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Profile control and water plugging are key technologies to enhance oil and gas recovery. Traditional plugging materials, due to short gelation time, low mechanical strength, and difficulty in balancing plugging and protection, thus limiting application in high temperature reservoirs. Herein, a degradable hybrid dual-crosslinked polymer was prepared by employing a copolymerization - dual-grafting and physical adsorption design strategy. The dual-crosslinked process and reaction mechanism were analyzed using infrared spectroscopy and differential scanning calorimetry. The mechanical properties, water dilution resistance, aging stability and degradability of the dual cross-linked composite were also investigated. The solvation forces enable silica particles to exhibit excellent suspension stability in a PEG solvent. The temperature ranges from normal atmospheric temperature (20 °C) to reservoir temperature (140 °C), with the apparent viscosity falling within the range of 10–1200 mPa·s, meeting the requirements for mixing and injection. The combination of free radical copolymerization and click reaction is utilized to control the gelation time (2–10 h) in high temperature environment (140 °C), which is favorable for regulating the action position of the plugging agent in the reservoir. The cured material exhibits excellent mechanical strength owing to the presence of dual-crosslinking and inorganic hybridization, with a compressive strength of 0.221 MPa and a peak strain of 55.3 %. Furthermore, this composite material undergoes hydrolysis through an addition-elimination reaction, transitioning from a solid to a liquid state within 24 h, thereby aiding in the restoration of productivity in the temporarily shielded target layer. Compared to traditional materials, this dual-crosslinked composite system have the advantages of controllable gelation time, high mechanical strength, aging resistance, and degradability, making it suitable for profile control in high temperature reservoirs (140 ℃, 21.81×104 mg/L). [Display omitted] [ABSTRACT FROM AUTHOR]

Refractory carbonaceous gold ore contains carbonaceous matters that seriously interfere with gold leaching. Therefore, this paper presented an in-depth experimental investigation on the inhibition gold-adsorbing behavior using Trichloroisocyanuric acid (TCCA). Various factors affecting the inhibition were analyzed. Moreover, the kinetics and isotherms associated with the adsorption were established to describe the gold adsorption of carbonaceous matters after TCCA treatment. A variety of analytical techniques were used to clarify the inhibition mechanism. The results showed the average gold adsorption percentage of elemental carbon decreased from 89.79 % to 9.33 % at pH 3.0, TCCA volume 15.17 mL, TCCA concentration 0.104 mol·L−1, 35 ℃ and 3 h. The average adsorption percentage of humic acid decreased from 56.19 % to 3.13 % at pH 5.0, TCCA volume 5.10 mL, TCCA concentration 0.012 mol·L−1, 35 ℃ and 4.5 h. The gold-adsorption behavior of the treated elemental carbon conformed to the pseudo-second-order and Langmuir model, accompanied by an activation energy of 9.42 kJ·mol−1. And the adsorption process of the treated humic acid could be explained by the pseudo-first-order and Langmuir model with an activation energy of 40.11 kJ·mol−1. TCCA molecules and their hydrolysis products covered the elemental carbon surface, resulting in a reduction in the size of the porous structure, which further affected the number and activity of surface-active sites. Treated with TCCA, the surface area of humic acid reduced from 42.84 m2·g−1 to 9.96 m2·g−1. Furthermore, spectroscopic analysis showed that the chemical groups of humic acid were destroyed, suggesting a sharp decrease in chemisorption capability. [Display omitted] • Adsorption percentage of the TCCA-treated elemental carbon decreased by 89.63 %. • Adsorption percentage of the TCCA-treated humic acid decreased by 94.47 %. • TCCA covered elemental carbon's surface to inhibit the surface activity. • TCCA destroyed humic acid's chemical groups of to decrease chemisorption ability. [ABSTRACT FROM AUTHOR]

Schematic presentation of a nanocomposite (Fe 3 O 4 – Mn 2 O 3) that was prepared via in-situ method for the magnetic solid phase extraction of Pb2+ at trace levels. Display Omitted This article focuses on adsorption and desorption of Pb2+ on a novel adsorbent consisting of Mn 2 O 3 and Fe 3 O 4. The adsorbent was prepared through combining Sol-Gel and precipitation methods to in-situ magnetization. Decreasing preparation time, synthesizing at room temperature, not using organic solvents are advantages of the presented approach. The characterizations were done by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, alternating gradient force magnetometer and Brunauer-Emmett-Teller. High surface area and strong magnetic property propose the nanocomposite as a magnetic solid phase extraction adsorbent. Under the optimum preconcentration conditions, (a) limit of detection of 0.36 μg L−1, (b) relative standard deviation (n = 5) of 0.94%, (c) preconcentration factor of 33.33 and (d) linearity of dynamic range of 10–200 μg L−1 show the applicability of the adsorbent. The adsorbent was found to be durable for 3 months and efficiently applicable during this time but it is not reusable. To understand the adsorption mechanism, isotherm adsorption, kinetic adsorption and thermodynamic adsorption were established. The sorbent was employed to preconcentrate Pb2+ from water and vegetables samples. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract A highly efficient and reusablezeolite was prepared using the biopolymer chitin as mesoporosity agent and applied to adsorb three cationic dyes. The zeolite was synthetized by the hydrothermal method and characterized. The potential of zeolite to adsorb crystal violet (CV), methylene blue (MB) and basic fuchsin (BF) was evaluated conducting kinetic, equilibrium, thermodynamic and regeneration studies. The treatment of simulated effluents was also performed. The modification with chitin biopolymer provided attractive adsorptive characteristics for the zeolite structure. The adsorption was attractive with adsorbent dosage of 2.0 g L–1 and pH of 7.5, 8.0 and 9.0, for CV, MB and BF, respectively. The adsorption kinetic was well described by the Homogeneous Surface Diffusion Model (HSDM). The equilibrium was adequately adjusted with the Langmuir (CV) and Sips models (MB and BF). Maximum adsorption capacities predicted by the isotherm models were 1217.3, 548.2 and 237.5 mg g–1 for CV, MB and BF, respectively. The modified zeolite can be used for fifteen adsorption cycles maintaining the same adsorption capacity. Also, the adsorbent was able to treat a simulated textile effluent providing 85% of color removal. These results demonstrated that the synthetized zeolite is a highly efficient and reusable material to adsorb cationic dyes. [ABSTRACT FROM AUTHOR]

