Understanding Surfactants: Classification and Applications
SURFACTANT AND ITS CLASSIFICATION
Surfactants are substances that reduce the surface tension (also called interfacial tension) between two liquids, a gas and a liquid, or a liquid and a solid. The term "surfactant" is an acronym for "surface active agents," which are compounds with dual hydrophilicity and hydrophobicity features. The name itself implies the surface activity of these classes of compounds and their propensity to adsorb at interfaces. The polar component, also known as the hydrophilic part or hydrophile, demonstrates a strong affinity for or attraction to polar solvents. The nonpolar portion is known as a hydrophobe or lipophile because it is attracted to oil. [1-5] Amphiphiles or tensides are other names for surfactants. More than 50 years ago, Paul Winsor was the first person to use the term "amphiphile." There are two Greek roots in it. Tensioactif is the name given to surfactant in French; tenside to it in German; and tensioactivo to it in Spanish. [6, 7]
Figure 1
CLASSIFICATION OF SURFACTANT
Surfactant are usually amphiphilic organic compound containing both hydrophobic group (their tails) and hydrophilic group (their head). Consequently, surfactant has both water soluble and water insoluble components. There are four groups of surfactant based on the presence and absence of charge or the type of charge on the head.
. Figure 2Figure 2.
(1) Anionic Surfactant
(2) Cationic Surfactant
(3) Amphoteric Surfactant
(4) Non-ionic Surfactant
Anionic Surfactant:
Surfactants are often categorised using polar head groupings. Anionic surfactant has a net charge in its head. If the charge is negative, the surfactant is more specifically referred to as an anionic surfactant.
The Anionic Surfactants have Sulphate, Sulfonate, Phosphate and carboxylate, containing negative charged functional groups.
Body washes, hand soaps, kitchen cleansers, and laundry detergents all contain anionic surfactants. They are the most common and functional surfactants. In terms of removing oily residue, they are the most efficient. But as the strongest surfactants, they also irritate the skin.
Anionic surfactants, the most well-liked and frequently utilised type, are present in practically all cleaning supplies. According to estimates, anionic compounds account for 46% of the $46 billion worldwide surfactant market in 2015 [8].
Table No: 1. Sulphate type Anionic Surfactant
Table No. 2: Sulphonate type anionic Surfactant
Table No. 3: Carboxylate type anionic Surfactant
Table No. 4: Other anionic Surfactant
Cationic Surfactant:
Surfactants with a positively charged functional group are known as cationic surfactants. Cationic surfactants are made up of a polar and a non-polar component, much like any other surfactant.
. The most common applications for cationic surfactants, the bulk of which are quaternary ammonium compounds, include emulsifiers, corrosion inhibitors, rinse aids, antistatic agents, and fabric softeners (e.g., for asphalt).
Cationic surfactants have been found in freshwater and marine environments and can persist in the environment, becoming a source of eco-toxicity. These contaminants have been linked to unintentional leaks, inadequate sewage treatment, and specific industrial applications, like antifouling coatings or remediating materials [9-13]. While there is still a shortage of information for seawater, the majority of the documented eco-toxicity studies have focused on the destiny and danger of cationic surfactants in freshwater ecosystems. [14-16]
Table No. 5: Some Cationic Surfactant
3. Amphoteric Surfactant
Amphoteric surfactants have lengthy hydrophobic hydrocarbon chains, hydrophilic centres that are both positively and negatively charged, and they are all joined by a spacer group. This kind of surfactant preserves overall charge neutrality. The number of methylene segments in the spacer, the positive and negative charged groups' relative positions, and the length of the hydrophobic hydrocarbon chain all affect the properties of amphoteric surfactants. The pH level of the solvent affects the ionic activity of amphoteric surfactants. They behave anionically at a higher pH and cationically below the isoelectric points. In the vicinity of the isoelectric point, they assume the shape of zwitterions. A distinction between pH-sensitive and pH-insensitive amphoteric surfactants is actually possible.Due to its precise molecular structure, this surfactant possesses a number of special qualities, including high water solubility, high surface activities, a wide isoelectric range, low critical micelle concentration (CMC), high foam stability, low toxicity, low irritating ness, excellent biodegradability, bioactivity, interface change, and more. Amphoteric surfactants have generated a great deal of interest in the scientific community for a wide range of applications, including cosmetics, chromatography, increased oil recovery, electrochemistry, nanoscience, polymer chemistry, and wastewater treatment.[17]
Table No. 7: Amino acid type amphoteric Surfactant
Table No. 8: Betaine type Amphoteric Surfactant
4. Nonionic Surfactant
A neutral surfactant is referred to as a nonionic surfactant. In other words, their hydrophilic end is uncharged. The ability of this chemical compound to effectively emulsify oils and remove organic soils is one of its key qualities. The cloud point, a special characteristic of this surfactant that determines when it begins to separate from the cleaning solution, is another distinctive feature.
