Surface Adsorption Properties Research Articles

Magnetic Multi-Wall Carbon Nanotubes for Methyl Orange Removal from Aqueous Solutions: Equilibrium, Kinetic and Thermodynamic Studies

The magnetic iron oxide nanoparticles (SPION) were prepared using the co-precipitation method. The magnetically modified multi-wall carbon nanotubes (MWCNT) were obtained by the same method. The magnetic nanoparticles were used as adsorbents for methyl orange (MO) removal from aqueous solutions. The surface properties of adsorbents were analyzed by XRD, TGA, FTIR, and SEM. The adsorption was carried out on batch type. The kinetic, equilibrium and thermodynamics parameters were obtained by experimental results. The maximum adsorption capacity was obtained at pH 3 for both of the adsorbents. Theoretical adsorption capacities were found as 0.31 mg/g for SPION and 10.54 mg/g for MWCNT/SPION composites from Langmuir isotherm parameters. The MWCNT/SPION composites can adsorb 95% of methyl orange from water. The kinetic parameters and thermodynamic parameters were calculated.

Adsorption characteristics of N’-undecylenamidopropyl-N”-trimethylammonium methyl sulfate at the air–water interface

The dynamic surface tension and adsorption properties of the aqueous solutions of N’ -undecylenamidopropyl- N” -trimethylammonium methyl sulfate, an eco-friendly cationic surfactant, were evaluated by a maximum bubble pressure method at various life times.

Tailoring surfaces of hybrid ceramics for gas adsorption – From alkanes to CO2

Hybrid ceramics are promising adsorbents since they feature adjustable surface adsorption properties. In this study hybrid ceramic adsorbents are systematically prepared with different surface characteristics in order to demonstrate and extent the applicability of hybrid ceramics as adsorbents for a number of volatile organic compounds as well as CO2. Therefore, hybrid ceramics are prepared by pyrolysis of polysiloxanes containing methyl, phenyl and aminopropyl groups.The preparation process is adapted to the synthesis of amino group bearing monoliths, limiting the pyrolysis temperature to 350°C. Vapors of different polarity as well as CO2 are used for investigation of surface characteristics resulting at different pyrolysis temperatures. Consequently, a broad range of surface characteristics can be derived from precursors with different organic groups and their pyrolysis products. The porosity of adsorbents is also varied in the micro to mesopore range by precursor composition and pyrolysis temperature. Moreover, high CO2 sorption capacities up to 2.3 mmol/g can be achieved. Amino group bearing adsorbents without micro- or mesopores show increased CO2 sorption capacities at 100°C. CO2 sorption capacities at 0–40°C can be increased by precursors with methyl or phenyl groups or in the presence of mesopores. This demonstrates that hybrid ceramics are tunable for a versatile set of adsorption tasks.

A series of amide functionalized isoreticular metal organic frameworks

2,2-Diamido-1,1′-biphenyl-4,4′-dicarboxylic acids were synthesized with amido functions of different chain lengths and used as starting materials for isoreticular metal organic frameworks (IRMOFs). The IRMOFs were characterized by means of different methods such as single crystal X-ray diffraction, X-ray absorption spectroscopy, powder X-ray diffraction, solid state NMR and IR spectroscopy, powder X-ray diffraction (PXRD), FT-IR and solid state NMR spectroscopy, N2 physisorption measurements and thermogravimetric analyses (TGA). We here present a detailed study on how systematic variations of the length of the alkylamide side chains influence certain features of the material such as structure, specific surface and gas adsorption properties. In general, this series of MOF materials exhibit high capacities for the storage of gases such as short alkanes and alkenes as well as CO2.

