Adsorption Of Aniline Research Articles

Surface Activity of Monomeric and Polymeric (3-alkyloxy aniline) Surfactants

ABSTRACT The adsorption and micellization processes of 3-alkyloxy aniline namely [3-decyloxy aniline (C10M), 3-dodecyloxy aniline (C12M) and 3-cetyloxy aniline (C16M)] and their polymers [C10P, C12P and C16P] have been investigated using surface tension (γ) measurements at different temperatures. The synthesized monomers and polymers have been characterized by IR and elemental analysis. The surface and thermodynamic parameters of these monomeric and polymeric surfactants are investigated. The results show that the critical micelle concentration (CMC) of the polymeric surfactants is lower than that of monomers. The CMC values decreases as the hydrophobic chain lengthens for both monomeric and polymeric surfactants. The surface parameters show the ability of monomeric and polymeric surfactants to adsorb at the air/water interface and decrease the surface tension. The thermodynamic parameters reveal that the micellization process is spontaneous for all investigated surfactants. The specific conductance measurements show that the specific conductance increases with increasing chain length of the substituted alkyl groups, the synthesized polymeric surfactants have higher values of specific conductance than the corresponding monomers and the specific conductance increases with rising solution temperature.

An Investigation into the Adsorption of Aniline from Aqueous Solution Using H-Beta Zeolites and Copper-Exchanged Beta Zeolites

Zeolite beta, a large-pore zeolite, was investigated in this study with a view to examining it as a potential adsorbent for the removal of aniline from aqueous solutions. Two different metal-loaded zeolites were prepared by exchanging H-beta zeolite (SiO2/Al2O3 = 75:1) with copper. The influence of exchanged copper on the uptake level was assessed. The effect of varying the silica-to-alumina ratio of the H-beta zeolite on the aniline uptake level was also examined, using three different H-beta zeolites with ratios of 25:1, 75:1 and 150:1 as adsorbents. The sorption experiments indicated an uptake level of ca. 110–120 mg/g for each zeolite and this level was also adsorbed by the copper-modified H-beta zeolites (SiO2/Al2O3 = 75:1). In all cases, the adsorption process followed the Langmuir model for adsorption and the level of aniline adsorbed was largely unaffected by a change in temperature or the presence of extra framework copper. The stability of the exchanged copper on these zeolites was then examined by measuring the quantity of copper leached from each zeolite into solution as a function of pH. Minimum copper leaching was observed in the pH range 5–11. This provided a stable pH working range for the adsorbent materials.

Removal of aniline from aqueous solution by PVC-CDAE ligand-exchanger

The adsorption of aniline from aqueous solutions onto cobalt(II)-poly(vinyl chloride)-carboxylated diaminoethane (PVC-CDAE) resin has been studied using a mini-column apparatus at 25+/-0.1 degrees C. First of all, experimental data obtained from the breakthrough curves were tested by using the Scatchard plot analysis, to have a preliminary prediction about the types of interaction of the resin with aniline. Our aim was to determine the model which best describes the experimental data. The aspect of the Scatchard plot indicated that the aniline adsorption did not follow the Langmuir model and the presence of two types of binding sites for aniline on the resin. However, the dynamics of aniline uptake were represented by the Freundlich model reasonably well. The kinetics of aniline adsorption from aqueous solution on the cobalt(II)-PVC-CDAE have also been tested using continuous column runs and rate-controlling step of the process was determined. In this study, homogeneous diffusion model was adapted to a column system to describe the change in the aniline concentration at the column exit beginning from breakthrough point as a function of time. Kinetic studies revealed that the rate-controlling step of the aniline adsorption was predominately film diffusion controlled rather particle diffusion.

Adsorption from aqueous solution based on the synergism between hydrogen bonding and hydrophobic interactions

AbstractThe adsorption of aniline, N‐methyl aniline, and N,N‐dimethyl aniline on carboxyl resin(D152) in different media, water, ethanol, and hexane have been studied. In water the adsorption affinity of three sorbates on D152 increased with an increasing number of methyl groups on N atoms, which indicated that the adsorption of the three sorbates on D152 was driven by a hydrophobic interaction. But the adsorption enthalpy of the three sorbates exceeded the van der Waals force and was in the range of hydrogen bonding interactions, which indicated that the hydrogen bonding also played an important role. In hexane the adsorption affinity decreased with the increasing number of methyl groups on the N atom, presenting the reverse order to that in water. This fact revealed that the hydrogen bonding played a predominant role for the adsorption in hexane. In ethanol, there was no adsorption of three sorbates on D152 resin, because both the van der Waals force and the hydrogen bonding interaction between the resin and sorbate were depressed. The hydrogen bonding between resin and sorbates in water was also depressed, but the hydrogen bonding adsorption remained. This result suggested that there might be a synergetic effect between the van der Waals and hydrogen bonding interactions in the adsorption of sorbate on D152 resin in water. The synergetic effect was explained thermodynamically. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 841–845, 2005

