Short Adsorption Time Research Articles

Mechanisms of Polymer Adsorption onto Solid Substrates.

Controlling polymer/substrate interfaces without modifying chemistry is nowadays possible by finely tuning the formation of adsorbed layers. The complex processes leading to irreversible attachment of chains onto solid substrates are governed by two mechanisms: molecular rearrangement and potential-driven adsorption. Here we introduce an analytical method to differentiate these two mechanisms. By analyzing experiments and simulations, we investigate how changes in thermal energy and interaction potential affect equilibrium and nonequilibrium components of the adsorption kinetics. We find that the adsorption process is thermally activated, with activation energy comparable to that of local noncooperative processes. On the other hand, the final adsorbed amount depends on the interface interaction only (i.e., it is temperature independent in experiments). We identify a universal linear relation between the growth rates at short and long adsorption times, suggesting that the monomer pinning mechanism is independent of surface coverage, while the progressive limitation of free sites significantly limits the adsorption rate.

Amidoxime-based adsorbents prepared by cografting acrylic acid with acrylonitrile onto HDPE fiber for the recovery of uranium from seawater

An amidoxime-based polymeric adsorbent was prepared by pre-irradiation grafting of acrylonitrile and acrylic acid onto high-density polyethylene fibers using electron beams, followed by amidoximation. Quantitative recovery of uranium was investigated by flow-through experiment using simulated seawater and marine test in natural seawater. The maximum amount of uranium uptake was 2.51 mg/g-ads after 42 days of contact with simulated seawater and 0.13 mg/g-ads for 15 days of contact with natural seawater. A lower uranium uptake in marine test can be attributed to the short adsorption time and the contamination of marine microorganisms and iron. However, the high selectivity toward uranium against vanadium may be beneficial to harvest uranyl ion onto adsorbents and the economic feasibility for recovery of uranium from seawater.

Sequestration of methylene blue (MB) dyes from aqueous solution using polyaniline and polyaniline–nitroprusside composite

This paper reports polyaniline–nitroprusside (PANI–NP) composite prepared via in situ polymerization of polyaniline in the presence of sodium nitroprusside complex using ammonium persulphate oxidant. Comparison between the MB dye elimination from aqueous solution using polyaniline and polyaniline–nitroprusside composite is investigated with UV–visible spectroscopy. The maximum adsorption capacity for PANI and PANI–NP composite at 25 °C are 412.80 and 496.85 mg g−1, respectively. About 80% removal of MB occurs in 1 h using pure PANI from (50 mg MB/100 mL) aqueous solution and 99.37% removal is observed in just 5 min, when PANI–NP composite is used. Adsorption kinetics is in good agreement with pseudo-first order for polyaniline and pseudo-second order for polyaniline–nitroprusside composite. The adsorption data fits well with the Langmuir model for both PANI and PANI–NP composite. Langmuir and Tempkin model suggests chemisorption type of interactions between the MB and adsorbents. Thermodynamic study revealed that the adsorption of MB on PANI and PANI–NP composite is exothermic and spontaneous in nature. Moreover, regeneration and reuse of PANI–NP composite as adsorbent is possible only at higher temperature. FTIR studies further confirm the successful adsorption of MB on PANI and PANI–NP composite. On the basis of vey short equilibrium adsorption time and very high adsorption capacity for MB dye, PANI–NP composite could be used as a most efficient adsorbent for the removal of cationic dyes from any real sample.

Adsorption of methyl orange by synthesized and functionalized-CNTs with 3-aminopropyltriethoxysilane loaded TiO2 nanocomposites

This study aims to develop a highly efficient adsorbent material. CNTs are prepared using a chemical vapor deposition method with acetylene and synthesized mesoporous Ni-MCM41 as the carbon source and catalyst, respectively, and are then functionalized using 3-aminopropyltriethoxysilane (APTES) through the co-condensation method and loaded with commercial TiO2. Results of X-ray powder diffraction (XRD), Raman spectra, and Fourier transform infrared spectroscopy (FTIR) confirm that the synthesized CNTs grown are multi-walled carbon nanotubes (MWNTs). Transmission electron microscopy shows good dispersion of TiO2 nanoparticles onto functionalized-CNTs loaded TiO2, with the diameter of a hair-like structure measuring between 3 and 8 nm. The functionalized-CNTs loaded TiO2 are tested as an adsorbent for removal of methyl orange (MO) in aqueous solution, and results show that 94% of MO is removed after 10 min of reaction, and 100% after 30 min. The adsorption kinetic model of functionalized-CNTs loaded TiO2 follows a pseudo-second order with a maximum adsorption capacity of 42.85 mg/g. This study shows that functionalized-CNTs loaded TiO2 has considerable potential as an adsorbent material due to the short adsorption time required to achieve equilibrium.

