Simultaneous Competitive Adsorption Research Articles

Separation of similarly structured isoflavones by simultaneous competitive and selective adsorption on UiO-66 metal-organic framework

Natural products often contain a large number of structurally similar compounds, however, from which the isolation of monomer compounds is complex and time-consuming. In this study, for the first time, a Zr-based metal-organic framework (MOF), UiO-66, was used for the separation of three isoflavones (genistein (GEN), puerarin (PUE), and daidzein (DDZ)) with similar structures. UiO-66 was demonstrated to have a distinct high adsorption capacity (qe, 105.42 ± 2.36 mg/g) for GEN with high separation factors from PUE (α, 35.52 ± 1.22) and DDZ (α, 7.41 ± 0.76), dramatically increasing the purity of GEN from ∼33–92% after primary separation. According to SEM-EDS and XPS characterizations together with RDF analysis, GEN and PUE were adsorbed on the surface of UiO-66 at the same dominant Zr cluster site (O…Zr), while DDZ was bound onto the inferior site via weak hydrogen bonding (H…O), indicating the separation of GEN from PUE was in a competitive manner, while the separation from DDZ was selective. For these three drugs, their adsorption kinetics and adsorption isotherms conformed Pseudo-second-order kinetic model and Langmuir model, respectively, indicating that the monolayer adsorption of isoflavones on UiO-66 surface was the dominant mechanism. The thermodynamic study demonstrated that both adsorptions of GEN and PUE were spontaneous (ΔG0 < 0), whereas the DDZ adsorption is non-spontaneous (ΔG0 > 0). Compared to traditional separation techniques, this study provided a simple and efficient approach to isolate structurally similar compounds from natural products in drug discovery.

Competitive adsorption of water and chemical warfare agents on transition metal embedded graphene

Adsorption of three CWA molecules (soman, sarin and mustard gas) was systematically explored on transition metal (Chromium and Vanadium) embedded graphene models under dry and wet conditions. Density Functional Theory calculations first revealed that both metal@graphene substrates show a very high affinity for all CWAs under dry conditions, sarin being expected to be even more strongly coordinated since its associated adsorption energies above 43 kcal.mol−1 are higher than the values calculated for soman and mustard gas. Two different wet scenarios were further explored with the consideration of a pre-humidification and a simultaneous competitive adsorption of water with CWAs. These calculations evidenced that the presence of water decreases the CWA adsorption energy for sarin and soman in the two embedded graphene models by maximum 20%. Interestingly, we demonstrated that this decrease is much less pronounced (3.3%) in the case of gas mustard adsorbed on chromium embedded graphene. Such metal embedded carbon substrates are thus predicted to maintain globally high level of CWA capture performances under humidity which corresponds to the most common operating conditions of protective gas masks. An In-depth analysis of the interactions between the CWAs and the metal embedded graphene in the presence of water was further conducted to gain insight into the origin of this energetic trend at the electronic-level.

Controlling the kinetics of visible-light-induced photocatalytic performance of gold decorated graphitic carbon nitride nanocomposite using different proteins

In this work, the interaction of different proteins with two dimensional (2D) graphitic carbon nitride (GCN) nanosheets decorated with gold nanoparticles (Au NP) is reported along with their influence in controlling the visible-light-induced photocatalytic activity. The decoration of Au NP on 2D GCN nanosheets improves the photocatalytic activity as Au NP plays an important role in trapping and storing the conduction band electrons of GCN nanosheets. The structural, morphological and optical properties of Au-GCN (AGCN) nanocomposite have been investigated using scattering and spectroscopic techniques. Methylene blue (MB) dye was chosen as a representative system for the studying of visible-light-induced photocatalytic activity of AGCN nanocomposite in the presence of different proteins. Bovine serum albumin (BSA), trypsin and cytochrome C having different chain lengths and physicochemical properties were used to control the kinetics of the photocatalytic activity of GCN and AGCN nanocomposites. Due to the simultaneous competitive adsorption of MB and proteins, the photocatalytic activity of the nanocomposites got enhanced in the presence of BSA, while it got inhibited or slowed down in the presence of trypsin and cytochrome C, respectively. The observed photocatalytic activity could be correlated with the surface charges present on the proteins and the mechanistic understanding developed in this study can be beneficial in controlling the kinetics of the photocatalytic activity of semiconductor-based photocatalysts using proteins as activators or inhibitors.

