Adsorption and adsolubilization of surfactants on titanium dioxides with functional groups

Adsorption of ionic surfactants on titanium dioxide with dodecyl chain groups or quaternary ammonium groups (XNm, where m is the carbon number of the alkyl chain, 4–16) was investigated. The adsorbed amount of cationic surfactants (dodecyltrimethylammonium bromide, DTAB; 1,2-bis(dodecyldimethylammonio)ethane dibromide, 2RenQ) on titanium dioxide with dodecyl chain groups increased with increasing concentration of the dodecyl chain due to hydrophobic interaction, where the adsorbed amounts of DTAB at saturation was considerably greater than those of 2RenQ. Adsorption of an anionic surfactant (sodium dodecyl sulfate, SDS) on XNm occurred mainly due to both electrostatic attraction force and hydrophobic interaction, depending on the alkyl chain length on XNm. On the other hand, adsorption of cationic surfactants, DTAC and 2RenQCl (their counter ions are chloride ions), on XNm was quite smaller compared with that of SDS due to electrostatic repulsion force. Adsolubilization of 2-naphthol in the surfactant-adsorbed layer on the titanium dioxides with the functional groups was also studied. The adsolubilized amounts of 2-naphthol on titanium dioxide with dodecyl chain groups were enhanced by adsorption of DTAB, but no distinct increase in the adsolubilization was observed by adsorption of 2RenQ. In the case of XNm, the amount of 2-naphthol adsorbed in the absence of surfactants increased with increasing alkyl chain length on XNm. Further, an appreciable increase in the adsolubilization of 2-naphthol on XNm with adsorption of 2RenQCl was observed. It was found from the admicellar partitioning coefficients that the adsolubilization of 2-naphthol preferably occurs on XNm by adsorption of SDS or 2RenQCl compared with that by DTAC. These differences in the adsolubilization were discussed by microproperties of the surfactant-adsorbed layers estimated using a spin probe.     

Adsolubilization of 2-naphthol into adsorbed layers of triblock PEO-PPO-PEO copolymers on hydrophobic silica particles

Adsolubilization of 2-naphthol into an adsorbed layer of triblock poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO, Pluronics) copolymers on hydrophobically modified silica particles has been investigated. Four kinds of Pluronics (P103, P105, P123, and F108) were employed in order to understand the effect of the hydrophobicity of the surfactants on the adsolubilization. The amount of the Pluronics adsorbed of the maximum/saturation adsorption level was increased with a decrease in the HLB value, suggesting that the more hydrophobic Pluronics (P103 and P123) adsorb preferentially onto the hydrophobic silica surface over the more hydrophilic Pluronics (P105 and F108). The greater adsorbed amount of the more hydrophobic surfactants resulted in a greater amount of 2-naphthol adsolubilized into the adsorbed Pluronics layers. In the case of simultaneous addition of the Pluronics and 2-naphthol, the amount adsolubilized into the adsorbed P123 and P103 layers increased in their low-surfactant-concentration regime, reached a maximum, and then decreased with a further increase in the Pluronics concentration. On the other hand, for both the P105 and F108 copolymers, a decrease in the adsolubilized amount was not observed over the whole range of copolymer concentration investigated. This difference is attributed to a difference in the hydrophobicity of the micellar aggregates in solution and of the adsorbed layers on the hydrophobic surface. When 2-naphthol was added after replacement of the Pluronics supernatant by a surfactant-free solution, the final decrease in the adsolubilization was insignificant for all the Pluronics. Indeed, the maximum amount of adsolubilization was comparable to the corresponding amount obtained in the case of simultaneous addition.     

