Mixed Cationic-nonionic Surfactants Research Articles

A Highly Sensitive Spectrophotometric Method for Gallium Determination with Chrome Azurol S in the Presence of Mixed Cationic-Nonionic Surfactants and its Application in Plant Analysis

ABSTRACTA simple and very sensitive spectrophotometric method determining microgram quantities of gallium (Ga) has been developed. The method is based on the complex of Ga(III) with Chrome Azurol S (CAS) in the presence of benzyldodecyldimethylammonium bromide (ST) and polyoxyethylenesorbitan monopalmitate (Tween 40). The complex forms in weakly acid solution (pH 3.8) and shows the absorption maximum at 627 nm. The molar absorptivity (ε) of this system is 1.87 × 105 L mol−1 cm−1, and it is clearly higher than ε of other spectrophotometric methods of gallium determination. The detection and quantification limits (LOD, LOQ) are 7.6 × 10–3 and 0.023 µg mL−1, respectively. Beer‘s law is obeyed in the range from 0.02 to 0.60 µg mL−1 of Ga. The precision and accuracy are good. This first spectrophotometric method of Ga(III) determination in the four-component system has been successfully applied for the analysis of mushrooms and grasses with low content of gallium.

Flotation and adsorption of muscovite using mixed cationic–nonionic surfactants as collector

The performance of the mixed dodecylamine chloride (DDA)/octanol (OCT) surfactants on muscovite flotation was investigated using flotation tests, and their adsorption mechanisms on muscovite and air/water interface were clarified using contact angle measurement, surface tension and molecular dynamics (MD) simulations. The flotation results indicate that the recovery of muscovite rapidly decreases when the pH increases in the presence of only DDA, whereas the recovery of muscovite is high (>77%) over a wide range of pH in the presence of the mixed DDA/OCT surfactants with a ratio of 2/1. Contact angle measurements further confirm that the mixture displays a stronger collecting power than DDA and is a superior collector for the muscovite flotation. The surface tensions of DDA, OCT and their mixture indicate that the mixture is more efficient than DDA at decreasing the air–water interfacial tension and exhibits much better surface activities. MD simulations show that the mixture interacts with the muscovite mainly through electrostatic attraction and hydrogen-bonding. DDA ion is dominant in the interaction between the mixture and muscovite. OCT molecules are co-adsorbed onto the muscovite through the hydrogen-bond interaction and hydrophobic association with DDA ions. Compared with DDA, a well-compacted monolayer is formed on the muscovite surface in the presence of mixed surfactants, indicating a much stronger hydrophobic character of muscovite.

Adsorption of mixed cationic-nonionic surfactant and its effect on bentonite structure

The adsorption of cationic-nonionic mixed surfactant onto bentonite and its effect on bentonite structure were investigated. The objective was to improve the understanding of surfactant behavior on clay mineral for its possible use in remediation technologies of soil and groundwater contaminated by toxic organic compounds. The cationic surfactant used was hexadecylpyridinium bromide (HDPB), and the nonionic surfactant was Triton X-100 (TX100). Adsorption of TX100 was enhanced significantly by the addition of HDPB, but this enhancement decreased with an increase in the fraction of the cationic surfactant. Part of HDPB was replaced by TX100 which decreased the adsorption of HDPB. However, the total adsorbed amount of the mixed surfactant was still increased substantially, indicating the synergistic effect between the cationic and nonionic surfactants. The surfactant-modified bentonite was characterized by Brunauer-Emmett-Teller specific surface area measurement, Fourier transform infrared spectroscopy, and thermogravimetric-derivative thermogravimetric/differential thermal analyses. Surfactant intercalation was found to decrease the bentonite specific surface area, pore volume, and surface roughness and irregularities, as calculated by nitrogen adsorption-desorption isotherms. The co-adsorption of the cationic and nonionic surfactants increased the ordering conformation of the adsorbed surfactants on bentonite, but decreased the thermal stability of the organobentonite system.

