Biodegradable Nonionic Surfactant Research Articles

Cloud point extraction of heavy metal ions for wastewater remediation: an equilibrium and kinetic study

Abstract Surfactants offer a promising alternative for the efficient and environmentally friendly removal of organic pollutants and toxic heavy metal ions from various media. Their high efficiency and environmental compatibility make them a valuable option for remediation efforts. This study focuses on the cloud point extraction (CPE) of ions from aqueous solutions using biodegradable nonionic surfactants combined with ionic surfactants instead of chelating agents. Phase diagrams of binary surfactant/water systems were first constructed. The effects of salt, inorganic contaminants, and ionic surfactants on the cloud point (Tc) were then investigated. At temperatures above the cloud point, two distinct phenomena were observed and monitored over time: phase separation and phase clarification. The kinetic process was studied using the Turbiscan Lab Expert. Extraction results were evaluated based on four responses: extraction yield (E%), residual concentrations of solute (Xs,w) and surfactant (Xt,w) in the dilute phase, and volume fraction of coacervate at equilibrium (Φ C). Empirical modelling gives a satisfactory agreement between experimental and calculated values. The capacity of CPE to simultaneously remove an organic pollutant and a toxic heavy metal was demonstrated.

Design of green DES-based aqueous two phase systems for lipolytic enzymes extraction

This study pioneers a novel green and cost-effective separation process using reline deep eutectic solvent (DES) for extracting Thermomyces lanuginosus lipase (TlL) from aqueous solutions. For the first time, it has been shown that various potassium organic salts combined with reline DES can induce phase separation in aqueous solutions of the biodegradable non-ionic surfactant Tergitol 15-S9, presenting a groundbreaking alternative to the banned surfactant Triton X-100. This work uniquely applies three different equations to describe the experimental solubility curves. The selection of reline DES is particularly innovative as it avoids significant deactivation effects with three commercial lipases: Candida antarctica lipases A and B, and TlL, with the latter undergoing a detailed study. This includes an unprecedented analysis of its thermodeactivation kinetics in reline DES aqueous solutions. Additionally, a novel investigation of immiscibility regions at different temperatures, involving comprehensive Tie-Line characterizations (slope and length), preceded the evaluation of lipase extraction. Remarkably, the study demonstrates that optimizing the feed composition to contain higher water concentrations can achieve exceptionally high extraction efficiencies (approximately 90%), suggesting a transformative potential for future applications in real aqueous cultures.

Treatment of hydrocarbon marine pollution with cloud point extraction

AbstractThe release of hydrocarbons (HC) into the marine environment has serious consequences, both economically and ecologically. This work presents an efficient process to remove HC pollution from seawater: cloud point extraction (CPE), considered to be a reliable, inexpensive, and environmentally friendly method, using the readily biodegradable nonionic surfactants Lutensol ON30 and Tergitol 15‐S‐7. A real salt water sample with a high chemical oxygen demand (COD = 1700 mg O2/L) was thus treated. First, the phase diagrams of the binary systems (water–surfactant), and the pseudo‐binary systems (water–surfactant–HC), were determined. Second, after a 24 h settling time, considered as optimal, the extraction results, that is, residual soluble COD, residual percentage of surfactant in the dilute phase and volume fraction of coacervate at equilibrium, were expressed in terms of temperature and initial surfactant concentration. For each parameter, the results obtained were modeled using the response surface methodology and represented on three‐dimensional diagrams. They show that the COD can be reduced to 10 and 15 mg O2/L, using Lutensol ON30 and Tergitol 15‐S‐7, respectively, under seawater temperature conditions. Finally, it was shown that the surfactant can be recycled. The present work demonstrates that CPE can reduce the HC content of seawater on a laboratory scale.

Reverse Micellar Dyeing of Cotton Fabric with Reactive Dye Using Biodegradable Non-Ionic Surfactant as Nanoscale Carrier: An Optimisation Study by One-Factor-at-One-Time Approach.