An insight into the mechanism of selective mono- N-methylation of aniline on Cu 1− xZn xFe 2O 4: a DRIFTS study

Abstract Mechanism of selective mono-N-methylation of aniline with methanol on Cu1−xZnxFe2O4 catalysts was investigated in detail. The interaction of reactants (aniline, methanol and methanol:aniline) and possible products (N-methylaniline (NMA), N,N-dimethylaniline (DMA) and o-toluidine (OT)) on catalysts surface was studied by temperature-dependent in situ FTIR spectroscopy. Methanol adsorbs dissociatively over catalysts surface at 373 K as methoxy species and is oxidized to formate species at high temperature through dioxymethylene and/or formaldehyde as a surface intermediate species. On the other hand, adsorption of aniline:methanol mixtures shows that methanol oxidation was completely hindered in the presence of aniline. Aniline adsorbs on the Lewis acid sites at ≤373 K with phenyl ring oriented in a perpendicular manner to the catalyst surface; however, N H bond scission occurs above 373 K. A comparison of adsorbed NMA and methanol:aniline (3:1) mixture on Cu0.5Zn0.5Fe2O4 shows NMA forms from the reaction mixture at 473 K. However, maximum activity at 573 K in catalytic reaction studies suggests that desorption limits the methylation kinetics. FTIR study displays stable aniline and methyl species on ZnFe2O4 even at 573 K; however, no methyl species is detected on Cu0.95Zn0.05Fe2O4 at 473 K due to methanol reforming reaction and that limits the overall reaction and hence low catalytic activity. It is proposed that methanol is protonated on catalysts surface by the labile H+ due to N H bond scission. Co-adsorption of acidity probes with aniline and methanol indicates that aniline methylation takes place at single acid–base site.

On the Adsorption of Aromatics on Oxygenated Activated Carbon in Nonaqueous Adsorption Media

In a previous study, H‐bonding was postulated as a mechanism of adsorption for aromatics on oxygen‐containing activated carbon. To verify this, the adsorption of phenol, aniline, benzene, and nitrobenzene was studied as a function of surface oxygen groups. It was determined that there is a linear correlation between total surface acidity and adsorption capacity for H‐bonding adsorbates in cyclohexane. Flow microcalorimetry (FMC) and ultrasonic desorption tests also indicate stronger and less reversible adsorption bonds for H‐bonding adsorbates. Reversibility of adsorption decreased with increasing surface oxygen concentration, indicating a strong relationship between the oxygen groups and adsorption mechanism.

STM and XPS Studies of the Oxidation of Aniline at Cu(110) Surfaces

Aniline chemisorption at clean and partially oxidized Cu(110) surfaces at 293 K is compared with the reaction of a 300:1 aniline/dioxygen mixture at the same surface using STM and XPS. Limited dissociation occurs at the clean surface but in the presence of chemisorbed oxygen efficient oxy-dehydrogenation takes place with water desorption and the formation of chemisorbed phenyl imide (C6H5N(a)) with a reaction stoichiometry that changes with coverage. The adsorption site of the phenyl group is identified by STM to be the 2-fold hollow and it is proposed that the nitrogen is situated over the short bridge site. Chemisorptive replacement of oxygen gives a maximum phenyl imide concentration of 2.8 × 1014 molecules cm-2 at which coverage the surface is dominated by a mixture of three ordered domains with structures described by , , and unit meshes. Adsorption of aniline and dioxygen mixtures however results in phenyl imide concentrations up to 3.4 × 1014 cm-2 molecules cm-2 and a highly ordered biphasic structure characterized by and domains. A discrepancy between the concentrations measured by XPS and those calculated from the STM structures is discussed in terms of π-stacking of the phenyl rings in the adsorbed monolayer. Finally the chemistry of aniline is compared with that of ammonia and the importance of the NH bond strength and the basicity of the amine discussed.

