Hexadecyl Pyridinium Research Articles

Investigation of Water Capillary Rise in Soil Columns Made from Clay Mineral Mixtures Pretreated with Cationic Surfactants

The study of the environmental pollution effect of surfactants is very important. Surfactants modify the wetting, surface tension, and capillary pore system of soil grains depending on their characteristics. During the research, the surface modification effect of a cationic surfactant (hexadecyl–pyridinium–chloride) was analyzed on mineral mixtures series assembled in various ratios with decreasing clay content (bentonite–loess–sand, kaoline–loess–sand). Cationic surfactants are adsorbed on the inner and outer surfaces of phyllosilicates, which could result in swelling. Our results were evaluated on the basis of the interfacial (surface tension of liquid phase, contact angle) and soil physical characteristics of the examined samples. The wetting properties and structural changes (eliminating the surface modification effect of humic materials) of mineral mixtures treated with surfactants were studied on the basis of capillary water rise. The results of our research could be used to interpret the water features of surfactant-polluted soils.

Organic cation exchanged montmorillonite and vermiculite as adsorbents for Cr(VI): Effect of layer charge on adsorption properties

The binding of anions at interlayer sites of organo-clay minerals is supposed to be stronger and more specific than on the external surfaces. In this study the Cr(VI) adsorption properties of two hydrous phyllosilicates, a montmorillonite and a vermiculite modified with Hexadecylpyridinium (HDPy), Hexadecyltrimethylammonium (HDTMA) and Benzethonium (BE) were investigated at pH 3–9. Structural features were determined by X-ray diffraction. The surface charge of the organo-clays at different pH was analyzed by polyelectrolyte titration in the cell of a particle charge detector. The effect of competing anions Cl−, NO3− and SO42− on Cr(VI) adsorption was determined.The interlayer space structures of the organo-vermiculites were paraffin-type, whereas it was pseudotrimolecular for the organo-montmorillonites. Besides organic cations also considerable amounts of inorganic cations were present in the interlayer space. As a consequence of organic cation treatment the surface charge of the clays shifted from negative to positive values up to 269mmolckg−1; it was highly affected by the specific surface area, layer charge and pH. Depending on the kind of organic cation, organo-vermiculites and -bentonites showed comparable adsorption capacity for Cr(VI), which was at pH 4.5 0.38 and 0.30molkg−1 for HDPy- and HDTMA-vermiculites, respectively and 0.37 and 0.26molkg−1 for the corresponding bentonites. For all organo-clays the adsorbed amount of Cr(VI) decreased with increasing pH. The effect of competing anions, Cl−, NO3− and SO42− on Cr(VI) adsorption appeared to be small. For organo-vermiculites a higher portion of anion adsorption sites was located in the interlayer space. In context with the high share of adsorption sites in the interlayer space it is suggested that both organo-vermiculites and organo-bentonites are promising adsorbents of Cr(VI) in water purification methods.

Synthesis of hydrothermally stable, hierarchically mesoporous aluminosilicate Al-SBA-1 and their catalytic properties

Hydrothermally stable mesoporous aluminosilicates Al-SBA-1 with hierarchical pore structure have been successfully synthesized under alkaline condition at 120 °C by employing organic mesomorphous complexes of polyelectrolyte (poly(acrylic acid) (PAA)) and cationic surfactant (hexadecyl pyridinium chloride (CPC)) as template. The Si/Al ratio could be as high as 5 and the incorporation of Al into the silica framework did not disturb the well-ordered cubic Pm ̅3n mesostructure. Meanwhile, the incorporation of Al could greatly increase the specific surface area and pore volume of the samples. The Al-SBA-1 materials exhibited a high hydrothermal stability and remained stable even after being treated in boiling water for 10 days. The catalytic activity of the Al-SBA-1 materials was investigated by employing the Friedel-Crafts alkylation of toluene with benzyl alcohol as a model reaction and they exhibited excellent catalytic property due to the incorporated acid sites and the hierarchically mesoporous structure.