Mixed adsorption mechanism for the kinetics of BLG interfacial layer formation at the solution/tetradecane interface

The adsorption kinetics of β-lactoglobulin (BLG) at the water/tetradecane (W/TD) interface as studied by drop profile analysis tensiometry is significantly controlled by the diffusional transport in the aqueous solution bulk. However, due to the contact with the hydrophobic oil phase the protein molecules change their conformation in order to adapt to the interfacial environment. This conformational change can be expressed via the adsorption activity constant. The analysis of the dynamic interfacial tensions leads to much lower activities at short adsorption times and low surface coverages. This allows to conclude that in the early stage of the adsorption layer formation the structure of the BLG adsorption layer at the W/TD interface is similar to that at the water/air (W/A) interface.

Rapid adsorption of toxic Pb(II) ions from aqueous solution using multiwall carbon nanotubes synthesized by microwave chemical vapor deposition technique

Multiwall carbon nanotubes (MWCNTs) were synthesized using a tubular microwave chemical vapor deposition technique, using acetylene and hydrogen as the precursor gases and ferrocene as catalyst. The novel MWCNT samples were tested for their performance in terms of Pb(II) binding. The synthesized MWCNT samples were characterized using Fourier Transform Infrared (FT-IR), Brunauer, Emmett and Teller (BET), Field Emission Scanning Electron Microscopy (FESEM) analysis, and the adsorption of Pb(II) was studied as a function of pH, initial Pb(II) concentration, MWCNT dosage, agitation speed, and adsorption time, and process parameters were optimized. The adsorption data followed both Freundlich and Langmuir isotherms. On the basis of the Langmuir model, Qmax was calculated to be 104.2mg/g for the microwave-synthesized MWCNTs. In order to investigate the dynamic behavior of MWCNTs as an adsorbent, the kinetic data were modeled using pseudo first-order and pseudo second-order equations. Different thermodynamic parameters, viz., ∆H0, ∆S0 and ∆G0 were evaluated and it was found that the adsorption was feasible, spontaneous and endothermic in nature. The statistical analysis revealed that the optimum conditions for the highest removal (99.9%) of Pb(II) are at pH5, MWCNT dosage 0.1g, agitation speed 160r/min and time of 22.5min with the initial concentration of 10mg/L. Our results proved that microwave-synthesized MWCNTs can be used as an effective Pb(II) adsorbent due to their high adsorption capacity as well as the short adsorption time needed to achieve equilibrium.

The effect of adsorption kinetics on the rate of surfactant-enhanced spreading.

A comparison of the kinetics of spreading of aqueous solutions of two different surfactants on an identical substrate and their short time adsorption kinetics at the water/air interface has shown that the surfactant which adsorbs slower provides a higher spreading rate. This observation indicates that Marangoni flow should be an important part of the spreading mechanism enabling surfactant solutions to spread much faster than pure liquids with comparable viscosities and surface tensions.

Microwave-assisted synthesis of multi-walled carbon nanotubes for enhanced removal of Zn(II) from wastewater

Removal of toxic metals is one of the biggest challenges in ensuring safe water for all as well as protecting the environment. Novel multi-walled carbon nanotubes (MCNTs) have been successfully synthesised by microwave techniques and improved to be an outstanding adsorbent for the removal of Zn(II) from wastewater. The adsorption of Zn(II) was studied and optimized as a function of pH, initial Zn(II) concentration, MCNT dosage, agitation speed, and adsorption time. In order to investigate the dynamic behavior of MCNTs as an adsorbent, the kinetic data were modeled using pseudo-first-order and second-order kinetic models. Different thermodynamic parameters, viz., ∆H°, ∆S° and ∆G° have also been evaluated and it has been found that the adsorption was feasible, spontaneous and endothermic in nature. Statistical analysis reveals that the optimum conditions for the highest removal (99.9 %) of Zn(II) are at pH 10, a MCNT dosage 0.05 g, an agitation speed and time of 160 rpm and 60 min, respectively, with an initial concentration of 10 mg/L. On the basis of the Langmuir model, q m was calculated to be 90.9 mg/g for microwave-synthesized MCNTs. Our results proved that MCNTs can be used as an effective Zn(II) adsorbent due to their high adsorption capacity as well as the short adsorption time needed to achieve equilibrium. Hence, MCNTs serve an important role in the removal of heavy metals from wastewater.

