Trace analysis of alkylphenol ethoxylates

A method for quantitative determination of trace amounts of alkylphenol ethoxylates (APE) in environmental water is described. Levels of 1 to 3 μg/L can be detected and resolved into their complete oligomer distribution (1EO to 18EO) while maintaining integrity of the oligomer distribution. This is a major improvement over previous methods; for the first time distortion of oligomer distribution due to work-up conditions of earlier methods has been prevented. Isolation of the APE from water is achieved using a simple and rapid dual-column procedure. The first column removes interfering ionic materials, the second traps the APE on alkyl-bonded silica. Assay of the extract employs HPLC with a fluorescence detector. The method was used for analyzing treated waste-water and river water. A much better picture of the biodegradation behavior of APE in the environment has emerged as a result of keeping APE oligomer distribution intact during sample extraction. There is no accumulation of alkylphenol and the low EO oligomers during wastewater treatment, although the oligomer distribution may become skewed toward these species. Concentrations in the receiving waters examined were very low, in the range of 1–2 μg/L total APE species (OEO to 18EO). Presented at the 1989 Annual AOCS Meeting in Cincinnati. Ohio.     

Analysis of nonionic surfactants in bench-scale biotreater samples

The effluents and activated sludges used in benchscale biotreater units have been analyzed for nonionic alcohol ethoxylates and their residues. Separate bench-scale units were fed linear alcohol ethoxylates (AE), highly branched and branched nonylphenol ethoxylates. Effluents and sludges were first pretreated by a foam sublation technique to provide a gross separation of surfactants from the environmental matrix. This step was followed by normal-phase high-performance liquid chromatography (HPLC) with either fluorescence detection (FD) or evaporative light-scattering detection (ESLD). The AEs were derivatized with phenylisocyanate and analyzed by normal-phase HPLC coupled with FD. At extremely low surfactant levels, pretreatment of large sample volumes resulted in interferences on derivatization. Hence, a normal-phase HPLC method with ELSD was developed. Although some interferences do appear using ELSD, this method appears to be a more viable alternative to derivatization/FD for very low levels of AE. HPLC with FD and ELSD detection methods are more quantitative and provide information on the polyoxyethylene chain than is possible with traditional methods like cobalt-thiocyanate active substance. Presented at the 82nd AOCS Annual Meeting & Expo, May 1991, Chicago, Illinois.     

Development and application of kinetic models for the primary biodegradation of non-ionic surfactants

The growing concern for the environment is promoting the use of surfactant products from renewable sources such as fatty alcohol ethoxylates. The high production and use of these products implies the need to develop models that enable predictions of their behaviour in biodegradation processes. The biodegradation tests were carried out according to the OECD 301 E test for ready biodegradability. In this work, kinetic models of general application to surfactant biodegradation are developed, both for substrates that do not support growth and for those that do, considering a residual substrate concentration as not being biodegraded. The models were applied to three commercial non-ionic surfactants, fatty alcohol ethoxylates with different carbon-chain lengths and degrees of ethoxylation, also analysing the initial surfactant concentration.     

The use of biodegradable linear alcohol surfactants in textile wet processing

Highly biodegradable linear alcohol surfactants have proven to be efficient wetting and scouring agents for use in all phases of textile wet processing. The linear alcohol surface active agents can be directly substituted for the conventional alkylphenol-based materials, which have previously been shown to be resistant to biodegradation. No loss in performance or handling characteristics are encountered by changing the surfactant hydrophobe from alkylphenol to linear alcohol. Surfactants based on the linear primary alcohols, which are widely used in biodegradable household detergents, are somewhat less desirable for use with textiles due to generally higher solidification points and less efficient wetting ability. Replacement of branched chain alkylphenol nonionics by more biodegradable linear alcohol ethoxylates has proceeded rather slowly in the textile industry. This is due to various factors, one of which is the reverse relationship between low five-day biochemical oxygen demand (BOD) requirements for industrial waste streams and the higher five-day BOD of the linear alcohol ethoxylates. Continued use of slower degrading alkylphenol ethoxylates is not, however, a satisfactory solution to the problem of the best choice of surfactant. Longer range oxygen demands on receiving waters are shown to exist as a result of such slower biodegradation of these alkylphenol nonionics. One of eight papers being published from the Symposium, “Surface Active Agents in the Textile Industry”, presented at the AOCS Meeting, New Orleans, April 1970.     

