Biodegradation alkylphenol ethoxylates

Hager CD (1998) Alkylphenol ethoxylates - biodegradability, aquatic toxicity and environmental activity. In Karsa DR (ed) Annual surfactant review. Sheffield Academic Press,... 

An exception to the above rule of the thumb is the alkylphenol ethoxylates. Biodegradation of these compounds yields the relatively stable C9APEOm with 0 < m<3 ethoxylate units or the respective carboxylates (Ahel, 1989). These ethoxylated products are more hydrophobic and bioaccumulative (Ekelund et al., 1990 Ahel et al., 1993) than the precursor surfactant molecules and are also of toxicological concern (Granmo et al. 1989, Jobling et al., 1996). 

Staples CA, Naylor CG, Williams JB, Gledhill WE (2001) Ultimate biodegradation of alkylphenol ethoxylates surfactants and their biodegradation intermediates. Environ Toxicol Chem 20 2450-2455... 

Nonionic surfactants contain (Fig. 23) no ionic functionalities, as their name implies, and include ethylene oxide adducts (EOA) of alkylphenols and fatty alcohols. Production of detergent chain-length fatty alcohols from both natural and petrochemical precursors has now increased with the usage of alkylphenol ethoxylates (APEO) for some applications. This is environmentally less acceptable because of the slower rate of biodegradation and concern regarding the toxicity of phenolic residues [342]. 

This paper will review the biodegradation of nonionic surfactants. The major focus will be on alcohol ethoxylates and alkylphenol ethoxylates—the two largest volume nonionics. In this paper the effect of hydrophobe structure will be discussed, since hydrophobe structure is considered more critical than that of the hydrophile in biodegradability of the largest volume nonionics. The influence of the hydrophobe on the biodegradation pathway will be examined with an emphasis on the use of radiolabeled nonionics. 

Alkylphenol Ethoxylates (APE). The hydrophobes of most commercial APE are made by reacting phenol with either propylene trimer or diisobutylene to form nonylphenol or octylphenol. These products contain an aromatic moiety and extensive branching in their alkyl chains. It has been shown that APE biodegrade more slowly and less extensively than LPAE (3.15-20). The difference is more pronounced when the treatment system is operating under stress conditions such as low temperatures and high surfactant loadings. 

The three transitions mentioned above, replacement of branched alkylben-zene sulfonates by linear alkylbenzene sulfonates, replacement of alkylphenol ethoxylates by alcohol ethoxylates and substitution of ester quats for stable quats are all driven by environmental concerns. Rate of biodegradation and aquatic toxicity are the major parameters taken into account, and, in order to pass the regulations that the European Union has adopted, a surfactant must pass the criteria of showing ... 

It is common practice to put the experimentally obtained values for biodegradation and aquatic toxicity into a kind of matrix, as is illustrated by Fig. 2. The shaded areas in the matrix are the approved areas . Out of the six product types discussed above linear alkylbenzene sulfonates, alcohol ethoxylates, and ester quats lie within the shaded areas, while branched alkylbenzene sulfonates, alkylphenol ethoxylates and stable quats do not. 

Pulp and Paper Industry. The pulp and paper industry is another area in which SAE can be widely utilized. In the deresination of pulp, C, SAE are suitable biodegradable surfactants to replace alkylphenol ethoxylates. 

Important classes of nonionic surfactants are aliphatic poly-ethoxylate alcohols (AEO), and octyl or nonyl phenol polyethoxylates (OPEO and NPEO). The alkylphenol ethoxylates (APEO) attracted special attention due to their supposedly endocrine disrupting properties (Ch. 8.3). LC-MS analysis may also involve nonylphenolethoxycarboxylates (NPEC), biodegradation products of NPEO, and halogenated analogues, generated in chlorine disinfection treatments in drinking water production plants. 

These compounds yield by their biodegradation the more toxic 4-nonylphenoT . Owing to their poor ultimate biodegradability and the possible environmental hazard of their metabolites, alkylphenol ethoxylates have been replaced in household applications, mainly by alcohol ethoxylates. However, for industrial applications, this replacement has not been carried out yet due to the excellent performance of alkylphenol ethoxylates and their low production costs . 

Nonionic surfactants like alkylphenol ethoxylates (APEO) and their biodegradation products alkylphenol diethoxylate (AP2EO), alkylphenol monoethoxylate (APIEO), and AP are isolated from aqueous solutions with a number of different stationary phases. Kubeck et al. ° used C18 cartridges to adsorb NPEO, but first the water samples were passed through a mixed-bed ion exchange resin to remove all ionic species. Eor SPE of alcohol ethoxylates (AEO) C8 cartridges have been successfully applied from which the surfactants were eluted with methanol followed by... 

Applications of alkylphenol ethoxylates are nearly the same as those of alcohol ethoxylates with stronger emphasis on technical needs. The production of alkylphenol ethoxylates is reduced gradually in view of their worse biodegradability and the established aquatic toxicity of their intermediates [40, 41]. 

Several metabolites are formed during the aerobic and anaerobic biodegradation of alkylphenol ethoxylates (APEOs). Significant amounts are found of alkylphenol, mono- and diethoxylated alkylphenols and the equivalent carboxylates, i.e. alkylphenoxyacetic acid and alkylphenoxyethoxyacetic acid. A simplified scheme, according to Thiele et al. (19), of the biodegradation... 

Figure 22.7. Aerobic and anaerobic biodegradation pathways of alkylphenol ethoxylates...

Both octylphenol and nonylphenol are found in the wider environment as a result of the biodegradation of the alkylphenolic polyethoxylates (APEOs) and are themselves recalcitrant breakdown products. The nonionic alkylphenol ethoxylated surfactants, namely... 

Alkylphenol ethoxylate (APE) surfactants make up approximately 10% of overall consumption. While effective in many industrial applications, they face a number of environmental challenges that could greatly reduce their use in the future. Of major importance are questions concerning their relatively slow rate of biodegradation and the possible toxicity of degradation intermediates, especially phenols and other aromatic species. In the United States and western Europe, many detergent manufacturers have voluntarily discontinued their use in household products. 

Steinle et al. [426] studied the primary biodegradation of different surfactants containing ethylene oxide, such as sulfates of linear primary alcohols, primary oxoalcohols, secondary alcohols, and primary and secondary alkyl-phenols, as well as sulfates of all these alcohols and alkylphenols with different degrees of ethoxylation. Their results confirm that primary linear alcohol sulfates are slightly more readily biodegradable than primary oxoalcohol sulfates and that secondary alcohol sulfates are also somewhat worse than the corresponding linear primary. 

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