Adsorption Kinetic Curves Research Articles

Preparation and Recognition Performance of Molecularly Imprinted Polymers for Cadmium with Surface-Imprinting Technique

A new Cd (II) ion-imprinted polymer (Cd (II)-IIP), which can be used for selective adsorption of Cd (II) from aqueous solutions, was successfully prepared based on silica gel particles with the help of surface molecular imprinting technology. The adsorption kinetic curve, adsorption isotherm and selective adsorption were measured by static method. The adsorption kinetics of IIPs for Cd (II) reached the equilibrium at about 10 min. The maximum adsorption capacity was 29.36 mg/g, and the IIPs had much higher adsorption quantity than NIPs. Competitive adsorption studies showed that Cd (II)-IIP offers the advantages of selectivity toward targeted Cd (II) compared with NIP in the presence other metal ions. The results showed that the IIPs possessed good specific adsorption capacity and selectivity for Cd (II).

Adsorption properties and preparative separation of phenylethanoid glycosides from Cistanche deserticola by use of macroporous resins

A simple and efficient chromatographic method for large-scale preparative separation of phenylethanoid glycosides (mainly contain echinacoside and acteoside) from Cistanche deserticola was developed. The adsorption properties of eight macroporous resins were evaluated. Three selected resins were further screened depending on the adsorption kinetics curves, in which HPD300 resin showed the best separation efficiency. The adsorption isotherm data on HPD300 resin were fitted to the Freundlich equation in certain concentration range. The dynamic adsorption and desorption experiments were carried out on columns packed with HPD300 resin to optimize the separation process. The breakthrough curves showed that acteoside had a higher affinity to the resin than echinacoside. The contents of echinacoside and acteoside in the product increased from 1.79% and 1.43% in the crude extracts to 16.66% and 15.17%, with recovery yields of 80.41% and 90.17%, respectively. The purity of total phenylethanoid glycosides in the product was 76.58%.

Adsorption Kinetics of DPPG Liposome Layers: A Quantitative Analysis of Surface Roughness

Roughness of a positively charged poly(allylamine hydrochloride) (PAH) polyelectrolyte surface was shown to strongly influence the adsorption of 1.2-dipalmitoyl-sn-3-glycero-[phosphorrac-(1-glycerol)] (DPPG) liposomes on it. The adsorption kinetic curves of DPPG liposomes onto a low-roughness PAH layer reveal an adsorbed amount of 5 mg/m², pointing to liposome rupture, whereas a high-roughness surface leads to adsorbed amounts of 51 mg/m², signifying adsorption of intact liposomes. The adsorption kinetic parameters calculated from adsorption kinetic curves allow us to conclude that the adsorption process is due to electrostatic interactions and also depends on processes such as diffusion and reorganization of lipids on the surface. Analysis of the roughness kinetics enabled us to calculate a growth exponent of 0.19 ± 0.07 and a roughness exponent of around 0.84, revealing that DPPG liposomes adsorbed onto rough surfaces follow the Villain self-affine model. By relating self-affine surfaces with hydrophobicity, the liposome integrity was explained by the reduction in the number of water molecules on the PAH surface, contributing to counterion anchorage near PAH ionic groups, reducing the liposome/PAH layer electrostatic forces and, consequently, avoiding liposome rupture.

Synthesis of Acrylamide Molecularly Imprinted Polymers Immobilized on Graphite Oxide through Surface-Initiated Atom Transfer Radical Polymerization

A novel acrylamide (AA) molecularly imprinted polymer was synthesized by atom transfer radical polymerization (ATRP) on graphite oxide (GO) particles. Propionamide (PAM) was used as a dummy template molecule, hydroxy ethyl acrylate (HEA) as a functional monomer, ethylene glycol dimethacrylate (EDMA) as a crosslinking agent, and acetonitrile as both solvent and dispersion medium. Scanning electron microscopy (SEM) images and infrared spectroscopy (IR) confirmed that the molecularly imprinted polymers (MIP) were successfully grafted onto the surface of the GO particles. The corresponding adsorption kinetic curves and adsorption isotherms showed that the AA adsorption reached equilibrium after 5 h, with large amounts of AA being adsorped in the first 100 min. The maximum AA adsorption capacity was 123.48 µmol g−1 according to Scatchard analysis, which indicated that the MIP possesses good AA adsorption capacity. This MIP-GO material was used to selectively determine AA in fried food samples.

