Kinetics of Adsorption of Anionic, Cationic, and Nonionic Surfactants (original) (raw)
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Colloids and Surfaces A-physicochemical and Engineering Aspects, 2004
Adsorption kinetics and equilibrium studies of sodium dodecylbenzenesulfonate (NaDBS) on cellulosic surface are investigated. Modifications in adsorption induced by cationic surfactant cetyltrimethylammonium bromide (CTAB) are studied. It is concluded that the rate of adsorption and the amount of adsorption are increased. Importance of these observations in detergency is indicated.
Adsorption of anionic and non-ionic surfactants on a cellulosic surface
Colloids and Surfaces A-physicochemical and Engineering Aspects, 2005
The adsorption of an anionic surfactant, sodium dodecylbenzenesulfonate (NaDBS) and a non-ionic surfactant, Triton X-100 (TX-100) has been studied on cellulose surfaces with and without the presence of electrolytes by using both spectrophotometric and titrametric methods. The adsorption isotherms are identified with four different regimes for both surfactants. Two important phenomena reflected in the adsorption isotherms are the steep increase in adsorption due to hemimicellisation below the critical micelle concentration (CMC) and the decrease in the adsorption above the CMC. Adsorption of anionic surfactant, NaDBS gets enhanced in presence of monovalent (K + ) or bivalent (Ca 2+ ) cation while for non-ionic surfactant, TX-100 there is no such enhancement in adsorption in presence of salt.
Colloid and Polymer Science, 2004
Surfactant adsorption at the solid-liquid interface is a phenomenon of significant importance for many industrial processes, such as selective flotation [1], cosmetic formulation, paint technology, and ceramic processing. The study of the adsorption of ionic surfactants on charged surfaces has led to the concept of aggregation and self-assembly of the surfactant at the solid-liquid interface . Three models for the adsorbed layer structure have been proposed. The reverse orientation model, first proposed by Somasundaran and Fuerstenau [7,, is based on a sequence of four steps for the surfactant adsorption. The first involves the individual surfactant adsorption via an ion-exchange mechanism exclusively; in the second step, the aggregation into hemimicelles takes place as a result of the reorganization, accompanied by an association process, which led to the formation of a surfactant monolayer oriented with the head groups in contact with the solid surface; the third step considers the increase of the density of the aggregated domains through further surfactant adsorption; finally, the fourth step involves the formation of bilayerorganized structures which saturate the surface. The second model, proposed by Harwell et al. , differs slightly from the previous one, in that patches of bilayer structures, termed admicelles, are formed as soon as the concentration of free surfactant attains a critical level, without hemimicelle formation at lower surfactant concentrations. A different model was proposed by Gu and coworkers , according to which the surfactant adsorption proceeds through two phases: the first results from electrostatic interactions between the surfactant head groups and the surface charges and the second involves lateral interactions among the alkyl chains which induce the formation of a bundle of adsorbed surface micelles that become progressively more closely packed as further surfactant is adsorbed.
Langmuir, 2007
In this work, the adsorption of cationic surfactant and organic solutes on oxidized cellulose fibers bearing different amounts of carboxylic moieties was investigated. The increase in the amount of-COOH groups on cellulose fibers by TEMPO oxidation induced a general rise in surfactant adsorption. For all tested conditions, that is, cellulose oxidation level and surfactant alkyl chain length (C12 and C16), adsorption isotherms displayed a typical three-region shape with inversion of the substrate-potential which was interpreted as reflecting surfactant adsorption and aggregation (admicelles and hemimicelles) on cellulose fibers. The addition of organic solutes in surfactant/cellulose systems induced a decrease in surfactant cac on the cellulose surface thus favoring surfactant aggregation and the formation of mixed surfactant/solute assemblies. Adsorption isotherms of organic solutes on cellulose in surfactant/cellulose/ solute systems showed that solute adsorption is strictly correlated to (i) the surfactant concentration, solute adsorption increases up to the surfactant cmc, where solute partitioning between the cellulose surface and free micelles causes a drop in adsorption, and to (ii) solute solubility and functional groups. The specific shape of solutes adsorption isotherms at a fixed surfactant concentration was interpreted using a Frumkin adsorption isotherm, thus suggesting that solute uptake on cellulose fibers is a coadsorption and not a partitioning process. Results presented in this study were compared with those obtained in a previous work investigating solute adsorption in anionic surfactant/cationized cellulose systems to better understand the role of surfactant/solute interactions in the coadsorption process.