Size Effects of NiO Nanoparticles on the Competitive Adsorption of Quinolin-65 and Violanthrone-79: Implications for Oil Upgrading and Recovery

Using Quinolin-65 (Q-65) and Violantrone (V-79) as model molecules for polar heavy hydrocarbons and resins, the nanosize effects of NiO nanoparticles on the competitive molecular adsorption on nanoparticles were conducted using multiwavelength UV–visible derivative spectrophotometry method. This is important for understanding the role of nanoparticles in oil upgrading and recovery processes. Computer simulations were also carried out to validate the experimental findings and provide more insights on the interactions between the Q-65 and/or V79 molecules and the NiO nanoparticle surface. Different-sized NiO nanoparticles (5, 40, and >100 nm) were synthesized by controlled thermal dehydroxylation of Ni(OH)2. Nanoparticles were characterized using XRD, BET, FTIR, and XPS. Macroscopic adsorption isotherms of Q-65 and V-79 molecules over 5 and 40 nm NiO nanoparticles were evaluated in toluene-based solutions as individual and binary solutions. On a normalized surface area basis, the number of Q-65 and V-79 molecules adsorbed per nm2 of the NiO surface was the highest for 40 nm NiO nanoparticles and lowest for 5 nm NiO. Results also indicated that NiO nanoparticles were more prone to adsorb V-79 than Q-65. Equilibrium binding constants for V-79 and Q-65, determined by the Langmuir adsorption model, showed the binding affinity for V-79 is size dependent. Simultaneous competitive adsorption between V-79 and Q-65 showed that V-79 concentration is an important factor influencing the uptake of both V-79 and Q-65, whereas the concentration of Q-65 affects only Q-65 uptake. Computational modeling results were consistent with the experimental results, confirming our conclusions about the adsorption process in this binary system.

Single and Binary Adsorption of Zn (II) and Cr (VI) Heavy Metals onto Synthesized Silica ‐Based MCM‐41

AbstractEffluents from numerous Industries like textile, paint, pharmaceutical, steel and electroplating industries liberate both Zinc [Zn (II)] and Chromium [Cr (VI)] heavy metals. In this work, adsorptive interaction of toxic Zn (II) heavy metal in aqueous solution with synthesized mesoporous silica based MCM‐41 was investigated. Further, the effects of presence of Cr (VI) heavy metal on the adsorption of Zn (II) and vice versa were investigated by simultaneous competitive binary adsorption from Cr (VI) and Zn (II) aqueous binary solution. Batch experiments were executed to see the effects of parameters like pH, adsorbent dose (m), adsorbate concentration and adsorption time (t). Optimum conditions for Zn (II) treatment were obtained as: initial pH (pHi) =7, m=0.1 g/L and t=2 h. Competitive adsorption of both Cr (VI) and Zn (II) from their binary solution was studied at 288− 308 K temperatures. Obtained equilibrium data were then fitted to different competitive multicomponent isotherm models like Langmuir (extended), Freundlich isotherm (extended), Sheindrof‐Rebuhn‐Sheintuch (SRS) isotherm and Redlich‐Peterson isotherm (modified) models, and various isotherm interaction parameters were calculated.

Noble metal-titania hybrid nanoparticle clusters and the interaction to proteins for photo-catalysis in aqueous environments

We report a systematic study of the controlled synthesis of new hybrid spherical TiO2 nanoparticle cluster (TiO2-NPC) homogeneously decorated with noble metal nanoparticles (NPs) by gas-phase evaporation-induced self-assembly. Silver NP (AgNP) was used as the representative noble metal NP. The degradation of methyl blue (MB) in the aqueous solution was chosen as the representative system for the study of photocatalysis, which were tested and evaluated with respect to irradiation conditions and the presence of bovine serum albumin (BSA). The results show that particle size and chemical composition of the hybrid nanostructure were tunable by choosing the suitable concentration of precursors. The photocatalytic activity of AgNP-decorated TiO2-NPC was strongly affected by the light irradiation and the ligand-nanoparticle interfacial interaction. The presence of BSA influenced molecular conjugation to the surface of the hybrid nanostructure. Under conditions of simultaneous competitive adsorption of MB and BSA, the combination of AgNPs improved the photocatalytic activity of the TiO2-NPC-based catalysts. Our work describes a prototype methodology to fabricate TiO2-NPC homogeneously decorated with noble metal NPs with well-controlled material properties. The mechanistic understanding developed in this study can be useful for the future optimization of material properties of hybrid nanostructures versus interfacial interactions with the surrounding molecules.

