Absorption Details

Absorption is the assimilation of the molecular system throughout the bulk of a solid or liquid medium. The process of absorption happens at a uniform rate throughout the bulk of the substance. Absorption does not bring about a change in temperature to matter. There are two types of absorption, namely physical and chemical absorption.

Absorption involves two substances: absorbate and absorbent. The process of the absorbent material retaining the absorbate is known as absorption.

Real-World Example of Absorption

The chemical industry extensively utilizes the process of absorption. Absorbers capture harmful acidic gases like hydrogen chloride and sulfur. The process of absorption is vital in this scenario as these gases can be quite harmful If released into the atmosphere in large quantities.

Power plants and coal-fired generators worldwide produce large tons of sulfur dioxide during several chemical reactions. This gas can react with ammonia and calcium in the air to form submicron sulfate particles. These particles can have a severe impact on human health. The utilization of the process of absorption helps minimize the amount of sulfur dioxide released into the atmosphere.

Types of Absorption

There are two types of absorption processes: physical absorption and chemical absorption. A chemical or reactive absorption process takes place whenever there is any chemical reaction between the solute and the solvent.

The absorption of ammonia into water is an example of the physical absorption of gas into a liquid. The usage of water and hydrocarbon oils as absorbents triggers a physical absorption process. These absorbents do not start a chemical reaction between them and the solute.

The usage of a strong, base-like aqueous sodium hydroxide as an absorbent to dissolve an acid gas triggers a chemical absorption process. This interaction triggers a rapid, irreversible reaction in the liquid phase. An example of chemical absorption is the purification of natural gas by passing it through a strong aqueous solution of ethanolamine. The chemical absorption process removes acidic gases like hydrogen sulfide and carbon dioxide.

Absorption vs. Adsorption

Adsorption is the accumulation of molecules, ions, or atoms on the surface of a solid or liquid. In the case of adsorption, only the surface of the adsorbent undergoes any changes in the molecular structure. Whereas in the case of absorption, the entire bulk molecular structure undergoes significant changes. The adsorbent is the substance on whose surface the adsorption process takes place.

The particles inside a substance’s bulk are not like the particles on the surface. The forces acting on the surface molecules are different from that acting on the molecules in the bulk of the substance.

Unlike adsorption, absorption occurs across the bulk of the solid or liquid substance. The process of absorption occurs at a uniform rate, whereas the rate of adsorption increases steadily and reaches equilibrium. Temperature changes do not influence absorption. Absorption is more pronounced in lower temperatures.