Removal of mercury from aqueous solution using mesoporous silica nanoparticles modified with polyamide receptor

Based on the principle of supramolecular recognition and fluorescent chemical sensors, a novel kind of material for the separation of toxic heavy metal ions was designed and synthesized. Mesoporous silica nanoparticles MCM-41 with high surface areas and large ordered pores were used as the supporting matrix. Poly-amide derivative, was grafted to the mesoporous silica nanoparticles for extracting and separating trace Hg2+ from aqueous solution, with a short adsorption time (t=3min) and a wide range of pH application (pH 3–11). The separation material could also extract trace mercury from Traditional Chinese Medicine, and has no influence on their effective components.

Dynamic surface tension of С10ЕО8 at the aqueous solution/hexane vapor interface as measured by bubble pressure tensiometry

Abstract The dynamic surface tension of aqueous solutions of C10EO8 at the interfaces with air and saturated hexane vapor was measured by the maximum bubble pressure tensiometer BPA for adsorption times t ≥ 0.01 s. It can be shown that the dynamic surface pressure of C10EO8 solutions in a saturated hexane atmosphere increases at short adsorption times with increasing surfactant concentration. The theory of diffusion controlled adsorption of two surfactants from the water and gas phases, respectively, was used for data analysis. The obtained experimental results agree with a model based on a reorientation of the C10EO8 molecules, assuming a strong intermolecular interaction between hexane and C10EO8 molecules in the surface layer. Alternatively, an additional enhancement of C10EO8 adsorption activity can be assumed due to the presence of hexane molecules at the interface.

Novel microwave-assisted multiwall carbon nanotubes enhancing Cu (II) adsorption capacity in water

Microwave induced multiwall carbon nanotubes (MWCNTs) synthesized use a tubular microwave chemical vapor deposition technique, using acetylene and hydrogen as the precursor gases, and ferrocene as the catalyst. The novel MWCNT samples tested for performances in terms of Cu (II) binding were synthesized and characterized using BET,HRTEM,FESEM analysis and using this sample adsorption of Cu (II) they were studied as a function of pH, initial Cu (II) concentration, MWCNTs dosage, agitation speed, and adsorption time. The effect of process parameters for the adsorption of Cu (II) such as pH, MWCNTs dosage, agitation speed, and adsorption time was optimized. The adsorption data followed both Freundlich and Langmuir isotherms. On the basis of the Langmuir model, qm was calculated to be 99 mg/g for microwave-synthesized MWCNTs. In order to investigate the dynamic behavior of MWCNTs as an adsorbent, the kinetic data were modelled using the pseudo-second-order and second-order. Different thermodynamic parameters, viz., ∆H°, ∆S° and ∆G° have also been evaluated and it has been found that the adsorption was feasible, spontaneous and endothermic in nature. The statistical analysis reveals that the optimum conditions for the highest removal (99.9%) of Cu (II) are at pH 5.5, MWCNTs dosage 0.1 g, contact time 35 min and agitation speed of 160 rpm. Our results prove that microwave-assisted MWCNTs can be used as an effective Cu (II) adsorbent due to the high adsorption capacity as well as the short adsorption time needed to achieve an equilibrium.

Water vapour adsorption by a coffee-based microporous carbon: effect on CO2capture

BACKGROUND Carbon materials are appealing adsorbents for postcombustion CO2 capture applications. In the present work, the adsorption of H2O, which is an abundant component in flue gases, and its influence on the adsorption of CO2 is evaluated using a microporous carbon. RESULTS The adsorption and desorption isotherms of H2O at 12.5, 25, 50, 70 and 85 °C were obtained for relative pressures between 0 and 0.95. The average isosteric heat of adsorption of H2O on PPC is 46 kJ mol−1. The equilibrium of adsorption and desorption of H2O on PPC can be reasonably well described by the DJD model over the entire temperature and pressure range evaluated. Breakthrough experiments carried out with synthetic flue gas showed that the adsorption of CO2 is not hindered by H2O at short adsorption times, relevant for the adsorption of CO2. Moreover, PPC can be fully regenerated recovering its full adsorption capacity after extended exposure to humid gas. CONCLUSIONS Although the adsorption capacity of CO2 can be reduced by the coadsorption of H2O, this effect only becomes significant at long adsorption times. By appropriately selecting the adsorption time in the cyclic process design the concentration of CO2 in the adsorbed phase can be maximized. © 2015 Society of Chemical Industry

Novel oligo(ethylene glycol)-based molecularly imprinted magnetic nanoparticles for thermally modulated capture and release of lysozyme.

