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Preparation method for expanded graphite

A technology of expanded graphite and spent fuel, applied in the chemical field, can solve the problems of increasing the disposal space of high-level radioactive waste, failing to satisfy the disintegration of graphite spheres, and the pollution of matrix graphite, so as to reduce the fragmentation rate, reduce the disposal space, and improve the effect of reuse

Inactive Publication Date: 2015-07-22
TSINGHUA UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0008] The above methods all use strong acid, strong oxidant, etc. to prepare expanded graphite from natural flake graphite, but use strong acid and strong oxidant to intercalate and oxidize spent fuel element balls in high temperature gas-cooled reactors, which will easily dissolve the accidentally broken coated particles in the solution. α radioactivity and strong γ radioactivity of fission products pollute a large amount of matrix graphite, resulting in a large amount of matrix graphite that cannot be reused or temporarily stored in the form of low-to-medium radioactivity due to pollution, increasing the disposal space of high-level radioactive waste; High pressure treatment, the existing chemical oxidation and electrochemical process conditions cannot satisfy the disintegration of graphite spheres, and form and prepare expanded graphite at low temperature, it is necessary to develop a new technology

Method used

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Examples

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Effect test

Embodiment 1

[0022] Configure KNO with a concentration of 3mol / L 3 The electrolyte solution was placed in the electrolytic cell, and the pH was adjusted to 3 with nitric acid. The lead plate was used as the cathode, and the simulated spent fuel element ball with a diameter of Φ60mm was used as the anode. At room temperature, a 25A current was passed through for constant current electrolysis. During the electrolysis process, the pH is controlled by an automatic pH adjustment instrument to be 3. After 5 hours, the electrolyte is filtered, and the filter cake is washed with deionized water until the pH of the filtrate is about 7. Then, it is naturally dried and expanded in an oven at 200°C for 1 hour. Separation of graphite and simulated fuel core after expansion, the specific surface area of ​​graphite particles obtained is 35m 2 / g, the expansion volume is 44mL / g.

Embodiment 2

[0024] Configure Na with a concentration of 2mol / L 3 PO 4 The electrolyte solution was placed in the electrolytic cell, and the pH was adjusted to 5 with nitric acid. Graphite was used as the cathode, and a simulated spent fuel element ball with a diameter of Φ60mm was used as the anode. At room temperature, a 40A current was passed through for constant current electrolysis. During the electrolysis process, the pH is controlled by an automatic pH adjustment instrument to be 5. After 3 hours, the electrolyte is filtered, and the filter cake is washed with deionized water until the pH of the filtrate is about 7. After natural drying, it is expanded in an oven at 150°C for 2 hours. After separation of graphite and simulated fuel core, the specific surface area of ​​graphite particles obtained after expansion is 23m 2 / g, the expansion volume is 25mL / g.

Embodiment 3

[0026] Configure Na with a concentration of 2mol / L 2 SO 4 The electrolyte solution was placed in the electrolytic cell, and the pH was adjusted to 7 with nitric acid. The titanium mesh was used as the cathode, and the simulated spent fuel element ball with a diameter of Φ60mm was used as the anode. At a temperature of 40°C, a current of 60A was passed through for constant current electrolysis. During the electrolysis process, the pH was controlled to be 7 by an automatic pH adjustment instrument. After 2 hours, the electrolyte was filtered, and the filter cake was washed with deionized water until the pH of the filtrate was about 7. Then, it was naturally dried and expanded in an oven at 120°C for 3 hours. Separation of graphite and simulated fuel core after expansion, the specific surface area of ​​graphite particles obtained after expansion is 50m 2 / g, the expansion volume is 48mL / g.

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Abstract

The invention belongs to the field of chemistry and particularly relates to a preparation method for expanded graphite. The method comprises the following steps: taking sulfate, phosphate or nitrate as an electrolyte solution, taking a simulated spent fuel ball as an anode, and taking an inert electrode as a cathode; performing electrolysis under a condition that the current is 25-70 A. Collected graphite particles have the specific surface area being 20-50 m<2> / g and the expansion volume of 20-70 mL / g. Due to the adoption of electrochemical intercalation and oxidation coupling methods, graphite oxide containing various free radical groups is easily formed under the action of high current, and graphite particles are refined, so that the formation temperature of the expanded graphite is reduced, energy resources are saved, the breakage rate of a simulated fuel core is reduced, reutilization of a large amount of matrix graphite is improved, and disposal space of high-level wastes is reduced.

Description

technical field [0001] The invention belongs to the field of chemistry, in particular to a preparation method of expanded graphite. Background technique [0002] Nuclear energy is an energy source with abundant reserves and high concentration on the earth. Nuclear power generation is more economical and clean, and can greatly reduce environmental pollution. The 21st century will be a period of great development of nuclear power generation. [0003] High-temperature gas-cooled reactor spent fuel element balls are pressed at 300MPa and calcined at 1600°C, of ​​which more than 95wt% is graphite. If most of the graphite can be stripped and prepared into expanded graphite for reuse, it will not only reduce the disposal space of high-level radioactive waste, but also save resources. [0004] Carbon atoms in graphite are arranged in a layered structure, and the bonding force between layers is much weaker than that between carbon atoms on the layer. Therefore, under certain condit...

Claims

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Application Information

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IPC IPC(8): C25B1/00C01B31/04
CPCC25B1/00C01B32/20
Inventor 文明芬陈靖王树威王建晨
Owner TSINGHUA UNIV
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