Synthesis and characterization of Ni-TiO 2 composite coatings by electro-co-deposition

Ultrafine TiO 2 dispersed nickel composite coatings have been prepared by direct current deposition process on steel substrate from Watt's bath to improve the surface mechanical property of conventional nickel coating. To resist agglomeration of ultra fine particles in plating bath due to high surface free energy and to get homogeneous coating, magnetic stirring was applied during deposition with prior ultrasonic agitation. For de-agglomeration, Hexa decylpyridinium bromide (HPB) was used in varying quantity in plating bath as surfactant. Characterization of TiO 2 powder as well as microstructure, hardness and wear properties of the coatings were studied by means of XRD, SEM, microhardness tester and ball-on-plate type wear tester. TiO 2 incorporation in the coatings was uniform and dispersion of TiO 2 was below 100 nm size along with the faceted nickel matrix. Selective amount of HPB addition produces hard orientation of nickel in the composite coating along with better TiO 2 co-deposition rate leading to higher microhardness and wear resistance. Wear is mainly adhesive in nature and the worn out TiO 2 particles shift it nominally to abrasive mechanism.

The Effect of Surface Charge and Wettability on H2O Self Diffusion in Compacted Clays

AbstractOrgano-clays are of interest in the modification of anion transport properties in engineered barriers. In the present study, surface charge and wettability were assessed for tracking changes in the effective diffusion coefficient (Deff) by the formation or suppression of bound H2O layers on the external surfaces of clays. Bentonite samples modified with three different organic cations in amounts of 0 to 400% of the cation exchange capacity were used. Diffusive transport was determined in H2O→D2O exchange experiments in a newly constructed cell adapted to the attenuated total reflectance (ATR) accessory of a Fourier-transform infrared (FTIR) spectrometer at two different dry bulk densities and various degrees of water saturation.All organo-clay combinations showed changes in surface charge after the addition of organic cations, from a negative value of 99 mmolc/kg for the original bentonite to a maximum positive value of 230.5 mmolc/kg for hexadecylpyridinium (HDPy)-montmorillonite. The positive charge resulted from adsorption of the organic cation in excess of the CEC. Hydrophobic surface properties with contact angles >90° were obtained for HDPy-montmorillonite samples with monolayers of organic cations on the external surfaces only. Here, where hydrophobicity suppressed the formation of bound H2O layers, the largest Deff o f 2.7×10−10 m2/s was observed in the high dry bulk density range (1.0–1.5 g/cm3) under water-saturated conditions. In the low dry bulk density range (0.6–0.9 g/cm3) this effect was weakened significantly because, with increasing pore size, the effect of bound H2O layers was reduced. In the high dry bulk density range at partial water saturation (40%), diffusive transport was hindered by the small water volume. Previous work found that, in the high dry bulk density range and water-saturated state, Deff was 2.4×10−11 m2/s for the original bentonite. Deff for all hydrophilic organo-clay samples was ⩽2.1×10−11 m2/s, somewhat less than for the hydrophobic sample. In hydrophilic organo-clay samples, retardation factors that retard the value for Deff, up toa magnitude of 0.5, include an increase in dry bulk density and a decrease in water saturation. In the water-saturated state at high dry bulk densities, hydrophobic surface properties suppressing the formation of bound H2O layers can increase Deff by one order of magnitude.

Inhibition effect of hexadecyl pyridinium bromide on the corrosion behavior of some austenitic stainless steels in H2SO4 solutions

The inhibition effect of hexadecyl pyridinium bromide (HDPB) as a cationic surfactant on the corrosion behavior of some Egyptian austenitic stainless steel SS 304L, SS 316H and SS 304H in 0.5M H2SO4 solutions was investigated by using potentiodynamic polarization technique and electrochemical impedance spectroscopy (EIS). The results indicate that HDPB is a good inhibitor for the samples under investigation in 0.5M H2SO4 solutions. In addition, the inhibition efficiency η% increases with the inhibitor concentration while decreases with the increasing temperature referring to physical adsorption. The adsorption of the inhibitor obeys a Temkin adsorption isotherm. Polarization curves show that HDPB is a mixed inhibitor in H2SO4 solutions. The results obtained from polarization and impedance measurements are in good agreement. Activation-free energies, enthalpies, and entropies for the inhibition process of HDPB were determined.