Preparation of new spongy adsorbent for removal of EDTA–Cu(II) and EDTA–Ni(II) from water

Abstract A new spongy adsorbent (PU-DTC) was prepared with a polyurethane (PU) adsorbent for removal of EDTA–Cu(II) and EDTA-Ni(II) from water. This new spongy adsorbent was characterized by using SEM and 13 C NMR and FT-IR spectroscopy. Adsorption kinetic curve indicated that this new spongy adsorbent could quickly remove EDTA–Cu(II) and EDTA–Ni(II) from water, and adsorption isotherm also indicated that PU-DTC had high equilibrium adsorption capacity for EDTA–Cu(II) and EDTA–Ni(II).

Effect of Textural Properties on the Adsorption and Desorption of Toluene on the Metal-Organic Frameworks HKUST-1 and MIL-101

The adsorption and desorption of toluene on metal-organic frameworks HKUST-1 and MIL-101 were studied. The adsorption isotherms and kinetic curves of toluene on HKUST-1 and MIL-101 were separately measured by gravimetric method. Temperature-programmed desorption experiments were carried out for estimating the interaction of toluene with the surfaces of HKUST-1 and MIL-101. Our experimental results showed that the isotherms of toluene on the adsorbents were well fitted by the Langmuir-Freundlich equation. The maximum amount of toluene adsorbed on MIL-101 was 15.1 mmol/g, which was much higher than that adsorbed on HKUST-1 (6.6 mmol/g). The high adsorption capacity of MIL-101 can be attributed to its higher surface area. However, the isotherm of toluene at P/P0 < 0.09 on HKUST-1 was much higher than that on MIL-101 owing to the smaller pore size of HKUST-1. It is suggested that HKUST-1 had better adsorption performance than MIL-101 at low concentration of volatile organic compounds. The desorption activatio...

Carbon dioxide adsorption in microwave-synthesized metal organic framework CPM-5: Equilibrium and kinetics study

The adsorption equilibrium and diffusion of CO2 in CPM-5 (crystalline porous materials) were experimentally studied using a volumetric approach at three different temperatures 273, 298, and 318K and gas pressures up to 105kPa. The Freundlich adsorption equilibrium model was applied to correlate the adsorption isotherms, and the classical microspore diffusion model was applied to obtain the adsorption kinetic curves and diffusivity of CO2 in CPM-5. The selectivity of CO2 over N2 was estimated from the single component isotherms at conditions relevant to post combustion applications (0.15bar PCO2 and 0.75bar pN2). It was found that at pressures up to 105kPa, the CPM-5 adsorbent has CO2 adsorption capacity of 3mmol/g, 2.3mmol/g, at 273K and 298K, respectively, which is significantly higher than those of MOF-5 under the same conditions. The selectivity factor was 14.2 and 16.1 at 273 and 298K, respectively. The CO2 diffusivity in CPM-5, estimated from the adsorption kinetic data measured at low pressures, are 1.86×10−12m2/s, 7.04×10−12m2/s, and 7.87×10−12m2/s at 273K, 298K and 318K, respectively. The initial isosteric heat of adsorption of CO2 on the CPM-5 is 36.1kJ/mol. CPM-5 shows attractive adsorption properties as an adsorbent for separation of CO2 from flue gas.

Adsorption Equilibria and Kinetics for the Adsorption of &lt;I&gt;p&lt;/I&gt;-Nitrophenol on a Phenoxy Groups Modified Hypercrosslinked Polystyrene Resin

Adsorption equilibria and kinetics of p-nitrophenol adsorbed on HJ-01 were investigated in this study. The result indicated that phenoxy groups were uploaded on the skeleton of HJ-01 successfully, the Friedel-Crafts reaction brought on prodigious changes for the Brunauer-Emmett-Teller (BET) specific surface area and pore structure while the nucleophilic substitution reaction had few effects. The adsorption experiments revealed that the acidic solution was suitable for p-nitrophenol adsorption, the adsorption isotherms could be characterized by the Freundlich isotherm equation and the adsorption thermodynamic parameters were all negative, the adsorption kinetic curves obeyed the pseudo-second-order rate equation.

