Dodecyl Ammonium Research Articles

Floatability of rare earth phosphors from waste fluorescent lamps

Zeta-potential measurements were made to determine the electric state of phosphor materials on the basis of which a feasibility study could be performed for the use of flotation in the recovery of fine ( d 50 < 13 μm) rare earth phosphors from waste fluorescent lamps. Tests were carried out with pure specimens of white (calcium halo-phosphate), red, green and blue (rare earth) phosphors, with a 17 : 1 : 1 : 1 ratio of their mixture, and with actual waste phosphor materials. The effects of a cationic (dodecyl ammonium acetate, DAA) and two anionic (sodium dodecyl sulfate (SDS) and sodium oleate (NaOl)) collectors on the floatability of materials, as well as that of Na 2SiO 3 dispersant on the separation characteristics, were investigated at different pH ranges. The process, applied to actual discarded waste phosphors gave, in a two-stage separation scheme, sink products assaying 17.7–23.8% and 21.5–25.9% rare earth phosphors for DAA and SDS flotation, respectively. The recovery and Newton's efficiency were about 70–90% and 0.26–0.37, 66–82% and 0.18–0.20, respectively for DAA and SDS flotation.

Preparation and properties of radiation crosslinked natural rubber/clay nanocomposites

Radiation crosslinking of natural rubber (NR)/clay nanocomposites was studied by using Standard Malaysian Rubber (SMRL) grade natural rubber and sodium montmorillonite (Na-MMT) clay that had been modified with cationic surfactants, dodecyl ammonium chloride (DDA) and octadecylamine ammonium chloride (ODA). The NR/clay nanocomposites were prepared by melt mixing to produce NR/Na-MMT, NR/DDA-MMT and NR/ODA-MMT composites. X-ray diffraction results indicated the intercalation of the NR into silicate nano-size inter-layers for NR/DDA-MMT and NR/ODA-MMT nanocomposites. An optimum electron beam dose of 250 kGy for crosslinking of NR, NR/DDA-MMT and NR/ODA-MMT was determined by gel content and tensile strength measurements. Upon electron beam irradiation, the tensile modulus of the nanocomposites keeps increasing with the increase of clay content up to 10 phr. However, the tensile strength and gel content of the nanocomposites show optimum values at a range of 3.0–5.0 phr clay content. From these results, NR/DDA-MMT shows higher tensile strength, whereas NR/ODA-MMT exhibits higher tensile modulus. The optimum tensile strengths of NR/DDA-MMT and NR/ODA-MMT are 12.1 and 9.5 MPa, respectively. TGA studies showed that NR/DDA-MMT and NR/ODA-MMT nanocomposites have higher decomposition temperatures in comparison with the NR/Na-MMT.

Synthesis and characterization of poly(urethane‐benzoxazine)/clay hybrid nanocomposites

AbstractPoly(urethane‐benzoxazine)/clay hybrid nanocomposites (PU/Pa–OMMTs) were prepared from an in situ copolymerization of a polyurethane (PU) prepolymer and a monofunctional benzoxazine monomer, 3‐phenyl‐3,4‐dihydro‐2H‐1,3‐benzoxazine (Pa), in the presence of an organophilic montmorillonite (OMMT), by solvent method using DMAc. OMMT was made from cation‐exchange of Na‐montmorillonite (MMT) with dodecyl ammonium chloride. The formation of the exfoliated nanocomposite structures of PU/Pa‐OMMT was confirmed by XRD from the disappearance of the peak due to the basal diffraction of the layer‐structured clay found in both MMT and OMMT. DSC showed that, in the presence of OMMT, the curing temperature of PU/Pa lowered by ca. 60°C for the onset and ca. 20°C for the maximum. After curing at 190°C for 1 h, the exothermic peak on DSC disappeared. All the obtained films of PU/Pa–OMMT were deep yellow and transparent. As the content of OMMT increased, both the tensile modulus and strength of PU/Pa–OMMT films increased, while the elongation decreased. The characteristics of the PU/Pa–OMMT films changed from plastics to elastomers depending on OMMT content and PU/Pa ratio. PU/Pa–OMMT films also exhibited excellent resistance to the solvents such as tetrahydrofuran, N,N‐dimethylformamide and N‐methyl‐2‐pyrrolidinone. The thermal stability of PU/Pa were enhanced remarkably even with small amount of OMMT. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 4075–4083, 2003

