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What are the preparation methods of activated carbon?
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The structural characteristics of activated carbon depend on the properties of the precursor, the carbonization, activation and chemical adjustment conditions of the raw materials. activated carbon gold recovery Choosing appropriate raw materials is an important factor affecting the properties of activated carbon. Activated carbon can be prepared from various types of carbonaceous materials. The source of raw materials is very wide. Depending on the raw materials used, the preparation methods used are also different.
Activated carbon raw materials generally have low ash content, high carbon content and the lowest possible volatility. Good raw materials are mainly coal (lignite, long-flame coal, bituminous coal, anthracite), wood, and nutshells. The preparation methods of activated carbon can be mainly divided into: carbonization method, activation method, carbon deposition method, thermal shrinkage and other methods.
- Carbonization method
A method of placing activated carbon carbonaceous raw materials in an inert atmosphere to obtain carbonized products under appropriate pyrolysis conditions.
Basic principle: Based on the complex decomposition and polymerization reaction of various groups, bridge bonds, free radicals and aromatic rings during the heating process, it is manifested in the development of pores, expansion and contraction of pore diameters of carbonized products. activated carbon manufacturers australia During the carbonization process, the thermally unstable components in the carbonaceous raw materials are released in the form of volatiles, thereby leaving pores on the semi-coke.
Application situation: It is suitable for high volatile raw materials and is the basis of all other methods. The main factors affecting the carbonization process are heating rate, carbonization temperature and constant temperature time. The heating rate used is generally 5~15℃/min, the carbonization temperature is mostly 500~1100℃, and the constant temperature time is 0.5~2h.
- Activation method
The activated carbon carbonaceous raw material is heated and gently processed in an active medium to develop its pore size method.
Basic principle: Based on the burning loss of part of the carbon of the carbonaceous raw material, the closed pores can be opened, so that the pore structure is developed, and the pore size reaches the required range. Commonly used activators are air, CO2, water vapor, H3PO4, KOH, NaOH and so on. In industrial practice, water vapor, which is easily available, is often used for activation.
Application: Suitable for activated carbon carbonaceous raw materials with small porosity and low volatile matter, or high porosity but small pore size.
- Carbon deposition
Refers to the pyrolysis of hydrocarbons or polymer compounds at high temperatures to accumulate carbon in the pores of porous materials to achieve the effect of plugging and adjusting pores.
Features: The process is complex, the operating conditions are strict, and the actual production cost is relatively high. Carbon deposition is often divided into vapor phase (CVD) and liquid phase deposition (LVD). For the vapor deposition process, the gas concentration in the reaction furnace is relatively uniform, which can effectively control the pore size of the activated carbon, but the disadvantage is that an external deposition gas source generator is required, and the flow rate needs to be adjusted, which is not conducive to operation; liquid deposition requires process Lower, easier to operate.
- Heat shrinkage method
The thermal polycondensation method refers to the process of further heat treatment of carbonaceous materials at a high temperature of 1000~1200℃ after carbonization and activation, so as to achieve the purpose of reducing the pore size.