Determination of diffusive transport in HDPy-montmorillonite by H2O-D2O exchange using in situ ATR-FTIR spectroscopy

AbstractThe anion adsorption capability of clays can be improved significantly by modification with certain organic cations. However, surface properties and the microstructure of the clay might change and limit the use of organo-clays in barrier systems. In this study an experimental setup is introduced which allows the rapid determination of effective diffusion coefficients (Deff) for H2O in clay samples. H2O→D2O exchange experiments on hexadecyl-pyridinium (HDPy)-montmorillonite samples were performed in a diffusion cell attached to the ATR unit of a Fourier-transform infrared spectrometer. The mean Deff for H2O in a D2O-saturated original montmorillonite is 2.44 × 10–11 m2/s in the bulk density range of 1.1–1.8 g/cm3. Hydrophobic surfaces increase the diffusivity only at high bulk densities in the saturated state. The mean Deff is lower when HDPy is applied in amounts ⩾80% of the cation exchange capacity in comparison with the original sample. At a saturation degree of the pores of 40%, Deff for all samples is one order of magnitude less than in the saturated state. Results on Deff obtained by ATR-FTIR spectroscopy are in good agreement with through-diffusion studies.

Controllable Formation of Nanorods through Electrostatic-Assisted Assembly of Star Poly(methacrylic acid) Induced by Surfactants

Star poly(methacrylic acid) (Star-(PMAA)6) was prepared by hydrolysis of star poly(tert-butyl methacrylate) (Star-(PtBMA)6). The self-assembly behaviors of Star-(PMAA)6 induced by surfactant hexadecyl pyridinium chloride (HDPC) were investigated. It is of great interest that rodlike aggregates with different lengths and diameters could be obtained from the complexation of Star-(PMAA)6 and HDPC by adjusting the length of the polymer arm and the ratio of [HDPC]/[carboxyl group] in the system. The self-assembly mechanisms for the formation of rodlike aggregates were discussed.

Photochemical Corrosion Inhibition of Mild Steel in Acid Mine Water

Abstract The corrosion inhibition of mild steel in acid mine water of pH 2.5 containing ferric and cupric ions with inhibitors such as urea ([NH2]2CO), guanylurea sulfate (C4H12N8O2·H2SO4), benzotriazole (C6H5N3), butylamine (C4H11N), hexadecyl pyridinium chloride (C21H38ClN·H2O), thiourea (CH4N2S), and potassium oxalate (K2C2O4·H2O) was studied. Thiourea and potassium oxalate gave 77% and 93% inhibition, respectively. Thiourea reduced ferric ions in solution and produced a sulfide film that caused hydrogen embrittlement. Corrosion inhibition by potassium oxalate was photosensitive due to the formation of a trisoxalato iron complex followed by photodecomposition to β-ferrous oxalate and its deposition on the steel sample, thereby inhibiting the corrosion of the steel. The mechanism of this first example of photochemical inhibition is postulated.

Significance of the long-chain organic cation structure in the sorption of the penconazole and metalaxyl fungicides by organo clays

Sorption–desorption of two different hydrophobic fungicides, penconazole and metalaxyl, by a series of clay minerals layered and non-layered (montmorillonite, illite, kaolinite, muscovite, sepiolite and palygorskite) modified with the two-chain cationic surfactant, dihexadecyldimetylammonium (DHDDMA) was studied by first time in this work. DHDDMA-clays showed a good capacity to sorb both fungicides from water. Freundlich sorption constants ( K f) increased 22–268-fold for penconazole and 4–112-fold for metalaxyl in relation to natural clays. High sorption irreversibility was observed for penconazole for all modified clays, while for metalaxyl this occurred only for some of the modified clays. Additionally, a comparative study of the sorption of the fungicides by clay minerals modified with organic cations of different structure was carried out by a statistical approach. Non-layered and layered clay minerals modified with the two-chain alkylammonium organic cation DHDDMA, and with single-chain organic cations octadecyltrimethylammonium (ODTMA) and hexadecylpyridinium (HDPY) were used as sorbents. The study indicated a significant linear regression between the distribution coefficients K d of fungicides and the organic carbon (OC) content of the organo clays ( r 2 ≥ 0.80, p < 0.001). According to this sorption of fungicides by partition between the aqueous solution and the organic medium created by the alkyl chains of the exchanged ammonium cations regardless of the type and structure of these cations is suggested. However, linear relationships between K d values of each pesticide by the different organo clays and their relative OC contents revealed higher increase in sorption for HDPY-clays (penconazole) and for ODTMA-clays (metalaxyl) pointing out different effectiveness of the OC provided by each organic cation. These effects were also supported by the values of K d relative to OC, K d oc . The results evidenced the different relative weight of alkyl cations to make organo clays effective barriers to prevent the mobility of pesticides from a point source of pollution.