Kinetic and Equilibrium Aspects of Adsorption and Desorption of Class II Hydrophobins HFBI and HFBII at Silicon Oxynitride/Water and Air/Water Interfaces

Hydrophobins are relatively small globular proteins produced by filamentous fungi. They display unusual high surface activity and are implied as mediators of attachment to surfaces, which has resulted in high scientific and technological interest. In this work we focus on kinetic and equilibrium aspects of adsorption and desorption properties of two representatives of class II hydrophobins, namely HFBI and HFBII, at a negatively charged hydrophilic solid/water interface and at the air/water interface. The layers formed at the air/liquid interface were examined in a Langmuir trough, whereas layers formed at the solid/liquid interface were studied using dual polarization interferometry (DPI) under different flow conditions. For comparison, another globular protein, lysozyme, was also investigated. It was found that both the adsorbed amount and the adsorption kinetics were different for HFBI and HFBII, and the adsorption behavior of both hydrophobins on the negatively charged surface displayed some unusual features. For instance, even though the adsorption rate for HFBI was slowed down with increasing adsorbed amount as expected from packing constraints at the interface, the adsorption kinetics curves for HFBII displayed a region indicating adsorption cooperativity. Further, it was found that hydrophobin layers formed under flow partly desorbed when the flow was stopped, and the desorption rate for HFBII was enhanced in the presence of hydrophobins in solution.

Photoresponsive Wettability in Monolayer Films from Sinapinic Acid

Sinapinic acid is an interesting material because it is both antioxidant and antibacterial agent. In addition, when illuminated with ultraviolet light, it can exhibit the so-called photodimerization process. In this paper, we report on the investigation of monolayer films from 3,5-dimethoxy-4-hydroxycinnamic acid (sinapinic acid, SinA) deposited onto poly(allylamine hydrochloride), PAH, films. SinA monolayers were prepared by using the layer-by-layer (LbL) self-assembly technique. Adsorption kinetics curves were well fitted by a biexponential function suggesting that the adsorption process is determined by two mechanisms: nucleation and growth of aggregates. By using wetting contact angle analysis, we have found that SinA monolayers exhibit photoresponsive wettability under UV irradiation (365 nm); that is, wettability decreases with increasing UV irradiation time. The photoresponse of wettability was attributed to photodimerization process. This hypothesis was supported by the dependence of surface morphological structure and absorption on UV irradiation time. The mechanism found in the well-known transcinnamic acid crystals is used to explain the photodimerization process in SinA monolayers.

Rapid removal of Cr(VI) ions from aqueous solutions by the macroporous poly(N, N′‐dimethylamino ethyl methacrylate) hydrogels

AbstractTo improve the adsorption ability of hexavalent chromium [Cr(VI)], the macroporous poly(N, N′‐dimethylamino ethyl methacrylate) [poly(DMAEMA)] hydrogels were successfully fabricated by free‐radical copolymerization in ethanol/water mixture using N, N′‐dimethylamino ethyl methacrylate (DMAEMA) as the monomer, N, N′‐methylenebisacrylamide (MBAA) as the cross‐linker, and Na2SO4 solution as the porogen. The effects of various parameters, such as the concentration of Na2SO4 solutions, the dosage of MBAA, pH values, adsorption kinetic, and isotherm curves, were all investigated through systematic experiments. Scanning electron microscope (SEM) was employed to characterize the various pore structures. The experimental results showed that the influence of Na2SO4 solution to the pore morphology in the matrix was significant. The poly(DMAEMA) hydrogels can effectively adsorb Cr(VI) ions in aqueous media, and the macroporous structures could obvious improve the response rate and adsorption capacity. These results prove that the macroporous poly(DMAEMA) gels can be treated as a potential material for environmental pollution control. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Steam- and carbon dioxide-gasification of coal combustion ash for liquid phase cadmium removal by adsorption

This paper is collocated after two other works in which sieved or demineralized coal combustion ashes were used as cadmium (Cd2+) sorbent for water treatments, and the changes in raw ash properties were followed upon steam- and CO2-gasification. In the present paper, ash samples activated by steam- or CO2-gasification were used to adsorb Cd2+ in model aqueous solutions, to elucidate the relationships among ash properties, gasification treatments, properties of the gasified ash and its sorption behavior. To this end, equilibrium and kinetic cadmium adsorption tests were carried out using the gasified ash (treated with either steam or CO2) as sorbent and under fixed operating conditions (for example, the contact time was 7days and the initial Cd2+ concentration in the aqueous solution to be treated varied between 5 and 50mgL−1 for equilibrium tests, while kinetic tests were carried out for times ranging from 10min to 7days using an initial Cd2+ concentration equal to 50mgL−1). Results were expressed in terms of adsorption isotherms, removal efficiency and kinetic curves. Post-processing of experimental data allowed to provide estimations of relevant parameters such as the equilibrium and the kinetic constants, the separation factor, the initial adsorption rate, the characteristic adsorption time. Besides a direct confrontation between the two gasification treatments, results were also compared with former experiments on the same raw material, and with the main outcomes emerging from the pertinent literature, confirming that the gasified materials resulted as very attractive sorbents for Cd2+ capture from wastewaters.

