Manuela Lechuga - Academia.edu (original) (raw)

Papers by Manuela Lechuga

Tenside Surfactants Detergents, 2002

Methods for the determination of non-ionic surfactants were compared. The biodegradation of fatty... more Methods for the determination of non-ionic surfactants were compared. The biodegradation of fatty alcohol ethoxylates was tested and the surfactant concentration over time analyzed using the iodine-iodide colorimetric method and Wickbold's method (also known as BiAS (Bismuth-Active Substances)). The advantages and disadvantages of bismuth quantification by spectrophotometry and potentiometry using Wickbold's method were also studied. By comparing these two different procedures for the analysis of ethoxylate non-ionic surfactants, we find that the determination of these surfactants in static biodegradation tests using the iodine-iodide method is a viable alternative, much better than Wickbold's method when there are more than 5 molecules of ethylene oxide (EO) in the surfactant. The main advantages of this method are that it requires less sample volume, less analysis time and is less costly to perform. In addition, since it can be performed directly on the sample, there i...

Food and Bioproducts Processing, 2021

Abstract Chemical and food industries are focusing on reducing the economic and environmental imp... more Abstract Chemical and food industries are focusing on reducing the economic and environmental impact of cleaning operations. This study aims to analyse the use of alkaline ozonated formulations to remove starch adhering to stainless steel surfaces, improving disinfection of mature biofilms with Listeria and Pseudomonas, and reducing the environmental impact of wastewater. Three key cleaning parameters have been analysed in a lab-simulated Clean-In-Place system (CIP): temperature (20−60 °C), time (20−120 min), and cleaning formulations containing ozone and surfactant (linear alkylbenzene sulfonate, alkylpolyglucoside, fatty ethoxylated alcohol, lauramine oxide) were assayed. Higher temperature, time, and ozone concentration improved starch removal and disinfection of the stainless-steel surfaces, as well as the environmental impact of cleaning wastewater. Therefore, ozone-based CIP protocols could provide new opportunities to achieve cleaner, greener, and safer industries by intensifying cleaning, disinfection, and wastewater treatment in one step, saving operational costs compared to conventional CIP techniques.

Due to the widespread use of nanoparticles in surfactant-based formulations, their release into t... more Due to the widespread use of nanoparticles in surfactant-based formulations, their release into the environment and wastewater is unavoidable, causing a toxic effect to biota and/or wastewater treatment processes. Because of concerns about the environmental impact of nanofluids, the study of the fate and environmental impact, hazards and toxicity of nanoparticles is beginning. However, the interactions between nanoparticles and surfactants as well as the biodegradability in mixtures have been little studied until now. In this work the environmental impact of nanofluids containing mixtures of surfactants and silica nanoparticles were evaluated. The systems studied were hydrophilic silica nanoparticles (size 7 and 12 nm), a non-ionic surfactant (alkyl polyglucoside), an anionic surfactant (ether carboxylic acid), and mixtures of them. The aerobic ultimate biodegradation and interfacial and adsorption properties of surfactants, nanoparticles and mixtures during the biodegradation proce...

Methods in Pharmacology and Toxicology, 2017

Journal of hazardous materials, Jan 20, 2018

In this work, the toxicity of hydrophilic fumed silica micro- and nanoparticles of various sizes ... more In this work, the toxicity of hydrophilic fumed silica micro- and nanoparticles of various sizes (7 nm, 12 nm, and 50 μm) was evaluated using the luminescent bacteria Vibrio fischeri. In addition, the toxicity of an anionic surfactant solution (ether carboxylic acid), a nonionic surfactant solution (alkyl polyglucoside), and a binary (1:1) mixture of these solutions all containing these silica particles was evaluated. Furthermore, this work discusses the adsorption of surfactants onto particle surfaces and evaluates the effects of silica particles on the surface tension and critical micellar concentration (CMC) of these anionic and nonionic surfactants. It was determined that silica particles can be considered as non-toxic and that silica particles reduce the toxicity of surfactant solutions. Nevertheless, the toxicity reduction depends on the ionic character of the surfactants. Differences can be explained by the different adsorption behavior of surfactants onto the particle surfac...