Structural, textural and protein adsorption properties of kaolinite and surface modified kaolinite adsorbents

The structural, textural and protein adsorption properties of kaolinite from clay sedimentary deposits, metakaolinite obtained by thermal dehydroxylation of kaolinite, and the organic derivative prepared by reacting kaolinite with the silane coupling agent tert-butyldimethylchlorosilane, were studied. The retention capacities for the proteins α-lactalbumin (A-LA), bovine serum albumin (BSA) and β-lactoglobulin (B-LG) and the nature of the interactions responsible for protein binding were studied by adsorption experiments, performed at room temperature and pH5.0. The protein adsorption capacity and the selectivity show a clear dependence on the chemical nature of the adsorbents surface and on the textural properties. Kaolinite behaves as a strong adsorbent for A-LA and BSA, and exhibits a very high affinity for B-LG. Metakaolinite shows good retention capacity for A-LA and B-LG, but does not retain significant amounts of BSA. The adsorption capacity of the organo–kaolinite hybrid considerably increases for BSA and A-LA. FTIR results indicate the absence of hydrogen bonding between the adsorbents surface and the polypeptides. The interactions responsible for protein binding are closely related to the hydrophilic or hydrophobic character of the adsorbent surface and the amino acid composition of the proteins, steric effects also should be considered for the adsorption patterns.

Carbon Nanomaterials and Related Nanostructures: Synthesis, Characterization, and Application

Since the discovery of buckyballs in 1985, the family of carbon materials has been rapidly growing. From zero-dimensional (0D) fullerene, 1D carbon nanotubes (CNTs), and recent 2D graphene to traditional 3D nanoporous carbon and nanodiamond, carbon nanomaterials exhibit a variety of structures and forms due to the existence of three hybridization forms, namely, sp3, sp2, and sp1, of carbon atoms. In recent years, they have increasingly gained interests from both scientific and industrial communities due to the unique physical and chemical properties. They show diverse potential applications in structure, electronics, energy, environment, water, and others. The purpose of this special issue is to report some latest research results on synthesis, characterization, and applications of carbon nanomaterials and related nanostructures. The accepted papers cover various carbon materials, namely, CNTs, graphene, carbon nanofibers, nanodiamonds, amorphous carbon films, carbon nanocomposite, graphite-like layered materials, and so on. These papers cover a wide range of topics related to synthesis and applications of these carbon nanomaterials in mechanics and tribology, thermal management, energy conversion (photoelectronic devices, solar cells, and photocatalysis), energy storage (lithium-ion batteries), and drug delivery fields. Moreover, two papers present theoretical calculation of carbon nanomaterials in electronic, optical, and surface adsorption properties using density functional theory.

Correlation study between photo-degradation and surface adsorption properties of phenol and methyl orange on TiO2 Vs platinum-supported TiO2

Adsorption of phenol and methyl orange on the surface of TiO2 and Pt–TiO2 photocatalysts was investigated by FT-IR spectroscopy. It was found that platinum plays an important role in the adsorption properties of the studied substrates on TiO2. Platinum deposits modified the phenol-photocatalyst interaction providing new adsorption sites on TiO2 surface. On Pt–TiO2 photocatalysts, phenol mainly interacts via formation of adsorbed phenolates species. It was also found that the adsorption of methyl orange on titania and Pt–TiO2 photocatalysts occurs via interaction of the azo group with surface Ti4+. Pt photodeposition significantly increases the TiO2 photoreactivity in phenol and methyl orange photo-degradation; however, this increase depends on the properties of the Pt deposits. Moreover, it was observed that platinum content is the main factor determining the substrate-photocatalyst interaction and therefore the Pt–TiO2 photocatalytic performance.

Surface Adsorption and Aggregation Properties of Novel l‐Lysine‐Based Gemini Surfactants