EVA/clay nanocomposite by solution blending: Effect of aluminosilicate layers on mechanical and thermal properties

Ethylene vinyl acetate (EVA)/clay nanocomposites were synthesized by blending a solution of ethylene vinyl acetate copolymer containing 12% vinyl acetate abbreviated as EVA-12 in toluene and dispersion of dodecyl ammonium ion intercalated montmorillonite (12Me-MMT) inN,N-dimethyl acetamide (DMAc). X-ray patterns of sodium montmorillonite (Na+-MMT) and 12Me-MMT exhibited d001 peak at 2θ?=7.4° and 2θ?=5.6° respectively; that is, the interlayer spacing of MMT increased by about 0.39 nm due to intercalation of dodecyl ammonium ions. The XRD trace of EVA showed no peak in the angular range of 3–10° (2θ). In the XRD patterns of EVA/clay hybrids with clay content up to 6 wt% the basal reflection peak of 12Me-MMT was absent, leading to the formation of delaminated configuration of the composites. When the 12Me-MMT content was 8 wt% in the EVA-12 matrix, the hybrid revealed a peak at about 2θ?=5.6°, owing to the aggregation of aluminosilicate layers. Transmission electron microscopic photograph exhibited that an average size of 12–15 nm clay layers were randomly and homogeneously dispersed in the polymer matrix, which led to the formation of nanocomposite with delaminated configuration. The formation of delaminated nanocomposites was manifested through the enhancement of mechanical properties and thermal stability, e.g. tensile strength of an hybrid containing only 2 wt% 12Me-MMT was enhanced by about 36% as compared with neat EVA-12.

FTIR analysis of water structure and its significance in the flotation of sodium carbonate and sodium bicarbonate salts

Abstract The production of soda ash from trona resources (sodium sesquicarbonate, Na 2 CO 3 ·NaHCO 3 ·2H 2 O) has completely displaced the production of synthetic soda ash in the USA. Further, the utilization of other trona resources is under consideration in China, Turkey, etc. Recent research has been concerned with the development of flotation technology for the trona industry. In this regard studies on the flotation behavior of sodium carbonate salts: trona, sodium carbonate monohydrate and decahydrate, as well as the flotation behavior of sodium bicarbonate, are reported for both cationic (dodecyl ammonium hydrochloride) and anionic (sodium dodecyl sulfate) collectors. It has been found that strong flotation of sodium bicarbonate (NaHCO 3 ) can be achieved with 100% recovery, while the other sodium carbonate salts do not float well. These results have been explained by FTIR analysis of aqueous solutions of Na 2 CO 3 and NaHCO 3 in a range of concentrations from very dilute to saturated conditions. The changes in the shape of the O–H stretching band of water are correlated with the flotation behavior of Na 2 CO 3 salts and NaHCO 3 . In addition, the absorption band of the carbonate ion at ca. 1385 cm −1 is used to monitor its interactions with water and/or other ions in solution. The infrared results demonstrate that Na 2 CO 3 acts as a water structure maker, leading to an extensively hydrated surface that accounts for the poor flotation of most sodium carbonate salts. In contrast, NaHCO 3 does not have this characteristic and consequently complete flotation is possible with both cationic and anionic collectors. These results support the previous water structure analysis for soluble salt flotation of alkali halides and other oxyanion salts.

Growth inhibition of plant pathogenic bacteria and fungi by extracts from selected South African plant species