In this study, oligo(ethylene glycol) (OEG)-based thermoresponsive molecularly imprinted polymers (MIPs) for lysozyme on the surface of magnetic nanoparticles were synthesized. Thermoresponsive monomer 2-(2-methoxyethoxy)ethyl methacrylate, chelate monomer N-(4-vinyl)-benzyl iminodiacetic acid, and acidic monomer methacrylic acid were selected as the ingredients for preparing the MIP layer. The thermoresponsive behavior of the novel imprinted magnetic nanoparticles was evaluated by dynamic light scattering and swelling ratios measurements. Interestingly, in analysis of lysozyme, the capture/release process could be modulated by changing the temperature, avoiding tedious washing steps. Meanwhile, high adsorption capacity (204.1 mg/g) and good selectivity for capturing lysozyme were achieved. Additionally, surface imprinting with magnetic nanoparticles as substrate allowed for short adsorption time (2 h) and rapid magnetic separation. Furthermore, the proposed imprinted magnetic nanoparticles were used to selectively extract lysozyme in human urine with recoveries ranging from 89.2% to 97.3%. The results indicated that the OEG-based monomers are promising for responsive MIP preparation, and the proposed imprinted material is efficient for thermally modulated capture and release of target protein.

Microwave assisted multiwall carbon nanotubes enhancing Cd(II) adsorption capacity in aqueous media

Novel multiwall carbon nanotubes (MWCNTs) have been successfully synthesized using tubular microwave chemical vapour deposition technique and proved to be an outstanding adsorbent for the removal of Cd(II) from aqueous solution. The effect of process parameters such as pH, MWCNTs dosage, agitation speed and time were investigated. The maximum adsorption capacities of Cd(II) were found to be 88.62mg/g and a statistical analysis reveals that the optimum conditions for the highest removal (98%) of Cd(II) are at pH 5, MWCNTs dosage 0.1g, agitation speed and time of 160rpm and 50min, respectively with the initial concentration of 10mg/L. The Langmuir and Freundlich isotherm models match the experimental data very well and adsorption kinetic obeyed pseudo-second order. Our results proved that MWCNTs can be used as an effective Cd(II) adsorbent due to the high adsorption capacity as well as the short adsorption time needed to achieve equilibrium.

Adsorption of polyethylenimine and its interaction with a genomic DNA on a silicon oxynitride surface characterized by dual polarization interferometry

Dual polarization interferometry was used to investigate the adsorption of polyethylenimine (PEI) on a silicon oxynitride chip surface, as well as to study the subsequent interaction between PEI and a genomic DNA. A compact homogeneous PEI layer formed initially as a result of their strong electrostatic attraction to the negatively charged chip surface. With the adsorption going on, a short time adsorption process with constant speed was observed and the subsequent PEI molecules loosely attached on the chip surface because of the electrostatic repulsion and crowded surface conditions. A loose and thick DNA layer formed on the PEI surface due to its rigidity. Further PEI deposition induced DNA conformation changes and the swelling of the PEI–DNA complex layer, which resulted in a dramatic layer thickness increase. Under high PEI concentration, the layer mass and thickness increments were partially lost as DNA was stripped off by PEI molecules. This result was interpreted in terms of overcharged DNA–PEI complex formation and the strong electrostatic repulsion between the first PEI layer and the newly formed overcharged DNA–PEI complexes. The explanation was proved by the case of the assembly process in PBS. No stripping effect was found even at a high PEI concentration in PBS because of the salt screening effect and the low charge density of PEI.

Kinetics and isotherm studies on the adsorption of an antiparkinsonism drug Entacapone from aqueous solutions using unsaturated polyester resin (UPR)

Growing concern about environmental issues has prompted the pharmaceutical industry to investigate appropriate and environmentally friendly treatment technologies. Removal of pharmaceuticals by adsorption is one of the most promising techniques, due to its convenience. In the present communication adsorption of Entacapone from wastewater using low-cost non-carbon adsorbent unsaturated polyester resin (UPR) has been reported. Results showed that adsorption of Entacapone onto UPR have some advantages such as high adsorption capacity and short adsorption time. Different thermodynamic parameters like Gibb’s free energy (ΔG°), enthalpy (ΔH°), and entropy (ΔS°) of the undergoing process have also evaluated through these adsorption models. The estimated values for ΔG° were −11.953 × 103 kJ mol−1 over UPR at 303 K (30°C) indicate toward a spontaneous process. The rate equations showed that the adsorption kinetic data generally fitted the rate equations from which the rate constants and diffusion rate constants were evaluated. However, the Lagergren pseudo first-order rate equation gave the best fit, and thus the process followed first-order rate kinetics.

