Activated carbon is a black powder, granular or pellet-shaped amorphous with porous carbon. The main component is carbon, and it also contains a small amount of oxygen, hydrogen, sulfur, nitrogen, and chlorine. It also has a fine structure like graphite, but the grains are small and the layers are irregularly stacked. Has a large surface area (500-1000 m 2 / g), has strong adsorption performance, can adsorb gas, liquid or colloidal solids on its surface; for gas, liquid, the mass of the adsorbed substance can be close to activated carbon The quality itself. Its adsorption is selective, and non-polar substances are easier to adsorb than polar substances. In the same series of substances, the higher the boiling point, the easier it is to be adsorbed, the higher the pressure, the lower the temperature, the higher the concentration, and the greater the amount of adsorption. Conversely, decompression and temperature increase are conducive to gas desorption. Commonly used for gas adsorption, separation and purification, solvent recovery, decolorant for sugar liquid, grease, glycerin, medicine, deodorant for drinking water and refrigerator, poison filter in gas mask, can also be used as catalyst or metal salt Catalyst carrier. The raw materials for the production of activated carbon in the early days were wood, hard nut shells or animal bones. Later, coal was mainly used. After carbonization and activation treatment, the activated carbon production methods were: ① steam and gas activation method. Activate carbon with water vapor or carbon dioxide at 850 to 900 ° C. ② Chemical activation method. Activated carbon can be obtained by using the gas released by the activator or impregnating the raw materials with the activator after high temperature treatment.
Activated carbon has a microcrystalline structure, and the arrangement of microcrystals is completely irregular. There are micropores (radius less than 20 [Angles] = 10-10 meters), transitional holes (radius 20 to 10,000), and large holes (radius 10,000 to 10,000). It has a large inner surface and a specific surface area of 500 to 1700 m 2 / g. This determines that activated carbon has good adsorption properties, and can adsorb metal ions, harmful gases, organic pollutants, pigments, etc. in wastewater and waste gas. Industrial application of activated carbon also requires high mechanical strength and good abrasion resistance, its structure strives to be stable, and the energy required for adsorption is small to facilitate regeneration. Activated carbon is used for decolorization and deodorization of oils, beverages, food and drinking water, gas separation, solvent recovery and air conditioning. It is used as a catalyst carrier and an adsorbent for gas masks.
The decolorization effect of activated carbon is strongest in water, and weaker in organic solvents. Generally add 0.1-3% (W / V) and stir for 30 to 60 minutes. The particle size of activated carbon has an effect on the decolorization time. Moreover, the decolorization effect of activated carbon produced by different manufacturers and different processing methods varies widely. The decoloring temperature and pH should be determined through experiments according to the properties of your product.
(1) Generally, it is better to use activated carbon at 75-80 degrees;
(2) The decolorization effect of activated carbon is the strongest in water, and the effect is also good in strong solvents, and the effect is poor in non-polar solvents;
(3) In general, it is better to use under pH3-6 condition;
(4) In general, the amount added is one-thousandth to three (or five);
(5) The decoloring time is generally 30-60 minutes;
(6) There are many types and types of activated carbon, such as sugar carbon, oil carbon, etc., choose an activated carbon that is suitable for your use.
Precautions:
(1) Do not add activated carbon to the boiling solution, because there is a danger of bumping.
(2) Decolorization with activated carbon should be added after the solid matter is completely dissolved. Although colored impurities can be dissolved in the boiling solvent, when the crystals are cooled and precipitated, some of the impurities will be adsorbed by the crystals to make the product colored. Decolorization of activated carbon is not added until the solid matter is completely dissolved
