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The work mentioned in the title of this comments-typed paper contains several calculations that disagree with some basic chemistry concepts. These misleading calculations mainly include (i) both kinetic and isotherm modeling through linear equations and (ii) calculating the thermodynamic parameters for the adsorption processes. Thus, we remind how to correct ways allowing to make these calculations. In our opinion, it is a source of confusion for the scientific community to continue using inappropriate methods as applied in the original paper. [ABSTRACT FROM AUTHOR]

We have examined the effect of bifunctional group in the same cross-linkage degree on the Li isotope fractionation in the cation exchange reaction in the aqueous solutions ranging in temperature from 278 to 333 K. For this purpose, the sulfonated pyridine-styrene-divinylbenzene resin with the cross-linkage degree of 50 wt%, embedded in porous silica beads was successfully synthesized by a typical polymerization method. The isotope separation coefficients (ε) per unit mass (ε/ΔMass) was 8.1 × 10–4 at 298 K. Therefore, the effect of bifunctional group against the ε/ΔMass value has been discussed, compared with those of previous works. [ABSTRACT FROM AUTHOR]

The complex permittivity spectra of dimethylamine (40 wt. % in water), trimethylamine (30 wt. % in water) and ethylamine (70 wt. % in water) have been obtained at different temperature using time domain reflectometry technique in the frequency range of 10 MHz-50 GHz. The relaxation mechanism for these systems is described by using Cole-Davidson model. The temperature dependant dielectric relaxation parameters such as static dielectric constant (ε0), relaxation time (τ) and distribution parameter (β) have been obtained by using non-linear least square fit method. The extracted static dielectric constant (ε0) and relaxation time (τ) values have been used to calculate thermodynamic parameter and Kirkwood correlation factor (geff). The enthalpy of activation ΔactH suggests that chemical kinetic is exothermic. Entropy of activation ΔactS suggests that the system is less ordered and Gibbs free energy of activation ΔactG reveals the molecular reorientation for all the three systems. Kirkwood factor for DMA40, TMA30 and EA70 is greater than unity which confirms the hydrogen bond interaction and parallel orientation of dipoles in molecules. [ABSTRACT FROM AUTHOR]

Abstract This study presents the synthesis of a CO 2 -responsive surfactant namely 2‑alkyl‑1‑hydroxyethyl imidazoline (HEA n IBs n = 16, 18, 20), which exhibits satisfactory surface and adsorption properties. The micelle formation and adsorption of the above imidazoline based surfactant in aqueous solution were studied in this work. CMC, the effectiveness of surface tension reduction, the maximum surface excess concentration, the minimum area occupied per surfactant molecule at the air/water interface, and the micelle aggregation number were obtained by measuring surface tension. Dynamic light scattering indicates that when the surfactant concentration is 1.2 times the CMC, the hydrodynamic radii of the three surfactants studied were almost equal to 8 nm. Electrical conductivity measurements indicate the micellization of surfactants in aqueous solution. In addition, typical thermodynamic parameters, including Δ G m 0, Δ G ads 0, Δ H m 0, Δ S m 0, Δ H m A , Δ S m A , and Δ C p, m 0 were evaluated. The thermodynamic parameters show that micelle formation is entropy-and-enthalpy co-driven from 298 K to 318 K. We expect to elucidate the self-assembly of CO 2 -responsive surfactant in an aqueous solution. Highlights • A kind of CO 2 -responsive surfactant namely 2‑alkyl‑1‑hydroxyethyl imidazoline was synthesized. • Through surface tension measurements, CMCs and other interface parameters were obtained. • Electrical conductivity measurements indicate the micellization of surfactants in aqueous solution. • Thermodynamic parameters of micellization were evaluated. [ABSTRACT FROM AUTHOR]

Abstract: Surfactant mixtures are used in many different industrial formulations. In this study, the mixed micelle formation behavior of 2 different cationic surfactants, namely dodecyltrimethylammonium bromide (DTAB) and benzyldimethylhexadecylammonium chloride (BDHAC), in the absence and presence of urea at various temperatures (298.15–318.15 K) was studied using the conductometric method. The attractive interaction between DTAB and BDHAC was estimated from the values of critical micelle concentration (CMC) and the CMC for ideal mixing (CMCid). Urea increases the CMC value as a result of the enrichment in the surface charge of the micelles/mixed micelles. The values of micellar mole fraction (X1Rub [Rubingh], X1M [Motomura], X1Rod [Rodenas]) and ideal micellar (X1id) of surfactant BDHAC were obtained by different models and are shown to exhibit the high contribution or effective involvement of BDHAC in mixed micelles and increase with increasing BDHAC mole fraction (α1). Activity coefficients (f1 and f2) were also evaluated from the relevant formula given in the literature. The negative values of the interaction parameters (β) show the attractive interaction among the studied components. Excess Gibbs free energy (∆Gex) of micellization revealed that the stability of mixed micelles is higher in aqueous solution than in urea solution. The thermodynamic parameters, namely the Gibbs free energy change, enthalpy change, and entropy change (∆Gom, ΔHom, and ∆Som, respectively), were also calculated from the conventional standard equations. [ABSTRACT FROM AUTHOR]

