Mechanistic Studies of Particulate Soil Detergency: I. Hydrophobic Soil Removal

The mechanism of particulate soil detergency using aqueous surfactant systems is not well understood. In this research, carbon black (model hydrophobic soil) removal from a hydrophilic (cotton) and hydrophobic (polyester) fabric is studied using anionic, nonionic, and cationic surfactants. The zeta potential, solid/liquid spreading pressure, contact angle and surfactant adsorption of both soil and fabric are correlated to detergency over a range of surfactant concentrations and pH levels. Electrostatic repulsion between fabric and soil is generally found to be the dominant mechanism responsible for soil removal for all surfactants and fabrics. Steric effects due to surfactant adsorption are also important for nonionic surfactants for soil detachment and antiredeposition. Solid/liquid interfacial tension reduction due to surfactant adsorption also aids in detergency in cationic surfactant systems. Wettability is not seen as being an important factor and SEM photos show that entrapment of soil in the fabric weave is not significant; the particles are only attached to the fabric surface. Anionic surfactants perform best, then nonionic surfactants. Cationic surfactants exhibit poor detergency which is attributed to low surfactant rinseability.     

Influence of Quartz,Kaolin, and Organic Matter on the Critical Micelle Concentration of Tween Surfactants and their Application in Diesel-Contaminated Soil Washing

Surfactant solutions are commonly used for the remediation of petroleum-contaminated soil due to their good petroleum removal performance, time-saving capability, and cost effectiveness. However, applying surfactants in excess concentrations could make oil recovery difficult. Moreover, residual surfactants in soil are toxic to microorganisms and plants. Thus, it is crucial to identify a suitable surfactant concentration for soil washing applications. The main objective of this study was to evaluate the effect of soil minerals (quartz and kaolin) and organic matter (OM) on the critical micelle concentration (CMC) of polyethoxylated sorbitan ester surfactants (Tween 20, 40, 60, and 80) and its effect on diesel removal from diesel-contaminated soil by soil washing. The results showed that Tween surfactants with shorter carbon chain lengths required higher CMC for diesel removal from quartz, while those with longer chains needed higher CMC for kaolin cleanup. FTIR results illustrated that oxygenated functional groups of Tween surfactants played an important role in their adsorption on quartz, while alkyl chains of Tween surfactants were responsible for their adsorption on kaolin. At a certain OM concentration, quartz and OM exhibited antagonistic effects, resulting in CMC reduction. In soil washing application, maximum diesel removal could be achieved from kaolin, in the presence of which surfactants exhibited the highest CMC. Based on FTIR results, the adsorbed surfactant could reduce the hydrophobicity of the kaolin surface, thus preventing the re-deposition of detached diesel.     

Examination of the parameters governing oily soil removal from synthetic substrates

The rate of removal of mineral oil soils from model polyester sub-strates by the roll-up mechanism shows a marked dependence on nonionic surfactant concentration even above the critical micelle concentration (cmc). Similarly, although the solid/water interfacial tension is observed to be constant, the equilibrium oil/water inter-facial tension in these systems consistently decreases as the nonionic surfactant concentration is increased. The dependence of removal time and oil/water interfacial tension on surfactant concentration above the cmc is most pronounced for nonionic surfactants having relatively high cmc. At a given concentration, surfactants exhibiting the lowest equilibrium oil/water interfacial tension generally provide the most effective soil removal, suggesting that the reported depen-dence of removal time on surfactant concentration is related to the commensurate lowering of the oil/water interfacial tension. Nonyl phenol ethoxylates perform exceptionally well with mineral oil on polyester substrates because of the combination of a low oil/water interfacial tension and high solid/water adhesion tension. Regardless of surfactant structure, mineral oil on Teflon FEP maintains a high contact angle in the water because the solid/oil interfacial tension is less than the solid/water interfacial tension. Oil removal in such systems occurs only by an inefficient necking and drawing process. Oleyl alcohol displays a high contact angle in the water on both Teflon FEP and Mylar substrates for reasons similar to that of mineral oil on Teflon FEP. Partial oil removal occurs from both substrates in selected built systems, presumably because a low oil/ water interfacial tension promotes necking and drawing. Given sufficient time, unremoved oils develop a liquid crystalline phase which results in slow oil removal via dispersion. Triolein soils also possess a relatively low solid/oil interfacial tension and similarly exhibt a high contact angle (in water) on both Teflon FEP and Mylar substrates in unbuilt surfactant systems. Builder addition lowers the oil/water interfacial tension and thereby prompts necking and drawing action.     