Simultaneous Separation of Two Oxyanions from Their Mixture Using Micellar Enhanced Ultrafiltration

Surfactant‐based separation of two oxyanions (Cr2O7 = and MnO4 −) from their mixture is studied to assess the potential of micellar enhanced ultrafiltration (MEUF). Cetyl(hexadecyl) pyridinium chloride (CPC) has been taken as the cationic surfactant. An organic polyamide membrane of a molecular weight cut off of 1000 is used. About 99% retention of the solutes is observed under unstirred batch mode. In order to improve the permeate flux and the retention of the solutes, cross‐flow studies are also conducted. The retention of solutes without using surfactant varies from 6 to 15% only, at a typical feed mixture concentration of 0.05 kg/m3 for each of the two solutes. Under the same operating conditions, the solute retention increases up to 99% using surfactant micelle. The effects of various operating conditions, e.g., concentrations of surfactant and solutes, transmembrane pressure drop and cross‐flow rate (for cross‐flow experiments), etc., on the permeate flux and observed retention are studied in detail in the batch as well as in the cross‐flow mode. Surfactants present in the permeate and retentate are then recovered by a two‐step chemical treatment process. In the first step, the surfactant is precipitated by potassium iodide and in the second step, it is recovered from the precipitate by the addition of cupric chloride. Optimum amounts of potassium iodide and cupric chloride are also experimentally obtained.

Effect of the modification of natural clay minerals with hexadecylpyridinium cation on the adsorption–desorption of fungicides

Clay minerals, montmorillonite (M), illite (I), kaolinite (K), muscovite (Mu), sepiolite (S) and atapulgite (A), modified with the organic cation hexadecylpyridinium (HDPY) were studied as sorbents of two fungicides of different hydrophobicity, penconazole and metalaxyl, using adsorption–desorption isotherms. The Freundlich constant values were low for the adsorption of the fungicides by natural clays and increased when the minerals were saturated with the organic cation. In HDPY-M, the K f constant increased 190-fold for the adsorption of penconazole and 67-fold for the adsorption of metalaxyl. Adsorption of the fungicides by the organo-clays at an initial concentration of 25 µg/mL was related to their organic matter content, the highest adsorption values being found in HDPY-M, HDPY-I and HDPY-A, and the increase in adsorption was greatest for the more hydrophobic fungicide penconazole. Desorption of fungicides from modified clays pointed to a high degree of stability for penconazole adsorbed by HDPY-M. In the remaining samples, the stability of this pesticide was low and the stability of metalaxyl adsorbed by all the organo-clays was also low. The results obtained point to the potential value of clay minerals modified with HDPY for immobilising pesticides with different degrees of hydrophobicity. Of special interest is the HDPY-M sample, which could be considered for use in clay barriers aimed at protection of soil and water pollution by hydrophobic pesticides.

