurry V is diluted to 8wt%, adding 1kg of foaming agent, 0.5kg of collecting agent, 5kg of inhibitor and 2kg of anionic surfactant into each ton of aphanitic graphite powder, and performing third open-circuit flotation to obtain slurry VI.

S7, after concentrating slurry VI to 17wt% of ore pulp, adding 5kg of intercalation agent into the ore pulp according to per ton of aphanitic graphite powder, grinding 20kg of grinding aid in a wet mill, wherein the feeding speed of the ore pulp of the mill is 28 liters/min, and the linear speed is 10 meters/second, and carrying out sixth-stage grinding; then diluting the slurry VI to 15wt%, adding 2kg of intercalation agent per ton of aphanitic graphite powder, and carrying out seventh stage grinding to obtain slurry VII.

And S8, diluting the slurry VII to 6wt%, adding 1kg of a foaming agent, 0.5kg of a collecting agent, 5kg of an inhibitor and 2kg of an anionic surfactant per ton of aphanitic graphite powder, and performing open-circuit flotation to obtain the slurry VIII.

The grinding adopts a mill comprising a wet mill;

the wet mill comprises a vertical stirring mill, a sand mill or a curved mill;

the grinding aid comprises a ceramic grinding aid;

the ceramic grinding aid can be sieved by a 30-mesh sieve;

the Mohs hardness of the ceramic grinding aid is more than or equal to 6.5;

the ceramic grinding aid comprises aluminum oxide, zirconium oxide, silicon carbide or silicon nitride;

the filter pressure of the filter pressing is 0.6MPAa, and the squeezing pressure is 1.2MPAa;

the drying temperature is 320-350 ℃.

The acid-base method comprises the steps of adding sodium hydroxide which is 3 times the mass of impurities in the flotation concentrate into the flotation concentrate, roasting at 750 ℃, and rinsing under acidic conditions.

The application of the few-layer graphene is applied to serving as an electrode negative electrode material or a wave-absorbing material.

Compared with the prior art, the invention has the following beneficial effects:

the invention can prepare few-layer graphene, the thickness of the few-layer graphene sheet is 1.2-1.8 nm, the size of the sheet is 0.5-5 mu m, and the number of layers is 3-5. The production cost of the low-layer graphene powder is low, the low-layer aphanitic graphene powder can be prepared in large quantity, and the prepared low-layer aphanitic graphene has good low-temperature discharge performance and can be used as a battery anode and cathode material and an electric conduction and heat conduction material.

Drawings

Fig. 1 shows a TEM photograph of the few-layered aphanitic graphene prepared in example 1. As can be seen from the figure, the overall morphology of graphene is in the shape of transparent chiffon. Although the thickness of the graphene cannot be accurately represented in the figure, the graphene sheet layer is extremely thin through the transparent chiffon shape of the edge of the graphene and the width of the edge tilting.

Fig. 2 shows AFM photographs of the few-layer aphanitic graphene prepared in example 1 and the analysis results thereof. AFM is one of the most effective methods of measuring the thickness of nanomaterials. The graphene shown in fig. 2 is a graphene sheet having a thickness of 1.5 nm. The thickness of single-layer graphene is generally about 0.7nm due to thermodynamic fluctuation and the influence of oxygen-containing functional groups on graphene, which indicates that the number of layers of graphene prepared in example 1 is 2 to 3.

Fig. 3 shows raman spectra of the few-layer aphanitic graphene prepared in example 1. The Raman spectrum analysis is used as the simplest and effective method for testing the graphene, and the reflected electronic structure and interaction between electrons can rapidly and qualitatively judge the quality and the number of layers of the graphene.

According to the empirical formula:

N＝I _2D /I _G

wherein I is _2D ，I _G Intensity of 2D peak and G peak, respectively, when N>1, graphene is a single layer; when N is approximately equal to 1, the graphene is a double layer; when N is<In 1, the graphene is a multilayer. The N of the graphene powder of the three varieties in the item is less than 1 through Raman analysis, which indicates that the prepared graphene is multi-layered.