This study investigates the feasibility of using biodegradable secondary alcohol ethoxylate (SAE) non-ionic surfactant as a building block for the formation of reverse micelles, functioning as reactive dye carriers for the dyeing of cotton fabric in non-aqueous octane medium. Ten dyeing parameters were optimised, by a one-factor-at-a-time approach, namely: (i) effect of colour fixation agent; (ii) surfactant-to-water mole ratio; (iii) surfactant-to-co-surfactant mole ratio; (iv) volume of soda ash; (v) volume of dye; (vi) solvent-to-cotton ratio; (vii) dyeing temperature; (viii) dyeing time; (ix) fixation time; (x) soda-ash-to-cotton ratio. The colour properties, fastness properties and physical properties of SAE-dyed samples were experimentally compared with the conventional water-dyed samples. The optimised condition was found when SAE samples were dyed as follows: (a) 1:20 surfactant-to-water ratio; (b) 1:8 surfactant-to-co-surfactant ratio; (c) 10:1 solvent ratio; (d) 40 min dyeing time; (e) 60 min fixation time; and (f) 70 °C dyeing and fixation temperature. The results showed that SAE-dyed samples have better colour strength, lower reflectance percentage and comparable levelness, fastness and physical properties than that of water-dyed samples. SEM images revealed that the dyed cotton fibres had no severe surface damage caused by an SAE-based reverse micellar dyeing system. The TEM image depicts that the reverse micelle was of nanoscale, spherical-shaped and had a core-shell structure, validating the presence of reverse micelle as a reactive dye carrier and the potential of an SAE-based reverse micellar system for dyeing of cotton fabrics.

Remediation of the Alluvial Aquifer of the Sardas Landfill (Sabiñánigo, Huesca) by Surfactant Application

Sardas Landfill at Sabiñánigo Huesca is polluted with Dense Non-Aqueous Liquid Phases (DNAPLs) composed of a complex mixture of chlorinated organic compounds (COCs). This DNAPL was produced as liquid waste from lindane production being dumped decades ago in the unlined landfills close to the lindane factory. This DNAPL migrated by gravity through the subsurface and accumulated in the contact between the alluvial and marls layers (about 15 m b.g.l.). Seven injections of an aqueous emulsion of a biodegradable non-ionic surfactant (E-Mulse 3®) were carried out at the most polluted areas of the Sardas alluvial. Injections were carried out between April and November 2021 using different surfactant concentrations (6.7, 20, 25 and 50 g/L), injection volumes (0.2 to 7 m3) and injection flow rates (0.08–0.85 m3/h). Injected fluids were extracted in the same well or surrounding wells, and the time elapsed between surfactant injection and extraction varied between 24 and 72 h. A total of 22 m3 were injected into the alluvial, and more than double this injected volume was extracted. Injection and extraction points were in the contact between the marls and the alluvial layer. Extracted fluid accumulated in tanks, and phases separated. DNAPL recovered here was mobilized rather than solubilized and managed as toxic waste. The aqueous supernatant was treated in a wastewater treatment plant with physicochemical treatment (including adsorption in activated carbon) before being discharged into the environment. The transport of the injected fluids was monitored by conductivity profiles using bromide (260–538 mg·L−1) as a conservative tracer. High radial dispersion of the injected fluid was found. Surfactant losses by adsorption in the alluvial and absorption in DNAPL were noticed, and both surfactant and contamination did not escape from the capture zone. Monitoring since 2018 of the COCS in groundwater and the DNAPL presence in the contact between alluvial and marls layers showed a significant reduction of COCs in the treated zone with the surfactant injections.

A microfluidic approach to fabricate sucrose decorated liposomes with increased uptake in breast cancer cells

Developing targeted drug delivery systems is an urgent need to decrease the side effects and increase the drug's efficiency. Most cancer cells show an increased sugar consumption compared to healthy cells due to the deregulation of sugar transporters. Consequently, liposomes, as a biocompatible nanocarrier, could be surface decorated by sugars to enhance drug targeting into cancer cells. Our work outlines a new strategy to easily manufacture sucrose decorated liposomes using sucrose stearate, a biocompatible and biodegradable non-ionic surfactant, with a scalable microfluidic approach. Sucrose decorated liposomes were loaded with berberine hydrochloride, a well-known phytochemical compound to investigate its effects on triple-negative breast cancer cells (MDA-MB-231). Using the microfluidic manufacturing system, we prepared berberine-loaded liposomes using a mixture of phosphatidylcholine and cholesterol with and without sucrose stearate with a size up to 140 nm and narrow polydispersity. Stability was confirmed for 90 days, and the in vitro release profile was evaluated. The formulations showed acceptable in vitro biocompatibility and significantly higher anti-proliferative effect on MDA-MB-231 cell line. These results have been confirmed by an increased uptake evaluated by flow cytometry and confocal microscopy. Taken together, our findings represent an innovative, easy, and scalable approach to obtain sugar decorated liposomal formulations without any surface-chemistry reactions. They can be potentially used as an anticancer targeted drug delivery system.