Electrodeposition of Lead from Acetate Electrolyte Containing Additives

SUMMARYThe electrodeposition of lead on to steel substrates from acidic acetate electrolyte containing hexadecyl pyridinium bromide (HDPB) and sodium dodecyl sulphate (SDS) has been investigated. In the acetate electrolyte containing a combination of HDPB and SDS, lead of good quality can be deposited. The optimum operating conditions necessary to produce a highly adherent lead deposit have been found to be: pH=5.0, j = 0.33 A dm−2, T=25°C and time= 10 min. The optimum bath has a throwing power of 19.5% which is relatively high compared with that reported for Pb electrodeposited from sulphamate and fluoroborate baths. X-ray diffraction analysis shows that the Pb deposited from the acetate bath is pure and the surface morphology of the deposit shows that the lead deposited from the optimum bath is compact, non-porous and composed of fine-grains covering the entire surface.

Resistance in series model for micellar enhanced ultrafiltration of eosin dye

A study has been performed to quantify the extent of flux decline during micellar enhanced ultrafiltration (MEUF) of an acid dye (eosin red) using hexadecyl (cetyl) pyridinium chloride as the cationic surfactant. Effects of the operating conditions, e.g., transmembrane pressure drop and feed-surfactant-to-dye ratio, on the permeate flux profile and observed retention have been investigated in an unstirred batch ultrafiltration (UF) cell. A simple resistance-in-series model has been used to quantify the flux decline. From the flux decline history, it has been found that the membrane permeability decreases rapidly due to reversible pore blocking and further flux decline is caused by the growth of a gel-type layer over the membrane surface. The different resistances and growth kinetics of the gel layer have been investigated as functions of the operating conditions.

The effect of hexadecyl pyridinium bromide and hexadecyl trimethyl ammonium bromide on the behaviour of iron and copper in acidic solutions

The effect of hexadecyl pyridinium bromide (HPB) and hexadecyl trimethyl ammonium bromide (HTAB) on the corrosion behaviour of iron and copper in hydrochloric and sulphuric acid solutions has been investigated by potentiodynamic polarization and Tafel extrapolation methods. The polarization curves indicate that the two compounds behave as mixed inhibitors, but the cathode is more inhibited. HPB is more effective than HTAB in both acids; this is explained on the basis of the charge located on the nitrogen atom on the two compounds. The inhibition efficiency of the compounds investigated is more effective for iron and copper metals in HCl than in H 2SO 4, which is explained on the basis of the potential of zero charge of the metal surface and the adsorption ability of both Cl − and SO 4 2− on the metal surface.

Quenching of BSA intrinsic fluorescence by alkylpyridinium cations: Its relationship to surfactant-protein association

Alkyl pyridinium ions readily quench the fluorescence arising from Trp groups incorporated to a dipeptide (Ala–Trp) or protein (BSA). The quenching of the dipeptide fluorescence takes place with a Stern–Volmer constant of 730 M −1 in aqueous solution, irrespective of the length of the alkyl chain (octyl, dodecyl or hexadecyl). On the other hand, the quenching of BSA fluorescence strongly depends upon the length of the alkyl chain. Octyl pyridinium ion presents a normal behavior, with K SV values of 310 and 280 M −1 in aqueous solution and in presence of 8 M urea, respectively. These values are independent of the protein concentration. Dodecyl and hexadecyl pyridinium ions are considerably more efficient as quenchers. Stern–Volmer plots show a strong upward curvature, the quenching efficiency decreases when the protein concentration increases, and is considerably reduced in presence of salt (phosphate) or urea. These results are explained in terms of a static quenching between the adsorbed alkyl pyridinium and the excited Trp groups. From the dependence of the quenching efficiency with the protein concentration it is obtained the alkyl pyridinium/BSA association constant. The values obtained indicate that the binding is dominated by hydrophobic (dependence with the alkyl chain length and urea concentration) effects and, in minor degree, by electrostatic interactions.

N2 and CO2 Adsorption by TMA- and HDP-Montmorillonites

N2 and CO2 gases adsorption by tetramethylammonium(TMA)-montmorillonites and hexadecylpyridinium(HDP)-montmorillonites was carried out using volumetric equipment at 25 °C and 0.1 MPa. The addition of organic compounds to montmorillonites was 1 and 4 times the cation exchange capacity (CEC) of the montmorillonites and the contact times between the TMA (or HDP) and the montmorillonites were 4 and 24 h. The adsorptions of CO2 by TMA-montmorillonites (0.383-0.477 mmol/g) were higher than those by HDP-montmorillonites (0.027-0.060 mmol/g). N2 gas retentions by organo-montmorillonites were small: in the range of 0.038-0.065 mmol/g TMA-montmorillonites and around 0.010 mmol/g HDP-montmorillonites. The interlamellar spacing of the organo-montmorillonites, the structure of the intercalated organic molecule, and the type of montmorillonites influenced the gas adsorption values.

