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PubMed2003

[Study on adsorption of tea polyphenol and caffine with polyamide resin].

The performance of adsorption of tea polyphenol and caffine with polyamide resin was investigated. The results obtained by spectrophotometry and HPLC show that the ability of adsorption of tea polyphenol with polyamide is stronger than that of caffine, in which hydrogen bond plays a very important role. The adsorption amount of caffine is 2.65 mg.g-1 with 7.5% adsorption ratio when 100 mL of 0.71 g.L-1 caffine is adsorbed on polyamide resine, but the adsorption amount of tea polyphenol is up to 148.13 mg.g-1 with 85% adsorption ratio when 700 mL of 1.98 g.L-1 tea polyphenol is adsorbed on polyamide resine. The dilution ratios of caffine and tea polyphenol are 74% and 90%, respectively, when they are diluted by 85% alcohol. The static adsorptions of caffine and tea polyphenol on polyamide resine reach equilibrium quickly in 80 min, and the plots of adsorption kinetics are nearly linear. Tea polyphenol and caffine are successfully separated on polyamide resine, and the obtained product contains more than 96% of tea polyphenol and 80% of EGCC with caffine less than 2.8%.

Adsorption↗

PubMed2004

Lead adsorption capacities of different components in natural surface coatings.

Pb adsorption capacities of Fe oxide, Mn oxide and organic materials in natural surface coatings( biofilms and associated minerals) collected in three lakes, two ponds and a river in Jilin Province, China and Cayuga Lake in US were studied. A novel extraction technique was employed to remove one or more component(s) from the surface coatings. Pb adsorption to surface coatings before and after extraction was performed to determine the adsorptive properties of the extracted component(s). The statistical analysis of observed Pb adsorption was carried out using nonlinear least squares fitting(NLSF) to estimate the Pb adsorption capacity of each component of surface coatings. For each body of water, the estimated Pb adsorption capacity of Mn oxide(mol Pb/mol Mn) was significantly higher than that of Fe oxide(mol Pb/ mol Fe). The value of estimated adsorption capacities of organic materials with the unit mol Pb per kg COD was similar to or less than that of Fe oxides with the unit mol Pb per mol Fe. Comparison of components of surface coatings in different waters showed that the estimated Pb adsorption capacities of components in surface coatings developed in different natural waters were different, especially for Mn oxides.

Adsorption↗

PubMed2004

Binary competitive adsorption of naphthalene compounds onto an aminated hypercrosslinked macroporous polymeric adsorbent.

An aminated hypercrosslinked macroporous polymeric adsorbent was synthesized and characterized. Adsorption isotherms for 1-amino-2-naphthol-4-sulfonic acid (1,2,4-acid) and 2-naphthol obtained from various binary adsorption environments can be well fitted by Freundlich equation, which indicated a favorable adsorption process in the studied range. Adsorption for 1,2,4-acid was an endothermic process in comparison with that for 2-naphthol of an exothermic process. 2-naphthol molecules put a little influence on the adsorption capacity for 1,2,4-acid. However, the adsorption to 1,2,4-acid depressed that to 2-naphthol in a large extent for the stronger electrostatic interaction between 1,2,4-acid and adsorbent. The predominant mechanism can be contributed to the competition for adsorption sites. And the simultaneous environment was confirmed to be helpful to the selective adsorption towards 1,2,4-acid based on the larger selectivity index.

Adsorption↗

PubMed2004

[Adsorption behaviors of herbicide glyphoste on soils].

The adsorption behaviors of herbicide glyphoste on three soils were studied. The influence of pH value and ion strength on adsorption was discussed. It was shown that the adsorption dynamic process of glyphoste on three soils all was first order reaction, and the adsorption isotherms all were linear, adsorption coefficients Kd ranged from 2.2207-3.5280 mL x g(-1). The adsorption percentage of glyphoste on three soils increased with the ionic strength decrease. The adsorption percentage of glyphoste on the Huhhot soil and Dongsheng soil increased with pH value gradually decrease (9-3), and the adsorption percentage of the Hangjing 2 soil early increased and late decreased with pH value gradually decrease (9-3).

