Adsorption of 1,1,3,3-tetramethyl-2-thiourea on the mercury electrode: dependence on the concentration of the base electrolyte

Adsorption of 1,1,3,3-tetramethyl-2-thiourea (TMTU) on a mercury electrode from 1, 0.5, and 0.1 M NaClO₄ is described by means of the adsorption isotherms constants calculated from the surface pressure as a function of electrode charge density and adsorbate bulk concentration. The adsorption parameters for the double-layer were calculated based on the data from the differential capacity-potential curves. The values of the relative surface excess increase with an increase in the concentration of NaClO₄. In each system studied, significantly smaller values of Γ_S for σ_M<0 were obtained, compared with the corresponding values for σ_M≥0. At positive values of σ_M, the values of ΔG° obtained from either the Frumkin or the Flory-Huggins isotherm are similar. However, the values of the parameter A obtained from the Flory-Huggins isotherm are lower.The dependence of Φ^M−2 on the relative surface excess at a constant charge density is nonlinear. The rectilinear segments of these dependences obtained for smaller values of Γ′ were analyzed in order to calculate the electrostatic parameters of the inner layer.     

Synthesis and photolytic properties of 1,5-di-N,N′-dialkylaminoanthraquinones containing acryloyl groups

Several l,5-di-N,N′-dialkyaminoanthraquinones containing acryloyl groups were synthesized and characterized by Fourier transform infrared (FTIR) and ¹H NMR spectroscopy. The photophysical and photoinduction properties of these anthraquinone derivatives were examined in solution, in combination with free radical producing agents such as hexa-aryl-bis-imidazoles (HABI). When UV–vis absorption and fluorescence spectroscopy were employed to investigate the photophysical process, results showed that the photobleaching rate of N-alkylaminoanthraquinones containing an acrylate group and HABI was much faster than the acrylate group-free N-alkylaminoanthraquinone/HABI combination. N-alkylaminoanthraquinone induced polymerization of 2-phenoxyethyl acrylate (POEA)/N-vinyl carbazole (NVC)/cellulose acetate butyrate (CAB) mixtures was studied using real-time infrared spectroscopy (RTIR). It was found that the rate of polymerization was faster if the acryloyl groups were connected to the N,N′-dialkylaminoanthraquinone structure and that 1,5-di-N,N′-dialkylaminoanthraquinone containing acryloyl groups was more sensitive to visible light system.     

The effect of tert-butanol adsorption on the two-step electroreduction of Zn and its dependence on the NaClO4 concentration

The influence of water molecules on the adsorption of organic substances and kinetics of electroreduction of inorganic depolarizers is very often overlooked. The electroreduction of Zn²⁺ is a typical example of a reaction controlled by both diffusion and charge transfer. This process in 1.0, 0.5 and 0.1 M NaClO₄ solutions at a mercury electrode in the presence of tert-butanol is expected to involve two consecutive one-electron transfer steps in the overall reaction. Solutions of tert-butanol were prepared to cover the concentration range from 0.01 to 0.3 M. Measurements were performed using an impedance method for a wide range of both the potential and frequency. The difference between the potential of the anodic and cathodic peaks, which was obtained from the cyclic voltammetry method, increases with an increase in the concentration of both tert-butanol and NaClO₄. From the dependences of , the true standard rate constants and the constants and characterizing the stage of the first electron transfer and the stage of the second electron exchange, respectively, were determined. The obtained results indicate that the inhibiting properties of tert-butanol are the weakest in 0.1 M NaClO₄. In addition the stage of the second electron transfer is less sensitive to the inhibiting effect of tert-butanol than the stage of the first electron exchange.     

Upper critical solution temperature—type cononsolvency of poly(N,N-dimethylacrylamide) in water—organic solvent mixtures

The behaviour of linear poly(N,N-dimethylacrylamide) (PDMAM) chains was studied by turbidimetry and viscometry in mixtures of water with the polar organic solvents methanol, dioxane and acetone. The swelling-deswelling behaviour of PDMAM gels in the same solvent mixtures was also investigated. Contrary to the behaviour in water-methanol mixtures, in water-dioxane and water-acetone mixtures a significant shrinkage of polymer chains and deswelling of polymer gels, followed by phase separation, was observed for high organic solvent fractions. Cononsolvency phenomena were found to be temperature-dependent, as demixing occurred upon decreasing temperature. This upper critical solution temperature (UCST) phase separation behaviour in mixed solvents was studied by turbidimetry and compared to the well-known lower critical solution temperature (LCST) behaviour of poly(N-isopropylacrylamide) (PNIPAM) in similar solvents mixtures.     