To minimize the long-term radiological risk and improve the accuracy of radioactive analysis, isolation of trivalent actinides and lanthanides is very necessary and much more challenging due to their similar chemical properties. Herein, the adsorption performance and mechanism of a novel porous BCPDTPA/SiO 2 -P extraction resin towards trivalent actinides (Am) and lanthanides (Eu) was investigated. The effects of adsorption parameters such as contact time, HNO 3 concentration, temperature, and Eu concentration on the adsorption were conducted by batch adsorption experiments. The adsorption mechanism of Am(Ⅲ) and Eu(Ⅲ) by BCPDTPA/SiO 2 -P resin was elucidated based on kinetics, thermodynamics, and isotherms analysis. The results showed that BCPDTPA/SiO 2 -P resin has a high affinity for Am(Ⅲ) compared to Eu(Ⅲ) within the range of experimental conditions. Kinetic studies revealed that the resin was in accordance with the pseudo-second-order equation by chemisorption as the rate-limiting step of the adsorption process. Thermodynamic parameters indicated that the adsorption was spontaneous and endothermic process. The adsorption isotherm followed the Freundlich isotherm model. As a result, the use of BCPDTPA/SiO 2 -P resin as a stationary phase for chromatographic separation of actinides(Ⅲ)/lanthanides(Ⅲ) can be expected due to its clear adsorption mechanism and selectivity. [Display omitted] [ABSTRACT FROM AUTHOR]

Magnesium acetate, magnesium oxalate and magnesium oxide were employed to prepare waste polyester textiles-based activated carbons with well-developed mesoporous structures. TG analysis was conducted to explore the pyrolysis process and pore-forming mechanism. N 2 adsorption/desorption isotherms, EA, XRD, SEM and FTIR were performed to investigate the influences of different Mg-containing compounds on the physicochemical properties of activated carbons. The results indicated that the samples prepared by two organic magnesium salts exhibited higher specific surface area and porosity than that by magnesium oxide. Diversity in pore structure, morphology and surface groups of the carbons were owing to the differences in grain size of MgO and pyrolysis pathway of Mg-containing compounds. The adsorption isotherm of Cr(VI) for the activated carbons fitted well with Freundlich model, indicating that the adsorption process accorded with the theory of multilayer adsorption. The maximum adsorption capacity of Langmuir model of the sample prepared from magnesium acetate was the highest, and the main adsorption mechanisms were confirmed as electrostatic interaction and reduction reaction. [ABSTRACT FROM AUTHOR]

The surface tension isotherms and dilational visco-elasticity for three nonionic surfactants (C 10 EO 8 , C 12 EO 5 and C 14 EO 8 ) were comparatively studied using the bubble and drop profile analysis tensiometry. The experiments based on drop profiles were analysed assuming the depletion of surfactant molecules from the bulk of the drop due to adsorption. To process the experimental results, two theoretical adsorption layer models (Frumkin and reorientation) were applied, while the reorientation model provides a better description of the experimental results. In addition, the visco-elasticity moduli obtained from drop and bubble profile experiments were compared. It was shown that at higher surfactant concentrations the drop profile method provides visco-elasticities systematically larger than those obtained from bubble profile experiments, even though the adsorption-related depletion has been correctly considered. The proposed correction protocol provides the option for direct comparison between data obtained by the drop profile analysis method with those from other methods. [ABSTRACT FROM AUTHOR]

Adsorption of uranium (U) from real mine contaminated water (U 1.652 mg/L) by phosphate rock apatite (PRA) was investigated in the batch experiment and flow column test system. In batch experiment, the equilibrium adsorption amount is 0.1133 mg/g with the highest uranium removal efficiency of 76.89% under the ratio of solid to liquid (1:100) in 15 h. And the pH of wastewater became neutral (pH 7.51) from acidic (pH 3.88) after adsorption equilibrium. The saturated adsorption amount (0.2021 mg/g) in batch experiment is higher than the maximum accumulative adsorption amount (0.0684 mg/g) in column experiment. Langmuir model and pseudo-second order kinetic model are fitted well and, indicating that PRA is a favorable adsorbent with monolayer coverage and a chemisorption for uranium. Moreover, the surface morphology of the adsorbent by SEM confirmed the surface changes after uranium adsorption. XRD spectra showed that two new mineral phase of Metaankoleite [K(UO 2 )(PO 4 )·3H 2 O], Chernikovite [H 2 (UO 2 ) 2 (PO 4 ) 2 ·8H 2 O] have been generated on PRA after uranium adsorption, but which were trace for relatively low uranium concentration in tested polluted water. In addition, the FT-IR spectra results confirmed the uranium in contaminated water was adsorbed onto the PRA in the form of (O = U = O) 2+ with the participation of the PO 4 3– in binding of it. [ABSTRACT FROM AUTHOR]

A new pulmonary surfactant with synthetic analogs of surfactant proteins SP-B and SP-C (CHF5633) was studied by the method of thin liquid films (foam and wetting films). For foam films dependences such as probability W for formation of black foam films vs. surfactant concentration ( C s ), disjoining (capillary) pressure isotherms (Π( h )) and film thickness ( h ) were studied. The minimum CHF5633 concentration for a black foam film formation was established in 75 μg/cm 3 (after 30 min). The results obtained were compared with those of therapeutic pulmonary surfactant preparations and in particular to Curosurf ® , the one that showed the best profile among the tested animal-derived surfactants with respect to black film formation, stability and homogeneity. It was shown that with respect to stability surfactant CHF 5633 (from W/C curves) was very close to Curosurf ® . The differences involved black foam film thicknesses which for the synthetic surfactant (at 200 μg/cm 3 ) were h = 14.7 nm and for Curosurf ® (at 200 μg/cm 3 ), h = 12.6 nm, i.e. film thickness of the synthetic surfactant was larger, probably due to the larger quantities of surfactant protein analogs SP-B and SP-C contained in it and/or to the different phospholipid composition. The same was observed for h ( C s ) dependence. For wetting films equilibrium thickness vs. degree of hydrophobicity on a solid surface was measured as well as wetting contact angles. Practically no significant difference in the wetting behaviour of the aqueous suspensions of natural surfactant preparation Curosurf ® and CHF 5633 was established, however about 25% less Curosurf ® was needed to achieve almost the same wetting behavior. [ABSTRACT FROM AUTHOR]