Adsorption↗

PubMed2005

Comparison of Pb and Cd adsorption to the surface coatings and surficial sediments collected in Xianghai Wetland.

Surface coatings and surficial sediments were obtained in four natural waters in Xianghai Wetland in China to study the role of surface coatings and surficial sediments in controlling the transporting and cycling of heavy metals in aquatic environments. Pb and Cd adsorption to the surface coatings and surficial sediments were measured under controlled laboratory conditions(mineral salts solution with defined speciation, ionic strength 0.05 mol/L, 25 degrees C and pH 6.0 for surface coatings; and 0.005 mol/L CaCl2 solution, 25 degrees C and pH 6.0 for surficial sediments). The Langmuir adsorption isotherm was applied to estimate equilibrium coefficients of Pb and Cd adsorption to the surface coatings and surficial sediments, and the component analyses of surface coatings and surficial sediments were also carried out. Correlation analyses between the maximum adsorption of Pb and Cd (adsorption max ) and the components in the surface coatings and surficial sediments suggested that there was a statistically significant trend for Pb and Cd adsorption( adsorption max ) to the surface coatings to increase with increasing in contents of Fe and Mn oxides in the surface coatings and surficial sediments. And the metal adsorption abilities of surface coatings were much stronger than those of surficial sediments, highlighting that in the same water, i.e. at the same pH and initial metal concentrations, the metals (such as lead and cadmium) in supernatant were feasible to be adsorbed by surface coatings than surficial sediments. The more importance of surface coatings than surficial sediments for adsorbing and cycling of heavy metals in aquatic environments was evidenced.

Adsorption↗

PubMed2005

Adsorption of beta-naphthalenesulfonic acid/sulfuric acid from their solution by weakly basic resin: equilibrium.

Experiments for single and bisolute competitive adsorption were carried out to investigate the adsorption behavior of beta-naphthalenesulfonic acid (NSA) and sulfuric acid (H2SO4) from their solution at 25 degrees C onto weakly basic resin D301R. Adsorption affinity of sulfuric acid on D301R was found to be much higher than that of NSA. The data of single-solute adsorption were fitted to the Langmuir model and the Freundlich adsorption model. The ideal adsorbed solution theory (IAST) coupled with the single-solute adsorption models were used to predict the bisolute competitive adsorption equilibria. The IAST coupled with the Langmuir and the Freundlich model for sulfuric acid and NSA, respectively, yields the favorable representation of the bisolute competitive adsorption behavior.

Adsorption↗

PubMed2006

[Adsorption and partition of PAHS on particles of the Yellow River].

Experiments were carried out to study the sorption of PAHs Benzo(a)pyrene, chrysene and Benzo(g, h, i)perylene on particles of the Yellow River. The contributions of adsorption and partition to the sorption of PAHs were investigated. Several significant results were obtained from the study: (1) The total sorption capacity increases with the particle content while the sorption capacity of unit weight particle decreases; the isotherms of Benzo(a)pyrene depend on the particle content. (2) Isotherms of Benzo(a) pyrene can be fitted with the Dual Adsorption-Partition model under different particle content; the measured value of the adsorption and partition are in accord with the theoretical value of the Dual Adsorption-Partition model. (3) The adsorption is predominant in the sorption of Benzo(a)pyrene. When the particle contents are 3, 8 and 15 g/L and the liquid equilibrium concentrations are 2.84, 2.35 and 3.4 microg/L, respectively, the contributions of adsorption are 67.8%, 65.6% and 62.69%, respectively. In addition, the contributions of adsorption have a decreasing trend with the increase of the particle content. (4) The sorption capacity of Benzo (a) pyrene being alone are bigger than that with other PAHs chrysene and Benzo(g, h, i)perylene coexisting in the water system, this also proves that the adsorption is predominant in the sorption of PAHs.

Adsorption↗

PubMed1986

Competitive adsorption of plasma proteins at solid-liquid interfaces.