Biodegradation, Aug 1, 2017

Recently, anaerobic degradation has become a prevalent alternative for the treatment of wastewate... more Recently, anaerobic degradation has become a prevalent alternative for the treatment of wastewater and activated sludge. Consequently, the anaerobic biodegradability of recalcitrant compounds such as some surfactants require a thorough study to avoid their presence in the environment. In this work, the anaerobic biodegradation of amine-oxide-based surfactants, which are toxic to several organisms, was studied by measuring of the biogas production in digested sludge. Three amine-oxide-based surfactants with structural differences in their hydrophobic alkyl chain were tested: Lauramine oxide (AO-R12), Myristamine oxide (AO-R14) and Cocamidopropylamine oxide (AO-cocoamido). Results show that AO-R12 and AO-R14 inhibit biogas production, inhibition percentages were around 90%. AO-cocoamido did not cause inhibition and it was biodegraded until reaching a percentage of 60.8%. Otherwise, we fitted the production of biogas to two kinetic models, to a pseudo first-order model and to a logisti...

Environmental science and pollution research international, Jan 3, 2017

This paper reports on a study that investigated the aquatic toxicity of new non-ionic surfactants... more This paper reports on a study that investigated the aquatic toxicity of new non-ionic surfactants derived from renewable raw materials, polyoxyethylene glycerol ester (PGE), and their binary mixtures with anionic and non-ionic surfactants. Toxicity of pure PGEs was determined using representative organisms from different trophic levels: luminescent bacteria (Vibrio fischeri), microalgae (Pseudokirchneriella subcapitata), and freshwater crustaceans (Daphnia magna). Relationships between toxicity and the structural parameters such as unit of ethylene oxide (EO) and hydrophilic-lipophilic balance (HLB) were evaluated. Critical micellar concentration (CMC) in the conditions of the toxicity test was also determined. It was found that the toxicity of the aqueous solutions of PGE decreased when the number of EO units in the molecule, HLB, and CMC increased. PGEs showed lower CMC in marine medium, and the toxicity to V. ficheri is lower when the CMC was higher. Given their non-polar nature,...

Chemosphere, 2017

Amine-oxides-based surfactants are completely biodegradable in aerobic conditions. Differences in... more Amine-oxides-based surfactants are completely biodegradable in aerobic conditions. Differences in the biodegradability are due to their structural differences. Biodegradability is lower due to the presence of an amide group in the alkyl chain. Initial surfactant concentration had a positive influence on the biodegradation. Biodegradability in acid conditions is slower and in some cases lower.

Environmental Science and Pollution Research, 2016

This paper reports a study of the anaerobic biodegradation of non-ionic surfactants alkyl polyglu... more This paper reports a study of the anaerobic biodegradation of non-ionic surfactants alkyl polyglucosides applying the method by measurement of the biogas production in digested sludge. Three alkyl polyglucosides with different length alkyl chain and degree of polymerization of the glucose units were tested. The influence of their structural parameters was evaluated, and the characteristics parameters of the anaerobic biodegradation were determined. Results show that alkyl polyglucosides, at the standard initial concentration of 100 mgC L(-1), are not completely biodegradable in anaerobic conditions because they inhibit the biogas production. The alkyl polyglucoside having the shortest alkyl chain showed the fastest biodegradability and reached the higher percentage of final mineralization. The anaerobic process was well adjusted to a pseudo first-order equation using the carbon produced as gas during the test; also, kinetics parameters and a global rate constant for all the involved metabolic process were determined. This modeling is helpful to evaluate the biodegradation or the persistence of alkyl polyglucosides under anaerobic conditions in the environment and in the wastewater treatment.

Ecotoxicology and Environmental Safety, 2016

The environmental risk of surfactants requires toxicity measurements. As different test organisms... more The environmental risk of surfactants requires toxicity measurements. As different test organisms have different sensitivity to the toxics, it is necessary to establish the most appropriate organism to classify the surfactant as very toxic, toxic, harmful or safe, in order to establish the maximum permissible concentrations in aquatic ecosystems. We have determined the toxicity values of various anionic surfactants ether carboxylic derivatives using four test organisms: the freshwater crustacean Daphnia magna, the luminescent bacterium Vibrio fischeri, the microalgae Selenastrum capricornutum (freshwater algae) and Phaeodactylum tricornutum (seawater algae). In addition, in order to compare and classify the different families of surfactants, we have included a compilation of toxicity data of surfactants collected from literature. The results indicated that V. fischeri was more sensitive to the toxic effects of the surfactants than was D. magna or the microalgae, which was the least sensitive. This result shows that the most suitable toxicity assay for surfactants may be the one using V. fischeri. The toxicity data revealed considerable variation in toxicity responses with the structure of the surfactants regardless of the species tested. The toxicity data have been related to the structure of the surfactants, giving a mathematical relationship that helps to predict the toxic potential of a surfactant from its structure. Model-predicted toxicity agreed well with toxicity values reported in the literature for several surfactants previously studied. Predictive models of toxicity is a handy tool for providing a risk assessment that can be useful to establish the toxicity range for each surfactant and the different test organisms in order to select efficient surfactants with a lower impact on the aquatic environment.