Competitive adsorption of fluoride and natural organic matter onto activated alumina

ABSTRACTNatural organic matter (NOM) is a major water constituent that affects the performance of water treatment processes. Several studies have shown that NOM can be adsorbed on the surface of oxides and may compete with other ions. The overall goal of this study was essentially to investigate the competitive adsorption between fluoride and NOM on activated alumina (AA). For this purpose, a humic acid (HA) was used as a model compound for NOM. The interaction of NOM with fluoride, the simultaneous competitive adsorption, and the effect of preloading AA with NOM were investigated. The specific absorbance of HA was determined at 254 nm. Size-exclusion chromatography measurements confirmed the adsorption of aromatic fractions of NOM onto AA. The presence of HA in the system inhibited fluoride sorption onto AA and the removal yield using fresh AA decreased from 70.4 % to 51.0 % in the presence of HA. The decrease was more pronounced using AA preloaded with HA, reaching 37.7 %. The interference of coexisting ions and their effect on fluoride removal capacity were evaluated, showing a severe impact of the presence of phosphate on the removal capacity unlike nitrates and sulfates, which slightly improved the fluoride sorption.

Kinetics comparison on simultaneous and sequential competitive adsorption of heavy metals in red soils

To compare the adsorption kinetics of Cu, Zn and Cd introduced into red soils simultaneously and sequentially as well as their distribution coefficients, the ability of red soils to retain heavy metals was evaluated by performing batch experiments. The results indicate that Cu is preferentially adsorbed by red soils no matter in simultaneous or in sequential situation. The adsorption amount of Cd is the minimum in simultaneous competitive adsorption experiment. As heavy metals are added into red soils sequentially, the heavy metal adsorptions are relatively hard to reach equilibrium in 2 h. Red soils retain more Cd than Zn, which is opposite to the result in simultaneous adsorption. The addition sequences of heavy metals affect their adsorbed amounts in red soils to a certain extent. The joint distribution coefficients of metals in simultaneous adsorption are slightly higher than those in sequential adsorption.

Quantitative Determination of Competitive Molecular Adsorption on Gold Nanoparticles Using Attenuated Total Reflectance–Fourier Transform Infrared Spectroscopy

Surface-sensitive quantitative studies of competitive molecular adsorption on nanoparticles were conducted using a modified attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy method. Adsorption isotherms for thiolated poly(ethylene glycol) (SH-PEG) on gold nanoparticles (AuNPs) as a function of molecular mass (1, 5, and 20 kDa) were characterized. We find that surface density of SH-PEG on AuNPs is inversely proportional to the molecular mass (M(m)). Equilibrium binding constants for SH-PEG, obtained using the Langmuir adsorption model, show the binding affinity for SH-PEG is proportional to M(m). Simultaneous competitive adsorption between mercaptopropionic acid (MPA) and 5 kDa SH-PEG (SH-PEG5K) was investigated, and we find that MPA concentration is the dominant factor influencing the surface density of both SH-PEG5K and MPA, whereas the concentration of SH-PEG5K affects only SH-PEG5K surface density. Electrospray differential mobility analysis (ES-DMA) was employed as an orthogonal characterization technique. ES-DMA results are consistent with the results obtained by ATR-FTIR, confirming our conclusions about the adsorption process in this system. Ligand displacement competitive adsorption, where the displacing molecular species is added after completion of the ligand surface binding, was also interrogated by ATR-FTIR. Results indicate that for SH-PEG increasing M(m) yields greater stability on AuNPs when measured against displacement by bovine serum albumin (BSA) as a model serum protein. In addition, the binding affinity of BSA to AuNPs is inhibited for SH-PEG conjugated AuNPs, an effect that is enhanced at higher SH-PEG M(m) values.