Determination of reactivity ratios and swelling characteristics of ‘stimuli’ responsive copolymers of N-acryloyl-N′-ethyl piperazine and MMA

‘Stimuli’ responsive copolymers of N-acryloyl-N′-ethyl piperazine (AcrNEP) and methyl methacrylate (MMA) were synthesized by free radical solution polymerization. The copolymers were analyzed as thin films by FTIR spectroscopy. The monomer reactivity ratios were determined by linearization methods of Fineman-Ross (F-R) and Kelen-Tüdös (K-T) giving the results r₁ (AcrNEP)=0.58 and r₂ (MMA)=0.91 by the F-R method and r₁=0.72 and r₂=1.08 by the K-T method. The latter r values in turn yielded Q=0.59 and e=−0.12 for AcrNEP. Crosslinked copolymer hydrogels of AcrNEP and MMA with various compositions were prepared in bulk and solution by photo-initiated free-radical polymerization. The gels were dual responsive to pH and temperature. The response to pH was reversible with a response time of 100 min with good reversibility and with no loss in swelling capacity. Water sorption of the gels was investigated gravimetrically and the collective diffusion coefficients were determined at 10, 25, and 50 °C. The water sorption of the gels in water was Fickian. The temperature dependence of the equilibrium water content was studied by the Gibbs-Helmholtz equation. The enthalpy of mixing decreased with an increase in the hydrophilic content (AcrNEP) of the gel. Other parameters such as type and amount of crosslinker, preparative conditions, nature of buffers, and salts were found to influence the swelling behavior.     

Cellulose in lithium chloride/N,N-dimethylacetamide, optimisation of a dissolution method using paper substrates and stability of the solutions

Activation and dissolution in lithium chloride/N,N-dimethylacetamide (LiCl/DMAc) of cellulose from paper substrates are studied. The importance of the multiple parameters involved such as salt concentration, sample source and preparation is shown in a literature review. The experiments are carried out in order to perfect the method of activation and dissolution of paper containing different kinds of additives, typically found in historic papers. The suitability and efficiency obtained in the different trials are evaluated. The final procedure involves the activation by solvent exchange, with a water/methanol/DMAc sequence, followed by dissolution in 8% LiCl/DMAc at 4 °C. A study of the stability of the cellulose solutions in the experimental conditions showed that no degradation nor aggregation occurred during the solvation process and even after several months and confirmed the non-aggressiveness of LiCl/DMAc.     

CO2 absorption properties of Brønsted acid-base ionic liquid composed of N,N-dimethylformamide and bis(trifluoromethanesulfonyl)amide

The solubilities of CO₂ and the liquid densities in a Brønsted acid-base ionic liquid, [DMFH][Tf₂N], composed of N,N-dimethylformamide (DMF) and bis(trifluoromethanesulfonyl)amide (HTf₂N) have been investigated at high pressures and at different temperatures. The results were compared with those in DMF and a typical 1-butyl-3-methylimidazolium analogue with the same anion, [BMIM][Tf₂N]. The mole fraction scaled solubilities of CO₂ in the three liquids showed a slight increase in the following order, DMF < [DMFH][Tf₂N] < [BMIM][Tf₂N], whereas more remarkable difference was observed in the volume scaled concentrations of CO₂, [BMIM][Tf₂N] < [DMFH][Tf₂N] « DMF, mainly due to the bulkiness of liquid entities.     

