Comportamiento ambiental de tensioactivos comerciales aniónicos y no iónicos
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The recovery of different types of surfactants formerly applied and up-coming new ones from spiked wastewater and ultra-pure water was examined by sum parameter determinations (substance-group-specific Methylene Blue (MBAS), Bismuth Active (BIAS) and Disulfine Blue Active Substances (DSBAS)) and by substance-specific mass spectrometric detection (MS). For MS determination atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI) was applied in the flow injection (FIA) and liquid chromatographic separation (LC) mode. Quantitation was performed in the multiple ion detection mode using mass and tandem (MS/MS) mass spectrometric detection. In parallel the ecotoxicological potential of these surfactants was determined by Daphnia magna and Vibrio fischeri toxicity testing. MS was found to provide more reliable data in surfactant analysis than the substance-group-specific methods. The toxicity of the up-coming new surfactants against water organisms should not be neglected.
This paper concerns the primary biodegradation of different commercial fatty-alcohol ethoxylate surfactants (FAEs), applying the OECD 301 E test for ready biodegradability. Changes were made both in the carbon-chain length of the surfactants as well as in the number of units of ethylene oxide (EO) in its molecule. The biodegradation were monitored, analysing the colony-forming units (CFU) formed during this process. From the biodegradation profiles drawn for the FAEs, parameters characteristic of the biodegradation process were defined: latency time (t
L), biodegradability at 50 h of assay (B), half-life (t
1/2), mean biodegradation rate until reaching biodegradability of 85% (V
M), and the residual concentration of the surfactant (S
R). The analysis of these parameters enabled the establishment of the influence of surfactant concentration and structure during the biodegradation process. The increase in the surfactant concentration lowered the rate of the biodegradation process and the biodegradability of the surfactant in addition to the half-life and residual concentration of the surfactant. The mean biodegradation rate, V
M, for fatty-alcohol ethoxylates increased with the number of EO units and molecular weight of the surfactant. At low initial test concentrations (less than 25 mg/L), the concentration of the residual surfactant rapidly diminished with biodegradation time. For higher concentrations, after an adaptation period of the microorganisms, the surfactant concentration declined exponentially and the biodegradation rate became far slower for all the surfactants. The parameters characteristic of the growth curves: specific growth-rate, k, and the yield of biomass production per gram of surfactant, Y
ap, made possible the quantification and corroboration of the results during the biodegradation process.
The aquatic toxicity of 34 alkyl polyglucosides (APGs) towards two fresh-water species, Thamnocephalus platyurus and Brachionus calyciflorus were studied. The toxicity tests were performed using so-called toxkits, and for each surfactant the results are presented as 10log (mean LC50) values. The toxicity data were combined with physico-chemical data for the APGs, and a Multivariate Quantitative Structure-Activity Relationship (M-QSAR) model was calculated. Partial Least Squares (PLS) regression was used to develop the M-QSAR model. The resulting linear M-QSAR model explained 93.6% of the variance in the biological response and had a predictability of 86.6% according to cross-validation. The physico-chemical properties with the strongest influences on the toxicity of the surfactants were the critical micelle concentration (c.m.c.) wetting, contact angle, and number of carbon atoms in their hydrophobic parts (C and redC).
Introduction: The use of surfactants continuously becomes more common, hence their increasing presence in the water environment. Because of their properties, these compounds to a different degree adversely affect all living organisms. Material and Methods: Four non-ionic, phosphoorganic surfactants, monoethanoloamine or diethanoloamine salts of octyl or lauryl alcohol, were tested. Physiological tests were carried out using the organisms representing decomposers - Sphaerotilus natans and producers - Scenedesmus quadricauda. Lethal tests were performed with consumers: Paramaecium caudatum and Daphnia magna. Results: The tested compounds at different concentrations inhibited or stimulated growth of bacteria and algae. One compound at the concentration of 1 mg/l caused an increase of the biomass of bacteria up to 308% relative to control. The concentration 10 000 mg/l only in one case caused complete inhibition of bacterial growth. One compound at the concentration 2000 mg/l caused an increase of the biomass of algae up to 233% and at the concentration 3000 mg/l only 4% of biomass was determined relative to control. EC50 values of the tested compounds after 48 hours of exposure for Paramaecium caudatum were 30-760 mg/l and for Daphnia magna were 14-133 mg/l, depending on the kind of compound. Conclusions: The tested phosphoorganic, non-ioinic surface active agents should be considered moderately toxic. Paramaecium caudatum and Daphnia magna were found to be the most useful bioindicators. Big differences in the sensitivity of the representatives of an aquatic biocenosis to the tested compounds can lead to the loss of balance between the trophic levels of the food chain in water environment.