Adsorption Behavior and Kinetics of Methyl Orange in Water on Activated Carbon

The adsorption behavior of methyl orange aqueous solution was investigated on husk-based activated carbon. The effects of key factors, i.e., degassing pretreatment, adsorption time, temperature, adsorbent dosage and initial concentration, on the adsorption efficiency were measured. The kinetic adsorption curves and adsorption isotherms were fitted with theoretical model. The results show that the removal efficiency of methyl orange could be significantly improved by degassing pretreatment, prolonging the time, lowering temperature or reducing the initial concentration. In the context, adsorption equilibrium will be achieved up 90min. Furthermore, adsorption rate will be enhanced by the increase of the amount of activated carbon. In conclusion, adsorption isotherm and adsorption kinetics can be fitted well with Freundlich equation and pseudo-first Lagergren model, respectively.

Preparation of new base-aluminum-chloride-loaded fiber as adsorbent for fast removal of arsenic(V) from water

Abstract A new base-aluminum-chloride-loaded fiber [PET-AA-NN-Al2(OH)nCl6−n] was prepared with polyethylene glycol terephthalate (PET) as adsorbent for fast removal of arsenic (V) from water. This new fibrous adsorbent was characterized by using SEM and C NMR spectroscopy. Adsorption kinetic curve indicated that this new fibrous adsorbent could fast remove arsenic (V) from water, and adsorption isotherm also indicated that PET-AA-NN-Al2(OH)nCl6−n had high equilibrium adsorption capacity for arsenic (V).

Fast removal of Pb2+ from water using new chelating fiber modified with acylamino and amino groups

Abstract The graft copolymerization of acrylic acid (AA) onto polyethylene glycol terephthalate (PET) fiber initiated by benzoy peroxide (BPO) was carried out in heterogeneous media. Moreover, modification of the grafted PET fiber (PET-AA) was done by changing the carboxyl group into acylamino and amino groups through the reaction with ethylenediamine. The new modified chelating fiber (NDWJN6) was characterized using elementary analysis, SEM and FT-IR spectroscopy. Adsorption kinetic curve indicated that NDWJN6 could fastly remove Pb 2+ from water, and adsorption isotherm also indicated that NDWJN6 had high equilibrium adsorption capacity for Pb 2+ .

Quantification and Enrichment of Esculeoside a from Fresh Tomato Fruits

Esculeoside A, the tomato saponins from Lycopersicon esculentum MILL, may be metabolized into various steroidal hormones such as pregnane derivatives that are expected to exhibit various bioactivities in the body, such as anti-osteoporosis, antimenopausal disorder and anti-tumor actions. In order to enrich large amount of esculeoside A for further scientific research, we firstly developed a high performance liquid chromatography (HPLC) with evaporative light scattering detection (ELSD) method for its quantification, and used it to examined the content of esculeoside A in different cultivated varieties of tomato fruits and tomato extract. Statistical analysis of the obtained data demonstrated that our method was simple, and has achieved desired linearity, precision and accuracy. Then we have explored the feasibility of using pectinase as a means for assisting esculeoside A extraction from fresh tomato fruits, and several factors such as the enzyme concentration, pH value of enzyme solution, temperature, incubation time which influenced on extraction were investigated. Moreover, in our previous study, the adsorption characteristics on several types of macroporous resins have been compared. Among them, D-101 resin showed the best separation behaviors on esculeoside A. So in the present paper, in order to get the best parameters for D101 adsorption, the adsorption kinetic curve, the appropriate ethanol concentration for elution and breakthrough volume were analyzed．

Fast removal of heavy metal ions and phytic acids from water using new modified chelating fiber

Abstract The graft copolymerization of acrylic acid (AA) onto polyethylene glycol terephthalate (PET) fiber initiated by benzoy peroxide (BPO) was carried out in heterogeneous media. Moreover, modification of the grafted PET fiber (PET-AA) was done by changing the carboxyl group into acylamino group through the reaction with dimethylamine. The modified chelating fiber (NDWJN1) was characterized using elementary analysis, SEM and FT-IR spectroscopy. Adsorption kinetic curves indicated that NDWJN1 could fast remove heavy metal ions and phytic acids from water effectively. Furthermore, batch kinetic studies indicated that heavy metal ions adsorbed to NDWJN1 could be fitted well by both pseudo-first-order and pseudo-second-order adsorption equations, but the intra-particle diffusion played a dominant role in the adsorption of phytic acids.