Vertical impacts of heated dairy product droplets onto stainless steel surfaces have been experimentally studied using high-speed photography. The experiments were carried out under conditions of controlled temperature and humidity within an environmental chamber, and a numerical model was used to simulate the initial heating and evaporation processes. The droplets consisted of non-Newtonian (shear-thinning) solutions of infant formula or whole milk reconstituted at 45 wt % total solids content in water. Data obtained from image analysis were used to determine the effect of air and surface temperatures up to 140 °C on droplets during impact and spreading. The results show that drop spreading following an initial drying treatment depends on the type of drying applied. Droplets spread further with increasing air temperature, whereas it was found that surface temperatures below 120 °C only had a minor effect on droplet spreading. Moreover, the drops spread less with increasing chamber air temperature when they were air-dried at room temperature in an acoustic levitator for two minutes prior to impact. These trends have been analysed by considering the fluid viscosity, which decreases with temperature in bulk samples, but increases within any outer crust of dried liquid. Impacts were recorded for drop diameters in the range 1.5–3 mm at an impact velocity of 2.90 ± 0.03 m/s. This research should assist with understanding spray-drying of dairy products, and will be more broadly applicable to drop impacts involving heat flows and complex, non-Newtonian fluids. [Display omitted] • Drop impacts of heated dairy products were studied using high-speed photography. • Drops that fell into a heated chamber prior to impact produced enhanced spreading. • Drops levitated prior to falling into the chamber produced reduced spreading. • The different outcomes are explained by variations in non-Newtonian rheology. • The study has broad relevance for spray drying and similar industrial processes. [ABSTRACT FROM AUTHOR]

Several classical sorption isotherm equations were fitted to experimental high-resolution data for type II multilayer isotherms. Both the models and the experimental data (sorption of Ar (87 K), N 2 (77 K), H 2 O (303 K), n-pentane (298 K), neopentane (273 K) on macroporous silica are taken from the literature. Further data include N 2 sorption on nonporous functionalized silica and α-alumina. The following equations are tested: Brunauer-Emmett-Teller (BET), its modification by Anderson, Aranovich, the ζ-isotherm, Harkins-Jura, Frenkel-Halsey-Hill (FHH), that of de Boer and Zwikker manifesting itself in later work of Fuller, Condon, and Adolphs, the dual-site Langmuir equation with monolayer clustering recently presented by Calzaferri et al., and at last the general cluster sorption isotherm (GCSI, Micropor. Mesopor. Mater. 316 (2021) 110909). The GCSI describes all experimental data with high accuracy, not only for homogeneous but also for heterogeneous surfaces with a Gaussian energy distribution. All other models fail more or less, depending on the initial slope of the experimental isotherm. Besides theoretical considerations, the quality of each isotherm modeling is evaluated by the pure statistical Akaike criterion. [Display omitted] [ABSTRACT FROM AUTHOR]

A model, which allows analyzing compression isotherms of mono- and multi layered films formed with particles at the air–water or oil–water interface is here proposed. The number of contacts established between particles in the layer was linked to surface pressure. The parameters used in the model permit calculating the energy of layer formation, and area per particle in the mono- or multi-layered films. These data reflect particle–particle and particle-subphase interaction and, consequently, particle organization in the film. The model was tested with micrometric glass beads and used for calculating the diameters of particles formed at the interface. The excellent representation of the experimental compression isotherms shows that the model can be used for constructing films with defined properties. [ABSTRACT FROM AUTHOR]

A novel bimetallic metal–organic gel (JLUE-MOG-Fe/Y) was fabricated through solvothermal method and employed for adsorptive removal of chlortetracycline hydrochloride (CTC) from aqueous solution. JLUE-MOG-Fe/Y, with outstanding stability, wide adaptability and excellent recyclability, showed strong CTC adsorption capacity as high as 584.83 mg·g−1 at 25 °C. The process of CTC adsorption on JLUE-MOG-Fe/Y was exothermic and spontaneous, and fitted well with the pseudo-second-order kinetic model and Freundlich isotherm model. Based on the adsorption experiments and characterization results, pore filling, coordination bonds, electrostatic interactions, π-π interactions, hydrogen bonds and hydrophilic/hydrophobic interaction participated in the adsorption process. [Display omitted] • Bimetallic metal organic gel used for CTC adsorption. • JLUE-MOG-Fe/Y showed strong stability, excellent recyclability and outstanding anti-interference ability. • The maximum adsorption capacity of CTC could reach 584.83 mg·g–1 at 25 ℃. • Adsorption mechanism involved coordination bonds, π-π interactions, hydrogen bonds, electrostatic interactions, etc. [ABSTRACT FROM AUTHOR]

Consistent incorporation of nonelectrostatic interactions in the chemical potential for electrical double layers at interfaces interacting across electrolytes under the constant potential or charge regulation boundary conditions has recently been presented for the case of ionic dispersion potentials. This gives rise to shifted adsorption equilibria, and thereby a shift in the predicted surface electrostatic potential. It also results in an additional component previously unaccounted for in the total double layer interaction force. The new force component due to ionic dispersion can be repulsive or attractive and can in some cases exceed entropic repulsion in magnitude. The altered force leads to the need to recalibrate electrostatic surface potentials and equilibrium constants when fitting to experimental force data. We explore the implications and consequences for model systems of mica surfaces, to illustrate the effect of salt concentration, and cellulose surfaces to illustrate the effect of pH. The final example is the more complex, asymmetric system of crude oil and glass interacting across salt solutions of varying concentration and pH. The DLVO theory augmented by ionic dispersion potentials is used to fit measured data for ζ -potentials of oil and glass, from which the calculated disjoining pressure isotherms are compared to measured macroscopic oil–glass adhesion data. [ABSTRACT FROM AUTHOR]

The static (film structure and elasticity) and dynamic features (surface dilatational properties) of whey protein concentrate (WPC) spread films at the air–water interface, as influenced by three commercial hidroxypropylmethycelluloses (HPMC), i.e., E4M, E50LV and F4M, were studied, at 20 °C, pH 7 and I = 0.05 M. To this end a fully automated Wilhelmy-type film balance was used. The results showed a significant influence exerted by HPMC surface active polysaccharides on the WPC film structure. After the polysaccharide addition in the aqueous subphase the π-through area isotherms changed, especially for the highest molecular weight HPMC, as the time increased. Moreover, the presence of HPMC also decreases the surface modulus and the relative viscoelasticity of the WPC protein films. These results can be interpreted in terms of the ability of the polysaccharides to absorb at the air–water interface by itself, penetrate into the spread protein film due to its surface activity and increasing surface pressure. The existence of limited thermodynamic compatibility between the protein and HPMC, occurring in the aqueous phase and at the air–water interface, could be the cause of the observed phenomena, which in turn would be determined by the molecular properties of the cellulose derivative. As mixtures of proteins and polysaccharides are often used in many technological applications, the results presented here should help to improve the processes involved in the formation and stabilization of complex colloidal formulations like foams and emulsion based on these biopolymers. [ABSTRACT FROM AUTHOR]