Journal of Surfactants and Detergents, 2011

The ultimate aerobic biodegradability and toxicity of three ether carboxylic derivative surfactan... more The ultimate aerobic biodegradability and toxicity of three ether carboxylic derivative surfactants having different alkyl chains and degrees of ethoxylation were investigated. Ultimate aerobic biodegradability was screened by means of dissolved organic carbon determinations at different initial surfactant concentrations. For comparison, the characteristic parameters of the biodegradation process, such as half‐life, mean biodegradation rate, and residual surfactant concentration, were determined. Increased surfactant concentrations decreased mineralization and lengthened the estimated half‐life. The results demonstrate that the ultimate aerobic biodegradability is higher for the surfactants with the shortest alkyl chain and highest degree of ethoxylation. Toxicity values of the surfactants, and their binary mixtures, were determined using three test organisms, the freshwater crustacea Daphnia magna, the luminescent bacterium Vibrio fischeri and the microalgae Selenastrum capricornut...

Formación universitaria, 2014

Se presentan diferentes estrategias docentes de aprendizaje autónomo del alumno en el

Journal of Surfactants and Detergents, 2014

The purpose of this study was to discuss the effect of the chemical structure of anionic and non-... more The purpose of this study was to discuss the effect of the chemical structure of anionic and non-ionic surfactants and surface activity on toxicity. Single and binary mixtures of three ether carboxylic derivative surfactants and three amine-oxide-based non-ionic surfactants were used. Toxicity was determined using three test organisms: freshwater crustaceans (Daphnia magna), luminescent bacteria (Vibrio fischeri), and microalgae (Selenastrum capricornutum). The toxicity of surfactants is related to the hydrophobic alkyl chain, the degree of ethoxylation, and the critical micelle concentration of surfactants. Relationships found agreed with the fact that the lower toxicity is shown by the shorter alkyl chain. There is a strong relation between surface activity and toxicity: the toxicity increased as the CMC of the surfactant or mixtures of surfactants decreased. Commercial products are formulated using surfactants mixtures, so it is important to know their behavior using an easily measured property: the least toxic mixtures were formed by the surfactants having lower individual toxicity. Around the CMC, our data show a synergism for the binary mixtures. The results have given rise to a classification of the different surfactants and their mixtures according to the organism test, as safe, harmful or toxic. V. fischeri was in general the most sensitive microorganism to the toxic effect of the surfactants, followed by Daphnia magna, while Selenastrum capricornutum was more tolerant. These results can be useful for selecting technically efficient surfactants and their mixtures with a lower ecotoxicity on the aquatic environment.

Procedia Engineering, 2012

The influence of ozonation of aqueous solutions of non-ionic surfactants was investigated in this... more The influence of ozonation of aqueous solutions of non-ionic surfactants was investigated in this study. The research was conducted using solutions of amine oxide based surfactants. These surfactants constitute a particular class of non-ionic surfactants that exhibit cationic behaviour in acid solution, they show good foaming properties and are skin compatible. The ozonation process was carried out at 25ºC in a stirred tank reactor for 30 min, where gaseous ozone was bubbled. The degree of mineralization achieved after the ozonation process was evaluated by measuring the total organic carbon before and after ozonation. The influence of ozonation on biodegradability of the solutions was studied using the biodegradation test by Pseudomonas putida. Biodegradation efficiency of the ozonated amine oxides based surfactants was also evaluated. It was found that the effectiveness of ozonation depended on the chemical structure of surfactant molecule. Ozonation only slightly improved biodegradation of these surfactants.

Journal of Surfactants and Detergents, 2013

The objective of this study was to investigate the influence of ozonation of anionic and non-ioni... more The objective of this study was to investigate the influence of ozonation of anionic and non-ionic surfactants on their aquatic toxicity. Toxicity values of various commercially important anionic and non-ionic surfactants have been determined using the luminescent bacterium Vibrio fischeri. Surface tension measurements were made to study the interfacial activity. The behavior depends on the chemical structure. Some intermediate ozonation products were found to be more toxic than the base surfactant and others were found to be less. Surfactants with aromatic rings such as linear alkyl benzene sulfonates, or surfactants with glycosidic groups such as alkylpolyglucosides, exhibit a lower toxicity after ozonation. On the other hand, ether groups present in the fatty-alcohol ethoxylates and ether carboxylic derivative surfactants, and carboxylic acid derivates present in the ether carboxylic derivative surfactants lead to increasing toxicity after ozonation. Surfactants with ether groups probably formed short-chain polyethoxylated compounds and carboxylic acids, which are possibly responsible for the surface-tension decrease that promotes the toxicity increase.