Adsorption of Aniline from Aqueous Solution Using Copper-Exchanged ZSM-5 and Unmodified H-ZSM-5

Three medium-pore aluminosilicates were investigated with a view to examining their potential as adsorbents for the removal of aniline from aqueous solutions. H-ZSM-5 was exchanged with copper to prepare two different metal-loaded zeolites. The aqueous stability of the copper-exchanged zeolites was then examined by assessing the quantity of copper leached from each zeolite into solution as a function of pH. The optimum stability range with minimal copper leaching occurred between pH values of 5 and 9. The adsorption of aniline from aqueous solution onto each of the three zeolites was carried out within this pH window and the influence of the exchanged copper on the uptake level was assessed. The sorption experiments indicated an uptake level of approximately 40 mg/g for each zeolite. In all cases, the process followed the Langmuir adsorption model with the level of aniline adsorbed being largely unaffected by a change in temperature or the presence of extra-framework copper.

Molecular properties and intermolecular forces?factors balancing the effect of carbon surface chemistry in adsorption of organics from dilute aqueous solutions

Presented paper recapitulates the results of 6 years' study concerning the effect of carbon surface chemical composition on adsorption of paracetamol, phenol, acetanilide, and aniline from dilute aqueous solutions on carbons. Adsorption–desorption isotherms, enthalpy, and kinetics of adsorption data are shown for the measurements performed at three temperatures (300, 310, and 320 K) at two pH levels (1.5 and 7) on commercial activated carbons. The data were obtained for four carbons: the initial carbon D43/1 and forms modified by applying concentrated HNO 3 , fuming H 2 SO 4 , and gaseous NH 3 . The modification procedures do not change the porosity in a drastic way, but lead to drastic changes of the composition of carbon surface layer. By applying MOPAC (a general-purpose semiempirical molecular orbital package), the physicochemical constants characterizing the molecules of adsorbates are calculated, including the distribution of the Mulliken charges, the dipole moments and ionization potentials, and the energies of interaction with the unique positive and negative charges. They are correlated with the parameters characterizing the adsorption (and kinetics) process of studied molecules on the mentioned above carbons. The mechanisms proposed in the literature for the description of adsorption from dilute aqueous solutions are verified, and a general mechanism of adsorption is proposed.

Molecular properties and intermolecular forces—factors balancing the effect of carbon surface chemistry in adsorption of organics from dilute aqueous solutions

Presented paper recapitulates the results of 6 years' study concerning the effect of carbon surface chemical composition on adsorption of paracetamol, phenol, acetanilide, and aniline from dilute aqueous solutions on carbons. Adsorption-desorption isotherms, enthalpy, and kinetics of adsorption data are shown for the measurements performed at three temperatures (300, 310, and 320 K) at two pH levels (1.5 and 7) on commercial activated carbons. The data were obtained for four carbons: the initial carbon D43/1 and forms modified by applying concentrated HNO3, fuming H2SO4, and gaseous NH3. The modification procedures do not change the porosity in a drastic way, but lead to drastic changes of the composition of carbon surface layer. By applying MOPAC (a general-purpose semiempirical molecular orbital package), the physicochemical constants characterizing the molecules of adsorbates are calculated, including the distribution of the Mulliken charges, the dipole moments and ionization potentials, and the energies of interaction with the unique positive and negative charges. They are correlated with the parameters characterizing the adsorption (and kinetics) process of studied molecules on the mentioned above carbons. The mechanisms proposed in the literature for the description of adsorption from dilute aqueous solutions are verified, and a general mechanism of adsorption is proposed.

Pervaporation properties of humic acid-added membranes

The saving and recycling of chemical substances, which may be hazardous to human health and ecosystems, constitute a desirable goal worldwide. It is important to use a natural polymer that has a highly specific function and an environmental friendliness. In this study, humic acid was added to a natural polymer, a pectin membrane, and a hydrophobic poly(1-trimethylsilyl-1-propyne) (PMSP) membrane to enhance the affinity for phenol or aniline. Also, the separation performance, based on the membrane materials and methods of addition, was investigated. The effect of the adsorption of phenol and aniline by humic acid was investigated. A high rate of aniline adsorption was observed. The interaction of the humic acids and the aniline was mainly observed by polar bonding. For the PMSP membrane with humic acid added to the surface, the humic acid exists in a colloidal state. During pervaporation, the permeation of water was prevented by the adsorbed solute. Because the permeability of aniline increased and the permeability of water significantly decreased, the PMSP membrane with humic acid added to the surface had a high permeate aniline concentration, and the permselectivity was improved. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 461–468, 2004

Redox Phenomena during Adsorption of Aniline on Fe‐ and Zn‐bound SDS Micelles

AbstractThe co‐adsorption of aniline by complex‐formation with Zn‐bound and Fe‐bound micelles of anionic surfactant SDS (sodium laurylsulphate) causes redox reactions. This happens both in cases where micelles become insoluble due to Fe‐induced flocculation and in cases where micelles remain in solution. The interest in the phenomenon is that micellar flocculation is a means of pollutant removal by itself and synergistic effects between both flocculation and oxidation may exist.