AbstractFour chiral l‐lysine‐based gemini surfactants with different spacers were synthesized, namely, disodium (18R,23R)‐12,20,21,29‐tetraoxo‐13,19,22,28‐tetraazatetracontane‐18,23‐dicarboxylate([C12‐2‐C12]Na2), disodium (18R,25R)‐12,20,23,31‐tetraoxo‐13,19,24,30‐tetraazadotetracontane‐18,25‐dicarboxylate([C12‐4‐C12]Na2), disodium(18R,27R)‐12,20,25,33‐tetraoxo‐13,19,26,32‐tetraazatetratetracontane‐18,27‐dicarboxylate([C12‐6‐C12]Na2), disodium(2R,2′R)‐ 2,2′‐(6‐chloro‐1,3,5‐triazine‐2,4‐diyl)bis(azanediyl)bis(6‐dodecanamidohexanoate) ([C12‐T‐C12]Na2). The chemical structures of the prepared compounds were confirmed by 1H‐NMR, ESI–MS and IR spectra. Further, the critical micelle concentration (CMC) of these surfactants in aqueous solutions was determined by surface tension and conductometry methods at 25 °C. Moreover, the adsorption and micellization behaviors of these surfactants were estimated by pC20, the minimum average area per surfactant molecule (Amin), and standard free energy for micellization and adsorption ( and ). The results show that the four gemini surfactants have low CMC values and significantly low surface tension. Furthermore, the surfactants show strong adsorption at the air–water interface. The CMC and Amin values of the surfactants were found to be in the order of [C12‐2‐C12]Na2 < [C12‐4‐C12]Na2 < [C12‐6‐C12]Na2 < [C12‐T‐C12]Na2, which were in agreement with the sequence of and . The circular dichroism of the surfactants indicated the formation of chiral aggregates above the CMC values.

The New Technology of Preparation Activated Carbon from Lignite

The lignite resource is rich in Xilingol League in Inner Mongolia. The two new methods were achieved to preparation activated carbon which used lignite as raw material. Firstly, the lignite was acidized by hydrochloric acid to prepare activated carbon. The catalytic materials in the ash as calcium, magnesium, iron and other elements were significantly reduced after that and the activated speed of the coal was significantly lower than the original coal, which are conducive to the development of uniform porous carbonized compound and decrease the hole broken. And a better surface area and adsorption properties of activated carbon was obtained. Secondly, with the carbonization and activation temperature at 800°C and 45 min, we can get the activated carbon with the excellent adsorption performance through fluidized catalysis of lignite.

Surface dynamics of the intermetallic catalyst Pd2Ga, Part II – Reactivity and stability in liquid-phase hydrogenation of phenylacetylene

The catalytic properties of unsupported Pd2Ga for the liquid-phase hydrogenation of phenylacetylene are investigated after different pre-treatments with focus on the stability of the catalyst during reaction. The surface of as-prepared Pd2Ga consists mainly on Pd and oxidized Ga species. Under the conditions of the liquid-phase hydrogenation of phenylacetylene, the intermetallic surface cannot be reformed in situ by reduction of Ga oxide. After a reductive pre-treatment in 5% H2/Ar at 400°C, an almost clean Pd2Ga surface can be obtained. Its hydrogenation activity is significantly lowered compared to elemental Pd, which is due to the intrinsic adsorption properties of the intermetallic surface. However, residues of H2O or O2 lead to oxidation of this surface. Excluding these impurities, the decomposition can be suppressed. In this case, the bulk material of Pd2Ga gets cracked during phenylacetylene hydrogenation. The controlled modification of the crystal and the electronic structure of Pd by formation of the intermetallic compound Pd2Ga are accompanied with a decreased stability.

The Formation of Surface Multilayers at the Air–Water Interface from Sodium Polyethylene Glycol Monoalkyl Ether Sulfate/AlCl3 Solutions: The Role of the Size of the Polyethylene Oxide Group

Neutron reflectivity, NR, and surface tension, ST, have been used to study the surface adsorption properties at the air-water interface of the anionic surfactant sodium polyethylene glycol monododecyl ether sulfate (sodium lauryl ether sulfate, SLES) in the presence of Al(3+) multivalent counterions, by the addition of AlCl3. In the absence of AlCl3 and at low AlCl3 concentrations monolayer adsorption is observed. With increasing AlCl3 concentration, surface multilayer formation is observed, driven by SLES/Al(3+) complex formation. The onset of multilayer formation occurs initially as a single bilayer or a multilayer structure with a limited number of bilayers, N, ≤3, and ultimately at higher AlCl3 concentrations N is large, >20. The evolution in the surface structure is determined by the surfactant and AlCl3 concentrations, and the size of the polyethylene oxide group in the different SLES surfactants studied. From the NR data, approximate surface phase diagrams are constructed, and the evolution of the surface structure with surfactant and electrolyte concentration is shown to be dependent on the size of the polyethylene oxide group. As the polyethylene oxide group increases in size the multilayer formation requires increasingly higher surfactant and AlCl3 concentrations to promote the formation. This is attributed to the increased steric hindrance of the polyethylene oxide group disrupting SLES/Al(3+) complex formation.