Adsolubilization of 2-naphthol into adsorbed layer of PEO-PPO-PEO triblock copolymers on hydrophilic silica

Adsolubilization of 2-naphthol into an adsorbed layer of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) triblock copolymers (Pluronics) on hydrophilic silica has been investigated. Four kinds of Pluronics (P103, P105, P123, and F108) were used in order to understand the effect of the hydrophobicity of surfactant on the adsolubilization. The order of the adsorption in the saturation level was found to be P123 approximately P103 > P105 > F108, meaning that Pluronics with higher hydrophobicity can adsorb preferentially to the silica surface. Indeed, this order was parallel to the order of the adsolubilization amount of 2-naphthol. In the case of co-addition of the Pluronics and 2-naphthol, the adsolubilization amount increased gradually at lower surfactant concentration regions, reached a maximum, and then decreased with increasing concentration of the Pluronics. The maximum amount appeared at critical polymolecular micelle concentration of each Pluronics. On the other hand, the final decrement was not observed when 2-naphthol was added after replacement of the Pluronics supernatant by the Pluronics free solution. These results suggest that adsolubilization behavior is influenced by the existence of the polymolecular micellar aggregates in the solution phase.     

Polyaniline film formation in hexadecyl trimethyl ammonium bromide admicelles on hydrous zirconia surface

Formation of a thin polyaniline film on hydrous zirconia (ZrO2) surface was carried out using adsorbed surfactant bilayers on ZrO2 as reaction sites. Aniline was adsolubilized in hexadecyltrimethylammonium bromide (HDTAB) admicelles formed on the surface of ZrO2 by adsorption. Subsequent polymerization of the adsolubilized aniline monomer showed effective conversion of aniline to polyaniline. The formation of the polyaniline coated ZrO2 has been confirmed by UV-visible spectroscopy, FT-IR spectroscopy, and conductivity measurements. Various parameters involved during the adsorption process were studied. Selection of pH 9.0 as the pH of all experimental feed solutions was governed by the knowledge of point of zero charge (PZC) of ZrO2. Effect of aniline concentration on HDTAB adsorption was studied and it was observed that increase in aniline concentration decreased the amount of HDTAB adsorbed on ZrO2. Addition of salt (0.05 M NaCl) in the feed solution increased HDTAB adsorption and drastically reduced the effect of aniline concentration on HDTAB adsorption.     

Competitive adsorption in the system: carboxymethylcellulose/surfactant/electrolyte/Al<Subscript>2</Subscript>O<Subscript>3</Subscript>

The adsorption of carboxymethylcellulose (CMC) in the presence or absence of the surfactants: anionic SDS, nonionic Triton X-100 and their mixture SDS/TX-100 from the electrolyte solutions (NaCl, CaCl₂) on the alumina surface (Al₂O₃) was studied. In each measured system the increase of CMC adsorption in the presence of surfactants was observed. This increase was the smallest in the presence of SDS, a bit larger in the presence of Triton X-100 and the largest when the mixture of SDS/Triton X-100 was used. These results are a consequence of formation of complexes between the CMC and the surfactant particles. Moreover, the dependence between the amount of surfactants’ adsorption and the CMC initial concentration was measured. It comes out that the surfactants’ adsorption amount is not dependent on the CMC initial concentration and moreover, it is unchanged in the whole measured concentration range. The influence of kind of electrolyte, its ionic strength as well as pH of a solution on the amount of the CMC adsorption at alumina surface was also measured. The amount of CMC adsorption is larger in the presence of NaCl than in the presence of CaCl₂ as the background electrolyte. It is a result of the complexation reaction between Ca²⁺ ions and the functional groups of CMC belonging to the same macromolecule. As far as the electrolyte ionic strength is concerned the increase of CMC adsorption amount accompanying the increase of electrolyte ionic strength is observed. The reason for that is the ability of electrolyte cations to screen every electrostatic repulsion in the adsorption system. Another observation is that the increase of pH caused the decrease of CMC adsorption. The explanation of this phenomenon is connected with the influence of pH on both dissociation degree of polyelectrolyte and kind and concentration of surface active groups of the adsorbent.     