Adsorption behaviors at the air-water interface were presented for disodium alcohol ethoxylate sulfosuccinates (AESS) with narrow and broad oxirane adduct distribution. The CMC and equilibrium surface tension γ of broad-range distributed (BRD) and narrow-range distributed (NRD) AESS (with average degrees of ethoxylation of 2) were measured by the Wilhelmy plate method, while the adsorption and thermodynamic parameters were calculated. The effect of temperature and inorganic electrolyte on adsorption behaviors of these two surfactants was also investigated. The results show that NRD AESS displays a lower CMC and higher γ compared with BRD AESS. At the same time, the maximum surface excess concentration Γ of NRD AESS was lower than that of BRD AESS because of its larger steric hindrance, leading to the different adsorption and thermodynamic parameters. The adsorption of NRD AESS and BRD AESS was weakened with increasing temperature and enhanced in the presence of inorganic electrolyte. [ABSTRACT FROM AUTHOR]

Molecular inclusion of two natural amino acids, viz., L-asparagine and L-aspartic acid as guest into the host cavity of α and β -cylodextrins in aqueous solution have been studied which have various applications in the field of present bio-medical science for controlled delivery of necessary amount of the guest at the targeted site for a period of time efficiently and precisely. Surface tension and conductivity studies establish the formation of inclusion complexes with 1:1 stoichiometry. The inclusion complexes have been characterized by various thermodynamic factors basing upon density and viscosity studies. Contributions of various groups of the guest amino acid molecules toward the limiting apparent molar volume and viscosity B -coefficient have been calculated, as well as the solvation and hydration numbers are determined to support the inclusion phenomenon. Formations of the inclusion complexes have been explained with the help of hydrophobic effect, H-bonding, electrostatic forces and structural effects. [ABSTRACT FROM AUTHOR]

In the last decade, increasing interest on the use of aqueous micellar solution has been found in the field of separation science. The unique physical and chemical properties of ionic liquids make them most suitable candidates as an additive with nonionic surfactants in cloud point extraction. A surfactant-mediated cloud point extraction process has been adopted for the removal of Coralene red dye using tetraethyl ammonium tetrafluoroborate ionic liquid as an additive with nonionic surfactant Triton X-100. The detailed study on effect of various operating parameters such as temperature, time, concentration of surfactant, dye and IL on extraction of dye has been carried out to find out optimum conditions. The extraction of dye was found to be increased with temperature, time, surfactant concentration and IL concentration. A developed Langmuir isotherm was used to compute the feed surfactant concentration required for the removal of Coralene red dye up to an extraction efficiency of 90 %. The effect of temperature and concentration of surfactant and dye on various thermodynamic parameters was examined, and it was found that the values of Δ G increased with temperature and decreased with surfactant and dye concentration. The values of Δ H and Δ S increased with surfactant concentration and decreased with dye concentration. The developed approach for IL-assisted cloud point extraction has proved to be an efficient and green route for extraction of Coralene red from water sample. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

The subject of this study concerns the effect of temperature and Cetyltrimethyl ammonium bromide (CTABr) in the presence of tetramethylammonium bromide [(Me)4N+Br-] at different temperature using conductometric method. CTABr showed a remarkable decrease in critical micelle concentration (CMC) in the presence of [(Me)4N+Br-]. The CMC values reduced to a certain minimum in all cases, with increase in the system temperature at different concentration of [(Me)4N+Br-]. The thermodynamic parameters (δGm0, δHm0 and δSm0) for the micelle system were estimated by applying the phase separation model while the data obtained allowed access to their usability on the micellization process. Enthalpy - entropy compensation was observed, with a constant compensation temperature of 296K. [ABSTRACT FROM AUTHOR]