Synthesis, adsorption and aggregation properties of new saccharide-cationic surfactants

A novel saccharide-cationic surfactants containing a quaternary ammonium as cation and saccharide-amide as nonion N,N-dimethyl-N-[3-(gluconamide/lactobionamide)]propyl-N-alkylammonium bromides (CnDGPB and CnDLPB, where n represents hydrocarbon chain lengths of 8, 10, 12, and 14) were designed and synthesized. Their surface activities, adsorption, and aggregation behavior in aqueous solution were investigated by surface tension, conductivity, dynamic light scattering (DLS) and transmission electron microscopy (TEM). Surface tension measurement was used to derive surface adsorption properties such as adsorption efficiency (pC20), the (CMC/C20) ratio, maximal surface excess concentration (Γmax), and minimum surface area per molecule (Amin) at the air–water interface. From the results of temperature dependent conductivity measurements we could obtain the degree of counterion binding (β), and the thermodynamic parameters such as standard free energy (ΔGmic0), enthalpy (ΔHmic0), and entropy (ΔSmic0) of aggregation. DLS and TEM analysis of C14DGPB aqueous solutions revealed the morphology of molecular self-assembles.

Electrochemical polarization effect on surface composition, electrochemical characteristics and adsorption properties of pyrite, arsenopyrite and chalcopyrite during flotation

The article presents experimental research of the influence exerted by electrochemical polarization on electrode potential, phase composition of surface compounds, adsorption of collector and floatability of basic sulfides of gold-bearing ore. It is shown that phase composition of surface compounds generated under different polarization modes affects adsorption of collectors and floatability of minerals.

Emulsifying and surface properties of citric acid deamidated wheat gliadin

The properties of citric acid deamidated wheat gliadin (d-gliadin) and d-gliadin emulsions at concentrations of 2% and 0.5% at pH 7 and 3 were investigated. d-gliadin exhibited high solubility at neutral pH and had a different molecular weight distribution compared with control gliadin. Stability of d-gliadin emulsion increased after heat treatment. Heat treatment led to a red shift of the fluorescence emission maxima of emulsions, indicating the rearrangement of d-gliadin molecules and increase of the protein structure flexibility at the oil–water interface. The emulsion was sensitive to NaCl up to 150 mM due to electrostatic screening effects. d-gliadin concentration influenced the droplet size and the saturation surface load of emulsion. d-gliadin slowly adsorbed on the oil–water interface during the adsorption process. Higher d-gliadin concentration exhibited higher surface pressure. Surface adsorption properties confirmed that d-gliadin was a good emulsifier in oil–water emulsions.

Silver nanoparticles deposited multiwalled carbon nanotubes for removal of Cu(II) and Cd(II) from water: Surface, kinetic, equilibrium, and thermal adsorption properties

A novel composite based on functionalized multiwalled carbon nanotubes (FMWCNTs) reduced with N,N-dimethylformamide and cross-linked with silver nitrate, i.e., Ag-MWCNTs, was fabricated for effective removal of Cu(II) and Cd(II) ions. The performance of Ag-MWCNTs was characterized by Fourier transform infrared, Raman spectroscopy, thermal gravimetric analysis, scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The adsorption characteristics were explored using well-established and effective parameters including pH, contact time, adsorbent dosage, initial metal ion concentration, and temperature. Optimum adsorption of Cu(II) and Cd(II) was observed at pH 6.0 and 7.0, respectively. Kinetic studies revealed that the adsorption data fitted well to the pseudo-second-order kinetic model and Langmuir model gave a better fit than the other models. Thermodynamic properties, i.e., ΔGo, ΔHo, and ΔSo, showed that adsorption of Cu(II) and Cd(II) onto Ag-MWCNTs was endothermic, spontaneous and feasible in the temperature range of 293–313K.