Effect of pH on adsolubilization of single and binary organic solutes into a cationic hydrocarbon surfactant adsorbed layer on silica

The adsolubilization behaviors of 2-naphthol, biphenyl, and their binary solutes in the hexadecyltrimethyl ammonium bromide (HTAB) adsorbed layer formed on silica have been studied with solution pH. Two feed concentrations of HTAB are employed: 1.5 and 3.0 mmol dm(-3). At the feed concentration of 1.5 mmol dm(-3) HTAB, most of HTAB are adsorbed on the silica as a monolayer, while a bilayer formation occurs at the feed concentration of 3.0 mmol dm(-3). It is found that the adsolubilized amounts of respective single solutes increase with increasing solution pH except acidic region for biphenyl under a constant feed concentration of 2-naphthol (0.4 mmol dm(-3)) and biphenyl (0.047 mmol dm(-3)). The adsolubilization of binary solutes depends on the feed concentration of HTAB; at the low HTAB feed concentration, competitive adsolubilization between 2-naphthol and biphenyl occurs above pH 4.5, while at the high HTAB feed concentration the adsolubilization of biphenyl is enhanced by the incorporation of 2-naphthol over a whole pH region. These behaviors in the adsolubilization are discussed from the surfactant structure of HTAB adsorbed as well as the admicellar partitioning coefficients.     

Sorption of 2-naphthol and copper ions by cationic surfactant-adsorbed laponite

As one of applications of adsolubilization, a simultaneous sorption of 2-naphthol and copper ions by cationic surfactant-adsorbed laponite was carried out. Both the surfactant-adsorbed laponite using dodecyl trimethylammonium bromide (DTAB) and 1,2-bis(dodecyldimethylammonio) ethane dibromide (2RenQ) retained a high sorption capacity for copper ions, while the 2RenQ-adsorbed laponite completely adsolubilized 2-naphthol in a whole concentration region, but the DTAB-adsorbed laponite one decreased the adsolubilization gradually above the cmc of DTAB. Thus, it was found that laponite having cationic surfactant-adsorbed layer has a great capacity for a simultaneous removal of both toxic nonionic and ionic compounds.     

氧化铝-延展型表面活性剂的吸附胶束及其吸附增溶

合成了一系列直链烷基聚氧丙烯醚硫酸钠(C_cP_pS, c=8或16时, p=9;c=12时, p=3, 6或9)并鉴定了其结构. 与十二烷基硫酸钠(SDS)类似, C₁₂P₉S在氧化铝上的饱和吸附量以及对阳离子染料亚甲基蓝的吸附增溶行为共同证实该延展型表面活性剂在表面上形成了双层吸附胶束, 但由聚氧丙烯(PPO)连接基导致的橄榄球状分子及其导致的较大分子吸附面积, 使其吸附能力及其对亚甲基蓝的吸附增溶能力均稍弱于SDS. C₁₂P₉S@Al₂O₃对弱极性分子1-苯乙醇和难溶性分子苯乙烯的吸附增溶能力均明显强于SDS, 而且对1-苯乙醇的吸附增溶量达到SDS@Al₂O₃的8.5倍, 说明1-苯乙醇主要被增溶在C₁₂P₉S双层吸附胶束中PPO连接基所在的膨大部位, 这使延展型表面活性剂改性的氧化铝在废水处理和药物传递系统等领域具有潜在的应用前景.     

Role of sequential adsorption of polymer/surfactant mixtures and their conformation in dispersion/flocculation of alumina

The role of sequential adsorption of a non-interacting pair of polymer (polyacrylic acidPAA) and surfactant (sodium dodecyl sulfate-SDS) on alumina particles and in determining the stability of their suspensions was studied with particular attention to the conformation of the polymer. It was found that the sequence of addition is of critical importance in determining the dispersion/flocculation of this system. When SDS was added first, both PAA conformation and suspension stability varied with SDS concentration. Whereas when PAA was added first, the subsequent adsorption of SDS molecules had no effect on either the polymer conformation or the suspension stability. This is attributed to masking of SDS species by the larger polymer chains. SDS can not however be completely masked by PAA chains once the PAA concentration is decreased below the optimal concentration for flocculation. When the stirring duration was increased, the mode of addition showed no effect suggesting that the system then reaches equilibrium. Interestingly, a small amount of pre-adsorbed PAA was found to facilitate the adsorption of SDS.     