Are theoretical surface chemistry measurements really practical?

The principles and concepts of surface chemistry can be of enormous aid in the application of surfactant chemicals to practical cleaning and foaming problems. The use of surfactants for foam stability was seen to be dependent on rheological properties of the foam (bulk and surface viscosity) and to the energetics of the adsorbed surfactant monolayer (area/surfactant molecule, monolayer clasticity modulus, rate of monolayer spreading and rate of surfactant adsorption into the interface). From these principles, an equation predicting foam volume in the presence or absence of soil was derived and found to be in good agreement with experiment. In detergency, the performance was dictated by the thermodynamic work of adhesion between the soil and substrate. The adhesion was a function of surface properties (soil/water interfacial tension and soil/water/substrate). The role of agitation in detergency was shown to be that energy which was needed to overcome the adhesive bond between soil and substrate. The implicit form of the agitation term was discussed (dependent on substrate configuration, agitator system geometry and mechanics) but not explicitly deduced. The role of interfacial tension was discussed in relation to foam stability and detergency. In both applications, low interfacial tension is beneficial to performance. However, because other surface chemical effects play a role in performance in detergency and foam stability, it was noted that interfacial tension is not the sole correlating parameter with performance. The situations in which low interfacial tension is not sufficient to give improved detergency and foam stability performance were delineated. A possible new method of aiding in optimizing oil/surfactant performance also was discussed. Finally, the role of micelles in detergency was examined in light of very recent experimental work which suggests that micelles may be detrimental to detergency and foam stability performance. This study suggests that surfactants which form mesomorphic phases with soil give better performance. Micelles, instead of solubilizing soil in their hydrophobic cores, are said to be competing with the mesomorphic phase formation process, thereby hindering detergency performance. It is suggested by the sheer weight of new theoretical and innovative approaches to surface chemistry applied to detergency and foam stability performance that “theoretical surface chemistry measurements really (are) practical!”     

Adsorption of surfactants from water onto raw and HCl-activated clays in fixed beds

The removal of surfactants from water by adsorption onto raw and HCl-activated montmorillonite in fixed beds was studied. Three surfactants hexadecylpyridinium chloride (cationic), sodium dodecyl sulfate (anionic), and Triton X-102 (non-ionic) were selected in the concentration ranges lower than their critical micelle concentrations in fixed bed experiments. It was shown that the adsorption of anionic surfactant onto Ca-montmorillonite (SAz-1) decreased with increasing pH but that of cationic surfactant increased. The adsorption capacity of non-ionic surfactant was maximized at pH 7.0. For given clay, the adsorption capacities of surfactants were strongly pH-dependent. The adsorption capacity and adsorption rate of non-ionic surfactant onto SAz-1 could be largely improved after acid activation of the clay. Such an improvement was due to the fact that the dissolution of Al³⁺ or Fe²⁺ of montmorillonite occurs in acid solution. The calculated breakthrough curves in fixed bed agreed with the measured ones (standard deviation < 6%). The 50% C/C₀ breakthrough time (τ) decreased with increasing liquid flow rate. The effects of flow rate on the adsorption constant and adsorption capacity were also discussed.     