Adsorption equilibrium and kinetics of p-xylene on chromium-based metal organic framework MIL-101

The adsorption and diffusion properties of p-xylene on the chromium-terphthalate-based crystals (MIL-101) and the surface energy of MIL-101 were investigated by using gravimetric and inverse gas chromatography (IGC) techniques. The nanocrystal MIL-101 (∼100 nm) was synthesized by using microwave irradiation method. Adsorption isotherms and kinetic curves of p-xylene on the MIL-101 were measured at temperatures of (288, 298, 308 and 318) K and vapor pressures up to 6 mbar, respectively. Results show that the amount adsorbed of p-xylene on the synthesized MIL-101 was up to 10.9 mmol/g at 288 K and 6 mbar. The isosteric adsorption heat of p-xylene on the MIL-101 was in the range of 24.8–44.3 kJ/mol, which decreased with an increase in amount adsorbed of p-xylene on the MIL-101. The diffusion coefficients of p-xylene within the MIL-101 were in the range of 2.80–10.1 × 10 −10 cm 2/s at 288–318 K with activation energy of 30.9 kJ/mol. Three polar probes (acetone, toluene and p-xylene) were used to characterize the surface property of the MIL-101 by using IGC technique. IGC measurement results showed that the specific component ( Δ G a s ) of the free energy of adsorption for polar probe molecules on the MIL-101 followed the order: p-xylene > toluene > acetone.

Adsorption and Diffusion of Ethyl Acetate on the Chromium-Based Metal–Organic Framework MIL-101

The adsorption equilibrium and diffusion of ethyl acetate (EA) on chromium-terphthalate-based crystals (MIL-101) are experimentally studied. The MIL-101 synthesized in this work shows an extra-high surface area of 5014 m2·g–1 (Langmuir). Adsorption isotherms and kinetic curves of EA on the MIL-101 are measured by a gravimetric method. Results show that the isotherms of EA can be fitted favorably by the Langmuir equation. The adsorption capacity of the MIL-101 for EA is up to 10.5 mmol·g–1 at 288 K and 54 mbar. Diffusion coefficients of EA within the MIL-101 are in the range of (1.617 to 2.264)·10–10 cm2·s–1 in (288 to 318) K with a lower activation energy of 8.361 kJ·mol–1. The isosteric heat of EA adsorption on the MIL-101 is within the range of (36.48 to 42.25) kJ·mol–1. The isosteric adsorption heat increased slightly with the amount adsorbed of EA, implying the existence of favorable lateral interactions between EA molecules. Multiple adsorption–desorption cycles are conducted at 298 K to examine the reversibility of EA adsorption on the MIL-101. Adsorptions were performed separately at (2, 3, 5, 7, and 10) mbar, and desorptions are performed at 0.05 mbar. Experimental results show that the EA adsorption on the MIL-101 is highly reversible and the desorption efficiency of EA is up to 98.4 %.

Interaction of supramolecular centers of silica surface with aromatic amino acids

Surface grafting of β-cyclodextrin onto aminopropylsilica has been carried out under mild conditions using 1,1′-carbonyldiimidazole as an activator. The obtained β-cyclodextrin-silica has been characterized by means of chemical and IRspectral analysis. Adsorption of para-aminobenzoic and para-aminosalicylic acids onto the surface of hydroxylated silica, aminopropylsilica, and silica with chemically attached β-cyclodextrin moieties has been studied in relation to duration of contact, equilibrium concentration, and solution pH. Chemical immobilization of β-cyclodextrin onto silica surface improves adsorption parameters for aromatic amino acids. The well-known mathematical models for the kinetic and equilibrium adsorption processes have been used, and the main adsorption parameters have been calculated. Kinetic curves of aromatic amino acids adsorption correspond to the model of pseudo-second order reaction. The major contribution to the equilibrium adsorption of para-aminobenzoic and para-aminosalicylic acids onto β-cyclodextrin-containing silica is due to the formation of surface inclusion complexes between grafted oligosaccharide molecules and aromatic amino acids.