Chitosan-Based Eco-Friendly Desiccants for Environmental Applications

Humidity refers to the amount of water vapor in the air and is an essential component to

ensure Indoor Air Quality (IAQ). Indoor Air Quality relates to air quality in and around

a building. Air quality affects the health and comfort of building occupants directly or

indirectly. The quality of air can be affected by gases like carbon mono-oxide, volatile

organic compounds, microbial contamination, humidity and temperature. Extremities

in humidity promote microbial growth including mold, fungus and mildew. Studies discuss

the essential role played by humidity for a comfortable living environment. For

a comfortable indoor environment humidity must be maintained within the optimum

range 40 - 60% . Humidity above 60% leads to allergic rhinitis and

asthma. Below 40%, problems with static electricity, skin irritation and dry eyes occur.

Also, the mucous membranes start to dry out, impairing the ability to defend against

upper respiratory illness. If not controlled, it will disrupt the functioning of military,

industrial, commercial and consumer electronics which might contain components sensitive

to ambient humidity thereby causing the instruments to malfunction and affect

their longevity. Fluctuations in indoor humidity are caused by natural transpiration of

living things, day-to-day household activities. Controlling indoor humidity within the

optimized range is practically impossible in cold weather because excessive condensation

and freezing occurs. A long-standing dispute continues about maintain the indoor

humidity level. Quite a lot of humidity controllers are used in the dehumidification

process to control the humidity level in residential buildings and in industries to retain

crispiness, to improve the prolonged existence of instruments.

Dehumidifier is the one which reduces and maintains the level of humidity in the air

by extracting water from the air. It can be used for household, commercial, or industrial

applications. Large dehumidifiers are used in commercial buildings such as indoor

ice rinks and swimming pools, as well as manufacturing plants or storage warehouses.

Desiccant dehumidifiers are also recognized as absorption dehumidifiers as it retains

dampness from air with the assistance of permeable hydrophilic materials. Desiccant

dehumidifiers use a special moisture absorbing material called a 'desiccant', that is exposed

to the conditioning air. A desiccant is a hygroscopic substance that induces or

sustains a nearby dryness state(desiccation). Commonly found pre-packaged desiccants

adsorb water by chemical bonding. The humidity - saturated material is then shifted to

a separate place, where it is "recharged" to drive off the humidity, typically by heating

it. During a cycle of dehumidification and regeneration process, the desiccant may be

mounted on a belt or other means. They are frequently used to maitain crispness in

food packaging. Desiccants are commonly used in industry to regulate water levels in

gas flows. Dehumidifiers that operate according to the concept of absorption are particularly

suitable at low temperature with elevated humidity concentrations. In various

industries, they are often used to attain moisture concentrations below 35%. Because

of the lack of compressor parts desiccant dehumidifiers are often lighter and quieter

than compressor dehumidifiers. They can also operate at lower temperatures than compressor

dehumidifiers as the unit does not rely on cooled coils for which the moisture

condensing efficiency decreases at lower temperatures