Biodegradable cationic surfactants

Yet another ingredient in laundry detergents is diethyl ester dimethyl ammonium chloride (DEEDMAC). It is a fabric softener. It is a cationic surfactant that is rapidly biodegradable. It works by reducing the friction between fibers, and between fibers and... 

The toxicity of these compounds [ 173,175] can be relatively high compared to other surfactants, but their poor solubility and their tendency to adsorb to solids or to complex with anionic substances considerably reduce the real risk and adverse effects for the aquatic environment. [30,31,176]. The use of alkylquats has been substituted by the more easily biodegradable and less toxic esterquats that are nowadays the cationic surfactants produced in higher volumes. 

Cationic surfactants are surface-active agents that have one or more functional groups in their molecule that ionise in aqueous solution to produce positively charged organic ions. The most representative cationic surfactants are quaternary ammonium derivatives in which the N atom is bonded to four alkyl groups. For many years, ditallow dimethylammonium chloride (DTDMAC) has been the most widely used product of this family. Its recalcitrance to biodegradation, however, has... 

Taking into consideration its physico-chemical properties, removal efficiencies, low biodegradability, predicted environmental levels, toxicity, and the need to provide sufficient safety margins for aquatic organisms, the demand for alternative cationic surfactants arose. Since 1991, DTDMAC has been replaced in some European countries due to producer s voluntary initiatives with new quaternary ammonium compounds, the esterquats. These contain an ester function in the hydrophobic chain (Table 1.3) that can be easily cleaved, releasing intermediates that are susceptible to ultimate degradation [24-26]. The effects of the phasing-out and replacement of DTDMAC can be demonstrated by the results of a Swiss study, where the surfactant... 

This Gemini cationic surfactant could not be recovered from samples of biodegradation experiments performed in a lab-scale aerobic bioreactor [50] either because of complete biodegradation (mineralisation) or because of irreversible adsorption at the surface of the biodegradation device. 

The anaerobic biodegradability and toxicity on anaerobic bacteria of cationic surfactants such as ditallow dimethylammonium chloride (DTDMAC) and two esterquats have been investigated in a recent study [52], For the esterquats studied, high biodegradation levels were obtained and no toxic effects on anaerobic bacteria were observed even... 

Cationic surfactants are used widely as fabric softeners, anti-static agents, antiseptic components and as the main ingredients in rinse conditioner products. However, there is little data on their occurrence in wastewater and removal during wastewater treatment. The concentrations of some cationic surfactants and their biodegradation intermediates, found in WWTP influents and effluents, are listed in Table 6.1.3. 

The increasing popularity of biodegradable materials, which are more susceptible to microbial attack, has boosted the demand for preservation. If the product does not already contain ingredients that are themselves preservatives, such as cationic surfactants, acids, or bases, preservatives may need to be added. The required level of preservatives can be related to water availability (AW), which is defined as the ratio between the water vapor pressure over a substance and the water vapor pressure over pure water at the same temperature [17], In general, an A W of below 70% should be targeted to prohibit microorganism growth [18],... 

Cationic surfactants produce a positively charged surfactant ion in solution and are mainly quaternary nitrogen compounds such as amines and derivatives and quaternary ammonium salts. Owing to their poor cleaning properties, they are little used as detergents rather their use is a result of their bacteriocidal qualities. Relatively little is known about the mechanisms of biodegradation of these compounds. 

Most surfactants used are anionic surfactants followed by nonionic ones. Cationic surfactants often pose environmental problems since they are not easily biodegradable. Amphoteric surfactants are expensive and therefore they are only used for special applications. 

Replacement of alkyl chains by an ester increases the values of k in the case of the (Cn)2Me2N+ cationic surfactants, indicating that hydrolysis is a more rapid biodegradation pathway than co-P-Oxidation. However, comparison of the k -values of C12S04 with that of DEEDMAC demonstrates that other structural moieties also have significant influence on biodegradability. The available data do not allow conclusions as to which factors are involved. 

Gerike P. 1982. Biodegradation and bioelimination of cationic surfactants. Tenside Detergents 19,162-164. 

Larson, R.J., and R.D. Vashon. 1983. Adsorption and biodegradation of cationic surfactants in laboratory and environmental systems. Dev. Ind. Microbiol. 24, 425-434. 

Ruiz-Cruz, J., and M.C. Dobarganas-Garcia. 1979. Relation between structure and biodegradation of cationic surfactants in river water. Grasas Aceites 30, 67-74. 

The new structures place a cleavable functionality within the twin tails of the cationic surfactant which aids in biodegradation by separating the positively charged nitrogen hy-drophile from the hydrophobic portion as shown in Figure 6.2. 

Despite the efficiency of DR cationic surfactant solutions and several successful large-scale field tests, commercial use of these solutions has not been widespread largely because of their slow biodegradation properties. A new series of biodegradable mixed zwitterionic/anionic surfactant solutions, which can be disposed of by normal sewage treatment, has been developed by Akzo Nobel with excellent field test results in the primary system of the same district heating system in Herning, Denmark. 

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