Biodegradation - Life of Science, 2013

Surfactants are a wide group of chemical compounds which have a large number of applications due ... more Surfactants are a wide group of chemical compounds which have a large number of applications due to their solubility properties, detergency, endurance of water hardness, as well as emulsifying, dispersing, and wetting properties. Surfactants have a characteristic structure, with one or several hydrocarbon chains that form the lipophilic part of the molecule (or the hydrophobic part of the molecule) and one or several polar groups that form the hydrophilic part. These compounds, also called surface-active agents, can have different lengths and degrees of unsaturation in the hydrocarbon chains, as well as in the polar groups, giving rise to a wide variety of surfactants with different properties. Surfactants can be classified as ionic or non-ionic, depending on the nature of the hydrophilic group. The ionic surfactants are disassociated in water, forming ions. Notable within this group are organic acids, and their salts are anionic surfactants, while bases-amines of different degrees of replacement-and their salts are cationic surfactants. Some surfactants contain both acid and basic groups. These surfactants may be anionic or cationic and are therefore called amphoteric, or ampholytic. Surfactants constitute a group of substances in which the main characteristic is their accumulation in the interfaces, solid-liquid or liquid-gas, weakening the surface tension of the liquid. This property enables the formation of foams and the penetration of solids as a wetting agent, leading to wide and varied applications of these compounds [1]. These substances are widely used in household cleaning detergents, personal-care products, textiles, paints, polymers, pesticides, pharmaceuticals, mining, oil recovery, and the pulp and paper industries. Detergents and cosmetics involve the mayor use of these compounds. After use, residual surfactants and their degradation products are discharged to sewage-treatment plants or directly to surface waters. Several of these compounds are not biologically degradable

Journal of Surfactants and Detergents, 2013

This study investigated the extent of primary and final biodegradation of anionic and non-ionic s... more This study investigated the extent of primary and final biodegradation of anionic and non-ionic surfactants to evaluate the combined use of ozonation and biodegradation in surfactant removal. The surfactants used were alkylpolyglucosides and linear alkyl benzene sulfonates. The anionic surfactant containing a benzene ring on its structure was oxidized faster than was the non-ionic surfactant. Both surfactants showed poor mineralization due to ozonation indicating an ozone attack primarily on carbon bonds. The results indicate that the removal of surfactants and of the total organic carbon is increased by the consecutive use of ozonation and biodegradation.

Water Science and Technology, 2009

The toxicity values of fatty-alcohol ethoxylates, nonylphenol polyethoxylate, and alkylpolyglucos... more The toxicity values of fatty-alcohol ethoxylates, nonylphenol polyethoxylate, and alkylpolyglucosides have been determined by applying assays with luminescent bacteria. Also, the relation between metabolites and ecotoxicity during the biodegradation process has been determined. The biodegradation tests were carried out according to the OECD 301 E test for ready biodegradability. In these tests a solution of the surfactant, representing the sole carbon source for the microorganisms, was tested in a mineral medium, inoculated and incubated under aerobic conditions in the dark. The toxicity of surfactants is related to their molecular structure (Quantitative Structure Activity Relationships, QSAR). For the alkylpolyglucosides, toxicity expressed as EC50 is related with the critical micelle concentration (CMC), the hydrophilic-lipophilic balance (HLB) of the surfactant, and the hydrophobic alkyl chain (R). The results indicate that toxicity increased as the CMC decreased and as the hydr...

Chemosphere, 2006

In the present work, we propose a simplified spectrophotometric method for determining anionic su... more In the present work, we propose a simplified spectrophotometric method for determining anionic surfactants, based on the formation of the ionic pair anionic surfactant-methylene blue (AS-MB). This method, in relation to the conventional analytic procedure, considerably reduces not only the quantity of chloroform used in extracting the ionic pair formed, but also the time and the quantity of sample necessary to perform the assay, eliminating the filtration stage. The method has been simplified by displacing the transfer equilibrium of the ionic pair AS-MB towards the organic phase, augmenting the volumetric relationship of chloroform/sample. The method proposed has been applied in the study of primary biodegradation kinetics of linear alkylbenzenesulfonate (LAS).

Chemical Engineering Journal, 2009

The growing concern for the environment is promoting the use of surfactant products from renewabl... more 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.