Extracts from 26 plant species representing 16 families, collected in the Free State Province of South Africa, were tested in vitro for their potential to inhibit the growth of eight plant pathogenic fungi and five plant pathogenic bacteria. None of the crude extracts showed any mycelial growth inhibition of the eight test fungi. All of the extracts inhibited the growth of one or more of the five plant pathogenic test bacteria, but to varying degrees. Crude extracts from Acacia karroo and Elephantorrhiza elephantina inhibited the growth of four bacteria, while that of Euclea crispa, Acacia erioloba, Senna italica and Buddleja saligna inhibited the growth of all five plant pathogenic bacteria. Of these, the crude extract of Euclea crispa was clearly superior to the rest as it compared more favourably to that of a commercial bactericide, Dimethyl Dodecyl Ammonium Chloride (DDAC). Subsequently, the Euclea crispa crude extract was fractionated by means of liquid-liquid extraction using four organic solvents, hexane, diethyl ether, chloroform and ethyl acetate, in order of increasing polarity. This was done in an attempt to assess the antimicrobial potential of the more concentrated fractions. Once again, none of the semi-purified fractions showed any antifungal activity. However, antibacterial activity was located in the more polar ethyl acetate fraction indicating that the substances involved were very similar in polarity and/or structure. From this it seems justified to further purify the ethyl acetate fraction of the Euclea crispa extract and attempt to identify the active substance(s) involved.

Synthesis and characterization of organosoluble, thermoplastic elastomer/clay nanocomposites

AbstractWe synthesized organosoluble, thermoplastic elastomer/clay nanocomposites by making a jelly like solution of ethylene vinyl acetate containing 28% vinyl acetate (EVA‐28) and blending it with organomodified montmorillonite. Sodium montmorillonite (Na+‐MMT) was made organophilic by the intercalation of dodecyl ammonium ions. X‐ray diffraction patterns of Na+‐MMT and its corresponding organomodified dodecyl ammonium ion intercalated montmorillonite (12Me‐MMT) showed an increase in the interlayer spacing from 11.94 to 15.78 Å. However, X‐ray diffraction patterns of the thermoplastic elastomer and its hybrids with organomodified clay contents up to 6 wt % exhibited the disappearance of basal reflection peaks within an angle range of 3–10°, supporting the formation of a delaminated configuration. A hybrid containing 8 wt % 12Me‐MMT revealed a small hump within an angle range of 5–6° because of the aggregation of silicate layers in the EVA‐28 matrix. A transmission electron microscopy image of the same hybrid showed 3–5‐nm 12Me‐MMT particles dispersed in the thermoplastic elastomer matrix; that is, it led to the formation of nanocomposites or molecular‐level composites with a delaminated configuration. The formation of nanocomposites was reflected through the unexpected improvement of thermal and mechanical properties; for example, the tensile strength of a nanocomposite containing only 4 wt % organophilic clay was doubled in comparison with that of pure EVA‐28, and the thermal stability of the same nanocomposite was higher by about 34 °C. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2065–2072, 2002

Phase Transition Processes in Surfactant Adsorption Layers

Adsorption data in the form of surface tension vs bulk concentration isotherms having strong changes in the slope have often been discussed in the literature in terms of phase transitions in the adsorption layer. It will be shown thermodynamically that these apparent kink points in the isotherms are unreal. A phase transition would cause a completely opposite change in the isotherm. Experimental surface tension data for sodium octanoate and dodecyl ammonium chloride obtained from the literature are reinterpreted on the basis of the Frumkin and reorientation isotherms.

A review of hematite flotation using 12-carbon chain collectors

A sample of naturally occurring, relatively pure hematite (98.5% Fe 2O 3) was used as a model for the study of the flotation of insoluble metal oxides. The isoelectric point of this sample was 2.7 and the point of zero charge was 6.7. A number of surfactants containing saturated 12-carbon chain groups were used as collectors over a wide range in pH. The flotation of this hematite with dodecanoic acid (lauric acid) showed a maximum recovery in the pH range 6–8.5, a sudden drop at pH 9, and a steady increase in recovery as the pH was raised from 9–12. The flotation of the hematite using potassium dodecyl hydroxamate showed a maximum recovery at pH 5.5, with little flotation at pH <3. At pH >10, the recovery fell except at high additions of collector. The flotation of hematite using sodium dodecyl sulphate showed a high recovery for pH <6, a trough in recovery between pH 7 and 9, and a secondary maximum in recovery at pH 10. Different flotation behaviour was observed when sodium dodecyl benzyl sulphonate was used. Using ARMAC C, (a commercially available dodecyl ammonium acetate), a flotation maximum was observed at pH 8, with steadily decreasing recovery as the pH was raised or lowered from this value. These results are discussed in terms of the surface chemistry of the hematite and the solution chemistry of the various collectors used.