EXTRACTION MECHANISM OF PALLADIUM WITH DIDODECYLMONOTHIOPHOSPHORIC ACID IN HEPTANE DILUENT

ABSTRACT

Kinetic study of the extraction of palladium(D) with didodecylmonothiophosphoric acid in n-heptane diluent was carried out using a stirred transfer cell to clarify the extraction mechanism. The effect of surfactants on the kinetics of palladium extraction was also investigated, to elucidate the role of surfactants used in liquid surfactant membranes. Moreover, the interfacial tension between the organic and aqueous phases was measured to elucidate the adsorption equilibrium of the surfactants. It was found that the interfacial activity of each surfactant is higher than that of the extractant. In the kinetic study of palladium extraction, the experimental results of the extraction rate was analyzed by the interfacial reaction model, taking into account of the adsorption of the surfactant and extractant. The rate-determining step of palladium extraction was the complex formation between four chloro-palladium complexes and the extractant at the interface, and the extraction rate constants of each palladium species were obtained. The extraction rate of palladium in n-heptane diluent was much faster than that in toluene. Additionally, it was suggested that there was particular interaction between the surfactant and extractant at the interface. The effect of the surfactant on the extraction rate was explained by taking into account the adsorption of the surfactant at the interface.     

Adsorption Behavior of Nonionic Surfactants Studied by Drop Volume Technique

This study shows that the drop volume technique can be used to determine the adsorption behavior and interfacial adsorption kinetics of surfactants at fluid interfaces. Using this tensiometric method, one can determine not only the interfacial tension of the pure phases, but also the critical concentration for the formation of micelles (CMC) in a surfactant system, the quasi‐static (equilibrium) interfacial tension, the diffusion coefficient as a function of surfactant concentration, and the maximum adsorption density at the interface. The determination of the dynamic interfacial tension allows to indirectly characterize the kinetics of surfactant adsorption. The time dependence of the interfacial coverage resulting from this adsorption process is well described by two approximation solutions (for short and long adsorption times), with the result that the diffusion coefficients calculated as a function of surfactant concentration using these two methods show good agreement. The droplet formation and dripping process of a surfactant solution in a capillary was found to be quite different depending on whether the process occurred in gaseous or fluid surroundings. In particular, the formation of satellite droplets was different for the two different media, in terms of both the volume and shape of the satellite droplets.     

Surface Parameters and Biological Activity of <Emphasis Type="Italic">N</Emphasis>-(3-(Dimethyl Benzyl Ammonio) Propyl) Alkanamide Chloride Cationic Surfactants

Three cationic surfactants containing amide groups were prepared by quaternization of dimethylaminopropylamine with benzyl chloride. FTIR and ¹H-NMR spectroscopy were used to confirm the chemical structure of the prepared cationic surfactants. The surface parameters were estimated using surface tension measurements at three different temperatures. The prepared cationic surfactant showed a lower CMC than conventional cationic surfactants. Thermodynamic parameters of adsorption and micellization depend mainly of alkyl chain length and temperature. The adsorption process is more favorable than micellization. The biological activity of the three surfactants was estimated using inhibition zone showing that amidoamine cationic surfactants have good activity and the surfactants C12Bn is the most effective one.     

Surfactant-Induced Wettability Alteration of Oil-Wet Sandstone Surface: Mechanisms and Its Effect on Oil Recovery

Different analytical methods were utilized to investigate the mechanisms for wettability alteration of oil-wet sandstone surfaces induced by different surfactants and the effect of reservoir wettability on oil recovery. The cationic surfactant cetyltrimethylammonium bromide (CTAB) is more effective than the nonionic surfactant octylphenol ethoxylate (TX-100) and the anionic surfactant sodium laureth sulfate (POE(1)) in altering the wettability of oil-wet sandstone surfaces. The cationic surfactant CTAB was able to desorb negatively charged carboxylates of crude oil from the solid surface in an irreversible way by the formation of ion pairs. For the nonionic surfactant TX-100 and the anionic surfactant POE(1), the wettability of oil-wet sandstone surfaces is changed by the adsorption of surfactants on the solid surface. The different surfactants were added into water to vary the core surface wettability, while maintaining a constant interfacial tension. The more water-wet core showed a higher oil recovery by spontaneous imbibition. The neutral wetting micromodel showed the highest oil recovery by waterflooding and the oil-wet model showed the maximum residual oil saturation among all the models.     

