Why the larger the surface area, the more adsorption

This generally refers to activated carbon.

Adsorption with colloids.

The surface of activated carbon is granular, and the inside is porous, and there are many capillaries about 1 onm la in size in the pores, and the internal surface area of activated carbon is 1 g.

Up to 700-1400 m2, and the inner surface of these capillaries and the surface of the particles are where the adsorption is located. The factors affecting the ability of activated carbon to remove organic matter are the area of activated carbon itself, the size of the pores and the molecular weight of the removed organic matter and its polarity, which mainly rely on the physical adsorption capacity to eliminate impurities, when the adsorption capacity reaches saturation, the adsorption of too many impurities will fall down and pollute the downstream water quality, so it is necessary to regularly use the backlash to remove the impurities on the adsorption.

The reason why colloids can adsorb ions is because colloids themselves are a substance with an electric charge, which has a structure of two or more layers with opposite charges. Because charges of different properties are concentrated in one layer, the outermost layer has a weak charge. This allows the adsorption of ions that are contrary to their electrical properties.

Matter has a tendent state called the lowest energy state. Because surface energy = specific surface * surface area, in this formula, the specific surface is a constant, so the larger the surface area, the higher the surface energy, precisely because the matter tends to the lowest energy state, so the higher the surface energy, the stronger its tendency, so it is necessary to reduce the surface energy by reducing its own surface area, so it has a strong adsorption force.

The process of adsorption is a process of decreasing surface energy, the larger the surface area, the greater the surface energy, and the greater the driving force of adsorption.

In general, yes, the greater the adsorption energy, the more stable the adsorption. The magnitude of the adsorption energy depends on the interaction force between the adsorbate and the adsorbate, and the larger the adsorption energy, the stronger the binding energy between the two and the higher the stability of adsorption.

1.Substances with adsorption capacity themselves have certain physical adsorption capacity, just like salt hydrophilic and magnetic magnetic.

2.This basic adsorption capacity acts through the surface, and the larger the [specific surface area], the larger the area that acts on it.

3.The adsorption capacity also depends on the surface angle, which is similar to the position of the corner in the macro case, where the stain is particularly difficult to remove due to the angle. The porous substance of the subject has a large number of such microscopic angles, and it is difficult for the substance to run away by physical means after entering.

So the adsorption capacity is strong. The nature of the surface of the object is different from the inside, and there is a situation where the surface is not saturated with short-range force, resulting in a higher surface energy than the bulk energy, which is manifested by the surface tension of the liquid and the solid, for the liquid can reduce the surface energy by reducing the surface area by deformation, and the solid can not flow and is much more difficult than the liquid deformation, the surface energy is mainly reduced by adsorbing other substances on the surface (this effect can also occur in liquids). If the chemical interaction between the adsorbent and the adsorbate is not considered, the greater the surface tension and the larger the surface area, the greater the adsorption capacity of the adsorbent in general.

The adsorption capacity of activated carbon or various forms of carbon materials is related to the specific surface area, and the type of functional groups on the surface, aromatity, CO, etc., which can affect its selective adsorption ability, such as carbon materials with high aromaticity can be more inclined to adsorb non-polar substances, and low aromatic materials tend to adsorb polar substances. Returning to the problem of large "surface area", a large specific surface area means more effective functional groups and more adsorption points, which is macroscopically manifested as strong adsorption capacity.

In addition, for some specific target compounds, it is not that the larger the specific surface area, the stronger the adsorption capacity, and the adsorption is the strongest under the condition of the optimal pore size, and too large or too small pore size is not conducive to the binding of target compound molecules. <>

Macroporous silica gel is generally used as a catalyst carrier, matting agent, toothpaste abrasive, etc. Therefore, different varieties should be selected according to different uses. Silica gel can be used as a desiccant and can be reused.

Silica gel is a porous substance with different particle sizes formed by the proper dehydration of silicate gel MSIO2·NH2O. It has an open porous structure, a large specific surface (surface area per unit mass), can adsorb many substances, and is a good desiccant, adsorbent and catalyst carrier. The adsorption of silica gel is mainly physical adsorption, which can be regenerated and reused.

Acid is added to the alkali metal silicate (such as sodium silicate) solution to acidify it, and then a certain amount of electrolyte is added for stirring, that is, silicate gel is generated; Alternatively, silicate gels can be formed by adding acid or ammonium salts to a concentrated sodium silicate solution. Silica gel is obtained by letting it stand for a few hours to age, then washing off soluble salts with hot water, drying at 60 70 and activating at about 300. The silicate gel is soaked in cobalt chloride solution and then dried and activated to obtain color-changing silica gel.

When it is used as a desiccant, it is blue before water absorption, and turns red after water absorption, and the degree of water absorption can be seen from the change of color, and whether it needs to be recycled. Silica gel is also widely used in the preparation of steam, petroleum refining and catalyst, etc., inorganic silica gel is used as a desiccant, which can be specific to the following aspects.

1.It is mainly used for moisture absorption and rust prevention of instruments, meters, equipment, etc. under closed conditions.

2.It is used in combination with ordinary silica gel desiccant to indicate the moisture absorption degree of the desiccant and judge the relative humidity of the environment. As a silica gel desiccant for packaging, it is widely used in precision instruments, leather, clothing, food, medicine and household appliances.

3.Silicone can be used as a <> for products in direct contact with the human body such as baby pacifiers because of its food-grade use

Adsorption principleAdsorption is a relatively common adsorption phenomenon, and it is a specific situation of adsorption phenomenon. Adsorption is a phenomenon in which a component of one phase is absorbed by another phase called an adsorbent, which usually has a large surface area.

Adsorption belongs to a kind of mass transfer process, the molecules inside the substance and the surrounding molecules have a gravitational attraction to each other, but the molecules on the surface of the substance, in which the force relative to the outside of the substance is not fully exerted, so the surface of the liquid or solid substance can adsorb other liquids or gases, especially in the case of a large surface area, this adsorption force can have a great effect.