In this study, the magnetic zirconium-iron composite oxide (MZIO) was prepared through coprecipitation method, and its adsorption performance on Cr(VI) was investigated. The MZIO was characterized by XRD, XPS, SEM, BET, and VSM. The effects of adsorption reaction conditions on Cr(VI) removal were systematically studied, including initial pH, MZIO dosage, initial Cr(VI) concentration, temperature, and coexisting anions. The addition of zirconium not only enhanced the specific surface area and γ-Fe 2 O 3 exposure but also supplied additional active sites, which boosted the adsorption action dramatically. Interestingly, characterization analysis revealed that MZIO played a key role in Cr(VI) reduction, which may be connected to the conversion of certain Fe3+ to Fe2+ after zirconium addition. MZIO could accommodate a wider pH range and complicated anionic conditions in water. The Cr(VI) adsorption process followed the pseudo-second-order kinetic model and the Langmuir isotherm model, with the maximum adsorption capacity of 49.43 mg/g. Thermodynamic parameters reflected a spontaneous and endothermic adsorption process. After five regeneration cycles, MZIO still showed strong removal stability and magnetic recovery ability. These results suggested that MZIO is a promising magnetic adsorbent for removing Cr(VI) from water, with high adsorption capacity and easy recovery and regeneration. [Display omitted] • The magnetic zirconium-iron composite oxide (MZIO) for Cr(VI) removal was synthesized. • MZIO presented a high adsorption capacity for Cr(VI) (49.43 mg/g). • The removal mechanism of Cr(VI) included electrostatic attraction, chemical reduction, and ligand exchange. • MZIO exhibited excellent magnetic separation ability and great cycling stability. [ABSTRACT FROM AUTHOR]

The adsorption kinetics, isotherms and thermodynamics of Cr(III) on graphene oxide (GO) were studied. The adsorption kinetic data were well described with pseudo-second-order model and the equilibrium data were well fitted by Langmuir model. The calculated thermodynamic parameters indicated that the adsorption of Cr(III) on GO was spontaneous and endothermic. The maximum adsorption capacity of Cr(III) on GO at pH 5.0 and T = 296 K was about 92.65 mg g-1, which was higher than other reported adsorbents. It was found that the adsorption of Cr(III) on GO was strongly dependent on solution pH, but weakly dependent on ionic strength. Fourier transform infrared (FTIR) spectra suggested that Cr(III) was adsorbed on GO mainly through the formation of inner-sphere complexes with the O-containing functional groups on GO surface. Results in this study suggested that GO was a suitable material for the preconcentration and removal of Cr(III) from water. [ABSTRACT FROM AUTHOR]

Dyes released from different industries are one of the major pollutants in the water system. So removal of dye before disposal to the main water stream is necessary. In this study, adsorption technique was adopted for removal of the cationic dye from aqueous system using reduced graphene oxide (rGO) as adsorbent material. The kinetic study of adsorption shows that the present system follows pseudo second order kinetic (linear) model. Adsorption isotherm investigation indicates that the adsorption of methyl green onto rGO nanosheets follows the isotherm models in the order Toth > Sips > Dubinin--Radushkevich (D--R) > Scatchard > Langmuir > Temkin > Freundlich model in the pH range 4--6. However, the order changes to D--R > Scatchard > Toth > Sips > Langmuir > Temkin > Freundlich model at pH 7 and 9. The adsorption capacity of methyl green onto the rGO nanosheets increases with increasing pH of the medium due to the change in the surface properties. Presence of other ions like Na+, Ca2+, Mg2+ and SO42- also influenced on adsorption due to the change in the surface properties. The magnitude of ΔG° values are found to be in the characteristic range of physisorption nature of adsorption. Further, the mechanism of the adsorption process was investigated by FTIR spectroscopy and it indicates that the adsorption is due to electrostatic interaction between methyl green dye molecule and rGO nanosheets. X-ray radial distribution function (RDF) analysis revealed the formation regular molecular packets of graphene. X-ray diffraction (XRD) analysis of the rGO nanosheets before and after adsorption of the dye molecule indicates that some textural changes occur in the rGO nanosheets upon adsorption of the methyl green dye molecule. [ABSTRACT FROM AUTHOR]

Highlights: [•] Concave down surface tension curvature is explained through a new isotherm. [•] A modified extended Langmuir model with a lyophobic parameter is derived. [•] Adsorption-desorption balance is founded on bulk-surface equilibrium. [•] Activity coefficient and standard adsorption energy agree with HMT hydrophilicity. [ABSTRACT FROM AUTHOR]

Highlights: [•] Activated carbon treated by KOH exhibited better adsorption properties than untreated one. [•] Thermodynamic parameters demonstrated the adsorption process was spontaneous and favorable. [•] It was probable to deduce adsorption mechanisms and design adsorption systems by the study of adsorption kinetics, isotherms and thermodynamics. [ABSTRACT FROM AUTHOR]

Highlights: [•] Dispersion isotherms of single-walled carbon nanotubes were obtained. [•] 5μmol/L of poly(ethylene glycol)-phospholipid was sufficient. [•] Adsorbed molecules, not vesicles, are responsible for dispersion. [•] The shorter chain phosphatidylcholine disperses better. [•] Glycerol-phospholipid is the most efficient host. [ABSTRACT FROM AUTHOR]

Highlights: [•] Poly (N-isopropyl acrylamide) (PNIPAM) monolayers showed negative hysteresis by the compression–expansion cycles. [•] Isotherm of a given expansion process almost coincided with that of the following compression process. [•] PNIPAM showed much larger surface dilational moduli than PEO and PVAc. [ABSTRACT FROM AUTHOR]

Highlights: [•] Different shapes and sizes of hysteresis loop have been observed for a set of pore with different sequences of connectivity. [•] The adsorption in one section of the pore is affected significantly by the state of the adjacent pores. [•] The presence and the position of the closed ends affect significantly the shape and size of the hysteresis loop. [•] Pore size distribution calculated using kernel of isotherms of independent open pores may be incorrect for connected pores. [Copyright &y& Elsevier]

