Principle of activated carbon adsorption
activated carbon is a kind of very small granular has a large surface area, and more tiny holes in the granular - capillary. The capillary has very strong adsorption capacity, due to the granular surface area is large, so a good contact with with gas (impurities). When these gases (impurities) encounter capillary by adsorption, purification effect. Activated carbon surface area of the study is very important, only the BET specific surface area detecting data of active carbon method detected result is reliable, domestic at present there are many instruments can only make direct comparison method of detection
In domestic has been eliminated. Specific surface area test unified the multi-point BET method at home and abroad, specific surface area measurement standards are developed at home and abroad is based on BET test method, please see our national standard (GB/T 19587-2004) - gas adsorption BET principle of solid material specific surface area measurement methods. Specific surface area testing is actually the more time-consuming jobs, as the adsorption capacity of sample is different, some sample testing may need to spend the whole dayTime, if the test process is not fully automated, the tester can not leave at any time, and should be highly focused, observe the dashboard, control the knob, a little careless will lead to the failure of the test process, which will waste a lot of valuable time of the tester.Adsorption capacity refers to the amount of adsorbents adsorbed on the adsorbent per unit mass under certain conditions. It is usually expressed in terms of K adsorbents /kg of adsorbent or mass percentage, which is a sign of the adsorption capacity of the adsorbent.
In industry, the amount of adsorption is called the activity of the adsorbent.
The activity of the adsorbent can be expressed in two ways 1) the static activity of the adsorbentUnder certain conditions, the equilibrium adsorption capacity of the adsorbent is its static activity.For a certain adsorption system, the static activity depends only on the adsorption temperature and the concentration or partial pressure of the adsorbed substance.
Dynamic activity of adsorbents
Under certain operating conditions, the gas mixture by adsorption bed, adsorption by adsorption, adsorption after a period of time, when starting from the adsorbent in the laminar flow of the gas adsorbed mass (or its concentration reaches a specified value), think bed fire, adsorption properties of adsorbent adsorption quantity at this time is called dynamic activity of adsorbent.
The activity is not only related to the characteristics of adsorbents and adsorbents, but also related to temperature, concentration and operating conditions.
The kinetic activity value of adsorbent is the main basis for the design of adsorption system.
The adsorption rateThe adsorption process often takes a long time to reach equilibrium, and the contact time is limited in the actual production process.Therefore, the amount of adsorption depends on the adsorption rate, and the adsorption rate is related to the adsorption process, the adsorption process can be divided intoThe adsorption process often takes a long time to reach equilibrium, and the contact time is limited in the actual production process.Therefore, the amount of adsorption depends on the adsorption rate, and the adsorption rate is related to the adsorption process, which can be divided into the following steps:
(1) External diffusion, the adsorbate from the main air flow through the air film around the particles to the outer surface of the adsorbent; (2) Internal diffusion, the adsorbate from the outer surface through micropores to the surface of the adsorbent micropores
(3) adsorption, the adsorbent reached the microporous surface of the adsorbent is adsorbed
(4) The desorbed adsorbate diffuses to the main body of the gas phase through internal and external diffusionPhysical adsorption process is generally controlled by internal and external diffusion, chemical adsorption is controlled by both surface dynamics and internal and external diffusion.Because of the complexity of the adsorption process and many influencing factors, it is difficult to derive the rate theoretically, so it is generally determined by experience or model experiment.