Tenside Surfactants Detergents, 2002

Methods for the determination of non-ionic surfactants were compared. The biodegradation of fatty... more Methods for the determination of non-ionic surfactants were compared. The biodegradation of fatty alcohol ethoxylates was tested and the surfactant concentration over time analyzed using the iodine-iodide colorimetric method and Wickbold's method (also known as BiAS (Bismuth-Active Substances)). The advantages and disadvantages of bismuth quantification by spectrophotometry and potentiometry using Wickbold's method were also studied. By comparing these two different procedures for the analysis of ethoxylate non-ionic surfactants, we find that the determination of these surfactants in static biodegradation tests using the iodine-iodide method is a viable alternative, much better than Wickbold's method when there are more than 5 molecules of ethylene oxide (EO) in the surfactant. The main advantages of this method are that it requires less sample volume, less analysis time and is less costly to perform. In addition, since it can be performed directly on the sample, there i...

Food and Bioproducts Processing, 2021

Abstract Chemical and food industries are focusing on reducing the economic and environmental imp... more Abstract Chemical and food industries are focusing on reducing the economic and environmental impact of cleaning operations. This study aims to analyse the use of alkaline ozonated formulations to remove starch adhering to stainless steel surfaces, improving disinfection of mature biofilms with Listeria and Pseudomonas, and reducing the environmental impact of wastewater. Three key cleaning parameters have been analysed in a lab-simulated Clean-In-Place system (CIP): temperature (20−60 °C), time (20−120 min), and cleaning formulations containing ozone and surfactant (linear alkylbenzene sulfonate, alkylpolyglucoside, fatty ethoxylated alcohol, lauramine oxide) were assayed. Higher temperature, time, and ozone concentration improved starch removal and disinfection of the stainless-steel surfaces, as well as the environmental impact of cleaning wastewater. Therefore, ozone-based CIP protocols could provide new opportunities to achieve cleaner, greener, and safer industries by intensifying cleaning, disinfection, and wastewater treatment in one step, saving operational costs compared to conventional CIP techniques.

Due to the widespread use of nanoparticles in surfactant-based formulations, their release into t... more Due to the widespread use of nanoparticles in surfactant-based formulations, their release into the environment and wastewater is unavoidable, causing a toxic effect to biota and/or wastewater treatment processes. Because of concerns about the environmental impact of nanofluids, the study of the fate and environmental impact, hazards and toxicity of nanoparticles is beginning. However, the interactions between nanoparticles and surfactants as well as the biodegradability in mixtures have been little studied until now. In this work the environmental impact of nanofluids containing mixtures of surfactants and silica nanoparticles were evaluated. The systems studied were hydrophilic silica nanoparticles (size 7 and 12 nm), a non-ionic surfactant (alkyl polyglucoside), an anionic surfactant (ether carboxylic acid), and mixtures of them. The aerobic ultimate biodegradation and interfacial and adsorption properties of surfactants, nanoparticles and mixtures during the biodegradation proce...

Methods in Pharmacology and Toxicology, 2017

Journal of hazardous materials, Jan 20, 2018

In this work, the toxicity of hydrophilic fumed silica micro- and nanoparticles of various sizes ... more In this work, the toxicity of hydrophilic fumed silica micro- and nanoparticles of various sizes (7 nm, 12 nm, and 50 μm) was evaluated using the luminescent bacteria Vibrio fischeri. In addition, the toxicity of an anionic surfactant solution (ether carboxylic acid), a nonionic surfactant solution (alkyl polyglucoside), and a binary (1:1) mixture of these solutions all containing these silica particles was evaluated. Furthermore, this work discusses the adsorption of surfactants onto particle surfaces and evaluates the effects of silica particles on the surface tension and critical micellar concentration (CMC) of these anionic and nonionic surfactants. It was determined that silica particles can be considered as non-toxic and that silica particles reduce the toxicity of surfactant solutions. Nevertheless, the toxicity reduction depends on the ionic character of the surfactants. Differences can be explained by the different adsorption behavior of surfactants onto the particle surfac...