Influence of Mixed Cationic-nonionic Surfactant Systems on the Spectral Properties of C.I. Mordant Blue 29 and Its Complexes with Iron(III)

Interactions of the anionic form of C.I. Mordant Blue 29 with cationic and nonionic surfactants have been studied by absorption spectroscopy. The dye interacts strongly with oppositely charged surfactants in the pre-micellar concentration range with an accompanying change in its spectral properties, while its interaction with the polyoxyethylene group of nonionic surfactants does not have such remarkable effects. In ternary mixtures, however, the influence of the polyoxyethylene group on the optical properties of C.I. Mordant Blue 29-tetradecyltrimethylammonium bromide and C.I. Mordant Blue 29-octadecyltrimethylammonium chloride systems is quite different. In addition, the influence of the interaction between the HL(3-) form of C.I. Mordant Blue 29 and the surfactants on the formation of chelate complexes with iron(III) has been studied. The optimized structures of Fe-Mordant Blue 29 complexes are also reported herein. Geometries have been calculated by the Hartree-Fock method with the cc-pVDZ basis set.

Enhanced soil retention for o-nitroaniline by the addition of a mixture of a cationic surfactant (Cetyl Pyridinium Chloride) and a nonionic surfactant (Polyethylene Glycol Mono-4-nonylphenyl Ether)

The sorption enhancement of o-nitroaniline on a soil by the addition of a mixture of a cationic surfactant (Cetyl Pyridinium Chloride, CPC) and a nonionic surfactant (Polyethylene Glycol Mono-4-nonylphenyl Ether, P0707), as compared with that by individual CPC and P0707, was investigated to examine their potential application in soil retarding for organic contaminants. The maximum sorption coefficients ( K d * ) of o-nitroaniline on modified soils by individual CPC and P0707 were 110 mL g −1 at an added CPC dose of 6000 mg L −1 and 12.5 mL g −1 at an added P0707 dose of 7000 mg L −1, respectively. They were approximately 78 and 8.87 times higher than the sorption coefficients ( K d ) of o-nitroaniline on the un-modified soil (1.41 mL g −1), suggesting that CPC and P0707 can enhance the sorptive capacity of soil for o-nitroaniline. The maximum K d * value of o-nitroaniline on modified soils by the mixture of CPC and P0707 was 144 mg L −1 (at CPC dose of 10,500 mg L −1 and P0707 dose of 6000 mg L −1), which is higher than that on the CPC (or P0707) modified soils and approximately 102 times higher than that on the un-modified soil. Therefore, mixed cationic–nonionic surfactants could be better than individual ones in soil modification to enhance retention of organic contaminants.

Mixed Cationic-Nonionic Surfactants Route to MCM-48: Effect of the Nonionic Surfactant on the Structural Properties

Structurally ordered MCM-48 silicas were facilely synthesized using the mixtures of cetyltrimethylammonium bromide (CTAB) and p-Octyl polyethylene glycol phenyl ether (OP-10) as co-templates with low molar ratio of CTAB to silica (0.139:1) and low concentration of mixed surfactants (ca. 5%) and within a wide range of OP-10/CTAB ratio (0.08–0.25). For comparison purpose, the cubic material was also prepared with only CTAB as the structure-directing agent under the same preparation conditions. The products obtained by different templating method were thoroughly characterized by XRD, N2 sorption, TEM, TG-DSC and 29Si MAS NMR. Measurement results from these techniques indicated that the introduction of nonionic OP-10 had significant effect on the structural properties of MCM-48 and the mixed surfactants' route allowed an efficient synthesis and a more condensed product compared to the only cationic CTAB templating protocol. Finally, our preliminary explanation for that why cubic MCM-48 materials could be obtained in this system and structural properties were sensitive to the OP-10/CTAB ratios was discussed in detail.

Mixed Cationic‐nonionic Surfactants and pH Adjustment Route to Synthesize High‐quality MCM‐48

AbstractUsing the mixture of cetyltrimethylammonium bromide (CTAB) and p‐Octyl polyethylene glycol phenyl ether (OP‐10) as templates, siliceous MCM‐48 materials can be synthesized with low molar ratio of CTAB to silica (0.139:1) and low concentration of mixed surfactants (ca.5%) and within a wide range of OP‐10/CTAB ratio (0.08˜0.25). The materials were characterized by X‐ray powder diffraction, N2 adsorption/desorption isotherm, TEM, TG‐DSC and 29Si MAS NMR. Measurements indicated that the use of mixed surfactants allowed better condensation and higher ordering of the cubic mesostructure; at the same time, some properties of these materials were sensitive to the OP‐10/CTAB ratio. It was also found that the reduced pH of the gel which had been crystallized for a certain time gave a highly reproducible synthesis with a high silica yield (about 95%). Furthermore, the reaction mechanism of the synthesis is discussed in detail.