The effect of the addition of the hydrophilic ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate [C 4 mim][BF 4 ] on the micellization of cetyltrimethylammonium bromide (CTAB) in aqueous solution was studied using electrical conductivity, density, speed of sound and spectroscopic techniques. From the CMC values and their temperature dependence, various thermodynamic parameters such as standard free energy (ΔG m 0 ), enthalpy (ΔH m 0 ) and entropy (ΔS m 0 ) of the micellization were determined in the temperature range of 288.15 K to 318.15 K. Fourier transform infrared spectroscopy (FTIR) and UV–vis spectroscopy were employed to get information regarding the interaction between the surfactant and ionic liquid aggregates. The calculated thermodynamic parameters |ΔH m 0 | is smaller than |TΔS m 0 | which suggests that the micellization is entropy driven. [ABSTRACT FROM AUTHOR]

Expanded graphite nanosheets (EG-nanosheets) were used for adsorption of Malachite Green (MG) from aqueous solution. The influences of dye concentrations, absorbent dosage, pH values and the temperatures on the adsorption were investigated as well. The dye adsorption experiments were carried out by utilizing batch procedure. EG-nanosheets were initially characterized by scanning electron microscopy (SEM), fourier transform infrared (FT-IR) and X-ray diffraction (XRD). Adsorption efficiency increased with increment in initial pH, dye concentration and temperature, but decreased with increment in adsorbent dose. The rate parameters of adsorption were evaluated by First-order, pseudo-second-order, and intraparticle diffusion models. These data indicated an endothermic spontaneous adsorption process and kinetically followed the pseudo-second order model with activation energy of +17.44 kJmol-1. Langmuir, Freundlich and Temkin equations were used for analyzing of experimental isotherm data and found that the Langmuir isotherm model showed good fit to the equilibrium adsorption data. The maximum adsorption capacity of 158.9 mg g-1 of Malachite Green was achieved (dye initial concentration of 100 mgL-1). Thermodynamic parameters such as changes in the free energy of adsorption (ΔGº), enthalpy (ΔHº) and entropy (ΔSº) were calculated. The negative values of ΔGº indicate that the malachite green adsorption process is spontaneous in nature and the positive value of ΔHº shows the endothermic nature of the process. Adsorption onto EG has proved to be highly efficient technique for the handling of dyecontaminated waters. [ABSTRACT FROM AUTHOR]

A simple method was developed for modification of polyacrylonitrile with triethylenetetramine (PAN-TETA) as absorbent of copper and cadmium ions. PAN-TETA and its metal complexes were characterized by FT-IR and SEM. FT-IR studies confirmed the presence of metal ions in the metal-PAN-TETA complexes. The obtained aminated polyacrylonitrile was evaluated for chelating of Cu(II) and Cd(II) ions. Batch adsorption studies were carried out on the effect of experimental parameters including pH, amount of adsorbent, contact time, initial concentration of metal ions, and temperature. Adsorption efficiency increased with increasing metal ions concentration, initial pH, and temperature. The adsorption kinetics followed pseudo-second-order kinetic model with correlation coefficients of 0.999. Experimental data were analyzed by model equations such as Langmuir and Freundlich isotherms. It was found that Langmuir isotherm model was better fitted with the adsorption data. The maximum sorption capacity of 109.26 and 99.67 mg g−1 for copper and cadmium ions were achieved in pH = 6, respectively. The negative value of Δ Gº indicated the spontaneous nature of the adsorption. The competitive tests verified that PAN-TETA had good adsorption selectivity for Cu (II) with the coexistence of copper and cadmium ions. © 2013 American Institute of Chemical Engineers Environ Prog, 33: 1139-1147, 2014 [ABSTRACT FROM AUTHOR]