Competitive adsorption of Cd, Cu, Pb and Zn by different soils of Eastern China

Simultaneous competitive adsorption behavior of Cd, Cu, Pb and Zn onto nine soils with a wide physical–chemical characteristics from Eastern China was measured in batch experiments to assess the mobility and retention of these metals in soils. In the competitive adsorption system, adsorption isotherms for these metals on the soils exhibited significant differences in shape and in the amount adsorbed. As the applied concentration increased, Cu and Pb adsorption increased, while Cd and Zn adsorption decreased. Competition among heavy metals is very strong in acid soils with lower capacity to adsorb metal cations. Distribution coefficients (Kdmedium) for each metal and soil were calculated. The highest Kdmedium value was found for Pb and followed by Cu. However, low Kdmedium values were shown for Zn and Cd. On the basis of the Kdmedium values, the selectivity sequence of the metal adsorption is Pb > Cu > Zn > Cd and Pb > Cu > Cd > Zn. The adsorption sequence of nine soils was deduced from the joint distribution coefficients (KdΣmedium). This indicated that acid soils with low pH value had lower adsorption capacity for heavy metals, resulting in much higher risk of heavy metal pollution. The sum of adsorbed heavy metals on the soils could well described using the Langmuir equation. The maximum adsorption capacity (Qm) of soils ranged from 32.57 to 90.09 mmol kg−1. Highly significant positive correlations were found between the KdΣmedium and Qm of the metals and pH value and cation exchange capacity (CEC) of soil, suggesting that soil pH and CEC were key factors controlling the solubility and mobility of the metals in soils.

Profiling Protein−Surface Interactions of Multicomponent Suspensions via Flow Cytometry

This study presents the use of flow cytometry as a high-throughput quantifiable technique to study multicomponent adsorption interactions between proteins and surfaces. Flow cytometry offers the advantage of high-throughput analysis of multiple parameters on a very small sampling scale. This enables flow cytometry to distinguish between individual adsorbent particles and adsorbate components within a suspension. As a proof of concept study, the adsorption of three proteins--bovine serum albumin (BSA), bovine immunoglobulin gamma (IgG) and fibrinogen--onto five surface-modified organosilica microsphere surfaces was used as a model multicomponent system for analysis. By uniquely labeling each protein and solid support type with spectrally distinguishable fluorescent dyes, the adsorption process could be "multiplexed" allowing for simultaneous screening of multiple adsorbate (protein) and adsorbent (particle surface) interactions. Protein adsorption experiments quantified by flow cytometry were found to be comparable to single-component adsorption studies by solution depletion. Quantitative distribution of the simultaneous competitive adsorption of BSA and IgG indicated that, at concentrations below surface saturation, both proteins adsorbed onto the surface. However, at concentrations greater than surface saturation, BSA preferentially adsorbed. Multiplexed particle suspensions of optically encoded particles were modified to produce a positively and negatively charged surface, a grafted 3400 MW poly(ethylene glycol) layer, or a physisorbed BSA or IgG layer. It was observed that adsorption was rapid and irreversible on all of the surfaces, and preadsorbed protein layers were the most effective in preventing further protein adsorption.

Competitive adsorption of Cd, Cu, Hg and Pb by agricultural soils of the Changjiang and Zhujiang deltas in China

Soils can often be contaminated simultaneously by more than one heavy metal. The sorption-desorption behavior of a metal in a soil will be affected by the presence of other metals. Therefore, selective retention and competitive adsorption of the soils to heavy metals can affect their availability and movement through the soils. In this study, the simultaneous competitive adsorption of four heavy metals (Cd, Cu, Hg, and Pb) on ten agricultural soils collected from the Changjiang and Zhujiang deltas, China was assessed. The results showed that the competition affected the behavior of heavy metal cations in such a way that the soils adsorbed less Cd and Hg, and more Pb and Cu with increasing total metal concentrations, regardless of the molar concentration applied. As the applied concentrations increased, Pb and Cu adsorption increased, while Cd and Hg adsorption decreased. The adsorption sequence most found was Pb>Cu>Hg>Cd. The maximum adsorption capacity for the heavy metal cations was calculated, and affected markedly by soil properties. The results suggest that Hg and Cd have higher mobility associated to the lower adsorption and that Pb and Cu present the opposite behavior. Significant correlations were found between the maximum adsorption capacity of the metals and pH value and exchangeable acid, suggesting that soil pH and exchangeable acid were key factors controlling the solubility and mobility of the metals in the agricultural soils.

Competitive adsorption of uncharged macromolecules from homopolymer–copolymer mixtures