Hydrolytic processes and condensation reactions in the cellulose solvent system N,N-dimethylacetamide/lithium chloride. Part 2: degradation of cellulose

Certain cellulose samples, especially those of higher molecular weight, are initially insoluble in N,N-dimethylacetamide (DMAc, 1)/lithium chloride, which is a very common solvent system for cellulosic materials. According to a common protocol, heating or refluxing these samples in DMAc, or in DMAc containing dissolved LiCl, represents one of several so-called ‘activation’ procedures, which are aimed at facilitating subsequent dissolution. In the present work, it is shown that the improved solubility achieved by this method is not only caused by a better activation or improved accessibility of the pulp, but also by a progressing degradation of the cellulosic material (DP loss).The degradation of cellulose in DMAc or DMAc/LiCl is due to two separate chemical processes. The first one, involving N,N-dimethylacetoacetamide (2) which is the primary condensation product of DMAc, causes a slow degradation by thermal endwise peeling. The glucose units peeled off the reducing end are released as furan structures (3). The mechanism appears to be a thermal cleavage of the glycosidic bond, which becomes quite selective towards the proximal anhydroglucose unit by a neighbor group-assisted effect according to quantum-chemical calculations. Due to its stepwise and thus slow mechanism, this pathway contributes only insignificantly to the overall cellulose degradation.The second degradation mechanism causes random chain cleavage and thus pronounced and rather fast changes in the molecular weight distribution. It involves N,N-dimethylketeniminium ions (5), whose presence in DMAc/LiCl at temperatures above 80 °C—the coalescence temperature of DMAc as determined by dynamic NMR—was unambiguously demonstrated by specific trapping in a thermal [2+2]-cycloaddition with lipophilic olefins. The keteniminium ion is an extremely reactive electrophile, which is able to directly cleave glycosidic bonds. The detrimental effect of this intermediate on the integrity of cellulosic pulps was confirmed by addition of an external degrading agent of the keteniminium type. Also the precursor compound, a ketene aminal, was confirmed to be present in heated DMAc or DMAc/LiCl by trapping with allyl alcohol in a spontaneous Claisen-type rearrangement.     

Inactivation of Escherichia coli in Na2SO4 electrolyte using boron-doped diamond anode

Electrochemical disinfection in chloride-free electrolyte has attracted more and more attention due to advantages of no production of disinfection byproducts (DBPs), and boron-doped diamond (BDD) anode with several unique properties has shown great potential in this field. In this study, inactivation of Escherichia coli (E. coli) was investigated in Na₂SO₄ electrolyte using BDD anode. Firstly, disinfection tests were carried on at different current density. The inactivation rate of E. coli and also the concentration of hydroxyl radical (OH) increased with the current density, which indicated the major role of OH in the disinfection process. At 20 mA cm⁻² the energy consumption was the lowest to reach an equal inactivation. Moreover, it was found that inactivation rate of E. coli rose with the increasing Na₂SO₄ concentration and they were inactivated more faster in Na₂SO₄ than in NaH₂PO₄ or NaNO₃ electrolyte even in the presence of OH scavenger, which could be attributed to the oxidants produced in the electrolysis of SO₄²⁻, such as peroxodisulfate (S₂O₈²⁻). And the role of S₂O₈²⁻ was proved in the disinfection experiments. These results demonstrated that, besides hydroxyl radical and its consecutive products, oxidants produced in SO₄²⁻ electrolysis at BDD anode played a role in electrochemical disinfection in Na₂SO₄ electrolyte.     

Thermo- and pH-sensitive dendrimer derivatives with a shell of poly(N,N-dimethylaminoethyl methacrylate) and study of their controlled drug release behavior

Novel dendrimer derivatives combining the temperature- and pH-sensitivities are synthesized. At first, polyamidoamine (PAMAM) dendrimers with generations 1-5 are synthesized by the reaction of ethylenediamine with methyl acrylate, and then the dendrimers are acylated by chloroacetyl chloride to obtain PAMAM-Cl, which can act as a macroinitiator for further synthesizing functional dendrimers. For fulfilling this goal, the polymers consisting of a dendritic PAMAM core and poly(N,N-dimethylaminoethyl methacrylate) (PDMA) shell are synthesized by atom transfer radical polymerization (ATRP). Their macromolecular structures are characterized by FTIR, ¹H NMR, DSC and particle size analyses, and their aqueous solutions are inspected by UV spectroscopy for understanding their thermo- and pH-sensitivities. The results show that novel dendrimer derivatives exhibit clearly thermo- and pH-respondings in accordance with the change of the environment. Using chlorambucil (CLB) as a model drug, the behaviors of the controlled drug release from polymers with different average graft length of PDMA are studied. The results indicate that the rate of the drug release can be effectively controlled by the pH value.     

