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In this work, we report atomic-scale reconstruction processes in Fe-Ce oxide-based composites (hydrothermally precipitated at Fe-to-Ce dosage ratios of 1:0, 2:1, 1:1, 1:2, and 0:1), upon treatment at 300 °C. The structural changes are correlated with the adsorptive removal of arsenate, phosphate, fluoride, bromide, and bromate. The presence of the carbonate-based Ce-component and surface sulfate in precursor samples creates favorable conditions for phase transformation, resulting in the formation of novel (unknown) layered compounds of Fe and Ce. These compounds are of the layered double hydroxide type, with sulfate in the interlayer space. In spite of general awareness of the importance of surface area in adsorptive removal, the increase in surface area upon thermal treatment did not increase adsorption of the studied anions. However, EXAFS simulations and the adsorption tests provided evidence of regularities between local structures of Fe in composites obtained at 80 and 300 °C and adsorption performance of most studied anions. The best adsorption of tetrahedral anions was demonstrated by samples whose simulated outer Fe shells resulted from oscillations from both O and Fe atoms. In contrast, the loss of extended x-ray absorption fine structure was correlated with the decrease of adsorptive removal. Both Fe K-edge and Ce L 3 -edge EXAFS suggested the formation of solid solutions. For the first time, the utilization of extended x-ray absorption fine structure is suggested as a methodological approach (first expressed in the companion paper) to estimate the surface reactivity of inorganic materials intended for use as anion exchange adsorbents. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pore opening-induced pore blocking is the mechanism for the limit to LCP. • LCP is described for desorption of condensate from closed cavities with wedge-like opening. • Experimental LCP for carbons at P/P 0 ∼ 0.4 is reproduced in simulations at boiling points. • Experimental LCP for silica at P/P 0 ∼ 0.5 is described correctly in simulations. • LCP is relatively insensitive to the geometrical aspects of the cavity. The limit to the lower closure point (LCP) observed experimentally in the desorption isotherm of gases in porous solids has been commonly attributed to the homogeneous cavitation of the condensate in cavities. It was proposed recently that the experimental limit to LCP could be described in simulations with the ink-bottle pore, provided that the length of the uniformly sized conduit connecting the closed cavity to the surrounding is shorter than 2 nm, and the evaporation is by way of pore blocking mechanism, rather than homogeneous cavitation. To substantiate this assertion, that deviates from the commonly belief of homogeneous cavitation, we further investigated in this paper with cavities having wedge-like pore opening , that better mimics real solids, and offer further explanation on the limit of the LCP to the pore blocking as the mechanism of evaporation with simulations of argon and nitrogen adsorption over a range of temperatures that are commonly used experimentally. It was found that simulation results correctly captured the experimental observations for carbon-based materials and silica-based materials in that the limit of LCP shifts to higher reduced pressures for weaker adsorbing silica, compared to stronger adsorbing carbon and for a given adsorbent it also shifts to higher reduced pressure for higher temperatures. [ABSTRACT FROM AUTHOR]

