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Whats the everyday difference between ...

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pingu748 | 18:46 Wed 27th Sep 2006 | Science
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Ionic & Non Ionic Surfactants ...
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An ionic surfactant has a net charge at the head. A non-ionic surfactant doesn't have a net charge at the head, although it does have a polar group (e.g. an alcoholic -OH group) at the head.
Question Author
Thank you !!!!!!!!! But am trying to ascertain why there is a requirement for both in Detergent ... do they interact to provide a cleaning "solution" (as in an end result) ... or do they have individual tasks ...
Let's try again by going back to basics.

A surfactant(surface active agent) is a chemical substance which when dissolved in water, gives the product containing the surfactant the ability to remove dirt from textiles, skin and other surfaces. Surfactants have the ability to clean grease, oil and other stains from surfaces because of their ability to fully wet surfaces to be cleaned allowing dirt to be readily loosened and the dirt they do remove in this way is kept suspended, emulsified or dispersed in the solvent medium.

Each surfactant molecule looks like a tadpole. The hydrophilic (water-loving) �head� is attracted to water molecules. The �tail� is hydrophobic (water-hating) and repels water. However, although the tail hates water, it manages to attach itself to dirt and grease during its thrashing around to avoid water. The end result of these two different mechanisms is that dirt is loosened and suspended in the water.

The addition of surfactants to water allows oil and grease stains, which are insoluble in water to be dispersed in the washing water. In the case of a washing machine, the agitation helps remove the dirt/oil and assists in keeping it suspended in the water. The same applies in a dishwasher.

Surfactants are also referred to as wetting agents. They lower the surface tension of the substance in which they are dissolved. This decrease in surface tension allows the easy removal of dirt and grease off the soiled objects and assist in keeping them in solution. The hydrophilic head stays in the water, breaks up the stain and pulls the stain towards the water but away from the substrate. The stain particles are then suspended in the washing water.

(continued)
In anionic surfactants, the head has a negative charge. These types of surfactants are the most commonly used for such purposes as washing clothes and shampoos. Anionic surfactants have a superb ability to repel dirt from fabrics in solution.

The problem with anionic surfactants is that calcium and magnesium ions in the water, a condition prevalent in hard-water areas, tend to deactivate this type of surfactant. This is because the positively charged ions in the water react with the negatively charge on the surfactant, reducing its effectiveness. The harder the water, the less effective anionic surfactants become. Chemicals called sequestrants are sometimes used in attempts to overcome this problem, but they are not ideal remedies. Alkyl Sulphonates and soap are typical examples of anionic surfactants.

In cationic surfactants, the head is positively charged. Cationic surfactants are used to provide softness in fabric conditioners. They also allow anionic surfactant to work in closer proximity to one another at the stain site leading to more efficient stain removal. In general, they are best at removing grease stains.

There are also non-ionic surfactants, which do not have a charge. This allows them to be used in soft or hard water equally effectively. These are the best grease removers and are used washing-up liquids, household cleaners and a range of laundry products. Typical non-ionic surfactants include ethers of fatty alcohols.

There is also another class of detergents called amphoteric or zwitterions surfactants. These are all mild detergents used for toiletry and other personal use. Some of them are used as mild cleaning products too.

Depending on the pH of the water, amphoteric detergents can be anionic, cationic or non-ionic in solution. Amphoteric surfactants mix well with other detergents. They provide plenty of foam when dissolved in water and are very gentle on the skin.
So yes, as you suggested in your last post, it is correct to think of each type of detergent as having a different task.

I hope that's answered your question!
Question Author
Answered it ??

I should say so !!

Fantastic & very much appreciated ...

Pingu
Thanks. I'm glad to have helped.

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