New cationic surfactant as corrosion inhibitor for mild steel in hydrochloric acid solutions

The inhibiting effect of cationic surfactant N, N, N‐dimethyl 4‐methylbenzyl dodecyl ammonium chloride on mild steel in hydrochloric acid solutions was investigated by surface and thermodynamic measurements, weight loss tests, polarization measurements and EDS techniques. The data obtained from surface and thermodynamic measurements with the inhibitor indicate that the area per molecule slightly increases with increasing temperature and both absorption and micellization processes are spontaneous. Weight loss measurement showed that the inhibition efficiencies increased with increasing surfactant concentration and attained a maximum around their critical micelle concentration. Polarization studies reveal that the inhibitor behaves as a mixed type in hydrochloric acid solutions and acted on the cathodic reaction without modifying the mechanism of the hydrogen evolution reaction. EDS measurement showed high coverage of surfactant on the mild steel surface.

Intelligent networks based on poly(oxyethylene)

AbstractFilms of PEO and PEO blends were efficiently crosslinked by exposure to ultraviolet radiation with high‐pressure mercury lamp. Photochemical crosslinking proceeded in the presence of photoinitiator such as benzophenone or pentaerythritol triacrylate. PEO networks obtained by UV irradiation in the presence of potassium salts (thiocyanate, perchlorate and triflate) as templates showed enhanced cation binding ability for Li+ and Na+ cations. Cationic networks were prepared from crosslinked PEO modified with ethyl methacrylate dimethyl dodecyl ammonium bromide. Stimuli‐sensitive hydrogels (pH and temperature) were prepared from combinations of PEO and poly‐N‐isopropyl acryl amide, polyvinyl methyl ether, polyvinyl acetate and poly‐2‐vinyl pyridine subjected to UV irradiation.

Dielectric study of sodium dodecyl sulphate (SDS) adsorption onto galena. Comparison with sodium amyl xanthate and dodecyl ammonium chloride

The strong decrease of the permittivity of powdered galena with the addition of sodium dodecyl sulphate (SDS) can be linked, as in the case of sodium amyl xanthate, to the chemical nature of its bond with the galena surface: physical adsorption of dodecyl ammonium chloride has no dielectric effect in the range 0.4–100 MHz. Voltammetry and electrokinetic measurements show that the adsorption is independent of potential, contrary to the case of xanthate, and results from an exchange between SDS and anionic species onto the surface. X-ray photoelectron (XPS) and diffuse reflectance by infrared Fourier transform (DRIFT) spectroscopies have been investigated to identify the species responsible for the collection mechanism.

Untersuchungen zum Verhalten von Dodecylammoniumchlorid ın Gegenwart von Additiven / Studies on dodecyl ammonium chloride in the presence of additives

The micellar behaviour of the cationic surfactant dodecyl ammonium chloride (DAC) was determined in different concentrations of methanol, propanol-1, butanol-1, butanol-2, t-butanol in water as well as in pure water at 30°C and also in 0.5 M alkanol + water systems within the range of 30 to 45°C by conductivity and surface tension measurements. Various thermodynamic parameters could be evaluated.

Volumeneigenschaften der Mischungen von N-Alkylammoniumchloriden und Na-Dodecylsulfat / The volumetric properties of mixtures of N-alkylammonium chlorides and sodium dodecyl sulphate

The densities of octyl, dodecyl and hexadecyl ammonium chlorides sodium dodecyl sulphate and aqueous solutions of these surfactants and their mixtures were determined. From the results obtained, the apparent molar and molecular volumes were determined and compared to those calculated theoretically on the basis of the length and width of the surfactant molecule and the apparent intermolecular distance. Good agreement was found between the molecular volume of the surfactants in the solid state determined from density and calculated theoretically. By comparison of the theoretical and experimental molecular volume of the surfactants, the influence of the octyl and hexadecyl ammonium chlorides and sodium dodecyl sulphate on the c.m.c. of dodecyl ammonium chloride was deduced. It was found that the presence of octyl ammonium chloride in an aqueous solution of dodecyl ammonium chloride increases its c.m.c., but the presence of hexadecyl ammonium chloride and sodium dodecyl sulphate decreases it.