Measurements and modeling of high-pressure excess molar enthalpies and isothermal vapor-liquid equilibria of the carbon dioxide + N,N-dimethylformamide system

Mixtures of supercritical CO₂ and N,N-dimethylformamide (DMF) are very often involved in supercritical fluid applications and their thermodynamic properties are required to understand and design these processes. Excess molar enthalpies () for CO₂ + DMF mixtures were measured using an isothermal high-pressure flow calorimeter under conditions of temperature and pressure typically used in supercritical processes: 313.15 and 323.15 K at 9.00, 12.00, 15.00 and 18.00 MPa and 333.15 K at 9.00 and 15.00 MPa. The Peng-Robinson and the Soave-Redlich-Kwong equations of state were used in conjunction with the classical mixing rules to model the literature vapor-liquid equilibrium and critical data and the excess enthalpy data. In most cases, CO₂ + DMF mixtures showed very exothermic mixing and excess molar enthalpies exhibited a minimum in the CO₂-rich region. The lowest value (−4526 J mol⁻¹) was observed for a CO₂ mole fraction value of 0.713 at 9.00 MPa and 333.15 K. On the other hand, at 9.00 MPa and 323.15 and 333.15 K varies linearly with CO₂ mole fraction in the two-phase region where a gaseous and a liquid mixture of fixed composition are in equilibrium. The effects of pressure and temperature on the excess molar enthalpy are large. For a given mole fraction, mixtures become less exothermic as pressure increases or temperature decreases. These excess enthalpy data were analyzed in terms of molecular interactions, phase equilibria, density and critical parameters previously reported for CO₂ + DMF. All throughout this paper, the key concepts and modeling tools originate from the work of van der Waals: the paper is intended as a small piece of recognition of van der Waals overwhelming contributions to thermodynamics.     

Electrochemical behavior of LiCoO2 in a saturated aqueous Li2SO4 solution

The electrochemical behavior of a commercial LiCoO₂ with spherical shape in a saturated Li₂SO₄ aqueous solution was investigated with cyclic voltammetry and electrochemical impedance spectroscopy. Three redox couples at E_SCE = 0.87/0.71, 0.95/0.90 and 1.06/1.01 V corresponding to those found at ELi/Li⁺=4.08/3.83, 4.13/4.03 and 4.21/4.14 V in organic electrolyte solutions were observed. The diffusion coefficient of lithium ions is 1.649 × 10⁻¹⁰ cm² s⁻¹, close to the value in organic electrolyte solutions. The results indicate that the intercalation and deintercalation behavior of lithium ions in the Li₂SO₄ solution is similar to that in the organic electrolyte solutions. However, due to the higher ionic conductivity of the aqueous solution, current response and reversibility of redox behavior in the aqueous solution are better than in the organic electrolyte solutions, suggesting that the aqueous solution is favorable for high rate capability. The charge transfer resistance, the exchange current and the capacitance of the double layer vary with the charge voltage during the deintercalation process. At the peak of the oxidation (0.87 V), the charge transfer resistance is the lowest. These fundamental results provide a good base for exploring new safe power sources for large scale energy storage.     

Investigation of lithium transport through LiMn2O4 film electrode in aqueous LiNO3 solution

Lithium transport through LiMn₂O₄ film electrode was investigated in aqueous saturated LiNO₃ solution by analyses of the potentiostatic current transient and ac-impedance spectra. It was found that the current transient hardly shows the Cottrell behaviour, and the initial current is linearly proportional to the potential step. This strongly suggests that lithium transport through the film electrode proceeds in aqueous LiNO₃ solution by the same mechanism involving the cell-impedance-controlled constraint, as does lithium transport in non-aqueous organic solution such as LiClO₄ in propylene carbonate (PC). However, the cell-impedance in aqueous LiNO₃ solution was determined to be much smaller by more than one order in value than that cell-impedance in non-aqueous LiClO₄-PC solution over the whole potential range, indicating lithium transport is markedly enhanced in aqueous electrolyte. From the comparison between the ac-impedance spectra obtained in aqueous and non-aqueous electrolytes, the reduced cell-impedance in aqueous electrolyte can be accounted for by the kinetic facility for the interfacial charge-transfer reaction in the absence of the resistive surface film as well as by the high conductivity of the electrolyte itself.     