Biodegradation, Aug 1, 2017

Recently, anaerobic degradation has become a prevalent alternative for the treatment of wastewate... more Recently, anaerobic degradation has become a prevalent alternative for the treatment of wastewater and activated sludge. Consequently, the anaerobic biodegradability of recalcitrant compounds such as some surfactants require a thorough study to avoid their presence in the environment. In this work, the anaerobic biodegradation of amine-oxide-based surfactants, which are toxic to several organisms, was studied by measuring of the biogas production in digested sludge. Three amine-oxide-based surfactants with structural differences in their hydrophobic alkyl chain were tested: Lauramine oxide (AO-R12), Myristamine oxide (AO-R14) and Cocamidopropylamine oxide (AO-cocoamido). Results show that AO-R12 and AO-R14 inhibit biogas production, inhibition percentages were around 90%. AO-cocoamido did not cause inhibition and it was biodegraded until reaching a percentage of 60.8%. Otherwise, we fitted the production of biogas to two kinetic models, to a pseudo first-order model and to a logisti...

Environmental science and pollution research international, Jan 3, 2017

This paper reports on a study that investigated the aquatic toxicity of new non-ionic surfactants... more This paper reports on a study that investigated the aquatic toxicity of new non-ionic surfactants derived from renewable raw materials, polyoxyethylene glycerol ester (PGE), and their binary mixtures with anionic and non-ionic surfactants. Toxicity of pure PGEs was determined using representative organisms from different trophic levels: luminescent bacteria (Vibrio fischeri), microalgae (Pseudokirchneriella subcapitata), and freshwater crustaceans (Daphnia magna). Relationships between toxicity and the structural parameters such as unit of ethylene oxide (EO) and hydrophilic-lipophilic balance (HLB) were evaluated. Critical micellar concentration (CMC) in the conditions of the toxicity test was also determined. It was found that the toxicity of the aqueous solutions of PGE decreased when the number of EO units in the molecule, HLB, and CMC increased. PGEs showed lower CMC in marine medium, and the toxicity to V. ficheri is lower when the CMC was higher. Given their non-polar nature,...

Chemosphere, 2017

Amine-oxides-based surfactants are completely biodegradable in aerobic conditions. Differences in... more Amine-oxides-based surfactants are completely biodegradable in aerobic conditions. Differences in the biodegradability are due to their structural differences. Biodegradability is lower due to the presence of an amide group in the alkyl chain. Initial surfactant concentration had a positive influence on the biodegradation. Biodegradability in acid conditions is slower and in some cases lower.

Environmental Science and Pollution Research, 2016

This paper reports a study of the anaerobic biodegradation of non-ionic surfactants alkyl polyglu... more This paper reports a study of the anaerobic biodegradation of non-ionic surfactants alkyl polyglucosides applying the method by measurement of the biogas production in digested sludge. Three alkyl polyglucosides with different length alkyl chain and degree of polymerization of the glucose units were tested. The influence of their structural parameters was evaluated, and the characteristics parameters of the anaerobic biodegradation were determined. Results show that alkyl polyglucosides, at the standard initial concentration of 100 mgC L(-1), are not completely biodegradable in anaerobic conditions because they inhibit the biogas production. The alkyl polyglucoside having the shortest alkyl chain showed the fastest biodegradability and reached the higher percentage of final mineralization. The anaerobic process was well adjusted to a pseudo first-order equation using the carbon produced as gas during the test; also, kinetics parameters and a global rate constant for all the involved metabolic process were determined. This modeling is helpful to evaluate the biodegradation or the persistence of alkyl polyglucosides under anaerobic conditions in the environment and in the wastewater treatment.

Ecotoxicology and Environmental Safety, 2016

The environmental risk of surfactants requires toxicity measurements. As different test organisms... more The environmental risk of surfactants requires toxicity measurements. As different test organisms have different sensitivity to the toxics, it is necessary to establish the most appropriate organism to classify the surfactant as very toxic, toxic, harmful or safe, in order to establish the maximum permissible concentrations in aquatic ecosystems. We have determined the toxicity values of various anionic surfactants ether carboxylic derivatives using four test organisms: the freshwater crustacean Daphnia magna, the luminescent bacterium Vibrio fischeri, the microalgae Selenastrum capricornutum (freshwater algae) and Phaeodactylum tricornutum (seawater algae). In addition, in order to compare and classify the different families of surfactants, we have included a compilation of toxicity data of surfactants collected from literature. The results indicated that V. fischeri was more sensitive to the toxic effects of the surfactants than was D. magna or the microalgae, which was the least sensitive. This result shows that the most suitable toxicity assay for surfactants may be the one using V. fischeri. The toxicity data revealed considerable variation in toxicity responses with the structure of the surfactants regardless of the species tested. The toxicity data have been related to the structure of the surfactants, giving a mathematical relationship that helps to predict the toxic potential of a surfactant from its structure. Model-predicted toxicity agreed well with toxicity values reported in the literature for several surfactants previously studied. Predictive models of toxicity is a handy tool for providing a risk assessment that can be useful to establish the toxicity range for each surfactant and the different test organisms in order to select efficient surfactants with a lower impact on the aquatic environment.