Optimization of nonionic/anionic surfactant blends for enhanced oily soil removal

Previously reported results for alcohol ethoxylate surfactants have shown that optimum removal of both nonpolar and sebum- like liquid soils from polyester/cotton fabric occurs at the phase inversion temperature (PIT) of the surfactant- water- soil system. A similar correlation between phase inversion and optimum detergency has been identified for detergent systems containing mixtures of nonionic and anionic surfactants such as alcohol ethoxylates and alcohol ethoxysulfates. Experimental techniques other than direct detergency studies are described which allow determination of the optimum nonionic/ anionic surfactant ratio for removal of a particular soil at a specified temperature. In addition, implications of these results for development of temperature- insensitive detergent formulations containing alcohol ethoxylates are discussed.     

Use of certain alcohol ethoxylates to maintain protease stability in the presence of anionic surfactants

Anionic surfactants, including linear alkylbenzene sulfonate (LAS), are known to decrease the stability of detergent proteases, possibly by hastening autoproteolytic processes. Thus, protease shelf life in enzyme-containing, heavy-duty liquid laundry detergents (HDL) is typically maintained by adding stabilizers, by limiting the level of interfering anionics, or by utilizing more compatible anionics, such as alcohol ethoxysulfates (AES). This study examines the stability of Savinase^® detergent protease in HDL formulations based on LAS and containing different alcohol ethoxylates (AE) for protection against protease inactivation. Dose response curves demonstrated that all commonly used anionic surfactants except AES promote loss of protease activity. In HDL formulations with equal percentage compositions of LAS and AE, the structure of the selected AE was found to have a profound influence on protease stability. Inclusion of AE with chain length ≥C₁₄ and ethoxylate levels >70% resulted in greater protease stability. HDL containing LAS and these protective AE could be formulated to achieve protease stability matching those of simulated commercial products. Unlike polyhydric stabilizers, the AE by themselves confer no additional stability to the protease. It is more likely that the stabilizing effect of the “protective” AE is due to decreased availability of LAS to the protease.     

Mammalian Toxicity Testing of Semilinear and Branched Alcohol Ethoxylates

Alcohol ethoxylates (AE) are commonly used nonionic surfactants with widespread adoption in consumer and industrial applications. The toxicology profile of this general class of molecules has been extensively reported previously. This report serves to make accessible previously unpublished toxicological data from 59 toxicology studies on AE produced from branched and semilinear alcohols produced by ExxonMobil, with alcohol backbones ranging from C9 to C15. Information on acute oral toxicity, acute dermal toxicity, genetic toxicity, skin irritation, eye irritation, skin sensitization, and oral repeat-dose toxicity are presented here. These data significantly enrich the database on the toxicity of branched AE and support that the degree of branching presents no unique toxicological hazards in relation to that of semilinear AE in this report, as well as in comparison with similar data published on a range of linear, semilinear, and branched AE.     

Degradation of Recalcitrant Surfactants in Wastewater by Ozonation and Advanced Oxidation Processes: A Review

Surfactants are used in varieties of industrial cleansing processes as well as in consumer products. Spent surfactants normally enter domestic or industrial wastewater and are treated biologically. However, some of them are resistant to biodegradation and are released into the environment. Thus, the toxicity and environmental persistence of these surfactants are emerging concerns. Based on extensive review of the literature, ozonation and advanced oxidation using various combinations of ozone, hydrogen peroxide, ultraviolet light irradiation, and iron salts were found effective in degrading recalcitrant surfactants, including linear alkylbenzene sulfonates, alkylphenol ethoxylates, and quaternary ammonium surfactants. Biodegradability of these surfactants was improved after the treatment to some extent in the aqueous solution as well as in real wastewaters.     