表面活性剂对Al2O3吸附MoO4^2—的影响

土壤自溶液中吸附MoO_4~(2-)会影响植物生长。前人对这一吸附过程已作过一些研究。本文报导阴离子表面活性剂十二烷基硫酸钠(SDS),阳离子表面活性剂氯化十六烷基吡啶(CPC)和非离子表面活性剂吐温-20(TW-20)对Al_2O_3吸附MoO_4~(2-)的影响。 实验所用吸附剂为层析用中性Al_2O_3(上海五四农场化学试剂厂),SDS(化学纯,广东石岐化工厂),CPC(化学纯。上海试剂一厂),TW—20(试剂级),其余试剂均为分析纯,含钼液用Na_2MoO_4配制。     

Adsorption of cationic cellulose derivative/anionic surfactant complexes onto solid surfaces. II. Hydrophobized silica surfaces

The effect of the anionic surfactant SDS (sodium dodecyl sulfate) on the adsorption behavior of cationic hydroxyethyl cellulose (Polymer JR-400) and hydrophobically modified cationic cellulose (Quatrisoft LM-200) at hydrophobized silica has been investigated by null ellipsometry and compared with the previous data for adsorption onto hydrophilic silica surfaces. The adsorbed amount of LM-200 is found to be considerably larger than the adsorbed amount of JR-400 at both surfaces. Both polymers had higher affinity toward hydrophobized silica than to silica. The effect of SDS on polymer adsorption was studied under two different conditions: adsorption of polymer/SDS complexes from premixed solutions and addition of SDS to preadsorbed polymer layers. Association of the surfactant to the polymer seems to control the interfacial behavior, which depends on the surfactant concentration. For the JR-400/SDS complex, the adsorbed amount on hydrophobized silica started to increase progressively from much lower SDS concentrations, while the adsorbed amount on silica increased sharply only slightly below the phase separation region. For the LM-200/SDS complex, the adsorbed amounts increased progressively from very low SDS concentrations at both surfaces, and no large difference in the adsorption behavior was observed between two surfaces below the phase separation region. The complex desorbed from the surface at high SDS concentrations above the critical micelle concentration. The reversibility of the adsorption of polymer/SDS complexes upon rinsing was also investigated. When the premixed polymer/SDS solutions at high SDS concentrations (>5 mM) were diluted by adding water, the adsorbed amount increased due to the precipitation of the complex. The effect of the rinsing process on the adsorbed layer was determined by the hydrophobicity of the polymer and the surface.     

表面活性剂对HDEHP萃取动力学的影响

用上升液滴法测定二(2-乙基己基)磷酸(HDEHP)从硫酸盐介质中萃取Co^2^+的速率。研究体系中加入不同表面活性剂所引起萃取速率的不同改变: 三辛基氧化膦(TOPO)因与HDEHP形成可萃取的Co^2^+活性分子缔合物, 降低了萃取过程活化能而使反应加速; 十二烷基磺酸钠(SDS)和十六烷基三甲基溴化铵(CTMAB)因占据发生萃取反应的界面区, 减小了HDEHP与Co^2^+反应的机会而使反应减速; SDS还因其在界面形成较强的负电场(层), 造成Co^2^+的附加势能而使萃取速率有更大幅度的降低。     

Sorption of 2,4-dichlorophenol on modified hydrotalcites

The adsorption of anionic surfactants (sodium dodecyl sulfate (SDS) and sodium bis[2-ethylhexil]sulfosuccinate (AOT)) on hydrotalcite (HT) and the adsorption of 2,4-dichlorophenol (DCP) on HT and its modified forms from aqueous solutions was studied. The modification was carried out by calcinations (heat treatment) and hydrophobization using different anionic surfactants. The anionic surfactant isotherms were of the H-type. It was assumed that first the ion exchange mechanism takes place until approximately the anion exchange capacity of HT is reached and hereafter, the hydrophobic mechanism occurs forming surfactant bilayers. While the DCP adsorption was very poor on HT, significant uptake of DCP took place on calcined HT which was attributed to the simultaneously occurring rehydration and adsorption during the reconstruction of the layered structure. On anionic surfactant-HT complexes (“organo-hydrotalcites”) DCP was considerably adsolubilized in the anionic surfactant layers intercalated in HT. The AOT–HT complex appeared the more effective adsorbents for DCP.     