Micelle Formation of Dodecylammonium Surfactant with Mixed Counterions: Perfluorocarboxylate and Alkanesulfonate Ions

Micelle formation was studied for four mixing combinations of dodecylammonium (DA) salts having perfluorocarboxylate ions (trifluoroacetate (PA) and pentafluoropropionate (PP) and alkane sulfonate ions (methane sulfonate (MS) and ethane sulfonate (ES)) as their counterions, i.e., DAPA/DAMS, DAPA/DAES, DAPP/DAMS, and DAPP/DAES. The fluorocarbon anions as counterions exhibited that the degree of counterion binding to micelle (β) as well as the extent of stabilizing micelles and lowering ability of critical micellization concentration (CMC) are greater than hydrocarbon anions. The “mixed micelle formation” was examined in terms of CMC as a function of mole fraction (Xi) in each surfactant mixture. The CMCs of the mixed surfactant systems studied here, correspond to those of “surfactant with mixed counterions”. However, by regarding tentatively those combinations as binary mixed surfactant systems, the CMC vsXicurves (singly dispersed phase curves) as well as CMC vs micellar composition (Yi) curves (micellar phase curves) were simulated by applying the present authors’ and Rubingh's equations which have been derived respectively with and without taking into account mutual added-salt effect (or the β value for each pure system). A negative deviation from ideal mixing was observed for each combination, indicating that mixing of fluorocarbon anion with hydrocarbon anion as counterion of DA salts results in more stabilized micelle formation. Plotting the derivative of specific conductance (κ) by total concentration of surfactant (Ct),dκ/dCtagainstCt, the curves showed a constant value at the sufficiently higher concentration range than CMC, and the constant values were found able to be related to the degree of dissociation of micelles (α). Even for the mixed systems, the α or β values were estimated from the conductivity data. The greater power to stabilize micelle formation by fluorocarbon ions was interpreted on the basis of concept of “contact hydrophobic interaction” proposed by Mukerjee (Mukerjee, P.,Colloids Surf. A: Physicochem. Eng. Aspects84,49 (1994)).

The Influence of Surfactants on the Crystallization of Calcium Oxalate Hydrates

Abstract The influence of sodium dodecyl sulphate, SDS, dodecyl ammonium chloride, DDACl and octaethylene glycol mono-n-hexadecyl ether, C16EO8, on the crystallization of calcium oxalate from 0.3 molar sodium chloride solutions is discussed. Under the given experimental conditions the thermodynamically stable monohydrate, COM was the predominant crystal form. Both ionic surfactants inhibited growth and aggregation of COM and, by preferential adsorption at different crystal faces, induced different habit modifications. In addition, micellar solutions of SDS promoted crystallization of the metastable calcium oxalate dihydrate, COD. The nonionic surfactant, C16EO8, stimulated nucleation and/or initial crystal growth of COM, most probably by providing active centers for heterogeneous nucleation.

Kinetics of Adsorption of Protein at the Oil-Water Interface in the Presence of Cationic and Anionic Surfactants

The interfacial tension (γ) of heptane-water system has been measured as functions of time (t) at a fixed concentration (C l p ) of protein bovine serum albumin at a given value of pH, ionic strength and temperature. The concentration C l s of anionic surfactant SDS and those of cationic surfactant cetyl trimethyl ammonium bromide cetyl pyridinium bromide, myristyl trimethyl ammonium bromide and dodecyl trimethyl ammonium bromide respectively have been kept constant during the measurement of interfacial tension lowering (Π). From the rate of change of Π with t, the first order rate constants k 1 and k 2 for the adsorption process have been evaluated for low and high ranges of time. Values of k 1 depend upon magnitude of C l s . pH and ionic strength of the medium. The effect of hydrocarbon chain length and the nature of hydrophillic group of the surfactant, on k 1 have been examined at different values of pH and ionic strength of the medium. The values of k 2 are found to be insensitive to the charge of all these parameters reason of which has been discussed. The data have been analysed by Ward-Tordai-McRitchi-Alexander equation for the estimation on area (ΔA) swept out by surfactant bound protein molecule during the protein adsorption at oil-water interface.