The relatively high cost, long synthesis duration and low adsorption capacity have limited the application of the primary metal-organic frameworks (MOFs) in the heavy metal removal. Herein, one-minute synthesized primary HKUST-1 MOF with excellent adsorption performance towards Pb2+ has been achieved. The adsorption equilibrium time and maximum uptake capacity of Pb2+ on HKUST-1were 60 min and 819.28 mg/g, respectively. Besides, HKUST-1 exhibited a stronger binding affinity to Pb2+ than the coexisting ions. The adsorption data fitted well with the pseudo-second order model (R2 = 0.9962) and Langmuir model (R2 = 0.9919), suggesting the adsorption behavior was dominated by monolayer chemisorption. Further, the destruction of HKUST-1 crystal structure after Pb2+ exposure and strong correlation between the released Cu2+ and adsorbed Pb2+ collectively confirmed the ion exchange could be the potential mechanism. Besides, the coordination interaction between Pb2+ and the free-standing carboxylate groups in the ligands of HKUST-1 also played an important role in the adsorption process. This work not only provides a new idea for Pb2+ removal by primary MOFs based on cation substitution, but also has great implications for constructing green and low-cost MOFs for the treatment of heavy metals contaminated water. [Display omitted] [ABSTRACT FROM AUTHOR]

The relatively high cost, long synthesis duration and low adsorption capacity have limited the application of the primary metal-organic frameworks (MOFs) in the heavy metal removal. Herein, one-minute synthesized primary HKUST-1 MOF with excellent adsorption performance towards Pb2+ has been achieved. The adsorption equilibrium time and maximum uptake capacity of Pb2+ on HKUST-1were 60 min and 819.28 mg/g, respectively. Besides, HKUST-1 exhibited a stronger binding affinity to Pb2+ than the coexisting ions. The adsorption data fitted well with the pseudo-second order model (R2 = 0.9962) and Langmuir model (R2 = 0.9919), suggesting the adsorption behavior was dominated by monolayer chemisorption. Further, the destruction of HKUST-1 crystal structure after Pb2+ exposure and strong correlation between the released Cu2+ and adsorbed Pb2+ collectively confirmed the ion exchange could be the potential mechanism. Besides, the coordination interaction between Pb2+ and the free-standing carboxylate groups in the ligands of HKUST-1 also played an important role in the adsorption process. This work not only provides a new idea for Pb2+ removal by primary MOFs based on cation substitution, but also has great implications for constructing green and low-cost MOFs for the treatment of heavy metals contaminated water. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: Mixed monolayer of merocyanine 540 (MC540) dye and octadecylamine (ODA) at the air/water interface has been prepared using the co-spreading method. The pressure–area (π–A) isotherm studies revealed that the mixtures of MC540/ODA at a different ratio formed a stable monolayer at the air/water interface and these floating layers were easily transferred onto hydrophilic substrates as the Y-type Langmuir–Blodgett (LB) film. The specific area per molecule in the π–A isotherm of the mixed monolayer of MC540/ODA was larger than that of the pristine ODA. The area can also get increased up to 40mN/m surface pressure by the increase of the dye concentration in the mixtures. The LB films of MC540/ODA mixture were formed at 30mN/m surface pressure by transferring the mixed monolayer at the air/water interface on hydrophilic glass substrate via vertical dip-coating as mono- and multilayer films. The photophysical properties of MC540 in chloroform and LB films have been investigated using the absorption, steady-state and time-resolved fluorescence spectroscopy techniques. H-aggregate formation of MC540 both in chloroform and LB film were concluded from the spectroscopic results. The morphology of the one-layer mixed LB film of MC540/ODA on the glass substrate has been characterized by AFM (atomic force microscopy). The non-contact mode AFM image of the one-layer mixed LB film showed that the film surface consisted of MC540/ODA nanoclusters. In conclusion, our results contribute to understanding the strong interaction between MC540 and ODA at the air/water interface, and show the effects of some parameters on the mixed LB films of MC540. [Copyright &y& Elsevier]

Abstract: We studied the formation and stability of stearic acid (SA) based films on aqueous sub-phases via Langmuir trough and imaging ellipsometry experiments. The aqueous phase was based on Artificial Sea Water (ASW), a multicomponent salt solution with a total molarity of 0.53. The composition of this solution was varied via dilution (1, 10 and 100 times) and adjustment of the pH (3, 7, 10). Also water sub-phases without the ASW salts were studied. Pressure–area isotherms of the SA monolayers show an enhanced stability of the film against fracture when the pH and/or the salt concentration of the sub-phase are increased. Isobars of SA measured below the pressure needed for film fracture, indicate distinct mechanisms for loss of material: (1) at low pH and salt concentration, three dimensional (3D) structures are formed at the air/water interface via nucleation and growth and (2) at high pH and salt concentration, diffusion-controlled dissolution of molecules in the sub-phase occurs. The formation of multilayer structures was corroborated with ellipsometry images of the films after Langmuir–Blodgett transfer. [Copyright &y& Elsevier]

Abstract: Surface complexes of cysteine amino acid onto TiO2 films at pH 2.0, 5.0 and 8.0 were characterized by IR spectroscopy. The FTIR spectra at pH 2.0 show the coexistence of surface complexes with protonated and deprotonated carboxylate groups. This points to the occurrence of electrostatic interactions between the zwitterionic form of cysteine and the positively charged TiO2 film. A Langmuir isotherm analysis was performed to obtain the binding constants values, which are consistent with electrostatically adsorbed surface species. At pH 8.0, the TiO2 film is charged negatively, and the amino acid molecules approach the TiO2 surface through the amino protonated groups. This new arrangement generates a larger surface concentration at saturation coverage. [Copyright &y& Elsevier]

Abstract: Mixed Langmuir and Langmuir-Blodgett films of dissimilar components, arachidic acid and a phthalocyanine of zinc, have been investigated. These compounds form mixed films with phase separation, with domains at the sub-micro scale which are detected by AFM in LB films but not observed by BAM. These domains present different contrast in the surface potential images obtained with SP-AFM and in the friction images. The analysis of the isotherms and of the AFM images, at several compositions, reveals that the components are immiscible. The difference in height between the arachidic acid and the phthalocyanine of zinc phases is in accordance with the heights of the molecules, and points to the presence of a monolayer in the zinc phthalocyanine phase. AFM has revealed as a necessary technique to elucidate the miscibility in mixed films at the nanometric scale. UV–Vis spectroscopy shows changes in the spectra bands of LB films in respect to those in solution, due to the organization of the molecules in the LB film. [Copyright &y& Elsevier]