Different polymeric materials carrying synthetic adsorbents have been reported in literature for heavy metal removal. We have developed a simple method for functionalizing of polyacrylonitrile (PAN) with two volume percent (50 and 100) of triethylenetetramine (PAN-TETA 50 and 100). For the first time, PAN-TETA was used as an absorbent of silver and lead ions from aqueous solutions. PAN-TETA and their metal complexes have been studied by FT-IR and scanning electron microscope. The analysis method confirmed the presence of metal in PAN- TETA complexes. The prepared functionalized PAN were applied to remove heavy metal ions, such as Pb(II) and Ag(I) from aqueous solutions. The optimization of experimental conditions and parameters including initial pH, contact time, adsorbent dose, initial metal and ions concentration, and temperature for the removal of heavy metals were investigated. The adsorption increased with increasing metal ions concentration, initial pH, and temperature. Pseudo-firstorder, pseudo-second-order, and intraparticle diffusion models were considered to evaluate the rate parameters. The adsorption followed pseudo-second-order kinetic model with correlation coefficients greater than 0.997. Attempts were made to fit the isothermal data using Langmuir, Freundlich, and Temkin equations. The maximum sorption capacity of 108.14mgg -1 and 99.01mgg -1 for silver and lead ions were achieved at pH= 6, respectively. The values of thermodynamic parameters of ▵ G°, ▵ H,° and DS° indicated that the adsorption process was spontaneous and endothermic. The selectivity of two PAN-TETA for the adsorption of Ag(I) and Pb(II) were studied. The competitive adsorption tests verified that these functionalized polymers have good adsorption selectivity for Ag(I) with the coexistence of two ions. Desorption of the metal ions from PAN-TETA was studied in 0.5M HCl and very high desorption rates, greater than 91%, were achieved in all cases. Based on adsorption/desorption data, PAN-TETA is a promising adsorbent for heavy metals removal from the aqueous medium. [ABSTRACT FROM AUTHOR]

Abstract: The adsorption of silver ions onto Halloysite nanotubes (HNTs) was investigated in aqueous solution in a batch system. The natural HNTs used as adsorbent in this work were initially characterized by TEM. The amounts of the silver ions adsorbed onto HNTs were influenced by initial silver ion concentration, temperature, pH, contact time and adsorbent dose. Adsorption increased with increasing initial silver ion concentration, initial pH, and temperature. Pseudo-first-order, pseudo-second-order and intraparticle diffusion models were considered to evaluate the rate parameters. The adsorption followed pseudo-second-order kinetic model with correlation coefficients greater than 0.999. The experimental isotherm data were analyzed using the Langmuir, Freundlich and Temkin equations. The Langmuir isotherm model showed significant fit to the equilibrium adsorption data and the maximum adsorption capacity of 109.79mgg−1 (99.8% removal) of silver ions was achieved. The thermodynamic parameters of activation such as Gibbs free energy, enthalpy and entropy were also evaluated. The results indicate that HNTs could be employed as effective nanoadsorbent for the removal of heavy metal ions. [Copyright &y& Elsevier]

Abstract: In this paper, the interactions between cationic dyes and the ionic liquids (ILs) have been studied by 31P nuclear magnetic resonance (NMR), UV–Vis spectroscopy and conductometric measurements at different temperatures. It was shown that a decrease in the measured specific conductance of the (dye+IL) mixtures was caused by the formation of non-conducting or less conducting (dye+IL) associates. The associates were formed by 1:1 ratio of cation of the cationic dyes and anion of the ILs by using the 31P NMR and UV–Vis spectroscopy methods. The association constants were calculated by theoretical model based on the deviation from linear behavior, and the association constants were as high as 106 (L·mol−1)2. Thermodynamic results imply that the formation process of association was exothermic nature. It is expected that the associates reported here would have promising application as active materials for the preparation of ion-selective electrode used in the determination of ILs concentrations. [Copyright &y& Elsevier]

The effect of some electrolytes present in body fluid on micellar properties of the antibiotic drug streptomycin sulphate has been determined conductometrically over the temperature range 298.15–313.15 K with an interval of 5 K. The outcomes obtained from this study are further supported by fluorescence and UV measurements. The observed critical micelle concentration (CMC) data have been used to calculate standard thermodynamic parameters of micellization like free energy of micellization (Δ G m o ), entropy change of micellization (Δ S m o ), and enthalpy change of micellization (Δ H m o ) for the aqueous solution of surface active drug streptomycin in the presence of various electrolytes. These parameters of micellization have been explored in terms of hydrophobic and hydrophilic interactions present in water–drug–electrolyte ternary system. The Δ G m o , Δ H m o , and Δ S m o values indicate that the electrolytes favor the aggregation behavior of the drug and process of micellization is well accommodated by enthalpy and entropy determinants. The interionic interactions have been elucidated by applying the model of pseudo phase separation. Image 1 • Electrolyte effect on micellar behavior of streptomycin sulphate has been investigated. • Electrolytes facilitate the process of micellization thus decrease the CMC of the drug. • CMC values increase with rise in temperature. • Micellization is energetically spontaneous, enthalpy favored and entropy driven. • Interaction of electrolytic cations with drug follows Hofmeister series pattern. [ABSTRACT FROM AUTHOR]