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Detergents and Surfactants

Introduction Synthetic detergents have similar molecular structures and properties as soap. Although the cleansing action is similar, the detergents do not react as readily with hard water ions of calcium and magnesium. There are over a thousand synthetic detergents available in the United States. Detergent molecular structures consist of a long hydrocarbon chain and a water soluble ionic group. Most detergents have a negative ionic group and are called anionic detergents. The majority are alky sulfates. Others are "surfactants" (from surface active agents) which are generally known as alkyl benzene sulfonates.

Cationic Detergents Another class of detergents has a positive ionic charge and is called "cationic" detergent. In addition to being good cleansing agents, these detergents also possess germicidal properties which makes them useful in hospitals. Most of these detergents are derivatives of ammonia.

A cationic detergent is most likely to be found in a shampoo or clothes "rinse". The purpose is to neutralize the static electrical charges from residual anionic (negative ions) detergent molecules. Since the negative charges repel each other, the positive cationic detergent neutralizes this charge.

Neutral or non-ionic detergents Nonionic detergents are used in dish washing liquids. Since the detergent does not have any ionic groups, it does not react with hard water ions. In addition, nonionic detergents foam less than ionic detergents. The detergent molecules must have some polar parts to provide the necessary water solubility.

1 http://www.scientistlive.com/European-Science- News/Process_Technology/Nonionic_detergents%3A_what_are_they_and_when_to_use_the m/9445/

Nonionic detergents: what are they and when to use them The use of nonionic detergents has drawn increased attention in laboratory settings due to their ability to more effectively remove certain types of soils. There is some confusion, however, as to the nature of these cleaners why one type of cleaner is referred to as being “anonionic” and another, “aionic”, and when to use each of them for effective results in laboratory cleaning.

By industry standard, a detergent's charge (nonionic, anionic, cationic, zwitterionic or amphoteric) is determined by the charge of the emulsifier or surfactant in the cleaner. Thus a nonionic detergent is made up of a nonionic emulsifier and other ingredients. If a blend of anionic and nonionic surfactants is used, the detergent is referred to as being anionic. Use of the term nonionic, however, does not necessarily mean that the detergent is ion-free. For example, Alcojet is a nonionic detergent, but most of its other ingredients are sodium salts. As a result, Alcojet is a nonionic, highly ionic detergent.

Furthermore, while the type of charge determines the detergent's ionic type, by itself, it does not provide a basis on which to select a cleaner. In clarifying this issue, it is important to first look at how nonionic surfactants are used in formulating detergents. These surfactants are generally employed in three main types of formulations, based on their intended application:

1. Manual and immersion cleaning mechanisms. These are nonionic detergents (high- emulsifying nonionic detergents) that enhance the ability to remove oily residues. Typically they provide optimum oil-removing performance in a synergistic combination with anionic surfactants. These nonionic cleaners typically contain surfactants of the alcohol ethoxylate class. Examples: Liqui-nox and Citranox. 2. High agitation machine or pressure spray-in-air cleaning. These nonionic surfactants are more dispersing in nature with low-foaming and defoaming properties that enhance wetting, rinsing and particle removal while not interfering with mechanical cleaning action. These types of nonionic cleaners typically have nonionic surfactants of the block copolymer class. Examples: Alcojet and Det-o-jet. 3. Ion-free, non-conductive-residue leaving. Nonionic detergents can also be part of ion- free formulations designed so they are unable to leave ionic or conductive residues. These types of nonionic cleaners can contain either type of nonionic surfactant depending on whether they more are intended for soak emulsifying cleaning or high agitation cleaning. Example: Detergent 8.