However, due to their mildness, nonionic surfactants are frequently used in a variety of settings. Ethoxylated amines, ethoxylated alcohol, ethoxylated and alkoxylated fatty acids, etc. are a few well-known examples of nonionic surfactants.
Table no. 9 polyol ester type non ionic surfactant
Table No. 10 Alkanolamide type nonionic surfactant
![2-[bis(2-hydroxyethyl)amino]ethyl stearate](https://lh7-us.googleusercontent.com/qH9WzxDLe128WZdO4vTQ3_SotRHKSj7MEwBQ3Z69AeC_1YcWrRCreE1cRlUARvGuRScqfUBf3RYvTluFLgQCc_k0gARt3LHqYK4HDqzYSfnACwNX8Qr1pYzjGTfV8gHDb_8SEzz6mW6EdLoRX7957Xg=rw)
Table No. 11: APG type nonionic surfactant
Table No.12 Alkoxylates Type nonionic Surfactant
Table No. 13 Fatty Acid Alkyl Esters Type nonionic Surfactant
Reference
[1] K. Shinoda, Solvent Properties of Surfactant Solutions, Dekker, New York, 1967.
[2] H. E. Garret, Surface Active Chemicals, Pergamon, New York, 1975.
[3] M. J. Rosen, Surfactants and Interfacial Phenomena, Wiley, New York, 1978.
[4] A.T. Florence, D. Attwood, Surfactants Systems, Chapman and Hall London, 1983.
[5] Th. F. Tadros, Surfactants, Academic, New York 1984
[6] A. M. Schwartz, J. W. Perry, Surface Active Agents; their Chemists, Technology, R.E. Krieger, New York, (1978).
[7] Schwartz A.M., Perry J.W., Berch J., "Surface Active Agents and Detergents Volume II" R. Krieger Pub. Co., New York (1977).
[8]. Grand View Research, Inc. (2015). Surfactants Market Analysis by Product, by Application, and Segment Forecasts to 2022. www.grandviewresearch.com
[9]. B. Biswas, L.N. Warr, E.F. Hilder, N. Goswami, M.M. Rahman, J.G. Churchman, K. Vasilev, G. P an, R. Naidu, “Biocompatible functionalization of nanoclays for improved environmental remediation” Chem. Soc. Rev., 48 (2019), pp. 3740-3770, 10.1039/C8CS01019F.
[10]J. Figueiredo, T. Oliveira, V. Ferreira, A. Sushkova, S. Silva, D. Carneiro, D. Cardoso, S. Goncalves, F. Maia, C. Rocha, J. Tedim, S. Loureiro, R. Martins, “Toxicity of innovative anti-fouling nano-based solutions in marine species”Environ. Sci. Nano (2019), 10.1039/C5EN00098J
[11] E. Olkowska, M. Ruman, Ż. Polkowska, “Occurrence of surface active agents in the environment”,J. Anal. Methods Chem., 2014 (2014), pp. 1-15, 10.1155/2014/769708
[12] R. Piola, C. Grandison, “Assessments of quaternary ammonium compounds (QAC) for in-water treatment of mussel fouling in vessel internals and sea chests using an experimental seawater pipework system”,Biofouling, 33 (2017), pp. 59-74, 10.1080/08927014.2016.1261287
[13] X. Wang, J. Che, M. Wu, Y. Shi, M. Li, J. Shan, L. Liu, “The anti-fouling effect of surfactants and its application for electrochemical detection of bisphenol A.” J Electrochem. Soc. Interface, 165 (2018), pp. B814-B823, 10.1149/2.0401816jes
[14] M.T. Garcia, O. Kaczerewska, I. Ribosa, B. Brycki, P. Materna, M. Drgas, “Biodegradability and aquatic toxicity of quaternary ammonium-based gemini surfactants: effect of the spacer on their ecological properties,” Chemosphere, 154 (2016), pp. 155-160, 10.1016/j.chemosphere.2016.03.109
[15] M.T. Garcia, I. Ribosa, I. Kowalczyk, M. Pakiet, B. Brycki, “Biodegradability and aquatic toxicity of new cleavable betainate cationic oligomeric surfactants”J. Hazard. Mater., 371 (2019), pp. 108-114, 10.1016/j.jhazmat.2019.03.005
[16] O. Kaczerewska, B. Brycki, I. Ribosa, F. Comelles, M.T. Garcia, “Cationic gemini surfactants containing an O-substituted spacer and hydroxyethyl moiety in the polar heads: self-assembly, biodegradability and aquatic toxicity”, J. Ind. Eng. Chem., 59 (2018), pp. 141-148, 10.1016/j.jiec.2017.10.018
[17]. Ratan Sarkar,Aniruddha Pal,Atanu Rakshit,Bidyut Saha, “Properties and applications of amphoteric surfactant: A concise review”,Journal of Surfactant and Detergent: 22 July 2021,https://doi.org/10.1002/jsde.12542
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