Individual adsorption and simultaneous competitive adsorption of dissolved macromolecules from ternary polymer solutions (two polymers in one solvent), on negatively charged colloidal dispersions were studied. Poly(vinyl alcohol) (PVA), poly(vinyl pyrrolidone) (PVP) homopolymers and poly(vinyl alcohol- co-vinyl acetal, -vinyl propional and -vinyl butyral) copolymers with various acetal contents and chain structure were used in the experiments. The hydrophilic/hydrophobic character of the macromolecules, and also, the preferential adsorption from homopolymer–copolymer mixtures were systematically regulated by changing the chemical structure of the copolymers (acetal content and/or length of side chain). Independent adsorption isotherms for each polymer were determined in individual adsorption of the polymers and also, in simultaneous competitive adsorption of two polymers from mixtures. It was found that both the degree and the order of adsorption preference could be well regulated by changing the copolymer composition. Model calculations concerning a possible distribution of acetal groups in the copolymer chains provided further support to this experience. The hydrodynamic thicknesses of adsorbed polymer layers formed at particle/solution interfaces in individual and competitive adsorption have been measured by photon correlation spectroscopy. The adsorbed layers formed at high surface coverages from certain homopolymer–copolymer mixtures had the same thickness as that of the preferred component in the individual adsorption layer, illustrating that under conditions the weakly adsorbed macromolecules could be displaced completely from the interfaces.

Investigations of chemisorption and reaction at non‐aqueous electrochemical interfaces by in situ surface‐enhanced Raman spectroscopy

AbstractSurface‐enhanced Raman scattering (SERS) spectroscopy has been successfully extended to transition metal/non‐aqueous electrochemical interfaces recently in our laboratory. Some interesting and new findings are presented with the objective of illustrating the virtues of SERS as a versatile technique to examine not only aqueous but also non‐aqueous interfaces. Emphasis is placed on highly catalytic roughened platinum metal surfaces. Static interfacial structure information of Pt (Ag, Au)/acetonitrile was extracted from the relevant SERS spectral features of the surface species, including interfacial trace water, the production of dissociation reactions of acetonitrile (CN−), and some effects on these spectra exerted by interfacial inorganic ions. The simultaneous competitive adsorption and reorganization processes between these interfacial species and some intentionally added small organic molecules were also systematically investigated. The important aspect of the corrosion inhibition mechanism relevant to non‐aqueous media was then probed based on the success of observing SERS from non‐aqueous interfaces. These included mainly widely used N‐ and S‐containing inhibitors for iron, nickel, silver and gold. Finally, the archetypal surface catalytic oxidation mechanism of C1 molecules (formic acid and methanol) on Pt group metals was investigated by using SERS combined with traditional electrochemical techniques. The non‐linear vibrational Stark tuning effect of the poisoning intermediate CO and its oxidation processes are also described in comparison with experimental observations from aqueous solution and other metal surfaces. Copyright © 2005 John Wiley &amp; Sons, Ltd.

Simultaneous competitive adsorption of heavy metals by the mineral matrix of tropical soils

Disposal of sewage sludge, composts and industrial wastes onto agricultural lands is commonly and increasingly used in Brazil, potentially adding multi-component heavy metal solutions. Soil organic matter was removed from representative Brazilian soils and the simultaneous competitive adsorption on the mineral matrix of Cr, Ni, Cu, Zn, Cd and Pb was determined. The competition affected the behavior of heavy metal cations in such a way that the soils adsorbed less Ni, Zn and Cd and more Cr, Cu and Pb with increasing total concentrations, regardless of the molar concentration applied. On the other hand, the occupancy of the adsorption complex by the heavy metals was proportional to the relative concentration applied. As the applied concentrations increased Cr, Cu and Pb adsorption increased, while Ni, Zn and Cd adsorption decreased. The maximum adsorption capacity for the heavy metal cations was calculated, with the soils differing markedly. Ultisol and Alfisol soils showed the highest maximum adsorption values, in the order of 50.76 and 64.52 mmol kg −1, whereas some Oxisols showed the lowest values, in the order of 23.92 and 30.86 mmol kg −1. The results suggest that the first two soil types are capable of receiving and holding higher heavy metal loadings compared to the Oxisols, which are more vulnerable to heavy metal contaminant inputs.

Dependence of the Adsorption of Polymer Mixtures from Solution on the Amount of an Adsorbent

Simultaneous competitive adsorption from solutions of mixtures of poly(butyl methacrylate) and polystyrene and adsorption of each component from binary solutions have been studied for three ratios of the adsorbent mass to the solution volume, A/V. It was found that adsorption from both binary and ternary solutions strongly depends on the amount of an adsorbent, adsorption of poly(butyl methacrylate) being preferential. The characteristic adsorption isotherms of both polymers were constructed under conditions of equal equilibrium concentration of each component to estimate the parameters of preferential adsorption and their dependence on the A/V ratio. It was found that the A/V effect plays an important role in adsorption from polymer mixtures and determines the peculiarities of adsorption from polymer mixtures as well as from solution of single polymers. Changing the A/V ratio may be one way to regulate the composition of an adsorption layer consisting of two chemically different polymers. The reasons for the A/V effect are considered in the framework of the concept of the plurality of adsorption equilibria between two chemically different components and between fractions of different molecular mass of each component having various absorbability.