Abstract: Three new environmental friendly surfactants of cationic type were synthesized using natural vanillin. Their chemical structures were determined using elemental, IR, 1H NMR and 13C NMR spectroscopic analyses. The surface activity of the synthesized surfactant solutions was determined using surface and interfacial tension measurements at 25°C. The emulsification powers of these surfactants were measured against light paraffin oil. The biodegradation ability of the surfactants reached the maximum (75%) within 21 days. Corrosion inhibition characteristics of the green surfactants were determined on carbon steel in 1N HCl at 25°C using gravimetric and potentiodynamic techniques. The adsorption of inhibitors on carbon steel in 1N HCl follows Langmuir adsorption isotherm. Thermodynamic adsorption parameters (K ads, ΔG ads) of studied inhibitors were calculated using the Langmuir adsorption isotherm. The Tafel polarization results indicate that the inhibitors act as mixed inhibitors. The inhibition efficiency increases with an increase in the inhibitor dose, side chain length and surface activity of the inhibitors. The maximum inhibition efficiencies ranged between 95.09% and 98.53% at 400ppm. [Copyright &y& Elsevier]

Abstract: The main characteristics of Langmuir monolayers of acid amide amphiphiles with one and two alkyl chains are fundamentally different. This is demonstrated by comparison of surface pressure–area (π–A) isotherms, the mesoscopic morphology, and the two-dimensional lattice structure of the condensed phases in the case of the single-chain acid amides with N-myristoyl ethanolamine (TDAHA) and 3-hydroxy-N-tridecyl propanoic acid amide (HTPA) as well as in the case of the double-chain acid amide with N,O-dimyristoyl ethanolamine (TAOAE). The studies of the binary mixtures TDAHA/TAOAE, HTPA/TDAHA, HTPA/TAOAE (1:1) and ternary mixtures TAOAE/TDAHA/HTPA (1:1:1) performed at 5°C and 25°C allow the comparison with the single components. The results indicate convincingly that all binary 1:1 monolayers and the ternary 1:1:1 monolayer exist as homogeneously mixed systems. The dominance of the double-chain TAOAE in the binary and ternary monolayers mixed with single-chain acid amide amphiphiles TDAHA and HTPA in mesoscopic and molecular scale can be unequivocally concluded from the GIXD and BAM measurements. The probability for the presence of N,O-diacylated ethanolamine, such as TAOAE, as impurity in N-acylated ethanolamine, e.g. TDAHA, is high so that in such systems the most important interfacial characteristics are dominated by the impurity. [Copyright &y& Elsevier]

Abstract: The present work is devoted to the interaction in mixed solutions of the cationic polyelectrolyte PAH and the counter-charged anionic surfactant SDS at the water/oil interface. For this purpose interfacial tension and dilational rheology studies were performed to describe the formation of complexes of PAH and SDS. The dilational elasticity values depend on the concentrations of surfactant and polyelectrolyte and their mixing ratio. As expected the concentration dependence of the dilational elasticities of SDS and PAH-SDS mixtures are similar in the SDS concentration range 10−5 M till 10−3 M (at a fixed amount of PAH) and have a maximum which correlates with an observed minimum in the interfacial tension isotherm. The sharp decrease of the dilational elasticity values in a narrow range is presumably due to the destruction of two-dimensional rigid structures and the formation of microaggregates in the interfacial layer. From dilational viscosity measurements as a function of oscillation frequency one can conclude that with increasing surfactant concentration the SDS dominates in the interfacial adsorption layer whereas the polyelectrolyte–surfactant complexes remain in the bulk phase. [Copyright &y& Elsevier]

Abstract: The biosorption of phosphate from aqueous solutions using Fe(III)-treated Staphylococus xylosus cells was investigated. Langmuir and Freundlich isotherm models were applied to describe the adsorption equilibrium and found that Langmuir isotherm model fitted the equilibrium data better than Freundlich isotherm model. The biosorption capacity of Fe(III)-treated biomass for phosphate was found to be 70.92mg/g at optimum conditions of pH 3.0, biomass concentration 0.5g/L and equilibrium phosphate-biomass time 60min respectively. The sorption efficiency at initial phosphate concentration of 50mg/L was not influenced upon addition of SO4 2−, Cl−, CO3 2−, NO3 −, Mg2+ and Ca2+ ions from 0 to 800mg/L, whereas under the same conditions, phosphate sorption was increased with increase in concentration of Fe2+ ions. The kinetic models showed that phosphate sorption followed pseudo-second order kinetics. The calculated thermodynamic parameters indicated the spontaneous, exothermic and feasible nature of phosphate biosorption process. Phosphate was completely desorbed from 2.0g/L of phosphate-loaded biomass using 0.14M HCl and Fe(III)-treated biomass exhibited almost the same uptake capacities up to three subsequent biosorption/desorption cycles. [Copyright &y& Elsevier]

Abstract: The paper presents the numerical analysis based on the low temperature N2 adsorption isotherms of carbon foam microporous structures prepared by various methods from furfuryl alcohol by employment of the fast multivariant fitting procedure of the thermodynamical LBET class models. Various techniques, including chemical vapor polymerization, were employed to produce microporous carbons. To perform the analysis of the porous structure, the fast multivariant fitting procedure with the new adsorption numerical models of the LBET class was used. The results of the analyses carried out with the use of the fast multivariant fitting procedure of the LBET class models have provided valuable information concerning the microporous structure of the analyzed materials, with the determination of the reliability of the defined parameters of the LBET class models. Those studies have been completed by microscopic research aimed at visualization of the macroporous structure as a framework for the formation of micropores. [Copyright &y& Elsevier]

Monolayer behaviors of newly synthesized viologens (Vs) containing tolunitrile substituents have been investigated at the air–water interfaces. Surface pressure–area isotherms indicated that these viologens could not form stable monolayers on the surfaces of the subphases of pure water, Fe(BF4)2 and anionic polyelectrolyte of PSS (PSS: poly(styrenesulfonic acid-o-maleic) acid), while they could form insoluble monolayers on the surface of the subphase containing mixtures of Fe(BF4)2 and PSS, which was attributed to the formation of Fe–V metal–organic polyelectrolytes based on an interfacial coordinative reaction between the Fe2+ ions and viologen derivatives. With the use of Langmuir–Blodgett (LB) method, monolayers of Fe–V polyelectrolytes were transferred on the substrate surfaces. X-ray photoelectron spectra indicated that the LB film was composed of the elements of S, C, N, O and Fe, suggesting the formation of Fe–V/PSS hybrid multilayers. Cyclic voltammograms of the viologens revealed two reversible redox couples in the solutions, corresponding to two electron transfers of V2+ ↔V+· and V+· ↔ V0, respectively. For the indium tin oxide electrode covered by the LB films of Fe–V/PSS, only one broad redox couple was recorded in the potential range of 0 and −1.0V vs Ag/AgCl, which was attributed to the first redox couple of V2+ ↔V+· The charger transfer process of viologens in the solutions and Fe–V/PSS multilayers was investigated by the potential chronocoulometry method. [ABSTRACT FROM AUTHOR]