Determination of average molecular weight of commercial surfactants: Alkylpolyglucosides and fatty alcohol ethoxylates

A quick and simple method, based on elemental and moisture analyses, is proposed for estimating the mean molecular weight of alkylpolyglucosides and fatty alcohol ethoxylates, which are nonionic surfactants that are attracting growing interest for their ease of biodegradation. Analyses for the water content and the elemental composition were carried out for three alkylpolyglucosides (Henkel-Cognis): Glucopon 215, Glucopon 600, and Glucopon 650, as well as for five fattyalcohol ethoxylates (Kao Corporation): FINDET 10/15, FINDET 10/18, FINDEt 1214N/16, FINDET 1214N/23, and FINDET 1618/A18. Application of the method requires knowing the mean number of carbons in the fatty acid chains of the surfactant. This number, in the case of the alkylpolyglucosides assayed here, has been determined experimentally by high-performance liquid chromatography.     

Skin compatibility and ecotoxicity of ethoxylated fatty methyl ester nonionics

Ethoxylated fatty methyl esters (EFME) are nonionic surfactants obtained by direct insertion of ethylene oxide to fatty methyl esters in the presence of a composite metal oxide catalyst. Results of cumulative skin irritation testing of EFME on guinea pigs indicate that EFME are less irritating compared to ordinary alcohol ethoxylates (AE). Good skin compatibility of EFME is further illustrated by an in vitro hemolysis test and an in vitro cytotoxicity test. From the standpoint of environmental properties, EFME are readily biodegradable and are less toxic than AE. These results indicate the outstanding dermatological compatibility and good environmental compatibility of EFME.     

Nonionic surfactant polarity index determination by inverse gas chromatography

Polyglycol nonionic surfactants are widely used in industrial and consumer products. Two classes of these surfactants, made from selected combinations of 1,2-butylene oxide, propylene oxide and ethylene oxide, were compared to alcohol ethoxylate (AE) and nonyl phenol ethoxylate nonionic surfactants in this study. Polyglycol copolymers consisted of either a polypropylene glycol (PPG) or polybutylene glycol (PBG) central hydrophobe. Ethoxylation of the hydrophobes produced polyethylene glycol hydrophilic blocks. Differences in hydrophobe polarity were determined by inverse gas chromatography (IGC). IGC is a useful analytical method by which the physical and chemical characteristics of a material are studied. The stationary surfactant material under study was coated onto an inert support and used as the packing for the column. A probe mixture, containing simple organic molecules of varying polarity, was injected, and the retention characteristics were measured. The retention characteristics of the standard probe mixture were used to reveal relative polarity information about the stationary surfactant coatings. Polarities of the four hydrophobes were (in decreasing order): PPG, PBG, nonyl phenyl and fatty alkyl. Comparisons were then made between the calculated hydrophile-lipophile balance values and polarity indices of the hydrophobes and their ethoxylates. The effects of hydroxyl groups on polarity were also studied and quantified.     

Biodegradation of nonionic surfactants

This paper discusses the biodegradability of alcohol-based nonionics measured by the recommended legislative test procedures and how the results obtained are affected by the chemical structure of the surfactant, and thus provides guidance on the selection of materials. More detailed studies on the biodegradation of alcohol ethoxylates during the activated sludge sewage treatment process are also reported. Examination of a wide range of alcohol ethoxylates in the legislative tests shows that the majority of those nonionics of practical importance will be extensively biodegraded. Although the mathematical model used to design the treatability test is very simple and has frequently come under criticism, the predictions seem to be upheld and the results obtained appear to provide a reliable guide to what is likely to happen in practice. The sludge residence time, which has long been regarded as of particular importance by those involved in the field of sewage treatment, is clearly demonstrated to be a highly significant factor whose influence should be taken into account in any detailed laboratory study of treatability. The study of alcohol ethoxylates indicates that extensive primary biodegradation will occur even in overloaded treatment plants where sludge retention times (SRT) are likely to be short. The effect of temperature on the biodegradation is small and suggests that effective treatment will be achieved in such plants even at the lower temperatures experienced during winter. Ultimate biodegradation of alcohol ethoxylates was shown to be extensive under practical conditions and levels of “polyethylene glycol” intermediates discharged to surface waters will be low. Although alcohol ethoxylates are rapidly and extensively absorbed on activated sludge, this does not play a significant role in the removal process which is essentially one of biodegradation.     