Interaction of a Bacterial Endotoxin with Different Surfaces Investigated by in Situ Fourier Transform Infrared Attenuated Total Reflection Spectroscopy

The interaction of negatively charged lipopolysaccharide (LPS) from Pseudomonas aeruginosa (serotype 10) with different kinds of surfaces was investigated by FTIR ATR spectroscopy. The surfaces comprise a hydrophilic germanium plate, a hydrophobic dipalmitoylphosphatidic acid (DPPA) monolayer, a positively charged cross-linked aminopropyltriethoxysilane (ATS) polymer, and a positively charged lipid bilayer consisting of a DPPA inner monolayer attached to the internal reflection element (IRE) and an outer monolayer consisting of equal molar amounts of palmitoyloleoylphosphatidylcholine (POPC) and hexadecylpyridinium (HDPyr) as positively charged component. Whereas the hydrophilic and negatively charged LPS exhibited only weak adsorption to a hydrophilic Ge IRE and to a hydrophobic DPPA monolayer, it bound strongly to the positively charged surface of ATS and interacted also with the POPC/HDPyr membrane. However, in the latter case, the positively charged component (HDPyr) turned out to be not sufficiently strong anchored in the lipid matrix, because it was completely extracted by the endotoxin. The remaining POPC layer exhibited a significantly reduced molecular ordering compared with a compact POPC monolayer. The results demonstrate distinct interactions of the negatively charged LPS with positively charged surfaces and the ability of LPS to remove positively charged molecules from a biomembrane.

Evaluation of shale and organoclays as sorbent additives for low-permeability soil containment barriers.

A natural shale and four synthetic organoclays were compared as potential sorbent additives to containment barriers at hazardous waste sites. Trimethylphenyl ammonium bentonite (TMPA-bent) was shown in batch experiments to have the greatest sorption capacities for 1,2,4-trichlorobenzene, trichloroethylene, and methyl isobutyl ketone, followed by the shale and a commercial organoclay. Sorption capacities were lowest for hexadecyltrimethyl ammonium bentonite (HDTMA-bent) and hexadecyl pyridinium bentonite (HDP-bent). Operative sorption mechanisms for the organoclays depended on the size of the organic modifier, i.e., uptake by the TMPA-bent occurred via adsorption onto mineral surfaces, while that for the HDTMA-bent and HDP-bent took place by absorption into organic phases formed by their long hydrocarbon tails. The shale was found to be by far the most cost-effective sorbent, an important factor for large scale applications. Solids concentration effects (i.e., higher apparent sorption capacities at lower experimental sorbent concentrations) were exhibited by HDTMA-bent and HDP-bent. This can be attributed to aggregation of sorbent particles as a result of interactions among their hydrocarbon chains. Solids effects were observed to decline and eventually disappear as sorbent concentrations were increased. Such effects must be considered in applying batch sorption results to flow-through systems.

Swelling of TMA(tetramethylammonium)- and HDP(hexadecylpyridinium)-montmorillonites in water and toluene media: influence of the type montmorillonites

Organo-clays were prepared by exchange cations of the montmorillonite with tetramethylammonium (TMA)- and hexadecylpyridinium (HDP)-chloride. Two different montmorillonite types were studied. Two amounts of each organic substances (1 and 4 cation exchange capacity times of montmorillonite) were contacted with each montmorillonite clay for 1 and 24 h. The solids were characterized by X-ray diffraction and swelling index. The swelling was measured in water and toluene media. The structural characteristics of montmorillonites changed after organo treatment and showed different behaviour in water and toluene media. The type of montmorillonite, the organic cation intercalates (TMA, HDP) and condition of treatment influenced in the different swelling in water and toluene media.