The competitive adsorption of human serum albumin (HSA), human immuno-gamma-globulin (HIgG) and human fibrinogen (HFb) onto polystyrene (PS) at 20 degrees C and a pH of 7.35 (phosphate-buffered saline) was studied. Protein adsorption was studied using enzyme immunoassay. The results obtained with the immunoassay were compared with those obtained using radiolabelled proteins. Recent studies revealed that the adsorption behaviour of radiolabelled proteins onto surfaces differs from that of the non-labelled proteins, which may lead to misinterpretation of adsorption data. Differences in the adsorption behaviour of the labelled proteins as compared to non-labelled proteins can possibly be explained by the formation of modified proteins during the labelling procedure as shown by ion-exchange high-performance liquid chromatography (HPLC). The competitive adsorption of HSA, HIgG and HFb onto a PS latex was studied by measuring the depletion of proteins in solution. The decrease in protein concentration in solution was determined by HPLC techniques. A strong preferential adsorption of HFb was observed with maximum adsorption values of 0.6 micrograms/cm2.

Adsorption↗

PubMed1984

Mass action effects on competitive adsorption of fibrinogen from hemoglobin solutions and from plasma.

The strong effect of protein adsorption on blood and tissue compatibility is well known. Little is presently known about the mechanisms which control the composition of the adsorbed protein layer which forms upon exposure of surfaces to mixtures of proteins. Reexamination of the ability of hemoglobin to inhibit the adsorption of 125I fibrinogen to polyethylene revealed that the inhibition was strongly dependent on the fibrinogen concentration. These results suggested that fibrinogen adsorption from more complex mixtures such as plasma should also be strongly dependent on total concentration. Fibrinogen adsorption from plasma was found to be maximal at intermediate plasma concentrations, and was reduced at both low and high plasma concentrations. The plasma concentration at which this maximum occurred was 10% for polytetrafluoroethylene, 1% for polyethylene, and 0.1% for glass. The unusual concentration dependence is attributed to mass action effects on the competitive adsorption of proteins, specifically that competitive effectiveness is expected to increase as unoccupied surface adsorptive sites become less frequent. Analogous effects of adsorption time on competitive adsorption are also predicted due to the changing concentration at the interface as the buffer is gradually replaced by protein solution. These mass action effects are very similar to previous qualitative observations by Vroman and are therefore dubbed the " Vroman effect".

Adsorption↗

PubMed1996

Roles of different hydrophobic constituents in the adsorption of pulmonary surfactant.

Surface tension-time adsorption isotherms were measured at 37 degrees C for calf lung surfactant extract (CLSE) and subfractions of its constituents: the complete mix of surfactant phospholipids (PPL), phospholipids depleted in anionic phospholipids (mPPL), hydrophobic surfactant proteins plus phospholipids (SP&PL, SP&mPL), and neutral lipids plus phospholipids (N&PL). Adsorption experiments were done using a static bubble surfactometer where diffusion resistance was present, and in a Teflon dish where diffusion was minimized by subphase stirring. The contribution of diffusion to bubble adsorption measurements decreased as phospholipid concentration increased, and was small at 0.25 mM phospholipid. At this phospholipid concentration, PPL, mPPL, and N&PL all adsorbed more rapidly and to lower final surface tensions than dipalmitoyl phosphatidylcholine (DPPC) on the bubble. However, none of these phospholipid mixtures adsorbed to surface tensions below 46 mN/m after 20 min, behavior that was significantly worse than CLSE, SP&PL, and SP&mPL which additionally contained hydrophobic SP. Both CLSE and SP&PL rapidly adsorbed to surface tensions below 25 mN/m at 0.25 mM phospholipid concentration on the bubble, as did SP&mPL at a somewhat reduced rate. Further experiments defining the influence of hydrophobic protein content showed that addition of even 0.13% SP (by wt) to PPL improved adsorption substantially, and that mixtures of PPL combined with 1% SP had adsorption very similar to CLSE. Mixtures of SP combined with mPPL had faster adsorption than corresponding mixtures of SP:DPPC, and neither fully matched the adsorption rates of CLSE and SP&PL even at high SP levels (4% in SP:mPPL and 5.2% in SP:DPPC). These results demonstrate that although the secondary zwitterionic and anionic phospholipids and neutral lipids in lung surfactant enhance adsorption relative to DPPC, the hydrophobic SP have a much more pronounced effect in promoting the rapid entry of pulmonary surfactant into the air-water interface.