Fig. 4 shows the BET-BJH curves of the few-layer aphanitic graphene prepared in example 1. From the point of view; it can be seen from the foregoing that the langmuir surface area of the graphene sheet of the few-layered cryptocrystalline graphene prepared in example 1 is 50.3m ² /g。

Detailed Description

Example 1

S1, grinding 1 ton of aphanitic graphite crude ore with 40-80% of fixed carbon to 100-200 meshes of powder by using a Raymond mill, pulping in a stirring barrel until the pulp concentration is 30%, adding 8kg of sodium hydroxide into the pulp, uniformly stirring the pulp and the sodium hydroxide, and then feeding the pulp into a vertical stirring mill for first-stage grinding to obtain pulp I; the mill feed rate was 28 liters of pulp per minute and the line speed was 10 meters per second.

S2, diluting the slurry I to 10wt% by adding water, adding 1.5kg of sec-octyl alcohol, 0.8kg of kerosene, 5kg of water glass and 2kg of sodium hexametaphosphate, and performing first full open-circuit flotation, wherein the residence time of ore pulp in a flotation tank is ensured to be not less than 40 minutes during flotation, so as to obtain slurry II.

And S3, carrying out filter pressing on the slurry II by using a plate-and-frame filter press, regulating the water content of a filter cake to be about 60%, regulating the water content of the filter cake and part of the slurry II to be 25%, then carrying out second-stage grinding by using a vertical stirring mill, wherein the feeding speed of the mill is 28 liters of ore pulp/min by using a vertical stirring mill of 1000 liters, the linear speed of the mill is 10 meters/second, 5kg of sodium hydroxide is added during second-stage grinding, stirring is uniform during the slurry regulation, the ore pulp is diluted to be 23% of ore pulp concentration after the second-stage grinding, and 2kg of sodium hydroxide is supplemented, stirring is uniform with the ore pulp, then carrying out three-stage grinding by using a vertical stirring mill of 1000 liters, and the linear speed of the mill is 10 meters/second, and the feeding speed of the mill is 28 liters/second, thereby obtaining the slurry III.

S4, diluting the slurry III to 8 weight percent, adding 1kg of sec-octanol, 0.5kg of kerosene, 5kg of water glass and 2kg of sodium hexametaphosphate, uniformly stirring, and carrying out second open-circuit flotation to obtain slurry IV. The residence time of the ore pulp in the flotation tank is ensured to be not less than 40 minutes during flotation.

S5, carrying out filter pressing on a part of the slurry IV (the ore pulp concentration is about 12%) by using a plate-and-frame filter press, regulating the water content of a filter cake to about 60%, regulating the slurry concentration of the filter cake of the plate-and-frame filter press and a part of the slurry IV to 21%, and then placing the mixture in a vertical stirring mill for fourth-stage ore grinding. The feeding speed of the mill is 28 liters per minute, the linear speed of the mill is 10 meters per second, and 3kg of sodium hydroxide is added during four-stage ore grinding. Diluting the slurry IV to 19wt%, supplementing 1kg of sodium hydroxide, uniformly stirring, and carrying out fifth-stage ore grinding to obtain a slurry V. The feeding speed and the linear speed of the mill for the fifth section grinding are consistent with those of the fourth section grinding.

S6, diluting the concentration of the slurry V to 8%, adding 1kg of sec-octanol, 0.5kg of a capturing agent, 5kg of water glass and 2kg of sodium hexametaphosphate into the diluted slurry, uniformly stirring, and performing third-stage full open-circuit flotation to obtain the slurry VI. The residence time of the ore pulp in the flotation ore is ensured to be not less than 40 minutes during flotation.