Adsorption of sodium dodecyl sulfate onto clathrate hydrates in the presence of salt

This work presents the effect of NaCl on the adsorption of sodium dodecyl sulfate (SDS) at the cyclopentane (CP) hydrate-water interface. The adsorption isotherms and the SDS solubility in NaCl solutions are obtained using liquid-liquid titrations. The solubility data are determined at typical hydrate forming temperatures (274-287K) to ensure that the adsorption isotherms are obtained within SDS solubility limits in NaCl solutions. The isotherms show L-S (Langmuir-Step) type behaviors with 1mM and 10mM NaCl solutions while L type isotherm is determined for 25mM NaCl solutions due to the low SDS solubility in this salt concentration. Zeta potentials of CP hydrate particles in the aqueous solutions support the shape of the adsorption isotherm with the 1mM NaCl solution. The 1mM NaCl case shows the highest SDS adsorption amount among the cases with 0mM, 10mM, and 25mM NaCl solutions. In this case, the competition for adsorption between Cl(-) and DS(-) is not as strong compared to the 10 and 25mM NaCl cases and the presence of Na(+) ions may reduce the repulsion between DS(-) ions, which results in a higher adsorption of DS(-) ions and enhanced enclathration.     

Concentration of chlorophenols in water with sodium dodecylsulfate-gamma-alumina admicelles for high-performance liquid chromatographic analysis

Chlorophenols in water were sorbed onto sodium dodecylsulfate (SDS)-alumina (gamma-form) admicelles. The extent of sorption increased with increasing amount of SDS and decreasing solution pH. Conditions for good recovery were obtained when 100 mg SDS and 1.5 g alumina was used at pH 2. However, the yield decreased with a further increase in the SDS concentration due to the formation of normal SDS micelles. The extent of sorption also increased with increasing hydrophobicity of the chlorophenol, indicating that hydrophobic interactions predominate for the collection of analytes. When a cartridge column filled with admicelles was used, >90% of tetrachlorophenol and pentachlorophenol in 200 ml of water samples were rapidly recovered. The sorbed analytes were eluted with 1 ml acetonitrile. The accuracy and precision of the present method were demonstrated for the HPLC analysis with ultraviolet (290 nm) detection of microg l(-1) levels of tetrachlorophenol and pentachlorophenol in river water samples.     

Dynamics of adsorption of an oppositely charged polymer-surfactant mixture at the air-water interface: poly(dimethyldiallylammonium chloride) and sodium dodecyl sulfate

The dynamic adsorption behavior of mixtures of the cationic polymer poly(dimethyldiallylammonium chloride) [poly(dmdaac)] and the anionic surfactant sodium dodecyl sulfate (SDS) has been studied at the expanding liquid surface of an overflowing cylinder. A combination of ellipsometry and external reflection Fourier transform infrared spectroscopy was used to measure the adsorbed amounts of poly(dmdaac) and SDS as a function of the bulk surfactant concentration for various polymer concentrations in the range 0-0.2 g dm-3. Laser Doppler velocimetry was used to determine the surface age, which was approximately 1 s for solutions where the polymer adsorbed. The interfacial behavior is rationalized in terms of competition between surface activity and mass transport to the expanding surface. At low surfactant concentrations, adsorption of both poly(dmdaac) and SDS is enhanced as a result of the formation in solution of polymer-surfactant complexes that are more surface active than either component alone. The rate of adsorption of these complexes is diffusion-controlled, and their interfacial composition remains constant at three dmdaac units per SDS molecule over a 5-fold change in the surfactant concentration. For the higher polymer concentrations studied, the complexes saturate the air-water interface: the adsorbed amount is independent of the polymer concentration and remains constant also over a factor of 5 in the surfactant concentration. Once the number of bound surfactant molecules per dmdaac monomer exceeds 0.3, the complexes begin to form large aggregates, which are not surface active due to their slower mass transport. The adsorbed amount decreases rapidly on approach to the equivalence point (one SDS molecule per dmdaac monomer), and when it is reached, only a very small amount of material remains at the interface. At still higher surfactant concentrations, the free SDS adsorbs but there is no adsorbed poly(dmdaac). The dynamic adsorption data are compared with equilibrium measurements of the same system by Staples et al. (Langmuir 2002, 18, 5147), which show very different surface compositions and no significant change in surface coverage at the equivalence point.     