Effect of N(4)-substituent groups on transfer of 2-benzoylpyridine thiosemicarbazone derivates at the water/1,2-dichloroethane interface

Dependent on the pH of the aqueous phase, the transfer of protonated forms of 2-benzoylpyridine N(4)-phenyl thiosemicarbazone (BPPT) (which has antimicrobial, antifungal and anticytotoxic activities) and 2-benzoylpyridine N(4)-ethyl thiosemicarbazone (BPET) across water/1,2-dichloroethane (1,2-DCE) interface has been studied by cyclic voltammetry. The protonation constants of the ligands ( and ) were determined by spectrophotometry. The standard partition coefficients () and the standard Gibbs energies of ionic (cationic) species of ligands () were calculated from the standard transfer potentials (). The standard Gibbs energies of their transfer () and partition coefficients of neutral species (log P_N) were determined by shake-flask method. These thermodynamic parameters were evaluated as a quantitative and qualitative measure of the lipophilicities of two compounds. The differences between the partition coefficients of cationic and neutral form of compounds [diff(log PI⁺−N)] were interpreted by results obtained from voltammetric data. Effect of N(4)-phenyl and ethyl groups for transfer of 2-benzoylpyridine thiosemicarbazone derivatives at macro-liquid/liquid interface was investigated. The antimicrobial activity of BPET was tested against four types of bacteria and found to be active against Staphlylococcus aureus.     

Influence of ionic liquids on the direct electrochemistry of glucose oxidase entrapped in nanogold-N,N-dimethylformamide-ionic liquid composite film

Glucose oxidase (GOD) immobilized in nanogold particles (NAs)-N,N-dimethylformamide (DMF) composite film on glassy carbon (GC) electrode exhibits a pair of quasi-reversible and unstable peaks due to the redox of flavin adenine dinucleotide (FAD) of GOD. When ionic liquids (ILs) 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF₄) or trihexyltetradecylphosphorium bis (trifluoromethylsulfony) (P_666,14 NTf₂) is introduced in the film, the peaks become small. But ILs 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF₆) and 1-octyl-3-methylimidazolium hexafluorophate (OMIMPF₆) make the peaks large and stable. In different composite films the formal potential (E⁰′) of GOD is different. UV-vis spectra show that the GOD dispersed in these films almost retains its native structure and there are weak interactions between ILs and GOD. Electrochemical impedance spectra display that NAs can promote the electron transfer between FAD and GC electrode; and ILs can affect the electron transfer through interacting with GOD. The thermal stability of GOD entrapped in NAs-DMF-ILs composite films is also influenced by ILs, and it follows such order as: in NAs-DMF-OMIMPF₆ > in NAs-DMF-BMIMPF₆ ≈ in NAs-DMF-BMIMBF₄ > in NAs-DMF. In addition, GOD immobilized in NAs-DMF-OMIMPF₆ and NAs-DMF-BMIMPF₆ films shows good catalytic activity to the oxidation of glucose. The I_max of H₂O₂ and the apparent K_m (Michaelis-Menten constant) for the enzymatic reaction are calculated.     

Zwitterion effect in polyelectrolyte gels based on lithium methacrylate-N,N-dimethyl acrylamide copolymer

Zwitterionic compounds such as those based on 1-butylimidazolium-3-(n-butanesulfonate) have previously been shown to have positive effects on the transport properties of polyelectrolytes. The addition of the zwitterion has been found to, in some cases, increase the dissociation of the lithium ion and enhance the conductivity by almost an order of magnitude. In this work, we report the effects of adding the above-mentioned zwitterion into the polyelectrolyte gel system poly(lithium methacrylate-co-N,N-dimethyl acrylamide); the anionic group being a stronger base leads to different behaviour for this copolymer compared to previous work. Polyelectrolyte gels based on dimethyl sulfoxide and polyether solvents were investigated to determine the breadth of applicability of the zwitterion in improving lithium ion transport. Impedance spectroscopy and pulse field gradient-NMR diffusion indicate an increase in the number of available charge carriers with zwitterion addition in some gel systems, however, the effect is not universal.     

