The production process of powderedActivated carbon for food decolorization is mainly divided into two categories: physical method and chemical method. The core is to form a developed pore structure of the raw materials through processes such as carbonization and activation to enhance the adsorption capacity. The following is a summary of the specific production process and characteristics:
1. Raw material selection and pretreatment
Raw material type: mainly high-quality sawdust, fruit shells or anthracite. Different raw materials affect the pore structure and adsorption characteristics of activated carbon.
Pretreatment steps:
Screening and drying: After removing impurities, dry the raw materials to a suitable moisture content (usually ≤10%).
Crushing and impregnation (unique to chemical method): The chemical method requires the raw materials to be crushed to less than 180 mesh and impregnated with zinc chloride or phosphoric acid solution to increase the porosity.
2. Core production process
1. Physical method (gas activation method)
Carbonization: Under air-tight conditions, the raw materials are carbonized at a high temperature of 500~700℃ to remove volatiles to form preliminary pores.
Activation: Activation by water vapor or carbon dioxide at 800~950℃, so that the carbonized material further forms microporous and mesoporous structures.
Post-treatment: including rinsing (removing impurities), centrifugal dehydration, drying and grinding, and finally making black powdered activated carbon.
2. Chemical method (chemical activation method)
Activator selection: phosphoric acid or zinc chloride is commonly used as an activator, among which:
Phosphoric acid method: suitable for the production of food-grade activated carbon, with the characteristics of well-developed mesopores and no zinc salt, widely used for decolorization of sugars, monosodium glutamate, etc.
Zinc chloride method: suitable for the purification of amino acid industry and high-pigment solution, with large adsorption capacity but strict removal of zinc residues.
Activation process: The impregnated raw materials are carbonized and activated at 400~600℃, and a porous structure is formed through the synergistic effect of chemical reagents and carbon.
3. Quality Control and Technical Indicators
Key Indicators:
Methylene blue adsorption value: reflects the mesopore adsorption capacity, the physical method is 6~24 ml/0.1g, and the chemical method is 10~18 ml/0.1g.
Caramel decolorization rate: ≥90%~120%, directly affecting the decolorization effect of food.
Ash and acid-soluble matter: Food grade requires ash ≤3%, acid-soluble matter ≤0.8% (physical method) or ≤1% (chemical method).
Post-processing optimization: reduce ash by acid washing or alkali washing, and use screening to control particle size (usually 200 mesh pass rate ≥95%).
4. Application and precautions
Applicable fields:
Physical activated carbon: suitable for purification of low-pigment solutions such as beverages, food additives, and pharmaceutical intermediates.
Chemical activated carbon: dedicated to deep decolorization of high-pigment solutions such as glucose, sucrose, and citric acid.
Usage specification:
Pre-cleaning is required to remove dust and avoid adsorption of chlorine in tap water.
Replace regularly (recommended 1~2 times a month) to prevent "adsorption saturation" failure.
V. Development trend
Environmental protection process: New chemical methods (such as low-consumption technology of phosphoric acid) reduce wastewater discharge and achieve clean production.
Composite materials: By adding diatomaceous earth, resin and other ingredients to increase the filtration speed, for example, the composite of coconut shell and wood activated carbon can increase the decolorization efficiency by 30%.
The above process achieves directional design of pore structure by regulating the type of activator and temperature, thereby meeting the dual needs of the food industry for safety and efficient decolorization. If you need specific technical parameters or cases, please refer to relevant production standards (such as GB/T1380.4-1999).
1. Types of Activated carbon used for sucrose decolorization and purification
Wooden powdered activated carbon
Using high-quality sawdust as raw materials, it is made by physical or chemical activation and has a developed pore structure (micropores, mesopores, macropores), which is suitable for decolorization of sugar solution. It has a large adsorption capacity and fast filtration speed, and is often used for decolorization and purification of sugars such as glucose and sucrose.
Fruit shell activated carbon
Using coconut shells, nut shells, etc. as raw materials, it adsorbs plant pigments and impurities such as caramel color in the production process. It is suitable for large-scale syrup decolorization, especially for processing sucrose raw materials from different origins.
Coal-based Activated carbon
The cost is low, but the pore structure is slightly worse than that of wood charcoal, and it needs to be selected according to the characteristics of sugar solution. It is often used in industrial wastewater treatment. If it is used for decolorization of sugar solution, it needs to be optimized in combination with other processes.
2. Key factors affecting the decolorization effect of activated carbon
Adsorption performance indicators
Iodine value, methylene blue adsorption value: reflects the degree of pore development. The higher the value, the stronger the adsorption capacity.Particle size and mesh number: The smaller the mesh number of powdered activated carbon (such as 300 mesh), the larger the specific surface area and the faster the decolorization rate.Operating conditions
Dosage: Usually controlled at 0.1%-0.3%. Excessive dosage may lead to increased costs or adsorption saturation.Temperature: The optimal decolorization temperature is 50-80℃. High temperature may destroy the structure of activated carbon, while low temperature reduces the adsorption rate.pH value: The adsorption effect is best in an acidic environment (pH 3-6).Contact time: 30-60 minutes are required to ensure sufficient adsorption balance.Impurity characteristicsThe size, concentration and coexisting impurities (such as colloids and proteins) of pigment molecules in sugar solution will affect the selective adsorption of activated carbon.III. Separation methods and equipment for activated carbon that loses adsorption capacitySeparation methodFiltration method: Separate activated carbon and sugar solution by physical interception. Commonly used equipment includes:Plate-type closed filter: Equipped with compressed air purge function, it can squeeze carbon residue and increase liquid recovery rate.
Filter press: Pre-coating of filter aids (such as diatomaceous earth) is required to improve filtration efficiency.
Centrifuge: Suitable for rapid separation of high-concentration activated carbon slurry.
Countercurrent adsorption system: Granular activated carbon adopts countercurrent contact design, and saturated carbon is regularly removed and new carbon is added through pulse operation.
Auxiliary equipment
Security fine filter: Used to remove residual carbon powder (such as 50 micron filter) in the sugar solution after decolorization.
Vibration screening device: Helps the activated carbon bed to be evenly distributed and reduce clogging.