Salting out Tergitol 15S-based surfactants for extremolipases separation

In the present work, the ability of different sodium-based salts like Na2CO3, Na2HPO4, Na2SO4 and Na2SO3 to salt out aqueous solutions of two biodegradable non-ionic surfactants (Tergitol 15S7 and Tergitol 15S9) has been demonstrated. We have empirically characterized the immiscibility regions and models like Merchuk and Othmer-Tobias equations were employed for binodal and tie-line data, respectively. The effect of phase forming components on the lipolytic activity of two in-house extremolipases (from Thermus thermophilus HB27 and Halomonas sp-LM1C) was studied prior to approach the separation. It was concluded that ions bearing the lowest capacity to establish hydrogen bonds with water molecules like sulphate led to greater activation effect. Then, the ability of the proposed systems to extract both lipases was compared with a commercial one, lipase B from Candida antarctica, and it was concluded that 50% of activity decay was avoided when in-house extreme enzymes were employed.

Selective removal of over-paintings from “Street Art” using an environmentally friendly nanostructured fluid loaded in highly retentive hydrogels

HypothesisThe removal of over-paintings or graffiti is a priority for conservators and restorers. This operation is complex, especially when over-paintings lay on painted surfaces that must be preserved, as in the case of vandalism on street art, where the layers are usually chemically similar. Traditional methodologies often do not provide satisfactory results and pose health and eco-compatibility concerns. An alternative methodological approach based on an environmentally friendly nanostructured fluid loaded in a retentive hydrogel is here proposed. ExperimentsSix paints (based on vinyl, acrylic and alkyd polymers) were selected and studied by means of attenuated total reflection - Fourier transform infrared spectroscopy. The phase behavior of four alkyl carbonates (green, low-toxicity organic solvents) and a biodegradable nonionic surfactant in water was investigated with Small angle X-ray scattering (SAXS) in order to formulate a novel nanostructured cleaning system. The developed system, which also includes 2-butanol and an alkyl glycoside hydrotrope, was loaded in highly retentive hydrogels and tested in the selective removal of over-paintings from laboratory mockups and from real pieces of street art. FindingsThe selective and controlled removal of modern paints from substrates with similar chemical composition has been achieved using a specifically tailored NSF embedded in a retentive hydrogel. The proposed methodology and cleaning system provided excellent cleaning results, representing a new tool for the conservation of contemporary and, in particular, street art.

The Effect of Ni-Doped ZnO NPs on the Antibacterial Activity and Degradation Rate of Polyacrylic Acid-Modified Starch Nanocomposite

Acrylic acid-modified starch has been achieved by grafting the starch with an acrylic acid homopolymer by using the biodegradable nonionic surfactant Lutensol-XL-100 (decaoxyethyele n-decyl ether) and ammonium persulfate as a free radical originator. After obtaining the optimized starch-based plastic thin film, a nanocomposite (NC) was created by incorporating nickel-doped zinc oxide nanoparticles (ZnO@Ni NPs), which served as the control for the degradation rate of the composite plastic. The NC was characterized using FTIR, TGA, DSC, and SEM. The ZnO@Ni NPs induced an antibacterial property in the composite film with improved thermal stability and effective to control bacterial growth. The starch-grafted polyacrylic acid exhibited 23.21% biodegradability in 60 days while its NC showed 16.19% at the same time by a soil burial test. It was observed that the composite film exhibited a significant efficacy against the bacteria.