Thermal and FTIR spectroscopic analysis of the interactions of aniline adsorbed on to MCM-41 mesoporous material

The adsorption of aniline on Na-AlMCM-41 synthesized by us has been characterized by infrared spectroscopy, temperature programmed desorption (TPD), and differential thermal analysis methods. Aniline would be mostly bound to the mesostructure through weak pi interactions. On the mesostructure containing adsorbed water, the co-adsorption of aniline could occur by weak hydrogen bonding through surface water molecules. For water, two possible modes of adsorption have been identified. Different associations between aniline and hydrated and nonhydrated mesostructures have been evaluated in order to favor the posterior in situ polymerization of adsorbed aniline.

Adsorption of organics onto an high-area C-cloth electrode from organic solvents and organic solvent/water mixtures

The application of high-area C-cloth electrodes as effective adsorbent materials in organic solvents and in aqueous/organic solvent mixtures was studied using aniline and pyridine as model adsorbate solutes. These were selected in relation to understanding the adsorption and electrosorption behaviours of organic pollutants in such aqueous/non-aqueous mixtures and to development of methodology for clean-up of organic solvents or industrial waste-waters. The adsorption/electrosorption processes were followed by in situ UV-spectroscopy which also provided dynamical data for easy kinetic analysis. Large differences in the (apparent) double-layer capacity of the C-cloth observed in ethanol (EtOH), n-propanol, and acetonitrile (MeCN), in relation to that in water, suggest the significance of differences of solution conductivity determining the distributed electrolytic resistance in the pores of the C matrix, as in the model of de Levie. Adsorption of both aniline and pyridine was found to be significantly promoted by either galvanostatic or potentiostatic polarization of the C-cloth electrode, as previously found for aqueous solutions. Introduction of organic solvents into aqueous solution was shown to have strong positive or negative effects on the electrosorption processes depending on the respective solvents and adsorbates used, and the role of hydrophobic effects in adsorption from aqueous media. A common enhancement of extents of adsorption of both aniline and pyridine in each of the organic solvents investigated was also found by measurements of adsorption on open-circuit followed by electrosorption upon polarization.

The influence of pH and temperature changes on the adsorption behavior of organophilic clays used in the stabilization/solidification of hazardous wastes

The effect of temperature, pH, and Na+/Ca2+ concentration on the adsorptive behavior of organophilic clay used in the solidification/stabilization of hazardous wastes was addressed. The organophilic clay used was montmorillonite type clay modified by cation exchange with a mixed tallow amine as the sorbent. The contaminants used in this work were phenol, 2-chlorophenol, aniline, and chlorobenzene. 2-Butanone (also known as methyl ethyl ketone, MEK) was initially studied, but preliminary work showed that the organophilic clay poorly sorbed it and it was not studied further. A group of isothermal tests were performed to clarify specific sorption behaviors due to temperature effects, high pH, and concentration of the cations Na+ and Ca2+. The adsorption capacity of the organophilic clay decreased as follows: chlorobenzene > 2-chlorophenol > phenol > aniline. Desorption in high pH environments was seen for phenol and 2-chlorophenol. Changes in temperature, rise in the pH, or increases in Na+/Ca2+ concentrations had no effect on the adsorption of either aniline or chlorobenzene.Key words: organophilic clay, adsorption, hazardous wastes, solidification/stabilization, isotherm.

Adsorption of anilines and cresols on NaX and different cation exchanged zeolites (equilibrium, kinetic, and IR investigations)

The equilibrium isotherms and the rate of adsorption have been measured for anilines and cresols on different zeolites by the usual gravimetric method using Microforce balance system. The adsorption isotherms of different anilines on NaX and different exchanged zeolites were fitted in Langmuir, Nitta, and virial isotherms and various adsorption parameters were calculated. Diffusivity studies show that the rate of adsorption depends on the diameter of the molecule and the channel diameter. Diffusivities were observed to be concentration-independent and closely consistent with the Arrhenius relationship with activation energies as high as 96.6 kJ/mol. The infrared analysis of the induced bands of anilines and cresols on zeolites shows some additional bands related to N–H and O–H in anilines and cresols. The shift in these bands with respect to aniline and cresol spectra indicates the specific adsorption. Major shifts of the peaks are due to the lone pair–Lewis acid site interaction.

