Properties and applications of amphoteric surfactant: A concise review

Amphoteric surfactants have long hydrophobic hydrocarbon chain and hydrophilic positive as well as negative charged center connected with each other by a spacer group. Thus, this type of surfactant maintains overall charged neutrality. The properties of amphoteric surfactants depend primarily on the length of the hydrophobic hydrocarbon chain, the number of methylene segments in the spacer, the positive and negative charged groups, and their relative position. The ionic activity of amphoteric surfactants is influenced according to the pH value of the solvent. They display cationic behavior below the isoelectric points and anionic behavior at a higher pH. They take the shape of zwitterions in the area of the isoelectric point. In fact, amphoteric surfactants can be parted into pH‐sensitive and pH‐insensitive surfactants. The pH‐insensitive surfactants stay as zwitterionic form irrespective of the pH of the solution. This surfactant has some unique features because of its precise molecular structure as follows: high water solubility, high surface activities, a wide isoelectric range, low critical micelle concentration (CMC), high foam stability, low toxicity, low irritating, excellent biodegradability, bioactivity, interface change, and so on. Because of these special characteristics, amphoteric surfactants have been immensely interested in many applications in the scientific community, including cosmetics, chromatography, enhanced oil recovery, electrochemistry, nanoscience, polymer chemistry, and waste water treatment. This review aims to study about amphoteric surfactants, which have only one hydrophobic hydrocarbon tail and two oppositely charged hydrophilic headgroups connected with each other by a spacer group and its properties, applications in various academics and industrial fields.