Interaction of (hydroxypropyl) cellulose with anionic surfactants in dilute regime
Colloid and Polymer Science, 2006
Hydroxypropyl)cellulose (HPC) dilute aqueous solutions in the presence of sodium cholate (CS), sodium deoxycholate (DC), and sodium dodecylsulphate (SDS) were investigated. The hydrophobicity parameter (I 1 /I 3 ) from fluorescence has shown a critical aggregation concentration (CAC) lower than the critical micellar concentration (CMC). One or two breakpoints were observed in the curve conductivity vs surfactant concentration. The thermodynamic parameters of aggregation (ΔG 0 mic , Δ H 0 mic and ΔS 0 mic ) and the degree of counterion dissociation were calculated. Evidences for the secondary aggregation of CS/water system were found. The relative viscosity increases for HPC/bile salt solutions only at high surfactant concentrations, whereas for HPC/SDS, it passes through a maximum. The cloud points of both HPC/bile salt solutions at higher surfactant concentrations reach a temperature plateau value around 324 K, while for HPC/SDS, it exceeds 373 K at low SDS concentrations. Dynamic light scattering has demonstrated that the surfactants bind to HPC already at concentrations lower than CAC.
Langmuir, 2001
The effect of surfactants on the adsorption properties of ethyl(hydroxyethyl)cellulose (EHEC) and its hydrophobically modified analogue (HM-EHEC) at the solid-liquid interface has been studied by ellipsometry. The adsorption characteristics of EHEC and HM-EHEC without the presence of surfactants are also presented. The polar silica surface and a hydrophobized silica surface were used as substrates. On the polar silica surface, a small addition of the anionic surfactant sodium dodecyl sulfate (SDS) caused a 3-to 5-fold expansion of the preadsorbed EHEC or HM-EHEC layers, while the adsorbed amount was less influenced. On the hydrophobized silica surface, SDS could replace EHEC (>10 mM SDS), while some adsorbed HM-EHEC still could be detected well above the critical micelle concentration of SDS in the bulk (14 mM). The nonionic surfactant octa(ethylene oxide) dodecyl ether (C12E8) did not affect the adsorbed layer structure on silica, and the cationic surfactant cetyltriammonium chloride (CTAC) on hydrophobized silica showed similar effects as SDS but with a smaller magnitude. It is proposed that the adsorbed layer structure mainly is governed by polymer-surfactant interfacial interactions.
Adsorption kinetics of cationic surfactant onto pulp fibres
Adsorption of cationic compounds on cellulosic fibres totally changed their surface chemistry. The paper is focused on the modification of pulp fibres by a cationic surfactant (quaternary ammonium salts). The work deals with surfactant adsorption kinetics and modes of surfactant adsorption on the cellulosic fibre surface. It was found that the adsorption curve had a rising character. The results showed that the surfactant was not adsorbed onto the fibre surface in monolayer. It can be assumed that the surfactant was also adsorbed into the internal porous structure of the fibres. To monitor the surfactant adsorption on fibres, the method of streaming potential with polyelectrolyte titration was used.
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2011
a b s t r a c t TIR Raman spectroscopy has been used to study the adsorption of surfactants onto cellulose. The cellulose was prepared by Langmuir-Blodgett deposition of trimethylsilylcellulose onto silica followed by removal of the trimethylsilyl groups with acid to generate a hydrophilic surface. The reaction was followed in situ with Raman spectroscopy, revealing a two-step hydrolysis. Adsorption isotherms of hexadecyltrimethylammonium bromide (CTAB) and Triton X-100 (TX-100) on hydrophilic cellulose were obtained by TIR Raman scattering under quasi-equilibrium conditions where the bulk concentration was slowly but continuously varied. The isotherms of both surfactants are almost linear, in contrast to the isotherms on hydrophilic silica. The CTAB isotherm shows hysteresis depending on whether the concentration of the surfactant is increasing or decreasing due to a slow adsorption region. A mixture of TX-100 and CTAB shows ideal adsorption, in contrast to adsorption of the same mixture on silica where there is a strong cooperative interaction at low CTAB surface coverage.
Adsorption of a Cationic Surfactant onto Cellulosic Fibers I. Surface Charge Effects
Langmuir, 2005
This paper reports on a flowable lignocellulosic thermoplastic prepared from forestry biomass by solvent-free acetylation. The non-solvent approach relies upon a functionalizing agent derived from benzethonium chloride (hyamine) and sulfuric acid, which was chosen for its similar wetting attributes to an ionic liquid for the lignocellulose but was much less inexpensive to use. Besides acetylation, this functionalizing agent became chemically bonded to the lignocellulose by the sulfate group formed in situ, as demonstrated by 13 C NMR, infrared and elemental analysis. This attached species appeared to contribute strongly to the flowable nature of the product. The modified material showed good melt flowability by compression molding, as demonstrated in this study by the production of semi-transparent films and was characterized by differential scanning calorimetry and dynamic mechanical analysis. An experimental investigation of reaction parameters was included in the study, exploring the mechanism by which the cationic functionalizing agent modified the structure of lignocellulose.