Adsorption↗

PubMed1996

Human serum albumin adsorption on hydrogel contact lenses in vitro.

PURPOSE: To improve the understanding of the formation of protein deposits on hydrogel lenses. METHODS: A study of protein adsorption on three commercial hydrogel contact lenses of different materials, Etafilcon A (2-hydroxyethyl methacrylate [HEMA] polymer with sodium methacrylate and 2-ethyl-2-hydroxymethyl-1,3-propanediol trimethacrylate), tefilcon (poly[HEMA] cross-linked and copolymerized with ethylene glycol dimethacrylate), and vifilcon A (methacrylic acid polymer with ethylene glycol dimethacrylate, HEMA and N-vinyl pyrrolidone) was undertaken by using a single protein solution, human serum albumin (HSA), and a radiolabel-tracer technique. RESULTS: Static adsorption leading to multilayer adsorption was observed. Complete reversibility for adsorbed HSA on lenses did not exist. Some was tightly bound, whereas most was loosely bound and could be removed easily by rinsing in phosphate-buffered saline. Irreversible adsorption of HSA on the lenses was found to be time dependent and did not reach a maximum value even after 48 hours of adsorption. The amount of HSA adsorbed on the lenses-irreversibly as well as totally adsorbed protein-was in the order of vifilcon A > tefilcon > etafilcon A. Adsorption of HSA on the lenses increases with decreasing pH (range, 7.4 to 4) but always follows the above trend with respect to the different types of lenses. CONCLUSIONS: Irreversible binding of HSA on lenses is governed by the kinetics of protein denaturation. Electrostatic interactions may not play a major role in HSA adsorption on hydrogel lenses. Some other factors, such as hydrophobic dehydration, and special monomer units, such as N-vinyl pyrrolidone in the lens materials, may favor adsorption of HSA.

Adsorption↗

PubMed2005

Magnetic dye affinity beads for the adsorption of beta-casein.

Casein is well known as a good protein emulsifier and beta-casein is the major component of casein and commercial sodium caseinate. Dye affinity adsorption is increasingly used for protein separation. beta-Casein adsorption onto Reactive Red 120 attached magnetic poly(2-hydroxyethyl methacrylate) (m-PHEMA) beads was investigated in this work. m-PHEMA beads (80-120 microm in diameter) were produced by dispersion polymerization. The dichlorotriazine dye Reactive Red 120 was attached covalently as a ligand. The dye attached beads, having a swelling ratio of 55% (w/w) and carrying different amounts of Reactive Red 120 (9.2 micromol . g(-1)-39.8 micromol . g(-1)), were used in beta-casein adsorption studies. The effects of the initial concentration, pH, ionic strength and temperature on the adsorption efficiency of dye attached beads were studied in a batch reactor. The non-specific adsorption on the m-PHEMA beads was 1.4 mg . g(-1). Reactive Red 120 attachment significantly increased the beta-casein adsorption up to 37.3 mg . g(-1). More than 95.4% of the adsorbed beta-casein was desorbed in 1 h in a desorption medium containing 1.0 M KSCN at pH 8.0. We concluded that Reactive Red 120 attached m-PHEMA beads can be applied for beta-casein adsorption without significant losses in the adsorption capacities.

Caseins↗

PubMed1996

Anomalous Adsorption of Copper(II) on Goethite

The adsorption of copper(II) onto goethite is qualitatively different from that of other metal-mineral systems. At pH 5.0 the adsorption isotherms are sigmoid rather than hyperbolic, and the corresponding graphs of C/N versus C (where C is concentration and N adsorption density) have distinct minima. At pH 5.5 the isotherms have the more usual shape. The experimental data can be fitted by a model in which monomeric CuOH+ and dimeric Cu2(OH)2+2 compete for surface sites, the dimer adsorbing more strongly to the surface. As the concentration increases the proportion of the dimeric species increases, which leads to enhanced adsorption. At pH 5.5 adsorption of the monomer is sufficiently strong that normal behavior is observed at low concentrations, before there is sufficient dimer to compete effectively for sites. Data are presented for adsorption of Cu(II) to goethite at pH 5.0 and pH 5.5, at temperatures between 25 and 70°C. Adsorption is endothermic for both monomer and dimer. Enthalpies of adsorption range from 50 to 91 kJ mol-1, and entropies from 240 to 470 J K-1 mol-1.