Journal of Surfactants and Detergents, 2011

The ultimate aerobic biodegradability and toxicity of three ether carboxylic derivative surfactan... more The ultimate aerobic biodegradability and toxicity of three ether carboxylic derivative surfactants having different alkyl chains and degrees of ethoxylation were investigated. Ultimate aerobic biodegradability was screened by means of dissolved organic carbon determinations at different initial surfactant concentrations. For comparison, the characteristic parameters of the biodegradation process, such as half‐life, mean biodegradation rate, and residual surfactant concentration, were determined. Increased surfactant concentrations decreased mineralization and lengthened the estimated half‐life. The results demonstrate that the ultimate aerobic biodegradability is higher for the surfactants with the shortest alkyl chain and highest degree of ethoxylation. Toxicity values of the surfactants, and their binary mixtures, were determined using three test organisms, the freshwater crustacea Daphnia magna, the luminescent bacterium Vibrio fischeri and the microalgae Selenastrum capricornut...

Formación universitaria, 2014

Se presentan diferentes estrategias docentes de aprendizaje autónomo del alumno en el

Journal of Surfactants and Detergents, 2014

The purpose of this study was to discuss the effect of the chemical structure of anionic and non-... more The purpose of this study was to discuss the effect of the chemical structure of anionic and non-ionic surfactants and surface activity on toxicity. Single and binary mixtures of three ether carboxylic derivative surfactants and three amine-oxide-based non-ionic surfactants were used. Toxicity was determined using three test organisms: freshwater crustaceans (Daphnia magna), luminescent bacteria (Vibrio fischeri), and microalgae (Selenastrum capricornutum). The toxicity of surfactants is related to the hydrophobic alkyl chain, the degree of ethoxylation, and the critical micelle concentration of surfactants. Relationships found agreed with the fact that the lower toxicity is shown by the shorter alkyl chain. There is a strong relation between surface activity and toxicity: the toxicity increased as the CMC of the surfactant or mixtures of surfactants decreased. Commercial products are formulated using surfactants mixtures, so it is important to know their behavior using an easily measured property: the least toxic mixtures were formed by the surfactants having lower individual toxicity. Around the CMC, our data show a synergism for the binary mixtures. The results have given rise to a classification of the different surfactants and their mixtures according to the organism test, as safe, harmful or toxic. V. fischeri was in general the most sensitive microorganism to the toxic effect of the surfactants, followed by Daphnia magna, while Selenastrum capricornutum was more tolerant. These results can be useful for selecting technically efficient surfactants and their mixtures with a lower ecotoxicity on the aquatic environment.

Procedia Engineering, 2012

The influence of ozonation of aqueous solutions of non-ionic surfactants was investigated in this... more The influence of ozonation of aqueous solutions of non-ionic surfactants was investigated in this study. The research was conducted using solutions of amine oxide based surfactants. These surfactants constitute a particular class of non-ionic surfactants that exhibit cationic behaviour in acid solution, they show good foaming properties and are skin compatible. The ozonation process was carried out at 25ºC in a stirred tank reactor for 30 min, where gaseous ozone was bubbled. The degree of mineralization achieved after the ozonation process was evaluated by measuring the total organic carbon before and after ozonation. The influence of ozonation on biodegradability of the solutions was studied using the biodegradation test by Pseudomonas putida. Biodegradation efficiency of the ozonated amine oxides based surfactants was also evaluated. It was found that the effectiveness of ozonation depended on the chemical structure of surfactant molecule. Ozonation only slightly improved biodegradation of these surfactants.

Journal of Surfactants and Detergents, 2013

The objective of this study was to investigate the influence of ozonation of anionic and non-ioni... more The objective of this study was to investigate the influence of ozonation of anionic and non-ionic surfactants on their aquatic toxicity. Toxicity values of various commercially important anionic and non-ionic surfactants have been determined using the luminescent bacterium Vibrio fischeri. Surface tension measurements were made to study the interfacial activity. The behavior depends on the chemical structure. Some intermediate ozonation products were found to be more toxic than the base surfactant and others were found to be less. Surfactants with aromatic rings such as linear alkyl benzene sulfonates, or surfactants with glycosidic groups such as alkylpolyglucosides, exhibit a lower toxicity after ozonation. On the other hand, ether groups present in the fatty-alcohol ethoxylates and ether carboxylic derivative surfactants, and carboxylic acid derivates present in the ether carboxylic derivative surfactants lead to increasing toxicity after ozonation. Surfactants with ether groups probably formed short-chain polyethoxylated compounds and carboxylic acids, which are possibly responsible for the surface-tension decrease that promotes the toxicity increase.

