How to deal with the high temperature of graphite material with excessive sulfur content

the graphite crystal is a plane layered structure with a hexagonal network composed of carbon elements, and the layers are bonded by Van der Waals force, so the bonding is very weak and the distance between layers is large. Therefore, under appropriate conditions, many chemical substances such as acids, alkali metals and salts can be inserted between graphite layers and combine with carbon atoms to form a new chemical phase-graphite intercalation on compounds (GIC). When heated to a proper temperature, this interlayer compound can decompose rapidly in an instant, producing a lot of gas, which makes graphite expand into a worm-like new substance along the axis, that is, expanded graphite. This unexpanded graphite interlayer compound is expandable graphite, which is an important inorganic nonmetallic material. It has excellent properties such as superconductivity, hydrogen storage, catalytic chemical reaction, acid and alkali resistance, high temperature resistance, tensile strength, compression resistance, radiation resistance and good bending elasticity, and is widely used to replace asbestos sealing materials which are easy to cause cancer.

The common preparation methods of expandable graphite mainly include chemical intercalation method, electrochemical method, ultrasonic oxidation method, gas phase diffusion method and molten salt method. At present, chemical intercalation method and electrochemical method are widely used in the production of expandable graphite in China. Except for different oxidation procedures, they are the same in other procedures, such as primary deacidification, water washing deacidification, dehydration and drying. The initial raw material for chemical intercalation method is high-carbon flake graphite, and the rest chemical reagents such as concentrated sulfuric acid (H2SO4). The preparation method comprises the following specific steps: at a proper temperature, reacting hydrogen peroxide solution, natural flake graphite and concentrated sulfuric acid with different ratios for a certain period of time under constant stirring, then washing with water for deacidification to neutrality, centrifugal separation, dehydration and drying. The pH value of expandable graphite prepared by this method is above 2. In order to meet the requirements of products, it is necessary to wash the expandable graphite for deacidification to make its pH value above 3, which leads to high washing water consumption and sewage discharge. At the same time, the acid water produced in the washing process contains a lot of suspended solids that pollute the environment, and most manufacturers are in a natural discharge state, and there are no measures to solve the wastewater treatment, which has caused environmental pollution and seriously restricted the development of the industry.