Abstract: The generalization of Derjaguin–Frumkin approach for the description of wettability of curved interfaces is given. The equations for the calculations of the contact angle on concave and convex cylindrical and spherical surfaces based on the isotherms of the disjoining pressure are derived. Analysis performed has shown that for the radius of curvature comparable to the range of surface forces action increasing the surface curvature for convex surfaces results in the contact angle increasing, whereas for concave surfaces the wetting improves. It is shown that curving the substrate surface may cause philic/phobic or phobic/philic wettability transition. [Copyright &y& Elsevier]

Abstract: The adsorption of exopolysaccharides (EPS) on silver nanoparticles (SNPs) was influenced by pH, salt concentration, and zeta potential. In this paper, SNPs were stabilized using exopolysaccharides (EPS) produced by Aeromonas punctata as the capping agent. The effects of EPS concentration on the adsorption was studied by UV–visible absorption spectra. During interaction, a decrease in absorbance at plasmon peak of SNPs (425nm) was observed till 50mg/L of EPS, beyond that a blue shift towards 411nm was observed. The capping of SNPs by EPS was confirmed by Fourier Transform Infrared Spectroscopy. The adsorption of EPS on nanoparticles was found to be strongly dependent on zeta potential. The equilibrium adsorption data fitted well by Langmuir isotherm compared to Freundlich curve. The kinetics of adsorption was fitted by pseudo-second-order. Desorption of EPS from SNPs was observed at alkaline pH 12. The stabilized silver nanoparticles could be more amenable towards applications in biotechnology and bioengineering. [Copyright &y& Elsevier]

Abstract: Reliable prediction of the heterogeneous solid adsorbents pore size distribution (PSD) is the key element in the design and operation of all adsorption processes. Direct measurement of PSD is usually expensive and in many practical applications may not be feasible. Complex theories and sophisticated models are required to obtain a faithful estimation of PSD from a set of noisy measured isotherms. Various shortcomings of the traditional PSD recovery techniques (e.g. forward and regularization methods) are discussed. A robust method based on linear regularization theory is developed to extract PSD of heterogeneous solid adsorbents from highly noisy condensation isotherms with almost no a priori assumption. The performance of the proposed method is tested using various synthetic examples and different experimental data. The predicted results clearly demonstrate that the proposed method can successfully filter out the noise and recovers the proper PSD from a set of noisy condensation data with almost no initial assumption. The optimum level of regularization is crucial for appropriate recovery of pore size distribution, especially for lower orders of regularization technique. To the best of our knowledge the proposed method has not been addressed previously. [Copyright &y& Elsevier]

Abstract: The potential of natural clay as adsorbent for biotechnology processes was systematically investigated. Adsorption isotherms for several substrates and products of an alcohol dehydrogenase catalysed reaction were determined by static experiments. A distinct selective adsorption behaviour of natural kerolite clay was proven for aromatic ketones and alcohols in particular for acetophenone and phenylethanol. In aqueous media high adsorbed amounts (q) were stated for those molecules to be adsorbed (adsorptive) which possess both a carbonyl and a phenyl group. This led to an adsorbed amount of 17% (w/w) for acetophenone on kerolite clay. [Copyright &y& Elsevier]

Abstract: One and two-component colloidal particles, sulfate-treated polystyrene (S-PS), aldehyde-sulfate (AS-PS), and carboxylate-treated polystyrene particles (C-PS), were assembled at air/water interfaces by injecting particle dispersions. Surface pressure–area (π–A) isotherms were measured using the Langmuir–Blodgett technique. The isotherms for S-PS particles are reversible and independent of barrier speeds during the compression/relaxation cycles. The normalized isotherms of S-PS/AS-PS and S-PS/C-PS particle mixtures lie between those of single species. In addition, the self-assembled structures of particles were transferred onto mica substrates and characterized using a laser scanning confocal microscope. The morphology of the two-component layer has the characteristics of both single component layers with no significant phase separation. Finally, we have explored the potential applicability of a purely additive group contribution analysis to surface pressure–area isotherms. [ABSTRACT FROM AUTHOR]

Abstract: Surface and interfacial tension measurements have been performed at the water/air and water/hexane interface by drop profile analysis tensiometry for a series of alkyl trimethylammonium bromides with different chain lengths (C10, C12, C14 and C16). The effect of neutral phosphate buffer (10mM, pH 7) has been investigated and the results have been compared with literature data obtained for the same surfactants in the absence of salt. The use of a modified Frumkin isotherm (Ionic Compressibility) taking into account the mean activity of all ions in solution leads to a real improvement of the data interpretation, while the classical Frumkin Compressibility model yields similar results but overestimates the adsorption parameters. At the water/hexane interface, the hexane molecules are incorporated in the surfactant layer and it results a kind of competitive adsorption for the shortest chain surfactant (10 carbons). For the longest chains, the attractive interactions between the hydrophobic chains of the adsorbed surfactants are strong enough to replace the solvent molecules from the interface. [ABSTRACT FROM AUTHOR]

Abstract: A model for the selective adsorption phenomenon in an isotropic liquid considering a localized adsorption energy is proposed. The fundamental equations governing the adsorption phenomena are established, by considering the mass balance equation in a limited region close to the interface. The electric field distribution inside the sample and the behavior of the chemical potential are determined as a function of the initial concentration of the fluid phase. This model allows us to obtain isotherms that lie outside the Langmuir approximation, because the effective potentials relevant to the adsorption process are determined in a self-consistent manner. [Copyright &y& Elsevier]

Abstract: The thermodynamic behavior of mixed floating monolayers of zwitterionic phospholipids and trans-dehydrocrotonin (t-DCTN) at different molar fractions (x) of the diterpene has been investigated by measuring the surface pressure and surface potential Langmuir isotherms. Excess Gibbs energies of mixing have been calculated for different compositions of the floating monolayer at varying surface pressure values. Spreading of pure t-DCTN molecules at the air–water interface resulted in a compressed-type isotherm. For the t-DCTN/DBPC and t-DCTN/DOPC binary systems, the maximum stability was obtained at x t-DCTN =0.375 and 0.500 at a surface pressure of 15mN/m, with a minimum ΔG M value equal to −1.7kJ/mol. The analyses of the obtained thermodynamic parameters such as excess areas, excess free energies and free energy of mixing confirmed the miscibility of the phospholipids and t-DCTN in the binary systems. In these mixed monolayers, the phospholipid molecules seemed to exhibit higher long-range orientation order for intermediary values of t-DCTN molar fractions. As a whole, the above observations suggest that the t-DCTN molecules exert a condensing effect on the monolayers when mixed with the phospholipids. [Copyright &y& Elsevier]