Kinetic effects in mixed polymer layers at particle/solution interfaces: non-equilibrium states of uncharged polymers

The interfacial processes controlling the structure of mixed adsorption layers of uncharged polymers at particle/solution interfaces were studied. Under equilibrium conditions for simultaneous competitive adsorption from ternary polymer solutions, preferential adsorption parameters for the polymers in pairs have been determined on negatively charged colloidal dispersions and used as a measure of the affinity for surface sites of chemically different polymer molecules. The spatial properties of the interfacial polymer layers after various contact times were investigated by photon correlation spectroscopy (PCS), laser Doppler-electrophoresis (LDE) and at low polymer dosages, by flocculation kinetic measurements. It was found that long-term kinetic effects have a marked effect on the structure of composite interfacial layers. At low surface coverages, competition for partially covered particle surfaces of suitable polymers may lead to the formation of extended mixed adsorption layers. Displacement from the interfaces of the less preferred polymer results in either increase or decrease in time of both the hydrodynamic and the electrophoretic thicknesses in the mixed layers. The non-equilibrium states of the adsorbed macromolecules, existing over much longer period in the mixed layers than in the individual polymer layers, closely correlate to the preferential affinity for surface sites of the competing macromolecules.

Enhanced flocculation of colloidal dispersions by polymer mixtures

Bridging flocculation and electrolyte coagulation of negatively charged colloidal dispersions in the presence and absence, respectively, of uncharged polymers and polymer mixtures were studied. The relative coagulation and flocculation rates of particles in the presence of electrolyte and small polymer amounts were measured and the stability ratios have been calculated at various ionic strengths. Also, the structure of polymer layers formed in individual adsorption of polymers and in simultaneous competitive adsorption from binary polymer mixtures at particle/solution interfaces was investigated. The electrophoretic mobility and the diffusion coefficient of particles with and without adsorbed polymer were measured by laser Doppler-electrophoresis and photon correlation spectroscopy, respectively, and the electrophoretic and the hydrodynamic thickness of adsorbed polymer layers have been calculated. It was found that the adsorbed polymers may enhance or diminish the rate of successsful encounters between particles, even at low surface coverages, depending on the magnitude of the interparticle electrostatic repulsion. In addition, competitive adsorption of chemically different polymers for particle surfaces may result in considerable alteration in the conformation of macromolecules in the mixed adsorption layer. Close correlation was found between the effectiveness of polymers as flocculants and the thickness of adsorbed polymer layers formed at optimum polymer dosages on the particle surfaces. Binary mixtures of suitable polymers proved to be very efficient flocculants for the dispersions. The enhanced flocculating effect of some mixtures can be ascribed to extended polymer layers formed in competitive adsorption of chemically different macromolecules at particle/solution interfaces. These findings have relevance in many environmental technologies and offer a way of improving the effectiveness of solid–liquid separation processes.

Mixed Adsorption Layers of Uncharged Polymers at Particle/Solution Interfaces

Simultaneous competitive adsorption from binary mixtures of uncharged polymers on negatively charged colloidal dispersions and the structure of polymer layers formed at particle/solution interfaces were studied. From the adsorption isotherms determined in competitive adsorption at equal concentrations of two polymers in the bulk solution, preferential adsorption parameters for the polymers in pairs have been established, and used as a measure of the affinity of chemically different macromolecules for the solid surfaces. The diffusion coefficient of (monodisperse) particles with and without adsorbed polymer was measured by photon correlation spectroscopy, and the hydrodynamic thickness of adsorbed polymer layers has been calculated. The exchange of polymeric species adsorbed at the interfaces was detected by measuring the thicknesses of mixed layers after various contact times. The preferential adsorption parameters proved to be relevant markers for the various interfacial processes. Simultaneous adsorptio...

The sorption of lysozyme and ribonuclease onto ferromagnetic nickel powder 2. Desorption and competitive adsorption

The partial desorption of lysozyme or ribonuclease (RNase) from nickel powder was attained by pH switch and ion addition, and was found to decrease with adsorption time. Desorption by dilution was found to be insignificant. In the simultaneous competitive adsorption of these two proteins, selective adsorption could be achieved by controlling the pH. As for sequential adsorption, RNase-covered Ni can further adsorb lysozyme, but RNase removed lysozyme from lysozyme-Ni.