Comparison of Dye Adsorption of Three Forms of Chitosan

The purpose of this project is to explore the adsorption rates of different dye methods (direct, reactive, acidic, disperse, azo dyes) in three shapes of chitosan materials (film, microsphere, and scaffold) which were formed by 88% deacetylation degree of chitosan. Results of this research suggest that the samples with larger specific surface areas tend to have shorter adsorption times. Among the three samples, the chitosan scaffold reached the adsorptive saturation on the third day, showing the shortest adsorption time of the direct, reactive, acidic, dispersive and azo dyes, whereas the chitosan film reached the adsorptive saturation on the eighth day, giving it the longest adsorption time of the dyes.

Efficient adsorption of As(V) on poly(acrylo-amidino ethylene amine) nanofiber membranes

Poly(acrylo-amidino ethylene amine) (PAEA) nanofiber membranes have been synthesized by combining the electrospinning technique and subsequent chemical modification. The membranes were used to remove As(V) from aqueous solution. The adsorption kinetics, equilibrium isotherms, and pH effect were investigated in batch experiments. The Langmuir isotherm and pseudo second-order kinetic models agree well with the experimental data. The PAEA nanofibers are effective for As(V) adsorption at pH 3. Experimental results showed that the maximum adsorption capacity of the PAEA nanofibers with As(V) is 76.92 mg g−1, which is much higher than that of the PAEA microfibers (27.62 mg g−1). The adsorption rate of PAEA nanofibers is faster than that of PAEA microfibers due to its higher specific surface area. The PAEA nanofibers can be used as an effective adsorbent for the removal of As(V) in aqueous solution due to high adsorption capacity and short adsorption time to achieve equilibrium.

Adsorption behavior of non-conventional eco-friendly tyrosine glycerol ether surfactants

Due to the increasing demand for environmentally friendly surfactants, a novel non-conventional glycerol ether surfactant with 12 carbon atoms in the hydrophobic alkyl chain and the amino acid tyrosine in the hydrophilic head (TyrGE12) is synthesized. Measurements of dynamic surface tension by maximum bubble pressure tensiometry and drop profile tensiometry are carried out for alkali aqueous solutions over a wide concentration range and for surface ages spanning from milliseconds to hours. Critical Micelle Concentration (CMC) value, standard free energy of adsorption and other physicochemical properties are calculated based on static (equilibrium) surface tension measurements. Dynamic surface tension data are analyzed using approximate solutions of the Ward and Tordai model to estimate diffusion coefficients for short and long adsorption times. For concentrations above the CMC, the effective diffusion coefficient (D*) of monomers is also estimated. Diffusion coefficients for short adsorption times lie in a physically reasonable range whereas for long adsorption times the computed very low values indicate the presence of an adsorption barrier. Interfacial dilatational storage modulus and loss modulus measurements indicate a dominant elastic character of the adsorption layer for all the examined concentrations and oscillation frequencies. Local peaks in the values of both moduli, below and above CMC, imply that structural changes in the adsorption layer might be partially affected by the presence of micelles.

Dynamic surface properties of eco-friendly phenylalanine glycerol ether surfactants at the W/A interface

Dynamic surface tension and dilatational viscoelasticity data are presented for aqueous solutions of novel nonconventional eco-friendly phenylalanine glycerol ether surfactants, with 12 carbon atoms in the hydrophobic alkyl chain, PhGE12. Adsorption kinetics is studied in a broad range of concentrations and for time scales spanning from several milliseconds to several hours employing maximum bubble pressure tensiometry and drop profile tensiometry. Standard free energy of adsorption and diffusion coefficients for both short and long adsorption times are calculated and discussed. For short adsorption times diffusion coefficients lie in a physically reasonable range but for long adsorption times extremely low values are computed indicating the presence of an adsorption barrier. This barrier appears to mask any micellar kinetics effect for long adsorption times. Measurements of interfacial dilatational storage modulus and loss modulus indicate a visco-elastic character of the adsorption layer for all the examined concentrations and oscillation frequencies. Local peaks in the values of both moduli imply that structural changes occur with increasing concentration. However, these changes seem to be unrelated to the presence of micelles since they are observed at concentrations below the CMC.