Abstract: In this study the performances of all-atom (AA) and united atom (UA) models (fitted and unfitted) of the methane molecule are evaluated for the description of adsorption isotherms on graphite surfaces and in a collection of graphitic slit pores. We simulated collections of isotherms using the grand canonical Monte Carlo method with an all-atom model and adjusted united atom models in graphene layers made up of discrete atoms of carbon. The collections of isotherms are used to determine the pore size distribution (PSD) of four activated carbon samples. We also investigated the sensitivity of the system to the cutoff and solid–fluid standard parameterization. It was found that the simulated AA model isotherm shape on the graphite surface is much more similar to the experimental data than the UA model isotherm. The cutoff had little influence on isotherm and different solid–fluid standard parameterizations change the PSD. We also found that despite presenting similar fitting with the experimental isotherms, the models presented distinct PSDs. The unfitted united atom model (UA1) suggested less plausible PSDs, while the all-atom (AA) and the fitted united atom model (UA2) model provided apparently more realistic estimates of the internal structure of microporous carbons. [Copyright &y& Elsevier]

Abstract: This research focused on the structural and thermal changes of montmorillonite via mechanochemical treatment, and the effects on the properties of mesoporous montmorillonite were also discussed. X-ray diffraction (XRD), nitrogen adsorption–desorption isotherms, Fourier transform infrared spectra (FT-IR), thermal analysis and scanning electron microscopy (SEM) were employed to characterize the samples. The results show that montmorillonite has bigger interlayer spacing, better ability of attracting cations into interlayers, and more structural defects. By means of controlling grinding time, the stability of synthesized mesoporous montmorillonite is remarkably enhanced. The optimum grinding time of original montmorillonite is 1h. Furthermore, structural analysis indicates that the stability of resultant mesoporous montmorillonite depends on the stability of montmorillonite in pore wall. [Copyright &y& Elsevier]

Abstract: We applied the model of adsorption of ionic and non-ionic surfactant mixtures, being an extension of previously developed model of adsorption of ionic surfactants, for the description of the pH regulated surface activity of alkanoic acids. We determined the surface tension isotherms for aqueous solutions of octanoic acids and its sodium salt – sodium octanoate, with various additions of NaOH and HCl. A very peculiar shape of isotherms, which was the result of acid–base equilibrium and a large difference of surface activity of octanoate ions and neutral octanoic acid molecules, could be well described by the theoretical model. Additional measurements of surface potential isotherms were correlated with the surface tension and could also be described by our theoretical model. [Copyright &y& Elsevier]

Abstract: Spontaneous non-linear oscillations were observed during the transfer of commercial non-ionic surfactants, oxyethylated alcohols C8EO4 and C8EO5 through the water/heptane interface. The oscillations appear in a certain range of initial surfactant concentrations in the water phase. The experimental results are discussed using numerical simulations on the basis of the model proposed recently [N.M. Kovalchuk, D. Vollhardt, Oscillation of interfacial tension produced by transfer of nonionic surfactant through liquid/liquid interface, J. Phys. Chem. C 112 (2008) 9016–9022]. The explanation is proposed for the transition from non-oscillatory to oscillatory regime and again back to non-oscillatory regime observed by an increase in the initial surfactant concentration. The effect of the surfactant partition coefficient and the parameters of equilibrium isotherm on both upper and lower concentration limits is discussed. [Copyright &y& Elsevier]

Abstract: After a brief analysis of the three most widely used equations of state and adsorption isotherms, (those of van der Waals, Frumkin and Helfand–Frisch–Lebowitz with second virial coefficient) we analyze the definitions and the values of the main adsorption parameters (adsorption constant K s, minimum area per molecule α and interaction constant β) and derive new expressions for some of them. Since it turned out that all three adsorption isotherms perform rather poorly, when used to interpret adsorption data, we applied also three more general equations—one was derived for localized adsorption long ago, but we had to derive two new equations for non-localized adsorption. We subject all 6 equations—the simple ones and the three generalized, to rigorous numerical analysis and discussion of the results. Our overall conclusion is that in some cases all equations can describe qualitatively the observed phenomena, but only the new equation of state, proposed by us for non-localized adsorption on fluid interface (and the respective adsorption isotherm), lead to correct quantitative description of the adsorption and the related parameters. In we analyze the shortcomings and the source of errors in the fitting procedures. [Copyright &y& Elsevier]

Abstract: The adsorption kinetics, adsorption isotherm and the dilational surface rheology at low oscillation frequencies of sodium dodecyl sulphate (SDS) were studied by drop and bubble profile, and bubble pressure tensiometry. The effect of the inevitably present dodecanol in any SDS solution is taken into account by interpreting the experimental data with theoretical models valid for mixed surfactant solutions. In particular the dilational rheology method appears to be very suitable for demonstrating the continuously on-going hydrolysis reaction in a SDS solution, as the resulting dilational elasticities and viscosities change from a frequency dependencies characteristic to SDS to those expected for dodecanol adsorption layers. For surfactants as active as dodecanol, it turns out that all adsorption and rheological quantities depend significantly on the use of drop or bubble profile tensiometry, i.e. the small reservoir of available surface active molecules in a single droplet has to be considered quantitatively to obtain reliable data. [Copyright &y& Elsevier]

Abstract: A novel glutaraldehyde cross-linked epoxyaminated chitosan (GA-C-ENCS) prepared through chemical modification was used as an adsorbent for the removal and recovery of Cu(II) from aqueous media. The adsorbent was characterized by FTIR, SEM-EDS, ESR, TG/DTG, BET-surface area and potentiometric titration. The Cu(II) adsorption process, which was pH dependent showed maximum removal at pH 6.0. Adsorption equilibrium was achieved within 3h. The adsorption of Cu(II) followed a reversible-first-order kinetics. The equilibrium data were evaluated using the Langmuir, Freundlich and Dubinin–Radushkevich isotherm models. The best interpretation for the equilibrium data was given by the Dubinin–Radushkevich isotherm. The adsorption capacity of the adsorbent increased from 3.11 to 3.71mmolg−1 when the temperature was increased from 20 to 50°C. The complete removal of 20.7mgL−1 Cu(II) from electroplating industry wastewater was achieved by 0.4gL−1 GA-C-ENCS. Regeneration experiments were tried for four cycles and the results indicate a capacity loss of <7.0%. [Copyright &y& Elsevier]