Introduction of activated carbon
Activated carbon is a black porous solid carbon. Shanghai Xitan Environmental Protection Technology Co., Ltd. is made of coal by crushing, forming or carbonizing and activating to make coal particles uniform. The main component is carbon, and contains a small amount of oxygen, hydrogen, sulfur, nitrogen, chlorine and other elements. The specific surface area of ordinary activated carbon is between 500 ~ 1700 m2/g, which has strong adsorption performance and is a widely used industrial adsorbent.
Activated carbon classification
1. folded coal granular activated carbon
Coal-based granular activated carbon is refined from high-quality anthracite by advanced technology, and its appearance is black amorphous particles. It has the advantages of developed pore structure, large specific surface area, strong adsorption capacity, high mechanical strength, low bed resistance, good chemical stability, easy regeneration and durability.
2. Folding rice husk activated carbon
Rice husk produced during rice threshing is often thrown away as waste. Japanese researchers recently reported that they have developed a technology to make high-performance activated carbon from rice husk.
Hideyoshi Saito, a professor at Nagaoka University of Technology in Japan, pointed out in his paper that if rice husk is simply heated to make charcoal, the residual silicon dioxide in rice husk will hinder its function as activated carbon. However, silicon dioxide can be successfully removed by mixing the above-mentioned "rice husk charcoal" with potassium hydroxide and sodium hydroxide and then performing heat treatment. According to calculation, compared with ordinary activated carbon, the surface area and pores of this kind of rice husk activated carbon are equivalent to 2.5 times of the former.
3. Folding activated carbon fiber
This product is made of high-quality coconut shell powdered activated carbon as adsorption material, which is bonded to non-woven fabric matrix through polymer bonding material. It can effectively adsorb various industrial waste gases, such as benzene, toluene, xylene, formaldehyde, ammonia, sulfur dioxide and so on. Mainly used to make activated carbon masks, but also can be used as insoles. Widely used in chemical, pharmaceutical, coating and other industries, with remarkable antiviral and deodorizing effects.
4. Folding powdered activated carbon
Powdered activated carbon is made of high-quality charcoal and refined by special production process. There are two methods: physical method and chemical method. Steam activation, refining and crushing. The appearance of this product is black powder, which is insoluble in general solutions. Odorless and tasteless, it has the characteristics of large surface area, strong adsorption, high purity, fast filtration speed, stable quality, flocculation and filter aid. Widely used in decolorization, impurity removal and refining of food, medicine, monosodium glutamate and other products. It can also be used for water purification.
Main functions of activated carbon
1, decolorizing and filtering to decolorize the colored liquid.
2. Absorb all kinds of gases and vapors.
3. Used for chromatographic analysis.
4. Measure the reducing agents of methanol, tin and silicon.
5. Particles can be used as carriers of catalysts.
Influencing factors of activated carbon
① Properties of activated carbon adsorbent
The larger the surface area, the stronger the adsorption capacity; Activated carbon is a nonpolar molecule, which is easy to adsorb nonpolar or extremely low polar adsorbents. The particle size, pore structure and distribution of activated carbon adsorbent and surface chemical properties also have great influence on adsorption.
② Properties of adsorbate
It depends on its solubility, surface free energy, polarity, size and unsaturation of adsorbate molecules, concentration of adsorbate, etc.
③ PH value of wastewater
Generally speaking, activated carbon has a higher adsorption rate in acidic solution than in alkaline solution.
PH value will affect the state and solubility of adsorbate in water, thus affecting the adsorption effect.
(4) * * * storage materials
* * * When there are many adsorbents, the adsorption capacity of activated carbon to a certain adsorbate is worse than that of only containing this adsorbate.
⑤ Temperature
Temperature has little effect on the adsorption of activated carbon.
⑥ Contact time
It is necessary to ensure that the activated carbon has a certain contact time with the adsorbate, so that the adsorption is close to equilibrium and the adsorption capacity is fully utilized.
Safety precautions of activated carbon
1. Leakage treatment
Leakage: isolate the leaked contaminated area and restrict access. Cut off the fire. It is recommended that emergency personnel wear self-contained breathing apparatus and protective clothing.
2. Fire extinguishing treatment
Flammability: Flammable. Extinguishing agent: water, foam, carbon dioxide, sand. Fire extinguishing media available around the fire site.
Emergency treatment
Inhalation: leave the scene quickly and go to a place with fresh air. Keep the respiratory tract unobstructed. If you have difficulty breathing, give oxygen. If breathing stops, give artificial respiration immediately. See a doctor.
Ingestion: rinse your mouth with water. See a doctor.
Skin contact: Take off contaminated clothes immediately and rinse with plenty of running water for at least 15 minutes. See a doctor.
Eye contact: lift the eyelid immediately, rinse it thoroughly with plenty of running water or normal saline for at least 15 minutes, and seek medical attention.
What is the bulk density of activated carbon?
The bulk density of activated carbon refers to the mass per unit volume measured after the activated carbon is freely loaded into the container.
The relationship between the bulk density ρb of activated carbon and the bed density ρp is ρb=ρp( 1-ε).
ε is the porosity of activated carbon at rest, ρb is the bulk density of activated carbon, which needs to be measured, and ρp is the real density of activated carbon.
The bulk density of activated carbon can be divided into loose bulk density and tap bulk density.
Loose packing density
The packing density includes the average density of packed particles in the inner and outer holes of activated carbon particles and the gap between particles, which is obtained by dividing the total mass of uncompacted activated carbon in the natural packed state by the total volume of packed materials.
stacking density
The tap bulk density does not include the internal and external pores of activated carbon particles and the gaps between particles, but the average density of the whole tap activated carbon particles.
It should be added that the unit of bulk density of activated carbon is g/cm3 or kg/m3. It can be seen that the higher the density, the larger the activated carbon particles.
Calculation method of bulk density of activated carbon
ρ0'=m/V=m/(V0+VP+Vv)
Where ρ0 '- bulk density of activated carbon, kg/m3.
VP—— the volume of internal pores of activated carbon, m3.
Vv-volume of activated carbon gap, m3.
V0-the volume of activated carbon, excluding the internal pore m3 of activated carbon.
Note: The volume in the state of natural accumulation includes the pore volume inside activated carbon particles and the void volume between particles.