Compatibility of nonionic surfactants with membrane materials and their cleaning performance

Membranes applied in industrial processes, such as for the desalination of seawater as well as for dairy and beverage industry are subjected to fouling resulting in a decline of their performance. In order to regain the flux of the membranes, cleaning procedures are conducted, whereby inorganic scale is often removed with acids and organic matter with surfactants under alkaline conditions. Currently, either ionic surfactants or alkylphenol ethoxylates are utilised to clean membranes of organic matter. Other nonionic surfactants (i.e. fatty alcohol ethoxylates) are not applied, due to the assumption that they irreversibly adhere to the membrane surface and thereby clog the pores. At BASF we have studied the adsorption of a wide range of nonionic surfactants to membrane materials. It was shown, that the affinity of nonionic surfactants critically depends on their structure. Linear alkyl ethoxylates irreversibly adsorb to the membrane surfaces, whereas branched alkyl ethoxylates do not. In a second step, we tested the cleaning performance of nonionic surfactants. Similar to the results for adsorption, a structure-performance relationship was discovered where several branched alkyl ethoxylates showed excellent cleaning results. In a third step, combinations of nonionic surfactants, chelating agents and enzymes were tested in terms of cleaning efficiency. All tested combinations showed excellent cleaning performance on bacterial fouling layers.     

Effect of temperature on the biodegradation of linear alkylbenzene sulfonate and alcohol ethoxylate

The effect of temperature on the biodegradation of linear alkylbenzene sulfonate (LAS) and alcohol ethoxylate (AE) was evaluated using method OECD 303 A, Confirmatory test (Husmann units). The experiments were performed using an initial surfactant concentration of 10 mg/L and working temperatures of 25, 15, and 9°C, keeping the biodegradation units inside a thermostatic chamber. In all cases, the removal of both surfactants tested, LAS and AE, was higher than 90%, regardless of the temperature used in the test. We observed that longer acclimation periods were needed by the microorganisms at lower temperatures.     

Effects of the ethylene oxide distribution on nonionic surfactant properties

Detergent-range primary alcohols are readily converted into nonionic surfactants by reaction with ethylene oxide. Optimum performance properties for these surfactants generally are attained by varying the number of moles of ethylene oxide reacted with each mole of alcohol or by altering the structure of the primary alcohol. However, variations in the ethoxylate-adduct distribution also affect surfactant properties in such a way that products with relatively narrow distributions possess features which are highly desirable in many household and industrial applications. For a given cloud point narrow-range ethoxylates have lower molecular weights and therefore lower pour points than broad-range surfactants. Because narrow-range ethoxylates contain less unreacted alcohol and other water-insoluble species, they are capable of forming aqueous solutions with much lower cloud points than their broad-range counterparts. Aqueous solutions of narrow-range products have lower viscosities, exhibit lower gel temperatures and remain fluid over a wider concentration range than solutions of broad-range surfactans. While the foams obtained with narrow-range surfactants in the Ross-Miles test are higher initially, they are less stable than those produced by conventional nonionic surfactants. Draves wetting data show that narrow-range products wet cotton substrates more efficiently than normal-distribution materials. Narrow-range ethoxylates exhibit higher aqueous surface tension and higher polyester adhesion tension values than their broad-range counterparts. In addition, narrow-range surfactants reduce the interfacial tension against paraffin oil more efficiently and more effectively than broad-range products. These results, along with laboratory detergency data, suggest that the use of narrow-range ethoxylates may lead to cleaning systems with improved performance and/or physical properties.     

表面活性剂降解研究进展

简述了表面活性剂对环境的影响及其降解的发展概况，着重讨论了表面活性剂的各种生物降解的研究方法和特点，降解动力学，结构与降解性能间的关系，影响降解的环境因素及直链烷基苯磺酸盐（LAS），烷基硫酸盐（AS）等几类常见表面活性剂的生物降解机理。并对近年发展起来的表面活性剂光催化降解的研究方法，降解机理及降解动力学作了简要介绍。     

Effect of Selected Nonionic Surfactants on the Activated Sludge Morphology and Activity in a Batch System