S7, press-filtering a part of the slurry VI by using a plate-and-frame filter press, mixing the filter cake with the slurry VI until the concentration of the slurry reaches 17%, adding 5kg of sodium hydroxide and 20kg of aluminum oxide, uniformly stirring the mixture with the slurry, and carrying out sixth-stage grinding, wherein the parameters of the sixth-stage grinding and the fifth-stage grinding are the same; and (3) adding a small amount of water into the slurry VI after the sixth stage of ore grinding to dilute the slurry VI to 15% of ore pulp concentration, supplementing 2kg of sodium hydroxide, and uniformly stirring to perform the seventh stage of ore grinding to obtain the slurry VII. The seventh stage grinding is the same as the fifth stage grinding.

And S8, adding water into the slurry VII to adjust the slurry concentration to 6%, adding 1kg of sec-octanol, 0.5kg of kerosene, 5kg of water glass and 2kg of sodium hexametaphosphate, uniformly stirring, performing fourth-path flotation, ensuring that the retention time of the slurry in a flotation tank is not less than 40 minutes in the four-stage flotation, adding water into the slurry VII (with the solid content of about 12%) to adjust the slurry concentration to 6%, adjusting the slurry, adding 0.2kg of kerosene and 1kg of sodium hexametaphosphate, uniformly stirring, and performing fifth-stage open-circuit flotation, and ensuring that the retention time of the slurry in the flotation tank is not less than 40 minutes in the fifth-stage open-circuit flotation.

And (3) delivering the concentrate subjected to S9 five-stage flotation into a membrane filter press for filter pressing, wherein the filter pressure is 0.6MPaa, the pressing pressure is 1.2MPa, a filter cake after pressing is delivered into a powerful dryer for drying, the fuel of the powerful dryer is natural gas, the material is dried through a hot blast stove after being directly combusted by a burner, the inlet temperature of the dryer is 320-350 ℃, the outlet temperature is 120 ℃, the water content of the dried graphene powder is less than or equal to 1%, the thickness of the dried graphene powder is 1.2-1.8 nm, the sheet size is 0.5-5 mu m, the fixed carbon content is more than or equal to 92%, and the volatile matters are less than or equal to 2.5%. If the graphene powder with the fixed carbon of more than or equal to 99.5 percent is required to be purified, the graphene powder is required to be further purified by adopting an alkali acid method.

The cryptocrystalline graphene powder produced from raw ore through the process has a fixed carbon content of only 92%, contains about 2.5% of volatile matters and 5.5% of other impurities (mainly quartz and silicate minerals), can be used in rubber industry, electric conduction, heat conduction coating and modified asphalt industry, and needs further purification if being used in the fields of battery anode and cathode materials and other high-end materials, wherein the simplest method is an alkali acid method, and the method is as follows:

(1) Adding caustic soda flakes according to the impurity content of 3 times, namely adding 165kg caustic soda flakes (NaOH) per ton, uniformly mixing by a vortex ring mill, then sending into a large-sized atmosphere furnace for roasting (introducing nitrogen), wherein a roasting kiln is divided into four areas, namely a preheating area, a heating area, a roasting area and a cooling area, wherein the temperature in the roasting area is 750 ℃, the object is kept for 20 minutes in the passing time of the roasting area, after the roasted material is cooled to below 100 ℃ by a cooling screw, sending into a stirring barrel for leaching, the leaching temperature is 60 ℃, the leaching time is one hour after reaching 60 ℃, the pulp concentration is 8-10%, the leached pulp is sent into a membrane filter press for one section, the pressure is 0.6MPa, the pressing pressure is 1.2kg, the filter cake is sent into the stirring barrel for one section of rinsing, the first section of rinsing steam is heated to 60 ℃, the heat-preserving stirring is carried out for 20 minutes, then entering into a second section of filter pressing, the second section of filter pressing is a membrane filter press, the filtering pressure is 0.6MPa, the pressing pressure is 1.2MPa, the pressed material enters into the stirring barrel for two sections of rinsing, the second section of rinsing is needed to be heated to 60 ℃ and the water is sent into the three sections for pressure pressing, the three sections for pressure filtering and three sections for water pressure filtering and three sections for pressure filtering and three pressure segments for 1.2MPa are used for comprehensive pressure treatment. The main purpose of the process is leaching and rinsing, and the low modulus sodium silicate formed by NaOH, quartz and silicate in the roasting process.