Oxacillin antibiotic removal from aqueous solution using nonionic micellar system or ionic liquid: a comparative study based upon experimental optimization and response surface methodology

Oxacillin antibiotic was removed from aqueous effluents using the biodegradable nonionic surfactant Triton X-114 (TX-114) and the ionic liquid (IL) 1-butyl-3-methylimidazolium hexafluorophosphate ([C4C1im]PF6). The experimental results of oxacillin extraction from aqueous solution according to the surfactant (Xt) or ionic liquid (XIL) concentration and temperature (T) were expressed by the following parameters: antibiotic extraction extent (E%), remaining antibiotic concentration (Xs,w), residual surfactant (Xt,w) or ionic liquid (XIL,w) concentration in aqueous phase after extraction, and volume fraction of coacervate at equilibrium (ϕc). High extraction yields were reached under optimal conditions: 99% for TX-114 and 89% using [C4C1im]PF6. The concentration of antibiotic in effluent was reduced by about 7-fold and 6-fold using TX-114 and [C4C1im]PF6, respectively. Sodium sulfate addition (3 wt%) increased E% from 20% to 88% at only 2 wt% of TX-114. Finally, solute stripping from the micellar phase using Winsor II microemulsion extraction was investigated. Thereby, 90% of the TX-114 in the micelle-rich phase was separated into the organic phase (Om).

Plotting a nature-friendly separation process for recovering volatile fatty acids

The segregation capacity of cholinium bitartrate (N1112OHC4H5O6) in aqueous solutions of biodegradable non-ionic surfactants belonging to Triton family (Triton X-100 and Triton X-102) has been firstly addressed. The influence of temperature on the separation potential was analysed by carrying out the binodal curves and tie-lines from 293.15 K to 323.15 K. The immiscibility data were modelled by several empirical equations, and the tie-lines were adequately correlated by Othmer-Tobias, Bancroft and Setschenow models. Finally, the extraction capacity of the proposed biocompatible segregation agent was demonstrated for the first time in volatile fatty acids (formic acid, acetic acid, propionic, and butyric acid), recording very high levels of extraction when high surfactant concentrations are employed.

The Effectively Simultaneous Production of Cello-oligosaccharide and Glucose Mono-decanoate from Lignocellulose by Enzymatic Esterification.

Cello-oligosaccharide has drawn an increasing attention as the nutritional ingredients of dietary supplements, whose quality is affected by the concentration of monosaccharide. In the present study, an effective process was developed for the simultaneous production of cello-oligosaccharide and glucose mono-decanoate from lignocellulose by enzymatic esterification. During the process, the excessive glucose in cello-oligosaccharide was converted into glucose mono-decanoate, which is a well-known biodegradable nonionic surfactant. The filter paper was initially used as the model to investigate the feasibility of the process, in which the purity of resultant cello-oligosaccharide was increased from 33.3% to 74.3%, simultaneously producing glucose mono-decanoate with a purity of 92.3%. Further verification of 3 kinds of lignocelluloses (switchgrass, cornstalk, and reed) also indicated a good performance of the process. The present process provided an effective strategy to increase the purity of resultant cello-oligosaccharide with the simultaneous production of high value-added products of sugar monoester. Graphical Abstract Simultaneous production of cello-oligosaccharide and glucose mono-decanoate from lignocellulose.

Development and validation of eco-friendly micellar HPLC method for the simultaneous determination of hydrochlorothiazide and valsartan in bulk powder and pharmaceutical dosage forms

Ongoing greener in chromatography, new methodologies have to be developed using safer mobile phase composition and/or lower solvent consumption. The new methods should also consider the applicability in industrial facilities where selection criteria are based mainly on profit through cost and time. The drugs under study, valsartan (VAL) and hydrochlorothiazide (HCT), are co-formulated as tablet dosage form which is considered a widely consumed first-line treatment for hypertension. The use of the biodegradable non-ionic surfactant Brij-35 (0.1 M) in the aqueous phase increased the surface polarity of the bonded C18 stationary phase by its polyoxyethylene chain. This change gave faster separation of the analytes in short analysis time, enabled the use of methanol instead of acetonitrile which is more environmentally safe and also decreased its ratio required to enhance elution to only 25%. Fast isocratic separation was achieved at flow 1 mL min−1 where the retention times were 2.9 and 4.3 min for VAL and HCT, respectively, using UV detection at 254 nm. The method was validated according to ICH guidelines. High accuracy results were obtained at linearity range of 5–100 µg mL−1 for both drugs. LOD and LOQ were (1.01 and 3.05 µg mL−1) for VAL and (1.01 and 3.09 µg mL−1) for HCT, respectively. The method was successfully applied for determination of the drugs in their marketed dosage form. Since claiming greenness is not enough, the proposed method was compared favorably with published methods using the new assessment tool, GAPI index.