[Display omitted] Owing to the numerous potential applications of ZnO nanomaterials, the development of ZnO-based nanocomposites has become of great scientific interest in various fields. In this paper, we are reporting the fabrication of a series of ZnO/C nanocomposites through a simple "one-pot" calcination method under three different temperatures, 500 ℃, 600 ℃, and 700 ℃, with samples labeled as ZnO/C-500, -600, and -700, respectively. All samples exhibited adsorption capabilities and photon-activated catalytic and antibacterial properties, with the ZnO/C-700 sample showing superior performance among the three. The carbonaceous material in ZnO/C is key to expanding the optical absorption range and improving the charge separation efficiency of ZnO. The remarkable adsorption property of the ZnO/C-700 sample was demonstrated using Congo red dye, and is credited to its good hydrophilicity. It was also found to exhibit the most notable photocatalysis effect due to its high charge transfer efficiency. The hydrophilic ZnO/C-700 sample was also examined for antibacterial effects both in vitro (against Escherichia coli and Staphylococcus aureus) and in vivo (against MSRA-infected rat wound model), and it was observed to exhibit synergistic killing performance under visible-light irradiation. A possible cleaning mechanism is proposed on the basis of our experimental results. Overall, this work presents a facile way of synthesizing ZnO/C nanocomposites with outstanding adsorption, photocatalysis, and antibacterial properties for the efficient treatment of organic and bacterial contaminants in wastewater. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mixed micelles of cationic and non-ionic surfactants were studied in aqueous solution. • Mixed surfactant-modified zeolite (MSMZ) and SMZ were prepared and characterized. • The adsorption capacity of MSMZ for removal of DFS was higher than that of SMZ. • The experimental adsorption data of DFS by SMZ was correlated by Sips model. • The removal of DFS on MSMZ was strongly dependent on positive surface charge on zeolite. In this paper, the surfactant-modified clinoptilolite zeolite (with two methods) were used to remove diclofenac sodium (DFS) as a widely used drug in an aqueous solution. Clinoptilolite was modified by using pure cationic surfactant (cetyltrimethylammonium chloride, CTAC) and the mixed surfactants of CTAC + Triton-X100 (TX100). In the new approach, the synergistic effects between CTAC and TX100 were determined by surface tension measurements in different mole fractions and the optimum ratio (y 1 ≈ 0.8) was identified with the maximum synergism. According to the mole fraction of this composition, the surface of clinoptilolite was modified by mixed surfactants (MSMZ) for the adsorption of DFS and then results compared with modified zeolite with pure cationic surfactant (SMZ). The raw and modified (SMZ and MSMZ) zeolites were characterized by Fourier transform infrared spectroscopy (FT–IR), BET analysis, the scanning electron microscopy (SEM) images, Zeta potential and X-ray. The experimental data of adsorption in equilibrium conditions were also analyzed using different adsorption isotherm models (Langmuir, Freundlich, Hill, Khan, Sips, Redlich-Peterson and Toth) in non-linear forms, and finally, the best model consistent with experimental data is determined (SMZ:Sips and MSMZ:Toth). According to the best isotherm model, the amount of absorption capacity in MSMZ was obtained almost 57% higher than SMZ. In addition, the kinetic adsorption data were correlated with eight various models in order to selection the best model for these systems. The kinetic adsorption data were well described by fractal-like pseudo-first-order (FL-PFO) and IKL models for SMZ and MSMZ adsorbents, respectively. Eight error functions were used to estimate the best fitted isotherm and kinetic models. [ABSTRACT FROM AUTHOR]

[Display omitted] The phenomenon that calcium alginate does not exhibit high adsorption capacity as a carrier material has not been reasonably explained or solved. In this paper, a new viewpoint that the orbital energy level of metal ions and the binding degree of the α-l-guluronate and β-d-mannuronate units affect the adsorption performance of the composite was innovatively proposed. Taking barium alginate (BA) as an example, the possibility of replacing calcium alginate is discussed. Barium alginate/graphene oxide (BA/GO) membranes and three-dimensional (3D) barium alginate-bentonite-graphene oxide derived (3D-BA) hydrogels were prepared by vacuum freeze-drying to remove methylene blue. The structure and morphology of the prepared adsorbents were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, thermogravimetry and Fourier transform infrared spectroscopy. The effects of adsorbent dosage, doping ratio, temperature, contact time, pH value and initial dye concentration on the adsorption performance of BA composites were investigated. The adsorption capacities of the BA/GO and 3D-BA materials were 1011.3 and 710.3 mg/g, respectively. The BA/GO membrane exhibited stable filtration performance against high concentrations of dyes. Benefiting from the strong interaction between bentonite, sodium alginate and Ba2+, the 3D-BA hydrogel showed higher thermal stability and better adsorption efficiency than other materials. The Elovich kinetic model and Sips equation can appropriately describe the adsorption process. The results show that barium alginate is a better carrier material than calcium alginate. [ABSTRACT FROM AUTHOR]

[Display omitted] Polyacrylonitrile (PAN)-based materials have been studied for decades as uranium (U(VI)) adsorbents, because the further products of abundant nitrile groups, amidoxime (AO) groups, show great affinity for U(VI) ions. However, excessive amidoximation could cause the shrinkage of PAN fibers, resulting in decreased adsorption performance. Hence, an amino-reinforced amidoxime (ARAO) swelling layer was constructed on the PAN fiber surface (PAN-NH 2 -AO) by modification of the strongly hydrophilic amino group to prevent shrinkage. The molecular chains in the ARAO swelling layer would be swelled due to the adsorption of a large amount of water. Simultaneously, U(Ⅵ) ions can penetrate into the ARAO swelling layer with water molecules and coordinate with amino or AO groups, leading to increased adsorption performance. PAN-NH 2 -AO exhibited maximum U(VI) and water adsorption capacities of 492.61 mg g−1 and 20.32 g g−1 at 25 ℃ with a swelling ratio of 20.73%, respectively. The adsorption capacity of PAN-NH 2 -AO was 0.312 mg g−1 after a 91-day immersion in Yellow Sea, China. The study of the adsorption thermodynamics and kinetics of PAN-NH 2 -AO showed that the adsorption process was spontaneous homogeneous chemical adsorption. This paper proposes a novel method to obstruct amidoximation induced shrinkage and to maximize the potential application of PAN-based materials. [ABSTRACT FROM AUTHOR]