(2) Adding 100kg of 30% hydrochloric acid into a filter cake obtained after the second-stage rinsing and pressure filtration according to the dry amount of graphene powder per ton, leaching, removing alkali metal formed when the graphene powder and NaOH are roasted, heating to 60 ℃ by steam during leaching, keeping the temperature of 60 ℃ for leaching for one hour, leaching the pulp with the concentration of 8-10%, sending the leached pulp to a membrane filter press for first-stage pressure filtration, sending the first-stage pressure filtration filter pressure of 0.6MPa and the pressure of 1.2MPa, sending the filter cake after the first-stage pressure filtration to a stirring barrel for first-stage rinsing, sending the pulp with the concentration of 8% during rinsing, sending the rinsing liquid into water, heating to 60 ℃ by steam during rinsing, sending the filter cake after the squeezing to the stirring barrel for second-stage rinsing, heating to 60 ℃ during the second-stage rinsing, keeping the temperature, stirring, rinsing the pulp with the concentration of 8% during rinsing, sending the filter cake to the membrane filter press for second-stage pressure filtration, and sending the filter cake to the next-stage working procedure. The first stage of filter-pressing water is sent to the comprehensive treatment system, the second stage of filter-pressing water is returned to the leaching and pulp mixing system, and the third stage of filter-pressing water is sent to the first stage of rinsing system.

(3) The three-stage filter cake is sent to a powerful dryer for drying, the dried fuel is natural gas, the material is heated and dried by a hot blast stove after being directly combusted by a combustor, the inlet temperature of the dryer is 320-350 ℃ and the outlet temperature is 120 ℃, after the material passes through an alkali acid method, the fixed carbon content of the dried graphene powder is more than or equal to 99.5%, most of the dried graphene powder enters a cyclone collector, a small amount (about 20%) of the dried graphene powder enters a bag dust collector, the graphene powder entering the bag dust collector basically has no re-agglomeration phenomenon, enters a packaging system for packaging, most of the graphene powder in the cyclone collector has relatively high water content and has soft agglomeration phenomenon, the secondary depolymerization is needed, a vortex ring mill is selected for the depolymerizer, meanwhile, the inlet is fed by the natural gas hot blast stove at 140-150 ℃, the water content of the depolymerized graphene powder is less than or equal to 0.5%, and the graphene powder is not agglomerated any more, and is sent to the packaging machine for packaging.

In summary, the above is only a preferred embodiment of the present invention, but is not limited thereto. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. The preparation method of the few-layer aphanitic graphene is characterized by comprising the following steps of:

the intercalating agent comprises sodium hydroxide or potassium hydroxide;

the grinding adopts a mill comprising a wet mill;

the wet mill comprises a vertical stirring mill, a sand mill or a curved mill;

the grinding aid comprises a ceramic grinding aid;

the Mohs hardness of the ceramic grinding aid is more than or equal to 6.5;

the filter pressure of the filter pressing is 0.6MPa, and the squeezing pressure is 1.2MPa;

the drying temperature is 320-350 ℃;

2. The method for preparing the few-layer aphanitic graphene according to claim 1, wherein the method comprises the following steps:

3. The method for preparing the few-layer aphanitic graphene according to claim 1, wherein the method comprises the following steps:

4. The method for preparing the few-layer aphanitic graphene according to claim 1, wherein the method comprises the following steps:

5. The method for preparing the few-layer aphanitic graphene according to claim 1, wherein the method comprises the following steps:

6. The method for preparing the few-layer aphanitic graphene according to claim 1, wherein the method comprises the following steps:

7. The method for preparing the few-layer aphanitic graphene according to claim 1, wherein the method comprises the following steps:

and S8, diluting the slurry VII to 6wt%, adding 1kg of a foaming agent, 0.5kg of a collecting agent, 5kg of an inhibitor and 2kg of an anionic surfactant into each ton of aphanitic graphite powder, and performing fifth open-circuit flotation to obtain the slurry VIII.