Design of eco-friendly aqueous two-phase systems for the efficient extraction of industrial finishing dyes

Cholinium bitartrate (N1112OHC4H5O6) has been demonstrated to be a promising phase disengagement agent in aqueous solutions of biodegradable non-ionic surfactants belonging to Tween family. For the first time, these systems were demonstrated to be versatile tools to efficiently extract two of the most frequently used groups of dyes, like di-azo and anthraquinone dyes. To do that, the binodal curves of the aqueous two phase systems (Tween 20 or Tween 80 + N1112OHC4H5O6 + H2O) were characterized at different temperatures (between 293.2 K and 323.2 K) and ambient pressure (0.1 MPa). Besides, prior to apply these systems for dyes extraction, the tie-lines were characterized, and all the data were suitably described by empirical equations. Analysis from an environmental point of view of capacity of the proposed eco-friendly ionic liquid for the extraction of Acid Black 48 and Reactive Black 5 dyes from aqueous solutions reveals environmental and efficiency advantages when compared with conventional imidazolium-based ionic liquids.

Performance evaluation of environmentally benign nonionic biosurfactant for enhanced oil recovery

Chemical enhanced oil recovery (EOR) is a successful method for increasing crude oil recovery. However, chemicals commonly used for enhanced oil recovery operations possess adverse biological impacts. To meet the legislative requirement and environmental protection demands, the performance of a highly biodegradable nonionic surfactant derived from tannic acid, a possible alternative, was evaluated using a microfluidic technology for the replacement of chemically synthesis surfactant by green chemistry products. Aqueous microdroplets containing the surfactant in crude oils were used for measurements of interfacial tension (IFT) reduction. The degree of interfacial tension reduction by sodium dodecyl sulfate (SDS), one of the most popular conventional surfactants, was also quantified for performance comparison. The potential of the biosurfactant for IFT reduction of light crude oil was superior to that of SDS. To evaluate the feasibility of the biosurfactant in improvement of recovery efficiency, surfactant-assisted flooding was tested under a random microfluidic network at the optimal concentrations, and the results were in good agreement with IFT reduction tests. The utilization of the polymer in a biosurfactant synthesis process effectively enhanced high sweep efficiency by decreasing a viscous fingering effect. The biosurfactant proved to be adequate and can sufficiently alleviate environmental concerns adopted by chemical flooding EOR.

A Comparative Study on the Cloud Point Extraction Behavior of Copper(II) from Sulphate Medium by N,N′-Bis(Salicylidene)Ethylenediamine using Triton X-100 and Tergitol 15-S-7 as Non-ionic Surfactants

Abstract Cloud point extraction (CPE) experiments were carried out for separation of copper(II) from aqueous saline sulphate medium with the Schiff's base chelating extractant, N,N′-bis(salicylidene)ethylenediamine (H2SALEN), using the polyethoxylated alcohol Tergitol 15-S-7 as a biodegradable non-ionic surfactant. The obtained results were compared with those previously obtained in presence of Triton X-100. The effects of the main experimental parameters such as pH, extractant concentration, and non-ionic surfactant concentration on the cloud point extraction behavior of copper(II) with H2SALEN were studied and discussed. The use of both systems namely, Triton X-100/H2SALEN/Na2SO4 and Tergitol 15-S-7/H2SALEN/Na2SO4, led to very good extraction efficiency and concentrating ability for Cu(II) pollutant. Indeed, nearly 100 % extraction efficiency with a minimal volume fraction of the surfactant-rich phase, ϕs, was achieved at pH 7.25 and 8 in the systems Tergitol 15-S-7/H2SALEN/Na2SO4 and Triton X-100/H2SAL...