[Display omitted] There is an increased interest in the use of natural surfactant as replacements for synthetic surfactants due to their biosustainable and biocompatible properties. A category of natural surfactants which are attracting much current interest is the triterpenoid saponins; surface active components found extensively in a wide range of plant species. A wide range of different saponin structures exist, depending upon the plant species they are extracted from; but regardless of the variation in structural details they are all highly surface active glycosides. Greater exploitation and application requires a characterisation and understanding of their basic adsorption and self-assembly properties. Glycyrrhizic acid, extracted from Licorice root, is a monodesmosidic triterpenoid saponin. It is widely used in cosmetic and pharmaceutical applications due to its anti-inflammatory properties, and is an ingredient in foods as a sweetener additive. It has an additional attraction due to its gel forming properties at relatively low concentrations. Although it has attracted much recent attention, many of its basic surface active characteristics, adsorption and self-assembly, remain relatively unexplored. How the structure of the Glycyrrhizic acid saponin affects its surface active properties and the impact of gelation on these properties are important considerations, and to investigate these are the focus of the study. In this paper the adsorption properties at the air–water interface and the self-assembly in solution have been investigated using by neutron reflectivity and small angle neutron scattering; in non-gelling and gelling conditions. The adsorption isotherm is determined in water and in the presence of gelling additives, and compared with the adsorption behaviour of other saponins. Gelation has minimal impact on the adsorption; apart from producing a rougher surface with a surface texture on a macroscopic length scale. Globular micelles are formed in aqueous solution with modest anisotropy, and are compared with the structure of other saponin micelles. The addition of gelling agents results in only minimal micelle growth, and the solutions remain isotropic under applied shear flow. [ABSTRACT FROM AUTHOR]

Several hundred papers are published yearly reporting liquid-phase adsorption kinetics data. In general the data is analyzed using a variety of standard models such as the pseudo first- and second-order models and the Intraparticle-Diffusion model. The validity of these models is often assessed empirically via their ability to fit the data, independently of their physicochemical soundness. The aim of the present paper is to rationalize the analysis of liquid-phase adsorption kinetics data, and to investigate experimental factors that influence the adsorption kinetics, in addition to the characteristics of the adsorbent material itself. For that purpose we use a simple Langmuir adsorption–diffusion model, which enables us to identify three dimensionless numbers that characterize the working regime of any batch adsorption experiment: an adsorption Thiele modulus, a saturation modulus, and a loading modulus. The standard models are found to be particular cases of the general adsorption–diffusion model for specific values of the dimensionless numbers. This provides sound physicochemical criteria for the validity of the models. Based on our modeling, we also propose a general yet simple data analysis procedure to practically estimate the diffusion coefficient in adsorbent pellets starting from adsorption half-times. [ABSTRACT FROM AUTHOR]

This paper reports the first proof-of-concept of using bioinspired ZIF-8 based micromotors for efficient water remediation. Natural kapok fibers have unique hollow structure that contains cellulose and lignin, inspiring the design and fabrication of bubble-driving tubular micromotors as an active self-propelled micromachine for the removal of organic pollutants from water. The outer dense ZIF-8 layer can adsorb organic pollutants on the micromotors, and the inner catalyst acts as the engine decomposing fuel H 2 O 2 for providing bubble propulsion. The magnetic γ-Fe 2 O 3 enables the external magnetic control movement and recovery of micromotors. The maximum adsorption capacity of ZIF-8-based magnetic micromotors toward Congo red and doxycycline were high as 394 and 242 mg g−1, respectively, mainly due to the enhanced micromotor-pollutant contacts by their autonomous motion and the resulting mixing associated effect. This novel ZIF-8 micromotor also showed outstanding stability and reusability in aqueous solution, indicating that their great potential for future application in water treatment. [ABSTRACT FROM AUTHOR]