Journal Article↗

PubMed1997

Oleate Flotation of a Nigerian Baryte: The Relation between Flotation Recovery and Adsorption Density at Varying Oleate Concentrations, pH, and Temperatures

Crude Nigerian baryte was floated with sodium oleate as collector at varying oleate concentrations, pulp pH, and temperatures. Using "pure" baryte selected from the crude baryte, oleate adsorption densities at the baryte-water interface were determined also at varying oleate concentrations, pulp pH, and temperatures, using electrical conductivity measurements. The specific surface area of the pure baryte powder was determined using the method of adsorption of paranitrophenol in aqueous solution. The variation of oleate adsorption density and flotation recovery of baryte with oleate concentration, pulp pH, and temperature was studied. At ambient temperature (29°C) and pulp pH (8.2) flotation recovery of baryte increased with increasing oleate adsorption density, to a maximum recovery at the critical micelle concentration of sodium oleate. Flotation recovery increased with increasing adsorption density to about 100% recovery at maximum oleate adsorption density at pH 9.0 to 10.0 in the region of the zero point of charge (zpc) of the Nigerian baryte and to about 100% recovery and maximum oleate adsorption density at the temperature range 30 to 40°C, also at the zpc of the baryte. It is considered that oleate chemisorbs onto the Nigerian baryte predominantly at ambient temperature and up to 40°C; above 40°C the chemisorbed species probably dissociate from the mineral surface while the primary mode of adsorption becomes physical processes.

Journal Article↗

PubMed1997

Dynamic Surface Tension and Adsorption Kinetics from Micellar Solutions on Planar Surfaces

A qualitative theory of the dynamic surface tension and adsorption kinetics from micellar surfactant solutions on a planar surface is developed for the kinetic-diffusive-controlled adsorption process obeying any adsorption kinetics on a planar surface and any micellization-demicellization kinetics in the bulk. The time-dependent adsorption and dynamic surface tension is obtained in an analytical form for short and long times. It is shown that the adsorption process and dynamic surface tension over a wide range of surfactant (monomer) concentrations is governed by: (I) the adsorption kinetics of monomers and micelles for short times (0 </= t </= tcr1), (II) the adsorption kinetics of monomers and micelles on a planar surface and the micellization-demicellization kinetics in the bulk, and the diffusion of monomers and micelles for intermediate times (tcr1 </= t </= tcr2), and (III) the diffusion of monomers and micelles for long times (t >/= tcr2). Formulas were derived to estimate the relaxation times tcr1, tcr2, and the parameters characterizing the adsorption process over a wide range of times. The existence of the (I), (II), and (III) regimes are justified by using the experimental data for the dynamic surface tension of a micellar Brij 58 solution.