表面活性剂复配体系修复芘污染土壤实验

以芘污染土壤为对象,利用阴离子表面活性剂鼠李糖脂和非离子表面活性剂皂素进行复配实验,得出最佳复配比并对污染土壤进行修复处理;其次,研究表面活性剂浓度、pH及CaCl₂、MgCl₂、KCl三种离子浓度、洗脱液的回收次数等单因素对洗脱效果的影响;然后利用响应曲面分析,确定影响洗脱效果的主效应因素及其交互作用强度;最后用Box-Behnken模型优化复配体系处理芘污染土壤的实验条件。结果表明：①当复配比为0.2时,鼠李糖脂-皂素混合溶液的表面张力最低,对芘的协同增溶效果最好;②复配体系处理芘污染土壤的单因素实验中,复配药剂浓度、pH、Mg²⁺浓度分别达到1800mg/L、8、0.1mmol/L时,洗脱效率最高;③环境因素对芘去除效果的影响从大到小依次为pH>表面活性剂浓度>Mg²⁺浓度,表面活性剂浓度与pH对芘的洗脱产生较大的交互影响作用,而pH与盐浓度的交互作用最微弱;④Box-Behnken模型优化后得出最佳组合是混合表面活性剂浓度为1900mg/L、pH为5、Mg²⁺浓度为0.2mmol/L,得到的洗脱效率为89.25%。     

表面张力法测定环糊精与表面活性剂包结常数的几种数值处理方法

表面张力法是研究环精精与表面活性剂相互作用的有力工具,用表面张力--表面活性剂浓度（γ－Ｃ）曲线来计算包结化合物的形成常数是可行的。本介绍了六种用表面张力法计算环糊精－表面活性剂包结化合和形成常数的数值处理方法。     

Synthesis, Surface, Thermodynamic Properties of Some Biodegradable Vanillin-Modified Polyoxyethylene Surfactants

Four water-soluble non-ionic ethoxylated surfactants based on vanillin were synthesized (VE₁₅, VE₂₀, VE₄₀, and VE₆₀). The chemical structures of these surfactants were confirmed using FT-IR and ¹H-NMR spectra. The molecular weights of the compounds were determined using viscosity measurements and gel permeation chromatography. Surface tension as a function of the concentration of the surfactant in aqueous solution was measured at 25, 40 and 55?°C. From these measurements, the critical micelle concentration (CMC), effectiveness (??_cmc), efficiency (pC₂₀), maximum surface (??_max) excess and minimum surface area (A _min), were calculated. The surface activity measurements showed their high tendency towards adsorption and micellization and their good surface tension reduction, and low interfacial tension. The emulsion stability measurements showed the applicability of these surfactants as emulsifying agents. The thermodynamic parameters of micellization (??G _mic, ??H _mic, ??S _mic) and adsorption (??G _ads, ??G _ads, ?S _ads) showed their tendency towards adsorption at the interfaces and also micellization in the bulk of their solutions. The biodegradability of the prepared surfactants was tested in river water using die-away method and showed their readily biodegradation in the open environment.     

Synthesis, Surface and Thermodynamic Properties of Substituted Polytriethanolamine Nonionic Surfactants

Three series of nonionic surfactants derived from polytriethanolamine containing 8, 10, and 12 units of triethanolamine were synthesized. Structural assignment of the different compounds was made on the basis of FTIR and ¹H‐NMR spectroscopic data. The surface parameters of these surfactants included critical micelle concentration (CMC), surface tension at the CMC (γ_CMC), surfactant concentration required to reduce the surface tension of the solvent by 20 mN m^?1 (pC₂₀), maximum surface excess (Γ_max), and the interfacial area occupied by the surfactant molecules (A_min) using surface tension measurements. The micellization and adsorption free energies were calculated at 25 °C.     