The aim of the paper is to examine the adsorption kinetics of soft microgels and to understand the role of fundamental parameters such as electrostatics and deformability on the process. This knowledge is further exploited to produce microgel-stabilized emulsions using a co-flow microfluidic device. Uncharged microgels made of poly(N -isopropylacrylamide) are synthesized with variable cross-linker contents, and charged ones are produced by introducing pH sensitive co-monomers during the synthesis. The study is carried out by measuring the microgels adsorption kinetics by means of the pendant drop method. The surface pressure is derived from the previous results as a function of time and is measured as a function of the area compression using a Langmuir trough. Emulsions are produced using a microfluidic device varying the microgels concentration and their stability is visually assessed. The microgels deformability as well as higher particle concentrations favour their adsorption. The adsorption is not governed by diffusion, it is cooperative and irreversible. Conversely, the kinetics is slowed down for increasing cross-linking density. The presence of charges slows down the kinetics of adsorption. In the presence of electrolyte, the kinetics accelerates and becomes similar to the one of neutral microgels. The original features of microgel adsorption is highlighted and the differences with adsorption of polymers, star polymers, proteins, and polyelectrolytes are emphasized. Taking benefit from the adsorption kinetics, the required formulation conditions for producing microgel-stabilized emulsions using a co-flow microfluidic device are derived. There exists a critical concentration above which microgels spontaneously adsorb in a sufficient way to decrease the interfacial tension. This critical microgel concentration increases with the cross-linking density and is higher for charged microgels. Whatever the kinetics, the same surface pressure is finally reached. This peculiar behaviour is likely a consequence of the presence of dangling chains in the as-prepared microgels. Consequently, a microgel excess is required to produce emulsions using microfluidics where adsorption has to be spontaneous. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract The transition from monolayer to multilayer adsorption at the air-water interface in the presence of multivalent counterions has been demonstrated for a limited range of anionic surfactants which exhibit increased tolerance to precipitation in the presence of multivalent counterions. Understanding the role of molecular structure in determining the transition to surface ordering is an important aspect of the phenomenon. The focus of the paper is on the alkyl ester sulfonate, AES, surfactants; a promising group of anionic surfactants, with the potential for improved performance and biocompatibility. Neutron reflectivity measurements were made in aqueous solution and in the presence of NaCl, CaCl 2 , MgCl 2 and AlCl 3 , for a range of alkyl ester sulfonate surfactants, in which the headgroup and alkyl chain geometries were manipulated. In the regions of monolayer adsorption changing the AES headgroup and alkyl chain geometries results in an increased saturation adsorption and in a more gradual decrease in the adsorption at low concentrations, consistent with a greater adsorption efficiency. Changing the AES headgroup and alkyl chain geometries also results in changes in the transition from monolayer adsorption to more ordered surface structures with the addition of AlCl 3 and mixed multivalent electrolytes. A more limited surface layering is observed for the ethyl ester sulfonate, EES, with a C 14 alkyl chain. Replacing the C 14 alkyl chain with a C 18 isostearic chain results in only monolayer adsorption. The results demonstrate the role and importance of the surfactant molecular structure in determining the nature of the surface adsorption in the presence of different electrolytes, and in the tendency to form extended surface multilayer structures. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Metal organic frameworks (MOFs) are good absorbents that provide high specific surface area, modified pore surface and controllable pore size. The aim of this work is to prepare a MOFs material with good toluene adsorption property in the presence of water. In this paper, modified UiO-66 (University of Oslo 66) was successfully synthesized with polyvinylpyrrolidone (PVP) as structure-directing agent by a simple solvothermal method. The physical and chemical properties were obtained by a series of characterization instruments. Some missing-linker defect sites were observed on modified materials (defective UiO-66) and were known as the main active sites for toluene adsorption. The defective UiO-66 (PVP-U-0.5, 259 mg g−1) demonstrated 1.7 times toluene adsorption capacity of the pristine UiO-66 (151 mg g−1) when the PVP/Zr4+ ratio was 0.5. The interactions between toluene and UiO-66 and PVP-U-0.5 were assessed through the Henry's law constant (K H) and the isosteric adsorption heat (ΔH ads), which indicated that stronger interaction between PVP-U-0.5 and toluene molecules. Moreover, PVP-U-0.5 displayed good adsorption capacity (84 mg g−1) at high relative humidity (70% RH). Water temperature programmed desorption experiments revealed that PVP-U-0.5 had more hydrophobic property, which provided a further possibility for practical application for the removal of toluene. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Much attention has been paid to understanding the clustering mechanism of water adsorbed on carbonaceous adsorbents. Adsorbed water forms clusters around strong sites, such as functional groups and surface defects, and these clusters then coalesce if the strong sites are sufficiently close to each other. Simulations of water adsorption are notoriously time consuming because of the slow relaxation of the strongly-directional hydrogen bonds. Our objective in this paper is to gain a better insight into clustering and coalescence of water, without incurring large computing overheads. To this end we have chosen argon as an adsorbate, and a substrate that is a very weak adsorbent for argon. To mimic functional groups, the substrate surface is decorated with strongly adsorbing patches. The adsorbate forms nano-clusters with convex surfaces at pressures greater than the saturation vapour pressure. When these clusters are sufficiently close to each other, they coalescence to form larger fused clusters, and there is a decrease in the equilibrium pressure. The relationship between the radius of curvature of the developed nano-clusters and the equilibrium pressure follows the functional form of the Kelvin equation, but the energy parameter γ v M is smaller than the bulk value, implying that the clusters have a smaller cohesive energy. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract As the commercial use of nano metal oxides, including iron oxides, becomes more prevalent, there is a need to understand functionality as it relates to the inherent properties of the nanomaterial. Many applications of nanomaterials rely on adsorption, ranging from catalysis to aqueous remediation. In this paper, adsorption of selenium (Se), an aqueous contaminant, is used as a model sorbate to elucidate the relationships of structure, property, and (adsorptive) function of nano-hematite (nα-Fe 2 O 3). As such, six nα-Fe 2 O 3 particles were synthesized controlling for size, shape and surface area without capping agents. Sorbent characteristics of the six particles were then assessed for their impact on selenite (HSeO 3 −) and selenate (SeO 4 2−) adsorption capacity and mechanism. Mechanism was assessed using in-situ attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy and extended X-ray absorption fine edge spectroscopy (EXAFS). Regression analyses were then performed to determine which characteristics best describe adsorption capacity and binding mechanisms of Se on nα-Fe 2 O 3. The results demonstrate that crystal surface structure, specifically presence of the {0 1 2} facet promotes adsorption of Se and the presence of {0 1 2} facets promotes SeO 4 2− sorption to a greater extent than HSeO 3 −. The data further indicates that {1 1 0} facets bind HSeO 3 − with binuclear complexes while {0 1 2} facets bind HSeO 3 − via mononuclear inner-sphere complexes. Specific nα-Fe 2 O 3 facets also likely direct the ratio of inner to outer-sphere complexes in SeO 4 2− adsorption. [ABSTRACT FROM AUTHOR]