Biodegradation - Life of Science, 2013

Surfactants are a wide group of chemical compounds which have a large number of applications due ... more Surfactants are a wide group of chemical compounds which have a large number of applications due to their solubility properties, detergency, endurance of water hardness, as well as emulsifying, dispersing, and wetting properties. Surfactants have a characteristic structure, with one or several hydrocarbon chains that form the lipophilic part of the molecule (or the hydrophobic part of the molecule) and one or several polar groups that form the hydrophilic part. These compounds, also called surface-active agents, can have different lengths and degrees of unsaturation in the hydrocarbon chains, as well as in the polar groups, giving rise to a wide variety of surfactants with different properties. Surfactants can be classified as ionic or non-ionic, depending on the nature of the hydrophilic group. The ionic surfactants are disassociated in water, forming ions. Notable within this group are organic acids, and their salts are anionic surfactants, while bases-amines of different degrees of replacement-and their salts are cationic surfactants. Some surfactants contain both acid and basic groups. These surfactants may be anionic or cationic and are therefore called amphoteric, or ampholytic. Surfactants constitute a group of substances in which the main characteristic is their accumulation in the interfaces, solid-liquid or liquid-gas, weakening the surface tension of the liquid. This property enables the formation of foams and the penetration of solids as a wetting agent, leading to wide and varied applications of these compounds [1]. These substances are widely used in household cleaning detergents, personal-care products, textiles, paints, polymers, pesticides, pharmaceuticals, mining, oil recovery, and the pulp and paper industries. Detergents and cosmetics involve the mayor use of these compounds. After use, residual surfactants and their degradation products are discharged to sewage-treatment plants or directly to surface waters. Several of these compounds are not biologically degradable

Journal of Surfactants and Detergents, 2013

This study investigated the extent of primary and final biodegradation of anionic and non-ionic s... more This study investigated the extent of primary and final biodegradation of anionic and non-ionic surfactants to evaluate the combined use of ozonation and biodegradation in surfactant removal. The surfactants used were alkylpolyglucosides and linear alkyl benzene sulfonates. The anionic surfactant containing a benzene ring on its structure was oxidized faster than was the non-ionic surfactant. Both surfactants showed poor mineralization due to ozonation indicating an ozone attack primarily on carbon bonds. The results indicate that the removal of surfactants and of the total organic carbon is increased by the consecutive use of ozonation and biodegradation.

Water Science and Technology, 2009

The toxicity values of fatty-alcohol ethoxylates, nonylphenol polyethoxylate, and alkylpolyglucos... more The toxicity values of fatty-alcohol ethoxylates, nonylphenol polyethoxylate, and alkylpolyglucosides have been determined by applying assays with luminescent bacteria. Also, the relation between metabolites and ecotoxicity during the biodegradation process has been determined. The biodegradation tests were carried out according to the OECD 301 E test for ready biodegradability. In these tests a solution of the surfactant, representing the sole carbon source for the microorganisms, was tested in a mineral medium, inoculated and incubated under aerobic conditions in the dark. The toxicity of surfactants is related to their molecular structure (Quantitative Structure Activity Relationships, QSAR). For the alkylpolyglucosides, toxicity expressed as EC50 is related with the critical micelle concentration (CMC), the hydrophilic-lipophilic balance (HLB) of the surfactant, and the hydrophobic alkyl chain (R). The results indicate that toxicity increased as the CMC decreased and as the hydr...

Chemosphere, 2006

In the present work, we propose a simplified spectrophotometric method for determining anionic su... more In the present work, we propose a simplified spectrophotometric method for determining anionic surfactants, based on the formation of the ionic pair anionic surfactant-methylene blue (AS-MB). This method, in relation to the conventional analytic procedure, considerably reduces not only the quantity of chloroform used in extracting the ionic pair formed, but also the time and the quantity of sample necessary to perform the assay, eliminating the filtration stage. The method has been simplified by displacing the transfer equilibrium of the ionic pair AS-MB towards the organic phase, augmenting the volumetric relationship of chloroform/sample. The method proposed has been applied in the study of primary biodegradation kinetics of linear alkylbenzenesulfonate (LAS).

Chemical Engineering Journal, 2009

The growing concern for the environment is promoting the use of surfactant products from renewabl... more 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.