Removal of mercury from marine sediments by the combined application of a biodegradable non-ionic surfactant and complexing agent in enhanced-electrokinetic treatment

In this work, the Hg removal potentiality of an electrokinetic (EK) decontamination treatment enhanced by a biodegradable complexing agent (MGDA) also in combination with a biodegradable surfactant (Tween® 80) was investigated to decontaminate heavily contaminated marine sediments. The main results revealed that the nature of sediments and their interactions with different enhancing agents significantly influenced the remediation processes. A general increase of pH values along the sediment specimen was observed due to the strong buffering capacity of the carbonates, which are the main constituent minerals. This, in combination with the high organic matter and sulphide sediment content, resulted in very poor contaminant mobilization without any appropriate conditioning agents. The use of EDTA as a processing fluid resulted in a modest increase in Hg removal of ∼15%, whereas a further improvement in the Hg removal rate (∼39%) was achieved by replacing EDTA with MGDA as the anodic solution in response to its ability to form stable negative complexes with mercury, which can be moved towards the anode. A significantly higher Hg-removal of ∼71% was obtained by the simultaneous use of MGDA and Tween® 80 due to their synergic action in remedial processes and, especially, due to the improved selective action of the non-ionic surfactant adopted in favour of organo-Hg-complex removal. Compared with other Hg-removal technologies, the investigated enhanced-EK treatment allows the achievement of remediation targets, which can hardly met by one-stage processes. The data can be useful for predicting the remediation activity responses, as well as for guiding the design and scaling-up of EK treatment of Hg-contaminated sediments. In addition, the knowledge of the investigated Hg-removal mechanism can provide basic information, which is helpful for improving the development of further novel enhanced-EK technologies.

Cloud point or ionic liquid extraction of furfural from aqueous solution: a comparative study based upon experimental design

The goal of the present work was to compare cloud point extraction and extraction using ionic liquid for the separation of furfural from a dilute aqueous solution. Aqueous solutions of the biodegradable non-ionic surfactant Dehydol LT 7 (equivalent to C15E7) and the pure ionic liquid (IL) 1-butyl-3-methylimidazolium hexafluorophosphate ([C4C1im]PF6) were investigated as extraction solvents. Phase diagrams of binary (water/surfactant) and pseudo-binary (water/surfactant/solute) systems were plotted. The extraction results were expressed by the following responses: percentage of solute extracted, E (%), residual concentrations of solute and surfactant in aqueous phase (Xs,w and Xt,w, respectively), and volume fraction of coacervate at equilibrium (ϕC). For each parameter, the experimental results were fitted to empirical equations in three dimensions. The aim of this study was to find the best compromise between E and the other parameters (Xs,w, Xt,w, and ϕC, as low as possible). The comparison between experimental and calculated values allowed model validation. The highest extraction efficiency (98%) was reached with IL. Under optimal conditions, the solute concentration in the effluent was reduced to about 3 times using non-ionic surfactant against 31 times using ionic liquid. Finally, the possibility of recycling the ionic liquid has been proved.

Green Cosmetic Surfactant from Rice: Characterization and Application

During recent years, microwave irradiation has been extensively used for performing green organic synthesis. The aim of this study was to synthesize, through a microwave-assisted irradiation process, a natural surfactant with O/W emulsifying properties. Our attention was focused on polyglycerol esters of fatty acids that are biocompatible and biodegradable non-ionic surfactants widely used in food and cosmetic products. The emulsifier was obtained using vegetable raw material from renewable sources: polyglycerol derived from vegetable glycerol and rice bran oil fatty acids. The natural emulsifier obtained was then characterized and evaluated for its emulsifying properties using different doses, oil phases, rheological additives, waxes, etc. The potential application in solar products, in comparison with other natural emulsifiers, was also evaluated.

Redepositon of Impurities on Wool Fabric during Washing with Ecological Surfactants and Solvent Microemulsion

The aim of this paper was to study addition of a non-toxic solvent microemulsion to conventional wash formulations with the aim of improving the performance of the conventional washing. In this work, the redeposition performance during washing was studied after washing a wool fabric with addition of a solid impurity The non-toxic solvent used was dimethyl sulfoxide micro-dispersed with an amphoteric surfactant as emulsifier. The fabric was washed with SDBS and biodegradable non-ionic surfactants such as an alcohol ethoxylate (AE) with 7 m. EO and an alkyl polyglucoside with 1.4 glucoside groups (APG). The fabric used was EMPA 217 wool fabric. The anionic and non-ionic surfactants and mixtures of the non-ionic surfactants were used separately and in mixture in varying proportions for the washes. Carbon black was used as the solid impurity in the washing. Sodium carbonate and sodium chloride were used as builders. The fabric was washed at low temperature (30° C) with water of different hardness. In all the cases, the performance in terms of redeposition of the solid impurity (carbon black) was enhanced (decreased) for all the mixtures tested when using the microemulsion of DMS in the washing formulation.