Arsenic contamination due to anthropogenic and natural activities has posted a great risk to humans through several pathways. As such, development of cost-effective technologies for arsenic decontamination is very important from both social and economic standpoints. In this paper, we are reporting a novel adsorptive yttrium nanoparticles (YNPs)/polyvinyl alcohol (PVA) modified polysulfone (PSF) membrane for the efficient treatment of arsenic. In the preparation of membrane, the porous PSF membrane fabricated with hydrophilic polyacrylic acid (PAA) polymer was coated by a PVA thin layer and then loaded with YNPs through an in-situ precipitation method using an ammonia vapor. We found that spherical YNPs were uniformly distributed onto the surface and within the matrix of membrane. The adsorption capacity as high as 35.56 mg-As/g was obtained at pH around 7. The membrane worked well across pH 4.0–8.0, with the best performance at pH 5.0. 90% of ultimate adsorption capacity was achieved in 2 h with the initial arsenic concentration of 10 mg/L and at the membrane dosage of 0.2 g/L. The kinetics data can be better fitted by the pseudo-second-order model. The Langmuir isotherm well described the adsorption isothermal data. The filtration studies with an initial arsenate concentration of 94.8 μg/L showed that the treatment capacities of the composite membrane at pH 7.0 and 5.0 were 296 and 692 L/m 2 , respectively. The X-ray photoelectron spectroscopy (XPS) analysis suggested that ligand exchange between yttrium-hydroxyl groups and arsenate species may play as the main adsorption mechanism. Our study demonstrates that the membrane is a better material for arsenic decontamination than previously reported adsorptive membranes. [ABSTRACT FROM AUTHOR]

In this paper, the carbon-doped boron nitride nanoplate (C-BNNP) was prepared by pyrolyzing the precursor under N 2 and served as an excellent adsorbent for removal of Rhodamine B (RhB). The structure and composition of C-BNNP were characterized and its adsorption behavior for RhB was investigated. Compared with boron nitride nanoplate (BNNP) which was synthesized under NH 3 , C-BNNP displayed an enhancement of the adsorption capacity for RhB (833 mg/g). The adsorption activity was comprehensibly studied by kinetics, isotherm and thermodynamics. The adsorption kinetics followed pseudo-second-order model. The equilibrium adsorption data agreed well with the Langmuir isotherm. And the thermodynamics indicated that the adsorption process was a spontaneous, exothermic and physisorption process. In addition, the density functional theory was proposed that doping carbon in the BNNP decreased the chemical hardness of the adsorbent and enhanced the adsorption capacity of C-BNNP for RhB. [ABSTRACT FROM AUTHOR]

Surface free energy and roughness are two predominant factors governing the hydrophilicity/hydrophobicity of materials. This paper reported the surface roughness induced hydrophobicity of graphene foam by incorporating silica nanoparticles onto graphene sheet via a sol-gel method and subsequent modification using silane. Various techniques were employed to characterize the morphology, composition and surface properties of sample. The results showed that the as-prepared graphene foam exhibited a superhydrophobic surface with a high water contact angle of 156°, as well as superoleophilicity with excellent adsorption capacities for a variety of oil compounds. Benefiting from the integration of enhancement on the surface roughness and reduction on the surface free energy of material, the graphene foam developed in this study had the capability to effectively separate oil-water mixture with excellent stability and recyclability. [ABSTRACT FROM AUTHOR]