Esterification of ethylene-vinyl alcohol copolymers in homogeneous phase using N,N′-dimethylpropyleneurea as solvent

Ethylene-vinyl alcohol copolymers (EVAL) were esterified with 3,5-dinitrobenzoyl chloride using the cycled urea N,N′-dimethylpropyleneurea (1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone) (DMPU) as the solvent. Ethylene-vinyl alcohol-vinyl-3,5-dinitrobenzoate terpolymers (EVALVDNB) and ethylene-vinyl-3,5-dinitrobenzoate copolymers (EVDNB) were obtained. Both EVAL copolymers (6-73 mol% VAL) and esterified polymers, EVDNB, and EVALVDNB dissolve in DMPU. The substitution may become total under the experimental conditions. The degree of transformation was determined by ¹H NMR. EVDNB copolymers were characterised by IR spectroscopy and ¹H and ¹³C NMR. Thermal properties were studied by DSC. The glass transition temperature of the EVDNB copolymers having a low VDNB content (up to 14 mol%) is roughly constant, whereas above 50 mol% increases. Melting temperature decreases as the VDNB content is increased, owing to the fact that the VDNB groups are excluded from the polyethylene crystal lattice.     

Electropolymerization of 3,4-ethylenedioxythiophene, N-ethylcarbazole and their mixtures in aqueous micellar solution

Electropolymerization by cyclic voltammetry and chronoamperometry of N-ethylcarbazole (ETCZ) and 3,4-ethylenedioxythiophene (EDOT) was carried out in water-methanol (v/v: 1/3 0.01 M sodium dodecylsulfate (SDS) and 1.25 M perchloric acid on platinum button electrodes. Methanol improves the ethylcarbazole solubility and allows a well defined polymer growth on the working electrode. The SDS makes easier the ETCZ and EDOT electropolymerization. Indeed, the presence of micelles decreases the monomer oxidation potential and induces an acceleration of the polymerization. ETCZ and EDOT have similar monomer oxidation potentials in this medium. Moreover their polymers show a better stability than the polymers obtained without surfactants. Therefore, electropolymerization mixtures of these monomers was carried out with different ratios (v/v, 70/30, 50/50 and 30/70) in order to prepare copolymers and the resulting products were characterized by electrochemistry, IR and UV-visible spectroscopy and SEM.     

Aqueous mercury precipitation with the synthetic dithiolate, BDTH2

BDTH₂, 1,3-benzenediamidoethanethiol (common name) and closely related derivatives were specifically designed to become insoluble after the formation of linear, covalent bonds to aqueous mercury(II). BDTH₂ (IUPAC nomenclature, N,N′-bis(2-mercaptoethyl)isophthalamide) emerged as the preeminent reagent for the complete precipitation of mercury from water after several years of studies with a wide range of compounds having one, two, three, and four thiol groups. BDTH₂ does not become inactive through oxidation to disulfide and can be applied to mercury-containing water as acidic, basic, and ethanolic solutions. The BDT-Hg precipitate is extremely stable and leaches low-ppm levels of mercury only under extremely acidic and basic conditions. BDTH₂ is also effective in the aqueous precipitation of other soft, divalent metals, such as copper, cadmium, lead, and the main group elements, arsenic and selenium. The insolubility of the BDT-M compounds can be attributed to the presence of strong, non-polar, covalent M-S bonding within a water-insoluble organic framework. BDTH₂ has no known biological toxicity and is being sold as a nutritional supplement under the trade name OSR-1. This review describes the chemistry, precipitation, and leaching studies of BDTH₂ with mercury.     

Protection of mild steel corrosion with Schiff bases in 0.5 M H2SO4 solution

Three new Schiff bases, viz., N,N′-ethylen-bis (salicylidenimine) [S₁], N,N′-isopropylien-bis (salicylidenimine) [S₂], and N-acetylacetone imine, N′-(2-hydroxybenzophenone imine) ortho-phenylen [S₃] have been investigated as corrosion inhibitors for mild steel in 0.5 M H₂SO₄ using Tafel polarization and electrochemical impedance spectroscopy (EIS). The three Schiff bases function as good inhibitors reaching inhibition efficiencies of ∼97-98% at 300 ppm concentration. The fraction <theta> of the metal surface covered by the inhibitor is found to increase with inhibitor concentration. Of the three Schiff bases, the S2 shows better efficiency than the other two Schiff bases. The adsorption of the inhibitor follows Langmuir isortherm. Thermodynamic calculations indicate the adsorption to be physical in nature.