In this study, two nonionic surfactants, one alcohol ethoxylate (AE) and one alkylphenol ethoxylate (APE) were investigated with regard to their influence on the morphology of activated sludge flocs, microbial activity and wastewater treatment efficiency in a laboratory batch system. The experiments were carried out for a range of nonionic surfactants concentrations in wastewater from 5 to 500 mg L⁻¹. Additionally, these results were compared to the data obtained in previous experiments on anionics and performed under the same conditions. Both nonionics tested caused a decrease in the size of activated sludge flocs but they did not affect the shape of the flocs. The circularity index and convexity of flocs remained similar to the control run, containing no surfactant. The presence of nonionic surfactants within the tested concentrations range caused a decrease in biomass activity. In spite of morphological changes of activated sludge flocs and a decrease in microbial activity, only higher concentrations of nonionics in wastewater starting with the level of 50 mg L⁻¹ can induce pinpoint flocs and decrease wastewater treatment efficiency. APE showed a stronger impact on the decrease in floc size and microbial activity than alcohol ethoxylate did. APE was also more difficult to biodegrade than AE. Comparing the efficiency of wastewater treatment (in terms of COD removal) in the presence of nonionic and anionic surfactants at the same concentration of 50 mg L⁻¹, the degree of organic pollutant removal was found to be higher by about 10% for anionics than for nonionics.

Biodegradation of nonionic surfactants containing propylene oxide

Insertion of oxypropylene groups into the polyoxyethylene chain of fatty and oxo alcohol ethoxylates decreased the rate and extent of biodegradation. The magnitude of the effects was proportional to the PO-block size and the extent of branching in the alcohol. Data are presented from a series of PO-containing nonionic surfactants in semi-continuous activated sludge reactors over test periods of up to 12 weeks. Bioassays performed on effluents from the SCAS units showed little or no toxicity due to residual degradation metabolities towardPimephales promelas andDaphnia pulex and a stimulatory effect onSelenastrum capricornutum growth rate.     

Determination of Alcohol Ethoxylates derivatized with Naphthoyl Chloride,in Waste Water Treatment Plant Influent,Effluent and Sludge Samples by Liquid Chromatography Mass Spectrometry

A new analytical procedure for the determination of alcohol ethoxylates (AE) in environmental samples such as influents, effluents and sludge from waste water treatment plants (WWTPs) was developed. Although some work had been previously published on the detection of AE in water samples, this is the first paper that deals with AE in sludge. Alcohol ethoxylates were removed from water samples by sorption on polymeric discs followed by extraction with methanol. The methanol extracts were cleaned up with two alumina solid-phase extractions (SPE) at different conditions of solvent polarity, one before and the other after derivatization with naphthoyl chloride. A final polishing step was carried out on a Florisil SPE column. Liquid chromatography/mass spectrometry with electrospray ionization was used to quantify AE as naphthoyl derivatives. The detection limits for AE ethoxymers range from 0.07 to 0.005 μg/L in water samples. The method was applied to an Italian WWTP in order to follow the fate of AE during treatment, AE concentrations of 839 μg/L, 0.46 μg/L and 10.6 mg/kg were respectively found in the inlet, outlet and sludge samples. AE removals of each ethoxymer in the plant were in the range 99.6–100% and no difference was observed between high or low-mole ethoxymers and between AE with odd or even carbon chain lengths. An overall 99.7% removal was also determined on the mass balance of AE in the inlet, the outlet, and sludge of the plant.     

Characterization of alcohol ethoxylates as alcohol ethoxy sulfate derivatives by liquid chromatography-Mass spectrometry

The characterization of alcohol ethoxylates (AE) to determine ethylene oxide (EO) adduct distribution has been studied in our laboratory for many years by using high-performance liquid chromatography-mass spectrometry (LC-MS). This paper describes the LC-MS approach being used to analyze both nonderivatized and derivatized AE. We conclude that the best way to determine EO adduct distribution is by first converting the AE to alcohol ethoxy sulfates (AES) and then by using LC-MS with electrospray ionization in the negative ion mode. A convenient laboratory technique for converting small-scale samples of AE to AES has been discovered and is reported herein. Several examples of EO adduct distribution determined by this method are presented for both linear and isomeric AE samples.