How Synthetic Detergents Use Cationic Surfactants in the Wash
Most detergents are primarily composed of the anionic surfactants. Cationic surfactants are the opposite of anionic surfactants. These molecules have positively charged water-loving heads. Certain of these types of surfactants are added in smaller amounts to many detergent mixtures. The cationic surfactant molecules are attractive not only to the water (on one end) and the oil/dirt (on the other end) but they are also attractive to the anionic surfactants that they are in solution with. This is important in the laundry mix. Because of this mutual attraction between the anionic and the cationic surfactants, as these molecules load themselves onto the water/soil interface their mutual attraction allows them to pack more tightly onto the surface of the soil or oil than they would otherwise have been able to pack. This tighter packing leads to a more effective capture and dissolution of dirt and particularly of oil stains which the detergent is lifting off from the laundry fibers.
Cationic Surfactants and Fabric Softeners: A Little too Close for Comfort
Cationic surfactants are also added to detergent mixtures, and to laundry rinse water as fabric softeners. Usually a particular surfactant which is called an Esterquat, is used for this purpose. (www.scienceinthebox.com)
This means if you are adding fabric softener to your wash you are coating your laundry with a layer of rather large surfactant molecules. The problem with this, is that these molecules are not strongly bonded to the fabric that they are “softening” and are quite free to rub off onto your skin. Your skin will provide a rather attractive substrate for this type of molecule to adhere too. Given sufficient time, and quantity, a lot of this substance could end up right inside your skin cells.
Exactly the implication of this absorbent into the human body is not clear, but I would note that in a study on the toxic nature of a select group of anionic and nonionic surface active agents, one of the overall conclusions of the study was that the larger the molecular weight of the compound tested, the higher the toxicity levels observed in the results. The fabric softener Esterquat is definitely a larger molecule.
Nonionic Surfactants – Another Synthetic Detergent Ingredient
These controversial detergent ingredients do not have an actual electrical charge on their water-loving heads. Rather, they have simply a negative tendency at one end of their long carbon chain. This gives the non-ionic surfactant its water affinity. But since it does not have an ionic charge it is not influenced by mineral ions in the water.
The most commonly used non-ionic surfactants are ethers of fatty (long carbon chain) alcohols. Most laundry detergents include some non-ionic surfactants with the more common anionic surfactants. These surfactants are complementary in action to anionic surfactants. A synthetic detergent might include these surfactants to aid in hard water efficacy of the laundry detergent. The usual risk inherent in the use of synthetic chemicals in the home environment is taken when using a laundry detergent that includes this type of surfactant. Other health risks are possible as well.
In Europe today one of the nonionic surfactants called nonylphenol has been banned from use in detergent formulations. There is no such ban on this surfactant in United States, however. See ‘The Case of Nonionic Surfactants in Europe and America: To Ban or Not to Ban‘ to learn more about nonylphenol and its effect upon health and the environment.
Green laundry detergents should not include any chemicals such as these among their ingredients.
Amphoteric Surfactants – Household Synthetic Surfactant not Usually Used in Detergents
Amphoteric/zwetterionic surfactants are considered to be very mild in action. For this reason they are used in personal care and household cleaning products. These molecules respond to the acidity or alkalinity of the water in which they are dissolved. They may carry a positive charge, a negative charge, or no charge at all, depending upon the acidity of the water they are dissolved in and they do not tend to precipitate in the presence of electrolytes (mineral ions). How toxic are they really? As with all synthetic surfactants much more in-depth biochemical research is needed to properly answer this question.
This post is part of the series: All About Surfactants in Laundry Detergents
- Green Laundry Detergents and the Chemical Structure of Surfactants
- Are the Cleaning Compounds (The Surfactants) in Laundry Detergents Really Safe to Use?
- More Synthetic Surfactants: Fabric Softeners and Other Questionable Inventions
- The Case of Nonionic Surfactants in Europe and America: To Ban or Not to Ban
- Is Sodium Lauryl Sulfate a Natural Surfactant?