Journal Article↗

PubMed1997

Physical Adsorption of Bilayer Membranes on Silica

Isotherms for adsorption of bilayer-forming synthetic amphiphiles or phospholipids from vesicles onto hydrophilic silica particles (Aerosil OX-50) are obtained over a range of experimental conditions. Phosphatidylcholine (PC), dipalmitoylphosphatidylcholine (DPPC), dihexadecylphosphate (DHP), and dioctadecyldimethylammonium bromide (DODAB) dispersed in 10 mM Tris, pH 7.4, as small unilamellar vesicles present affinities for silica following the sequence DODAB > DPPC > PC > DHP. Among these, only DHP adsorption is below that expected for one bilayer deposition. Interaction at 65degreesC for 1 h between DPPC (or, at 25degreesC, for PC) vesicles and silica efficiently leads to bilayer deposition at maximal adsorption, if Tris is the buffer used. Preliminary centrifugation of the PC or DPPC vesicle dispersion is necessary to prevent overestimated adsorption. PC affinity for silica and its deposition as a bilayer depend on the nature of buffer used being much higher for Tris than for Hepes at pH 7.4. Formation of ion pairs between protonated amino groups in Tris and silanol groups on silica may lead to Tris adsorption and an increase in density of -OH groups on the solid surface. Therefore, formation of cooperative hydrogen bridges between -P=O in the phosphatidyl of the phospholipid bilayer and the -OH groups of Tris adsorbed on silica increases PC affinity for silica in the presence of Tris. For Hepes as buffer, PC affinity for silica is much lower and no plateau indicative of bilayer deposition is observed in the adsorption isotherm. Stabilization of supported phospholipid bilayers on solid surfaces requires several cooperative hydrogen bridges between the phospholipid and the solid surface. DODAB adsorption was unaffected by vesicle age and physical state of the bilayer vesicle. Adsorption isotherms for DODAB are of the high-affinity type with a maximum indicative of competition between intervesicle interactions and DODAB deposition on silica. Stabilization of DODAB bilayer deposition requires surface charge densities on silica higher than -1 μC/cm2. Copyright 1997Academic Press

Journal Article↗

PubMed1997

Adsorption Mechanism(s) of Poly(Ethylene Oxide) on Oxide Surfaces

Adsorption of poly(ethylene oxide) (PEO) on various oxides and the flocculation behavior of PEO-coated particles was investigated to elucidate the polymer adsorption mechanism(s). It was determined that strong Bronsted acid sites on the surface interact with the ether oxygen of PEO, a Lewis base, to induce adsorption and subsequent flocculation of the substrate particles. In general highly acidic oxides of the type MO3, M2O5, and MO2 are expected to adsorb and flocculate with PEO. Accordingly, MoO3, V2O5, and SiO2 were found to strongly adsorb PEO and exhibit flocculation. On the other hand, no significant adsorption was observed on oxides with a point of zero charge (pzc) greater than that of silica such as TiO2, Fe2O3, Al2O3- and MgO thereby indicating specificity of PEO-surface bonding site interactions. The other possible mechanisms of PEO adsorption such as complexation with adsorbed ions and electrostatic interactions with a positively charged surface were found not to play a major role in the PEO adsorption onto oxide particles. In this investigation, the adsorption and flocculation behavior of oxides with PEO and the underlying adsorption mechanism(s) are discussed. Copyright 1997 Academic Press. Copyright 1997Academic Press

Journal Article↗

PubMed1998

Electrostatic and Hydrophobic Effects of Oligopeptide Insertions on Protein Adsorption.

The effects of oligopeptide insertions on the adsorption of the protein ZZ, where Z is the IgG binding domain of staphylococcal Protein A, was investigated by in situ ellipsometry. In particular, the interplay between hydrophobic and electrostatic interactions as driving force for adsorption was investigated by studying the effects of oligopeptide insertions of the type Tn((AlaTrpTrpPro)n), Nn((AlaTrpTrpAspPro)n), and Pn((AlaTrpTrpLysPro)n) on the adsorption at silica, methylated silica, and diaminocyclohexane (DACH) plasma polymer surfaces. For comparison, the adsorption of the inserted peptide stretches was also investigated. It was found that the adsorption of all the peptides increases with the molecular weight at methylated silica. At silica, only the Pn peptides were found to adsorb. The net negatively charged proteins modified through peptide insertions did not adsorb at the hydrophilic and negatively charged silica, irrespective of the peptide insertion, whereas an extensive adsorption was found for the positively charged DACH surface for all the proteins investigated. For hydrophobic and negatively charged methylated silica, on the other hand, the peptide insertions were found to have a major influence on the protein interfacial behavior, and the adsorption followed the peptide stretch charge, thus increasing in the order ZZNn < ZZTn < ZZPn. These effects are discussed in terms of the relative importance of hydrophobic and electrostatic interactions as driving force for the adsorption. Copyright 1998 Academic Press.

Journal Article↗