In this paper, a novel strategy for the preparation of poly(levodopa) functionalized MgAl-layered double hydroxide (PDOPA- f -LDH) was developed based on the modified mussel inspired chemistry. The utilization of PDOPA- f -LDH for the removal of methylene blue (MB) from aqueous solution was also examined. Taken advantage of the self-polymerization of levodopa (DOPA) in alkaline solution and the strong affinity of catechol groups to the substrate surface, the LDH was covered homogeneously by a layer of polymer coating of DOPA, leading to the functionalization toward LDH. The structure, surface morphology, thermostability and elemental composition of as-prepared PDOPA- f -LDH were investigated by the transmission electron microscope, scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and X-ray photoelectron spectroscopy. Besides, the surface charge of the PDOPA- f -LDH was also investigated using zeta potential. The effects of various parameters, including contact time, initial MB concentration, solution pH and temperature, on the adsorption of MB onto PDOPA- f -LDH were systematically investigated. Results show that the adsorption capacity of functionalized LDH at 25 °C could reach up to 102 mg/g, which is much higher than that of pure LDH in the same experimental conditions. The adsorption kinetics and isotherm of MB adsorption were studied in batch experiments. The pseudo-second-order model is found to be the best to describe the adsorption kinetics. The isotherm result shows that the Freundlich isotherm is the better-fit-isotherm model to represent the equilibrium data. The values of thermodynamic parameters, including enthalpy change Δ H 0 , entropy change Δ S 0 and Gibbs free energy change Δ G 0 , were also determined. All the Δ G 0 values are negative; the Δ H 0 and Δ S 0 values of PDOPA- f -LDH were −7.824 kJ mol −1 and −0.01562 kJ mol −1 K −1 , respectively. And the activation energy of system ( E a ) is calculated as 24.69 kJ mol −1 . The fact suggests that the MB adsorption on PDOPA- f -LDH is a spontaneous and exothermic process. These obtained results indicate that the prepared PDOPA- f -LDH could be used as an interesting adsorbent with great potential to adsorb the cationic dyeing pollutants from aqueous media. [ABSTRACT FROM AUTHOR]

In this paper, a novel heterogeneous nanodendrimer with generation of G2.0 was prepared by individual grafting of diethylenetriamine, triazine and l -cysteine methyl ester on the modified aluminum–silicate mixed oxides as a potent adsorbent of Hg(II) ions from aqueous media. The prepared nanodendrimer was characterized by nuclear magnetic resonance spectrum ( 1 H NMR and 13 C NMR), Fourier transform infrared spectroscopy (FT-IR), Diffuse reflectance UV–Vis spectroscopy (DR UV–Vis), zeta potential (ζ), inductively coupled plasma atomic emission spectroscopy (ICP-AES), transmission electron microscopy (TEM), scanning electron microscopy (SEM), nitrogen adsorption experiments at −196 °C and elemental analysis. Equilibrium and kinetic models for Hg(II) ions removal were used by investigating the effect of the contact time, adsorbent dosage, initial Hg(II) ions concentrations, effect of solution’s temperature, interfering ions, and initial pH. The contact time to approach equilibrium for higher removal was 6 min (3232 mg g −1 ). The removal of Hg(II) ions has been assessed in terms of pseudo-first- and -second-order kinetics, and the Freundlich, Langmuir and Sips isotherms models have also been applied to the equilibrium removal data. The removal kinetics followed the mechanism of the pseudo-second order equation, where the chemical sorption is the rate-limiting step of removal process and not involving mass transfer in solution, which was further proved by several techniques such as zeta potential, FT-IR and DS UV–vis. The thermodynamic parameters (ΔG, ΔH and ΔS) implied that the removal of mercury ions was feasible, spontaneous and chemically exothermic in nature between 15 and 80 °C. The nanodendrimer indicated high reusability due to its high removal ability after 15 adsorption–desorption runs. The adsorption mechanisms of Hg(II) ions onto the nanodendrimer was further studied by diverse techniques such as FTIR, EDS, zeta potential, DR UV–Vis spectroscopy and SEM. The possible mechanism of the Hg(II) ions adsorption onto the nanodendrimer could be carried out through the various paths such as electrostatic interaction, complexation, toxic metal chelation and ionic exchange, which eventually resulted in the hydrolysis and precipitation of the adsorbed Hg(II). The l -cysteine methyl ester nanodendrimer could also remove the mercury ions from the Persian Gulf water even after five times of recycling. [ABSTRACT FROM AUTHOR]

