Question

Define biodegradable and non – biodegradable detergents.

Answer 1

Hint: A biodegradable compound is that which can be decomposed in nature by natural biological activity. While, a non – biodegradable compound is that which cannot be broken down or decomposed by the natural process. Detergents are compounds of long chain hydrocarbons that are used as cleansing agents.

Complete answer:
A detergent is a long chain hydrocarbon sodium or potassium sulfonate salt. It consists of a hydrocarbon chain as a tail and the ionic part as the polar head that has a general structure as $R-S{{O}_{4}}^{-}\,\,{{[Na]}^{+}}$(R is alkyl group). The hydrocarbon chain is water repellent or hydrophobic, while the ionic part is water dissolving and hydrophilic. A detergent is effective in hard water as it contains sulfonate salts. Detergents act as surfactants as they decrease the surface tension between the liquid making it effective in cleansing.
Detergents can be biodegradable and non – biodegradable as:
Biodegradable detergents are the detergents that can be easily decomposed by the biological activity of microorganisms like bacteria. They consist of a straight hydrocarbon chain so they can easily break down. For example, sodium alkyl benzene sulfonates sodium lauryl sulfate, etc.
Non – biodegradable detergents are defined as the ones which cannot be decomposed by the biological activity of microorganisms. This is because they contain a highly branched chain. For example, cetyl methyl ammonium bromide, (1, 3, 5, 7- tetramethylloctyl) benzene sulfonate, etc.
Hence, biodegradable detergents can be defined as simple hydrocarbon chains and non – biodegradable detergents have a branched hydrocarbon chain.

Note:
Apart from biodegradable and non – biodegradable, detergents are classified as anionic, having a net negative charge, cationic detergents having a net positive charge, non – ionic detergents that are uncharged (like maltoside, tween) and zwitterionic detergents having equal number of negative and positive charges (like CHAPS).