Zeta potential measurement of muscovite mica basal plane-aqueous solution interface by means of plane interface technique

The zeta potentials of muscovite mica basal plane were investigated by means of the plane interface technique as a function of pH in the presence of 0.001 M KCl, compared with those of fused silica. For the plane interface technique, the negative zeta potentials of a large muscovite mica sheet, i.e., the mica basal plane, were uniformly higher in magnitude than those of a large silica plate over the pH range from 2 to 11, whereas the zeta potentials of the mica basal plane were markedly dependent on pH in the pH range of 3 to 6. In the pH range of 2 to 3, the zeta potenteials of the mica basal plane showed remarkably negative values of −80 to −60 mV and became more insensitive to the reduction in pH. In particular, we could not observe the presence of an isoelectric point (iep) of the mica basal plane, which has never been encountered normally in the case of pure oxides. For comparison, the electrophoresis measurements were made for both mica and silica particles. The negative mobility zeta potentials of mica particles were smaller in magnitude than those of fused silica particles in the pH range of 3 to 11 even though the positively charged alumina-type sites on the mica particles were neutralized by sodium dodecyl benzene sulfonate (SDBS). This result was quite the reverse of the trend obtained from the plane interface technique. However, the variation in flotation recovery of the muscovite mica with dodecyl ammonium chloride (DAC) as a collector at pH 3 was very consistent with that of crystalline quartz (ζ ∼ −65 mV) with dodecyl trimethyl ammonium bromide (DTAB) at pH 7.4. This observation provided justification for the remarkably negative zeta potential (∼ −75 mV) of the mica basal plane obtained from the plane interface technique at pH 3.

Micellar effects on the alkaline hydrolysis of N‐alkyl‐4‐cyanopyridinium ions. An example of micelle‐induced regiochemical selectivity

AbstractThe rates of the reaction of N‐alkyl‐4‐cyanopyridinium (RCP) ions [alkyl = CH3 (MCP), n‐C4H9 (BCP), n‐C8H17 (OCP), n‐C12H25 (DCP)] with OH− ion in water are independent of chain length and RCP concentration up to 0.001 M. The ratios of the concentrations of the reaction products, N‐alkyl‐4‐pyridone (P) and N‐alkyl‐4‐carboxamidopyridinium (A), P/A, are similar for all substrates. In water the P/A ratios increase with pH, reaching a plateau value of ca 2 at pH ≥ 13. Added salts slightly decrease the reaction rate and do not affect the P/A ratios. In aqueous solutions, addition of dioxane increases both rates and P/A ratios. Micelles of hexadecyltrimethylammonium bromide (cetyltrimethylammonium bromide; CTAB) and 3‐(N,N‐dimethyl dodecyl ammonium)propane‐1‐sulphonate (SDP) catalyse the alkaline hydrolysis of OCP and DCP and increase the yield of pyridone with BCP, OCP and DCP. In micellar CTAB and SDP the attack of OH− on RCP occurs almost exclusively at the 4‐position of the pyridinium ring. Sodium dodecyl sulphate micelles inhibit the reaction and produce small changes in the P/A ratio. The regiochemical selectivity produced by micelles, leading to a preference for the attack of OH− at the pyridinium ring, was rationalized in terms of the low effective dielectric constant at the micelle–water interface.

Arsenic Exposures in Mississippi: A Review of Cases

Arsenic poisonings occur in Mississippi despite public education campaigns to prevent poisonings in the home. We reviewed 44 Mississippi cases of arsenic exposures occurring from January 1986 to May 1990. We compared the epidemiologic differences between unintentional and intentional poisonings. Cases were found and characterized through the two toxicology laboratories and hospital records. Arsenic-based rodenticides were the arsenic source in 23 of the 44 exposures. Other sources were monosodium methylarsenate (4 cases), dodecyl ammonium methane arsonate (5 cases), and other compounds (12 cases). Of the 44 exposures, 27 were unintentional, 7 were suicide attempts, 6 were homicide attempts, and 4 were of unknown intent. Of the 27 unintentionally exposed patients, 19 were black and 14 were male; their median age was 3 years. Of the 13 intentionally poisoned persons, 9 were male and 10 were black, with a median age of 28 years. Six of the seven patients who attempted suicide were white; four of the six victims of attempted homicide were black. We recommend removal of remaining bottles of arsenic-based rodenticides from store shelves, and we urge practicing physicians to warn patients of the dangers of using such rodenticides.