Polysaccharides are known to modify binding of proteins at interfaces and this paper describes studies of these interactions and how they are modified by pH. Specifically, the adsorption of human serum albumin on to polystyrene latex and to silica is described, focusing on how this is affected by hyaluronan. Experiments were designed to test how such binding might be modified under relevant physiological conditions. Changes in adsorption of albumin alone and the co-adsorption of albumin and hyaluronan are driven by electrostatic interactions. Multilayer binding is found to be regulated by the pH of the solution and the molecular mass and concentration of hyaluronan. Highest adsorption was observed at pH below 4.8 and for low molecular mass hyaluronan (≤150 kDa) at concentrations above 2 mg ml −1 . On silica with grafted hyaluronan, albumin absorption is reversed by changes in solvent pH due to their strong electrostatic attraction. Albumin physisorbed on silica surfaces is also rinsed away with dilute hyaluronan solution at pH 4.8. The results demonstrate that the protein adsorption can be controlled both by changes of pH and by interaction with other biological macromolecules. [ABSTRACT FROM AUTHOR]

Phosphate (P) removal is significant for the prevention of eutrophication in natural waters. In this paper, a novel adsorbent for the removal of P from aqueous solution was synthesized by loading zirconium oxide and iron oxide onto activated carbon nanofiber (ACF-ZrFe) simultaneously. The adsorbent was characterized by scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The results showed that P adsorption was highly pH dependent and the optimum pH was found to be 4.0. The isotherm of adsorption could be well described by the Langmuir model and the maximum P adsorption capacity was estimated to be 26.3 mg P/g at 25 °C. The kinetic data were well fitted to the pseudo-second-order equation, indicating that chemical sorption was the rate-limiting step. Moreover, co-existing ions including sulfate (SO 4 2− ), chloride (Cl − ), nitrate (NO 3 − ) and fluoride (F − ) exhibited a distinct effect on P adsorption with the order of F − > NO 3 − > Cl − > SO 4 2− . Further investigations by FT-IR spectroscopy and pH variations associated with the adsorption process revealed that ligands exchange and electrostatic interactions were the dominant mechanisms for P adsorption. The findings reported in this work highlight the potential of using ACF-ZrFe as an effective adsorbent for the removal of P in natural waters. [ABSTRACT FROM AUTHOR]

Accurate estimation of the isosteric heat of adsorption is mandatory for a good modeling of adsorption processes. In this paper a thermodynamic formalism on adsorbed phase volume which is a function of adsorption pressure and temperature has been proposed for the precise estimation of the isosteric heat of adsorption. The estimated isosteric heat of adsorption using the new correlation has been compared with measured values of prudently selected several adsorbent-refrigerant pairs from open literature. Results showed that the proposed isosteric heat of adsorption correlation fits the experimentally measured values better than the Clausius-Clapeyron equation. [ABSTRACT FROM AUTHOR]

This paper presents the results of the application of the advanced LBET and QSDFT methods compared to the BET and DR approach to the comprehensive analysis of the porous structure of activated carbons obtained by chemical activation of demineralised Kraft lignin with potassium and sodium hydroxides. Based on the analysis of nitrogen adsorption isotherms, the influence of the preparation process conditions on the porous structure formation was investigated. Particularly, the impact of the type of activating agent, the activation temperature, the hydroxide to lignin mass ratio, and the flow rate of inert gas on the porous structure formation was assessed. This work proves how useful the used methods of structure analysis are when evaluating the influence of preparation conditions on the formation of the porous structure of activated carbons. [ABSTRACT FROM AUTHOR]

The work investigates the influence of surface physicochemical properties of planar indium tin oxide (ITO) as a model substrate on T4 bacteriophage adsorption. A comparative T4 bacteriophage adsorption study shows a significant difference in bacteriophage adsorption observed on chemically modified planar ITO when compared to similarly modified particulate ITO, which infers that trends observed in virus-particle interaction studies are not necessarily transferrable to predict virus-planar surface adsorption behaviour. We also found that ITO surfaces modified with methyl groups, (resulting in increased surface roughness and hydrophobicity) remained capable of adsorbing T4 bacteriophage. The adsorption of T4 onto bare, amine and carboxylic functionalised planar ITO suggests the presence of a unique binding behaviour involving specific functional groups on planar ITO surface beyond the non-specific electrostatic interactions that dominate phage to particle interactions. The paper demonstrates the significance of physicochemical properties of surfaces on bacteriophage-surface interactions. [ABSTRACT FROM AUTHOR]

