Analysis Of Activated Carbon Adsorption Principle

The adsorption of Dates Activated Carbon can be divided into physical adsorption and chemical adsorption.

1. Physical adsorption

It mainly occurs in the process of removing impurities in the liquid phase and gas phase by Activated Carbon. The porous structure of Activated Carbon provides a large amount of surface area, making it very easy to absorb and collect impurities. Like magnetic force, all molecules have a mutual attraction. Similarly, a large number of molecules on the pore wall of activated carbon can generate a strong gravitational force, so as to attract impurities in the medium to the pore size.

In physical adsorption, it must be noted that the molecular diameter of the adsorbed impurities are smaller than the pore size of the activated carbon, so as to ensure that the impurities are absorbed into the pore size. Therefore, in practical applications, by continuously changing the raw materials and activation conditions to create activated carbon with different pore structure, which is suitable for the application of various impurities absorption.

2. Chemisorption

In addition to physical adsorption, chemical reactions often occur on the surface of activated carbon. Activated carbon not only contains the carbon but also contains a small amount of oxygen and hydrogen in the form of chemical bonds and functional groups on its surface, such as carboxyl groups, hydroxyl groups, phenols, lactones, quinones, and ethers. The oxides or complexes contained on these surfaces can chemically react with the adsorbed substances, thereby binding to the adsorbed substances and accumulating on the surface of the activated carbon.

The adsorption of activated carbon is the result of the combined action of the above two adsorptions.

When the adsorption rate and the desorption rate of activated carbon in the solution are equal, that is, the amount of activated carbon adsorption per unit time is equal to the amount of desorption, then the concentration of the adsorbed substance in the solution and the concentration on the surface of the activated carbon no longer change, and When equilibrium is reached, the dynamic equilibrium at this time is called activated carbon adsorption equilibrium, and the concentration of the adsorbed substance in the solution at this time is called equilibrium concentration.

3. Factors affecting the adsorption performance of activated carbon

The pH, chloride, and sulfate in the activated carbon are unqualified or the carbon particles are too fine, which makes the dyeing of the solution difficult to filter and affects the quality of the preparation.

The zinc and iron salts in the activated carbon are unqualified. If the iron salt content is high, certain drugs in the infusion such as vitamin c and sodium para-aminosalicylate can be discolored.

Poor bleaching power or unqualified results in increased impurity content of the preparation. The quality of activated carbon is poor, and the impurities contained in it can contaminate the drug solution, which often leads to unclear preparation clarity and particles, and affects the stability of the preparation. Therefore, when preparing a large number of liquids, it is necessary to use first-level needle activated carbon.

4. The influence of the usage of activated carbon on the quality of the preparation

Activated carbon is added in stages more efficiently than one-time addition. This is due to the fact that when activated carbon adsorbs impurities to a certain extent, the adsorption efficiency is reduced when adsorption and desorption are in equilibrium. Therefore, it is best to add activated carbon 2 to 3 times during production, which can significantly improve the quality of the preparation.

The raw materials of mannitol often contaminate the pyrogens, especially when the color of the prepared liquid is darker, the probability of contamination is higher. Because mannitol is not suitable for high temperature treatment, it is generally removed by adsorption. However, because of the high concentration of mannitol injection, pyrogen removal is often incomplete, and the pyrogen reaction rate during clinical use is higher than other varieties. In the formulation practice, it was found that the mannitol injection prepared by the secondary adsorption method can solve the above problems.

First of all, there is no clinical pyrogen reaction;

Second, the pass rate of the finished product is high, the insoluble particles are greatly reduced, and it is not easy to precipitate crystals after a long time;

Third, the limulus reagent method can be used instead of the rabbit pyrogen test.

When preparing the glucose solution, hydrochloric acid must be added first. After the foam attached to the liquid surface disappears, add activated carbon and stir evenly. If activated carbon is added first, the gas in the foam is adsorbed by the carbon particles, so that a gas film is formed on the surface of the carbon particles, which is not easily wetted by the solution and affects the adsorption of the activated carbon. From this point of view, when preparing the liquid material that is easy to foam, some defoaming means or other measures should be taken to ensure the adsorption effect of the activated carbon.