Synthesis of high magnetization hydrophilic magnetite (Fe3O4) nanoparticles in single reaction—Surfactantless polyol process

High magnetization hydrophilic magnetite nanoparticles have been synthesized in two different batches with mean particle sizes of 32.3 and 9.2 nm by inexpensive and surfactant-free facile one-pot modified polyol method. In the synthesis, polyethylene glycol was used as a solvent media and it has been found to play a key role to act as a reducing agent as well as a stabilizer simultaneously. It was shown that the size of the nanoparticles can be effectively controlled by modifying the reaction parameters such as reaction temperature, time and polyol/metal precursor ratio. X-ray diffraction and energy dispersive spectroscopy studies confirm the formation of a pure magnetite phase without the presence of any other phases. Transmission electron microscopy and the Fourier transform infrared spectroscopy results reveal that the particle size and surface adsorption properties are very much dependent on reaction parameters. The magnetic properties of the samples measured by physical property measurement system have shown that the as-synthesized magnetite nanoparticles possess a high magnetization of 85.87 emu/g at 300 K and 91.7 emu/g at 5 K with negligible coercivities. The structural and magnetic characterizations of these polyol coated, hydrophilic, monodisperse, superparamagnetic nanoparticles clearly indicate that they are suitable for biomedical applications.

A new helicase assay based on graphene oxide for anti-viral drug development.

Recently, graphene oxide (GO), one of the carbon nanomaterials, has received much attention due to its unique physical and chemical properties and high potential in many research areas, including applications as a biosensor and drug delivery vehicle. Various GO-based biosensors have been developed, largely based on its surface adsorption properties for detecting biomolecules, such as nucleotides and peptides, and real-time monitoring of enzymatic reactions. In this review, we discuss recent advances in GO-based biosensors focusing on a novel assay platform for helicase activity, which was also employed in high-throughput screening to discover selective helicase inhibitors.

Comparison on Pore Development of Activated Carbon Produced from Scrap Tire by Potassium Hydroxide and Sodium Hydroxide for Active Packaging Materials

Activated carbons were prepared by chemical activation from scrap tire with two chemical reagents, NaOH and KOH. The activation consisted of different impregnation of a reagent followed by carbonization in nitrogen at 700°C. The resultant activated carbons were characterized in terms of BET surface area, methylene blue adsorption and iodine number. The influence of each parameter of the synthesis on the properties of the activated carbons was discussed, and the action of each hydroxide was methodically compared. It is the first time that preparation parameters and pore texture characteristics are simultaneously considered for two closely related activating agents of the same char precursor. Whatever the preparation conditions, it was shown that KOH led to the most microporous materials, having surface areas and adsorption properties (methylene blue adsorption and iodine number) higher than those obtained with NaOH, which was in agreement with some early works. However, the surface areas, methylene blue adsorption and iodine number obtained in the present study were much higher than in previous studies, up to 951 m2/g, 510 mg/g and 752 mg/g, respectively, using scrap tire waste char:KOH equal to 1:1. The thorough study of the way each preparation parameter influenced the properties of the final materials bought insight into the activation mechanisms. Each time it was possible; the results of scrap tire waste chemically activated with hydroxides were compared with those obtained with anthracites; explanations of similarities and differences were systematically looked for.