The paper focuses on the removal of p-nitrophenol by an adsorption process. A magnetic adsorbent was synthesized by encapsulation of magnetic functionalized nanoparticles using alginate as a green biopolymer matrix. A cationic surfactant, cetylpyridinium chloride (CPyCl), was used to confer a hydrophobic character to the magnetic beads and thus to promote their adsorption efficiency. The effect of different parameters such as initial concentrations of both PNP and CPyCl, contact time and solution pH value on the adsorption of PNP in the presence of CPyCl was investigated. It should be noted that combination of magnetic and adsorption properties in a same material is an interesting challenge which could overcome the recovery problems of pollutant-loaded adsorbent. [ABSTRACT FROM AUTHOR]

The synthesis and characterization of nanoscale zerovalent iron particles (NZVI) supported on Spondias purpurea seed waste (S-NaOH-NZVI) was performed for the adsorption of phosphate (P) ions from waste waters. The effects of various parameters, such as contact time, pH, concentration, reusability and temperature were studied. The adsorption of phosphate ions has been studied in terms of pseudo-first- and -second-order kinetics, and the Freundlich, and Langmuir isotherms models have also been used to the equilibrium adsorption data. The adsorption kinetics followed the mechanism of the pseudo-second-order equation. The thermodynamic parameters (Δ G , Δ H and Δ S ) indicated that the adsorption of phosphate ions were feasible, spontaneous and endothermic at 25–80 °C. No significant loss of activity was observed; confirming that the S-NaOH-NZVI has high stability during the adsorption process even after 12th runs. The suggested adsorbent in this paper was also implemented to remove P from the Persian Gulf water. XRD, FTIR and EDX analysis indicated the presence of Fe 3 (PO 4 ) 2 ⋅8H 2 O (vivianite) on the S-NaOH-NZVI@P surface. [ABSTRACT FROM AUTHOR]

This paper reviews the results of several prior studies to highlight how the concept of the metal–organic framework/graphite oxide (MOF/GO) composites was developed towards their application as separation media for small molecule gases at ambient conditions. The studies are analyzed from a surface engineering standpoint. The MOF/GO composites have been developed considering both the advantages and drawbacks of the composite components: MOF provided a high porosity and reactive centers and GO a dense array of carbon atoms to increase dispersive interactions. The resulting materials showed a significant enhancement in porosity owing to the formation of pores at the interface of GO and MOF crystals. GO oxygen groups were identified as nucleation sites for the formation of the MOF crystals. Other heteroatoms like N also contributed to that effect and could positively enhance the composites structural/chemical heterogeneity. That heterogeneity governed the excellent performance of the composites as reactive adsorbents of NH 3 , H 2 S, NO 2 and physical adsorbents of CO 2 at ambient conditions. While the MOF structure collapsed upon exposure to toxic gases, it was preserved after CO 2 adsorption indicating the recyclability of these materials. Systematic studies of the composite properties showed that such factors as the GO level of oxidation, flake sizes of a graphite precursor and the geometry of MOF crystals are of paramount importance dictating the final morphology of the composite. The properties of the composites make them potentially suitable for gas sensing or energy harvesting. [ABSTRACT FROM AUTHOR]

This paper describes studies of functionalized mesoporous silica employed as adsorbent for Mn(II) from aqueous solutions. The surface area of MCM-41 and diethylenetriamine functionalized-MCM-41 used in this study were 760 and 318 m 2 g −1 (N 2 adsorption). A strong dependence on pH in the Mn(II) adsorption capacity and best results were obtained at pH 6.5–7. The adsorption onto the diethylenetriamine functionalized-MCM-41 followed the pseudo-second-order kinetic model and the highest reaction rate 0.324 min −1 was observed at low initial concentration 10 ppm. The equilibrium data showed excellent correlation with the Langmuir isotherm model and the maximum adsorption capacity of Mn(II) reached 88.9 mg/g for DETA-MCM-41 indicating that the adsorption occurs on a homogeneous surface by monolayer sorption without interaction between the adsorbed ions. These data contribute to the understanding of mechanisms involved in mesoporous silica and provide some practical clues to improve the adsorption efficiency (uptake capacity and kinetics) of Mn(II) ions. [ABSTRACT FROM AUTHOR]

The adsorption of polyalkylene glycols and co-polymers of ethylene oxide and propylene oxide on substrates relevant to textiles with varying surface energies (cellulose, polypropylene, nylon and polyester) was studied by using quartz crystal microgravimetry. Langmuirian-type isotherms were observed for the adsorption profiles of nonionic block polymers of different architectures. The affinity with the surfaces is discussed based on experimental observations, which highlights the role of hydrophobic effects. For a given type of block polymer, micellar and monomeric adsorption is governed by the balance of polymer structure (mainly, chain length of hydrophobic segments) and substrate’s surface energy. [ABSTRACT FROM AUTHOR]