A comparison on the catalytic activity of Zn 1− xCo xFe 2O 4 ( x = 0, 0.2, 0.5, 0.8 and 1.0)-type ferrospinels prepared via. a low temperature route for the alkylation of aniline and phenol using methanol as the alkylating agent

Abstract Depending on the variation of the Zn2+/Co2+ ratio in the Zn1−xCoxFe2O4 (x=0, 0.2, 0.5, 0.8 and 1.0)-type ferrospinels, the systems showed different activity trends for aniline and phenol methylation using methanol as the alkylating agent. An increase in Zn2+/Co2+ ratio increased the rate of N-monomethylation of aniline, whereas, a decrease in the ratio favored the rate of ortho methylation of phenol. An attempt has been made to interpret the observed trends based on the variation of surface acid–base properties of the catalyst surface with changes in the spinel composition. The efficiency of adsorption of aniline, phenol or methanol depends not only on the catalyst surface acid–base properties but also on the polarity of the adsorbing molecules. A controlled interplay of surface acid–base properties and polarity of the respective reacting molecules determines the efficiency of a particular reaction. In the case of aniline methylation, surface basicity plays a dominating role, whereas for phenol methylation surface acidity plays a dominating role.

Adsorption and Oxidation of Aniline and Anisidine by Chromium Ferrocyanide

The interaction of aniline and p-anisidine with chromium ferrocyanide has been studied. Maximum uptake of both anilines was observed around pH 7. The adsorption data obtained at neutral pH were found to follow Langmuir adsorption. Anisidine was a better adsorbate because of its higher basicity. In alkaline medium (pH>8) both aniline and anisidine reacted with chromium ferrocyanide to give colored products. Analysis of the products by GC-MS showed benzoquinone and azobenzene as the reaction products of aniline while p-anisidine afforded a dimer. IR analysis of the amine-chromium ferrocyanide adduct suggests that the outer metal ion of chromium ferrocyanide and amino group of amines are responsible for the interaction. A possible reaction mechanism for the product formation in alkaline medium has been proposed. The present study suggests that metal ferrocyanides might have played an important role in the stabilization of organic molecules through their surface activity in the prebiotic condensation reactions.

Effect of dopant mixture on the conductivity and thermal stability of polyaniline/nomex conductive fabric

AbstractElectrically conductive polyaniline (PANI)/[poly(m‐phenylene isophthalamide)] Nomex composite fabric was prepared by in situ polymerization of aniline doped by a mixture of hydrochloride (HCl) and various sulfonic acids such as benzenesulfonic acid (BSA), sulfosalicylic acid (SSA), and dodecylbenesulfonic acid (DBSA); their effect on conductivity and physical properties were then investigated. PANI/Nomex composite fabrics doped by a mixture of protonic acids exhibited higher conductivity than those doped by other single dopants such as camphorsulfonic acid (CSA), p‐toluenesulfonic acid (TSA), BSA, SSA, and HCl. The conductivity of PANI/Nomex fabrics especially doped by a mixture of HCl and DBSA was evenly maintained up to 100°C without depression of mechanical properties of Nomex. Their conductivity was also maintained under extension of the composite fabric. In addition, electrical conductivity of PANI/Nomex fabrics was highly increased by ultrasonic treatment, which facilitated better diffusion and adsorption of aniline by cavitation and vibration. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2245–2254, 2002

Surface Species Formed during Aniline Methylation on Zeolite H–Y Investigated by in Situ MAS NMR Spectroscopy

Abstract Aniline alkylation with methanol on zeolite H–Y has been studied using in situ 13 C MAS NMR spectroscopy under batch conditions. To clarify the main reaction pathways, the conversion of methanol as well as the interaction of aniline with surface methoxy groups were investigated under similar conditions. Methanol- 13 C and methyl iodide- 13 C were used as labeled reactants. Co -adsorption of aniline and methanol- 13 C on zeolite H–Y led to strongly adsorbed aniline molecules, assigned to aniline H-bonded to zeolite Bronsted acid sites, and three types of methanol species of different mobility: mobile methanol molecules with a liquid-like characteristics and two types of rigid methanol species with solid-like characteristics attributed to a methanol adsorption complex with aniline and surface methoxy groups, respectively. Among all the methanol species observed, only surface methoxy groups were shown to be responsible for aniline alkylation which takes place at temperatures from 373 to 523 K. The formation of surface methoxy groups was found to be a limiting step of the overall reaction. The primary alkylation product is N -methylaniline. Toluidines and N -methyltoluidines are formed at temperatures from 523 to 623 K after complete conversion of methanol to N -methylaniline. Therefore, isomerization or disproportionation of N -methylaniline was proposed to account for their formation.