Dynamic Surface Adsorption Properties of Sodium Dodecyl Sulfate Aqueous Solution

The dynamic surface adsorption properties of aqueous sodium dodecyl sulfate(SDS) solutions were investigated at different concentrations of NaCI using bubble pressure tensiometry MPTC.In the case of ionic surfactants,the existence of a diffuse electric double layer on the surface adsorption layer and around the micelle produces a surface charge.Here,we discuss the influence of the surface charge on the dynamic surface diffusion processes and the micelle properties.It was found that the SDS adsorption process occurred in the presence of a 5.5 kJ ? mol~(-1) adsorption barrier(E_a) that was generated by the surface charge;this barrier significantly decreased the effective diffusion coefficient(D_(eff)) of the dodecyl sulfate ions(DS~-).The ratio of the effective diffusion coefficient to the monomer self-diffusion coefficient(D) (D_(eff)/D) was only 0.013.This indicated that at the beginning,the adsorption of SDS followed the mixed kinetic-diffusion controlled model;this is different from the behavior observed for nonionic surfactants.The adsorption barrier was reduced when NaCI was added.E_a was less than 0.3 kJ ? mol~(-1) after the addition of 80 mmol ? L~(-1) of NaCI.This resulted in values of between 0.8 and 1.2 for D_(eff)/D,which was consistent with the diffusion-controlled model that describes the behavior of nonionic surfactants.The characteristic constants for the micelle dissociation rate(k_2) were determined from the dynamic surface tension of the SDS micelle solutions.The calculated k values decreased as the NaCI concentration was increased,which demonstrated the existence of surface charge on the SDS micelles;this surface charge increased the repulsive forces between the dodecyl sulfate ions,and promoted the dispersion of the micelles.

Modelling Cu(II) adsorption to ferrihydrite and ferrihydrite–bacteria composites: Deviation from additive adsorption in the composite sorption system

Bacterially associated iron (hydr)oxides are widespread in natural environments and are potent scavengers of dissolved metal ions. However, it is unclear whether metal sorption on these composites adheres to the additivity principle, and thus whether metal concentrations in environments where these composites comprise a significant proportion of the reactive iron phases can be modelled assuming component additivity. Here we address this issue for Cu adsorption on ferrihydrite–Bacillus subtilis composites. We precipitated pure ferrihydrite and ferrihydrite composites with different ferrihydrite:bacteria mass ratios, and measured Cu adsorption as a function of pH, Cu adsorbed concentration and composite mass ratio. We develop a molecular-level surface complexation model for Cu adsorption on pure ferrihydrite. We then combine our end-member models for Cu adsorption on B. subtilis (Moon and Peacock, 2011) and ferrihydrite to model the observed Cu adsorption on the composites, adopting a component linear additivity approach. By comparing observed Cu adsorption to that predicted by our composite model, constrained to the exact best fitting end-member stability constants, we find that Cu adsorption behaviour on ferrihydrite–B. subtilis composites deviates from additivity. Specifically, Cu adsorption on composites composed mainly of ferrihydrite is enhanced across the adsorption pH edge (pH ∼3–6), while on our composite composed mainly of bacteria adsorption is enhanced at mid-high pH (pH ∼5–6) but diminished at mid-low pH (pH ∼5–3), compared to additivity. In current surface complexation modelling constructs, Cu adsorption on composites composed mainly of ferrihydrite can be modelled in a component additivity approach, by optimising the stability constants for Cu adsorption on the ferrihydrite and bacteria fractions to values that are within the uncertainty on the end-member stability constant values. The deviation from additivity of these composites, apparent when using the exact best fitting end-member stability constants, is therefore either a modelling artefact due to uncertainties in the surface adsorption properties of the end-member phases, or is relatively minor and cannot be separated from these uncertainties that are inherently present in the parameterisation of the surface adsorption properties in the modelling. In contrast, composites composed mainly of bacteria express significant deviation from Cu adsorption additivity that cannot be modelled in a component additivity approach. We propose that the deviations in Cu adsorption from additivity are the result of physiochemical interactions between the composite fractions that change the surface charge of the ferrihydrite and B. subtilis fractions compared to the isolated end-member phases. The magnitude and direction of the additivity deviations due to these electrostatic effects are then a function of the affinity of Cu for the bacterial fraction and the mass fraction of bacteria in the composite.