Tunable synergism/antagonism in a mixed nonionic/anionic surfactant layer at the solid/liquid interface

The use of mixed surfactants for modification of solid surfaces is important for many applications, since beneficial synergism often occurs depending on the surfactant type and mixing conditions. Systematical information on the properties of surfactant mixtures at the solid/liquid interface can be helpful for optimizing the interactions between the surfactants and then their corresponding performance. In this work, a nonionic/anionic surfactant combination, n-dodecyl beta-d-maltoside (DM) and sodium dodecyl sulfonate (SDS), was selected for the study of adsorption on an oxide solid, alumina. Interestingly, the mixture of the two surfactants with opposite pH-dependence of adsorption on alumina exhibits some unique synergistic or antagonistic features that were found to be tunable in the region of pH 4-10. In addition, the DM/SDS molar ratio in the adsorbed layer was found to decrease with concentration in the saturated region at all the pH and mixing ratios tested. The decrease is attributed to the monomer concentration changes in solution due to the difference in surface activities of the two surfactants. The tunable features of this mixture at the solid/liquid interface provide a way to optimize the properties by changing the mixing conditions. This can be valuable in many applications, such as enhanced oil recovery, flotation, and solubilization.     

Removal of Disperse Dyes from Water Using Surfactant Treated Alumina

An alumina surface was modified by adsorption of an anionic surfactant, sodium dodecyl sulfate (SDS). Typical S‐shaped isotherm of surfactant on alumina was observed. The adsorption of Disperse Red‐11, Disperse Blue‐26 and Disperse Red‐156 on alumina and surfactant treated alumina has been investigated. The enhancement in adsorption of these disperse dyes on surfactant treated alumina is observed, which may be attributed to their solubilization in surfactant aggregates formed at the solid/liquid interface. The effect of pH on adsorption has been studied. The adsorption is greatly influenced by pH of the medium. The applicability of the Langmuir model and the Dual‐Mode sorption model (DSM) were tested for equilibrium data.     

Concomitant adsorption of poly(ethylene oxide)-b-poly(epsilon-caprolactone) copolymers and sodium dodecyl sulfate at the silica-water interface

Upon addition of silica to aqueous solutions of poly(ethylene oxide)-b-poly(epsilon-caprolactone) copolymers (PEO-b-PCL) and sodium dodecyl sulfate (SDS), adsorption of the solutes occurs at the silica-water interface. The amount of the adsorbed constituents has been measured by the total concentration depletion method. Small-angle neutron scattering experiments (SANS) have been carried out to investigate the structure of the adsorbed layer. Although SDS is not spontaneously adsorbed onto hydrophilic silica, adsorption is observed in the presence of PEO-b-PCL diblocks, in relation to the relative concentration of the two compounds. Conversely, SDS has a depressive effect on the adsorption of the copolymer, whose structure at the interface is modified. Copolymer desorption is however never complete at high SDS content. These observations have been rationalized by the associative behavior of PEO-b-PCL and SDS in water.     

Diffusion-controlled evaporation of sodium dodecyl sulfate solution drops placed on a hydrophobic substrate

In this work, the effect of SDS anionic surfactant on the diffusion-controlled evaporation rate of aqueous solution drops placed on TEFLON-FEP substrate was investigated with 11 different SDS concentrations. Drop evaporation was monitored in a closed chamber having a constant RH of 54-57% by a video camera. The initial contact angle, θ(i) decreased from 104±2° down to 68±1° due to the adsorption of SDS both at the water-air and the solid-water interfaces. The adsorption of SDS on the solid surface was found to be 76% of that of its adsorption at the water-air interface by applying Lucassen-Reynders approach. An equation was developed for the comparison of the evaporation rates of drops having different θ(i) on the same substrate. It was found that the addition of SDS did not alter the drop evaporation rate considerably for the first 1200 s for all the SDS concentrations. The main difference was found to be the change of the mode of drop evaporation by varying the SDS concentration. The constant θ mode was operative up to 80 mM SDS concentration, whereas constant contact area mode was operative after 200 mM SDS concentrations due to rapid drop pining on the substrate.