Additional factors in detergent selection Machine cleaning detergents need to work very quickly because a droplet of detergent sprayed onto a surface has only a very short time to perform any chemical cleaning before the next droplet sweeps it away. For this reason, these types of formulations tend to be very chemically 2 aggressive, having extremes of pH either highly alkaline (high pH) or highly acidic (low pH), along with other chemically aggressive ingredients such as oxidizing agents (bleach). In unique soaking applications where the soils being removed are labile to these cleaning mechanisms, these cleaners expressly designed for machine use can be very effective.

In general, a good choice for soak cleaning of oily residues on glassware is Liqui-nox (a synergistic blend of anionic and nonionic surfactants) or Citranox (the same blend with additional ingredients optimized for trace metal and inorganic complex removal with some loss of capability in removing oily soils).

If, however, an ion-free cleaner is absolutely essential for soak cleaning, Detergent 8 is an excellent choice. by Malcolm McLaughlin is vice-president, Alconox Inc, White Plains, NY, USA. www.alconox.com He is co-author of The Aqueous Cleaning Handbook.

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Some types of non-ionic detergents:

ALCONOX 1425 Alcojet 25lb Nonionic Low-Foaming Powdered Detergent. This Alconox Alcojet nonionic, low-foaming powdered detergent is packaged in a 25lb carton. It is used in labware washers, parts washers, and power-spray systems. It is used in both manual and ultrasonic cleaning. The corrosion inhibited formula is recommended for glassware, metals, plastic, ceramic, porcelain, rubber, and fiberglass. It is free rinsing for reliable results and no interfering residues. This detergent is USDA authorized. Dilute 1:200. pH: 12. [NOTE: see previous page about sodium salt content before using this product.]

LUNDMARK Wax Mint Disinfectant, Cleaner, Sanitizer, Fungicide A. Recommended for use in washrooms, locker rooms, kennels and such. Composed of a powerful nonionic, detergent blend and amines. Effectively lifts and suspends soil for free rinsing. 1 gallon.

KODAK PHOTO-FLO 200 16oz. Decreases the water-surface tension on the emulsion. Minimizes water marks and streaks on film. Promotes faster, more uniform drying.

LIQUI-NOX® is a special formulation of mild (pH 8.0-8.6), anionic and non-ionic detergents and wetting agents. It is biodegradable and performs equally well in cold or hot water. Phosphate free and safe for all metals, dilute Liqui-Nox is also an effective cleaner for plasticware.

DETERGENT 8 Low-Foaming Ion-Free Detergent. • Replace solvent cleaning • Concentrated to save you money • Biodegradable and readily disposable • Penetrating wetting power to save you time • Free rinsing to give you reliable results and no interfering residues 3

• Contains no phosphate, sulfur, chlorine, metal cation, halide, borate, silicate, carbonate, chlorocarbon, fluorocarbon or chelating ingredients. Used to clean: Circuit boards, electronic parts, phosphate sensitive labware, nuclear reactor cavities, delicate industrial parts and nuclear contaminated equipment during outage. FDA certified. Used to remove: Resins, rosins, oils, dirt, grime, particulates, residues, fluxes, chemicals and solvents. Surfaces cleaned: Corrosion inhibited formulation recommended for glass, metal, stainless steel, ceramic, plastic, and circuit boards. Can be used, with prompt rinsing, on soft metals such as copper, aluminum, silver, and gold. Aluminum can darken and mixed metal galvanic reactions can occur. Corrosion testing is advisable.

CHURCH & DWIGHT CO. XTRA 2X Concentrated Liquid Laundry Detergent. Twice as much cleaning power, half as much detergent. Biodegradable surfactants (anionic and nonionic). Safe for septic tanks. Contains no phosphate. 75 oz. jug.

COUNTRY SAVE Laundry Detergent, 4 Pack, 100 fl oz. Ultra Concentrated & Mildly Scented. 50 Washes. The Phosphate Free Formula That's Safe for the Environment. Low cost per wash. Great for Baby Clothes. Hypoallergenic. Allergy / Asthma Tested. Nontoxic. Biodegradable. All Temperature. Safe for Septic Tanks.

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