Reaction between Zinc and Hydrochloric Acid in Solutions Containing Alkyltrimethylammonium Bromide CnTAB (n = 8, 10, and 12) Cationic Surfactants: Influence of Surfactant Chain Length

The influence of C_nTAB cationic surfactant chain length (n = 8, 10, and 12) on the reaction rate of zinc powder and 0.1 M HCl hydrochloric acid in aqueous solutions was determined at room temperature. Solutions of single surfactants consisting of dodecyl, decyl, and octyl-trimethyl-ammonium bromide surfactants C_nTAB were prepared at room temperature. From the surface tension and conductivity measurements, the critical micelle concentration (CMC) values of the three surfactants were obtained in the presence and absence of the acid. No significant change was observed for CMC values in pure water and in 0.01 M HCl. Adsorption of C_nTAB surfactants onto 1% wt./vol zinc (in powder form), using surface tension measurements, was then investigated. The adsorption tendency of C_nTAB surfactants onto zinc powder followed the order: C₈TAB > C₁₀TAB > C₁₂TAB. The role of surfactants in the reaction rate between zinc powder and 0.1 M M HCl was then investigated using conductivity measurements. A significant difference in the reaction rate was found depending on the surfactant chain length. Reaction times of 3830, 4963, 14,172, and 20,053 s were found for the zinc reaction with (0.1 M HCl), (0.1 M HCl + 40 mM C₈TAB), (0.1 M HCl + 40 mM C₁₀TAB), and (0.1 M HCl + 40 mM C₁₂TAB), respectively, suggesting a significant dependency of the reaction rate on the C_nTAB chain length. Finally, some corrosion parameters such as the corrosion rate, corrosion inhibition efficiency, and their dependency on C_nTAB chain length were presented and discussed.     

Synthesis,Surface and Antimicrobial Activity of Piperidine-Based Sulfobetaines

A new method for the preparation of new heterocyclic amine surfactants based on sulfobetaines is proposed. Interfacial activities of the surfactants obtained in aqueous solution were studied by surface tension measurements. The critical micelle concentration, surface excess concentration, minimum area per surfactant molecule, and standard Gibbs energy of adsorption were determined. The adsorption properties of these compounds depend significantly on the alkyl chain length. Alkyl chain length also affects biological properties of the new surfactants, determining the minimum inhibitory concentration and size of inhibited growth zone. The compounds have high antimicrobial activity.     

Concentration Effects on Separation Selectivity in Foam Fractionation

Abstract

Removal of cadmium, copper, and nickel ions from aqueous solution by foam fractionation has been studied using a chelating surfactant, 4-dodecyl-diethylenetriamine. The rate of removal is a function of concentration of both metallic ions and surfactant. In the low concentration range for the metallic ions compared to that of the surfactant, the order of removal was found to be Cd²⁺ > Ni²⁺ > Cu²⁺. However, at higher concentrations of ions, the order becomes inverse, Cu²⁺ > Ni²⁺ > Cd²⁺. A selectivity coefficient for the separation of a specified ion from one or more ions using a chelating surfactant is shown to be dependent on the surface tension of the complex and the chelation constants. The relationship between separation selectivity of the removal of the metallic ions and concentration of both surfactant and metallic ions is discussed     

Adsorption mechanism of surfactants on nonwoven fabrics

For improved surface properties, nonwoven fabrics of polypropylene and poly(ethylene terephthalate) were treated with several kinds of surfactants, including anionic, cationic, and nonionic types. The adsorption isotherms of the anionic, cationic, and nonionic surfactants on the nonwoven fabrics were different. The adsorption isotherm of the cationic surfactant (dodecyl dimethylbenzyl/ammonium chloride) exhibited a maximum. The adsorption isotherm of the anionic surfactant (sodium dodecylbenzene sulfonate) was in the shape of the fifth Brunauer adsorption isotherm, and that of the nonionic surfactant (alkylphenol/ethylene oxide condensate) was similar to the fourth Brunauer adsorption isotherm. The time of the adsorption equilibrium was constant for the same types of adsorbate and adsorbent, and it was not related to the initial concentration. The specific surface resistance of the nonwoven fabrics decreased substantially after the adsorption of ionic surfactants. The nonwoven fabrics with the surfactants were characterized with scanning electron microscopy and X‐ray photoelectron spectroscopy. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3210–3215, 2003     

Amido-Amine-Based Cationic Gemini Surfactants: Thermal and Interfacial Properties and Interactions with Cationic Polyacrylamide