This paper describes the state of the art for determining surfactants in environmental samples and highlights the major achievements in this area over the past three years. The existing colorimetric procedures such as Methylene Blue Active Substances (MBAS) for anionics, Bismuth Active Substances (BiAS) for nonionics and Disulfine Blue Active Substances (DBAS) for cationics are increasingly regarded as screening methods. They are being replaced by specific and sensitive analytical procedures, which offer increased possibilities for determining the fate of individual surfactants in the environment. Today, such methods, based on HPLC, exist already for the determination of linear alkylbenzenesulphonate (LAS) and ditallowdimethylammonium chloride (DTDMAC), the major anionic and cationic surfactants respectively, in a broad range of environmental matrices. The validity of these procedures has been demonstrated in environmental monitoring work.
A series of chemical compounds belonging to the non‐ionic polyethoxylated surfactants family were selected: fatty alcohols, alkyl phenols and fatty amines. Their toxicity was determined against a biological test system: luminiscent marine bacteria, Photobacterium phosphoreum. Toxicity of chemicals was monitored by the decrease in intensity of the ligth emitted by bacteria as a consequence of their contact with surfactants. From the results obtained through the above mentioned biological toxicity test, a direct relationship between the hydrophobic chain length and the toxicity for a series of linear alcohols has been established. Also, for a series of ethoxylated alcohols, alkyl phenols and fatty amines, the toxicity of homologous is very dependent of the ethoxylation grade, e.g. the greater the HLB value of the homologous, the smallest its toxicity.
Synthesis of a cationic surfactant, Nα-lauroyl arginine methyl ester hydrochloride (LAM) has been carried out in gel emulsions of the system water/C14E4/decane. The yields of LAM synthesized in gel emulsions are comparable to those obtained in conventional dimethylformamide (DMF) media. The rate of LAM formation is faster in gel emulsions at short times, the reaction taking place without mechanical energy input and at 25°C.
Phase behavior of a mixed surfactant, sodium dodecyl sulfate + lipophilic poly(oxyethylene) dodecyl ether, in a brine-decane system was investigated at a constant brine/decane weight ratio equal to 1. Solubilization capability of the mixed surfactant reaches its maximum and microemulsion is formed when the surfactant is changed from hydrophilic to lipophilic in a given system. In the present system, lamellar liquid crystal (LC) intrudes in the single-microemulsion region, and three-phase microemulsions are not formed. The mixing fraction of nonionic surfactant in the total surfactant in the midst of the LC present region increases with increasing oil content due to the high solubility of nonionic surfactant in oil. The partition of nonionic surfactant molecules between the oil and the bilayer in the LC phase is analyzed by using the geometrical relationship of the phase equilibria in the phase diagrams, taking into account the solubility. The monomeric solubility of nonionic surfactant in oil is much less than that of an ordinary cosurfactant like hexanol, and the mixing fraction of nonionic surfactant in the bilayer decreases with increasing salinity. The interlayer spacing of the midlamellar liquid crystal between the two microemulsion regions was measured by small-angle X-ray scattering. The average effective cross-sectional area per surfactant is about 0.37 nm2 and is unchanged upon dilution. It is considered that there is a strong attractive interaction between the ionic group and the nonionic hydrophilic moiety of surfactants.
Acute and chronic toxicity tests using the cladoceran Daphnia magna were conducted on several alcohol ethoxylate surfactants. Exposure and homologue distributions were confirmed using specific analytical methods. These data were used to test currently available acute structure-activity relationships (SARs) and to develop a new chronic SAR to extrapolate test data to effluent or receiving water mixtures. Existing acute SARs adequately predicted the toxicity of these materials with an r(2) of 0.96 based on alkyl chain length and number of ethoxylates and 0.98 based on logK(ow). The additional chronic toxicity data allowed for development of a chronic SAR based on logK(ow) and produced an r(2) of 0.93. Slopes of new and published acute, chronic, and mesocosm SARs based on logK(ow) ranged from -0.61 to -0.87. These new data and refined SARs will assist in the toxicity prediction of mixtures in the environment.