What are some examples of adsorption?

What are some examples of adsorption?

When substances get accumulated over the surface of another, then the process is known as adsorption. It is dependent on two constituents, namely adsorbate and adsorbent.

Adsorbate – Definition

The entity which gets accumulated over the surface is the adsorbate and is usually gaseous or liquid in nature.

Adsorbent – Definition

The solid substance on which the adsorbate is adsorbed is known as adsorbent. Common adsorbents are: activated alumina, silica gel, activated carbon, molecular sieve carbon, molecular sieve zeolites and polymeric adsorbents. Mostly, adsorbents are made such as activated carbons, but some such as zeolites occur naturally.

Mechanism of adsorption – Definition

When the surface particles of the adsorbent go through the path of unbalanced forces from the bulk, then adsorption happens, but on the surface, atoms or molecules do not surround the particles. So, the attractive forces are unbalanced. These forces of the adsorbent play the role of attracting the adsorbate particles on its surface. When there is an increase in surface area per unit mass of the adsorbent at a given temperature and pressure, then adsorption also increases.

Exothermic nature of adsorption and the entropy change – Definition

When adsorption happens, then the surface energy decreases which occurs in the form of heat of adsorption. So, adsorption is an exothermic process, i.e.

is always negative.

Difference between adsorption and absorption

• Adsorption is a surface phenomenon whereas absorption is a bulk phenomenon.
• In adsorption, the concentration on the surface of adsorbent is different from the bulk whereas, in absorption, the concentration is same at all times.
• Adsorption rate is high in the initial stage and then it decreases whereas, in absorption, it is same throughout the process.

Adsorption – Definition

Adsorption is the process where atoms, ions, or molecules from agas, liquid, or dissolved solid gets attached to a surface. It then creates a film of the adsorbate on the surface of the adsorbent. It is two kinds: Physisorption and Chemisorption, for example, oxygen molecules (red) is adsorbed on a bimetallic surface of platinum (purple) and cobalt (green).

A material which can be adsorbed is known as adsorbate. For example, oxygen molecule adsorbed on cobalt is adsorbate.

Adsorbent is the material on which the adsorbate is adsorbed.

Common types of adsorbents are activated alumina, silica gel, activated carbon, molecular sieve carbon, molecular sieve zeolites, and polymeric adsorbents.

Sorption –Definition

When both adsorption and absorption go on simultaneously, then it is known as sorption.

Factors affecting adsorption of gases by solids –

• The type and surface area of the absorbent
• Naure of the gas that is being adsorbed
• Temperature
• Pressure
• How the solid adsorbent is activated

Heat of Adsorption – Definition

The amount of heat that is produced when 1 mole of the gas is adsorbed on the adsorbent is called heat of adsorption.

Examples of adsorption in daily life

• Silica and aluminium gel- The silica gel packets which are kept in the new items which we purchase helps to adsorbed the moisture over the surface of silica or aluminium gel particles.
• Pollution masks- If a pollution mask is cut, it will be found out that it consists of two or more layers of fabric, and between the layers, there are activated carbon granules or a filter sheet which acts as a purifier. The purpose of this is to adsorb the dust and smoke particles so that clean air reaches our nostrils. In this example, the activated carbon element or the filter sheet is the adsorbent, and the dust and smoke particles are adsorbates.
• Curing the disease- Adsorption is used to treat many diseases. When a drug is taken, the germs get deposited on its surface and later it is taken outfrom the body through natural processes.
• Charcoal gas masks- The charcoal masks used in mining are made by using the adsorption properties of the substance like charcoal to take out the toxic and poisonous gases to avoid any hazards.
• Purification of alum- When water is purified by inserting alum, then adsorption takes place. Here, the impurities collect itself to form a large cluster, which can be easily removed by sedimentation, sieving, etc.
• Removing hardness from water- Elements like calcium and magnesium make water hard. These elements can be removed by the process of ion exchange. Cation/anion resins are added to water and the elements which causes hardness gets stuck to the resins which can be filtered out easily. And then softened water can be obtained.
• Misty windows- During cold weather, we often observe water vapour on our glass windows and doors. This is an example of adsorption from daily life where a layer of water vapor gets settled on the surface of windows or doors.

Reference: surface chemistry from class 12 chemistry – find all the questions & answers