Experimental studies were conducted to investigate thermal and interfacial properties of two in‐house synthesized amido‐amine‐based cationic gemini surfactants namely: dodecanoic acid [3‐({4‐[(3‐dodecanoylamino‐propyl)‐dimethyl‐amino]‐butyl}‐dimethyl‐amino)‐propyl]‐amide dibromide ( 12‐4‐12 ) and dodecanoic acid [3‐({6‐[(3‐dodecanoylamino‐propyl)‐dimethyl‐amino]‐hexyl}‐dimethyl‐amino)‐propyl]‐amide dibromide ( 12‐6‐12 ). Thermogravimetric analysis showed the excellent thermal stability of surfactants and no structural degradation was observed at temperatures up to 250 °C. The long‐term thermal stability of the surfactants was investigated with the aid of spectroscopic techniques such as nuclear magnetic resonance (NMR (¹H and ¹³C) and Fourier transform infrared (FTIR) spectroscopy. Both surfactants were found to be thermally stable, and no changes in structure were observed after aging for 10 days at 90 °C. The interfacial tension of the surfactants was measured at three different temperatures (30, 60, and 80 °C), and the results showed a decrease in interfacial tension with increasing temperature and increasing spacer length of the surfactants. Rheological measurements were used to assess the interactions between the cationic gemini surfactant and cationic polyacrylamide. The addition of cationic surfactant reduced the viscosity and storage modulus of the polymer at low shear rate and frequency due to surfactant–polymer interactions and charge screening. The investigated surfactant–polymer system has great potential in high‐temperature carbonate reservoirs, where conventional anionic surfactants are not recommended due to high adsorption.     

Removal of radio-tagged protein and stearic acid soil from glass

Both algal protein and stearic acid soils are removed by water alone to near a 50% level; retained soil then becomes more difficult to remove. The bonding of protein soil to glass is stronger than that of tristearin, with indications that stearic acid soil is als slightly more adherent. The shape of the protein soil removal curves lacks the sigmoid shape of the tristearin or stearic acid soils, suggesting either the absence of sharp dependence upon critical micelle concentration, or the existence of adsorption largely at an essentially single energetic level. Both these soils are generally more effectively removed by anionic surfactants than was tristearin. Sodium tripolyphosphate is quite effective for removal of both soils, but combination with surfactants failed to provide the synergistic combinations found in tristearin removal. Nevertheless surfactant soil removal was improved by STP combination.     

Wettability alteration and reducing water blockage in tight gas sandstone reservoirs using mixed cationic Gemini/nonionic fluorosurfactant mixtures

The unrecovered hydraulic fracturing fluid will invade the matrix and induce water blockage, creating formation damage and hindering the oil or gas production rate. First, the synergistic effect of cationic Gemini surfactant (MQAS) and nonionic fluorosurfactant (N-2821) mixtures on reducing the surface tension and wettability alteration was investigated in this paper. The critical micelle concentration (CMC) of the surfactant mixture is one or two orders of magnitude lower than that of N-2821 and MQAS, indicating that the MQAS/N-2821 mixtures exhibit an apparent synergistic effect in reducing surface tension. Moreover, the maximal contact angle of MQAS/N-2821 mixtures reached 83.55° at α_N-2821 = 0.5, and the total surfactant concentration of 1 × 10⁻⁴ mol/L due to the adsorption of surfactant. The adsorption mechanism of surfactants on the surface of quartz sand was then examined. The adsorption kinetics is consistent with the pseudo-second-order model at different surfactant concentrations, while the Freundlich model is suitable for describing the adsorption behavior of surfactants on the sandstone surface. This finding indicates that surfactant adsorption is multilayered. The MQAS/N-2821 surfactant mixtures have excellent surfactant activity due to the relationship of the capillary pressure to the surface tension, pore radius, and contact angle; thus, the addition of surfactant mixtures can reduce the liquid saturation effectively. Furthermore, the sequential imbibition experiments indicate that MQAS/N-2821 mixtures alter the wettability of the core plug, which results from the adsorption of surfactants. Compared with brine water, the MQAS/N-2821 mixtures decreased the liquid saturation and increased the permeability recovery ratios of the core plug.