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PubMed2003

Protein adsorption at polymer-grafted surfaces: comparison between a mixture of saliva proteins and some well-defined model proteins.

Grafting a dense layer of soluble polymers onto a surface is a well-established method for controlling protein adsorption. In the present study, polyethylene oxide (PEO) layers of three different grafting densities were prepared, i.e. 10-15 nm2, 5.5 nm2 and 4 nm2 per polymer chain, respectively. The adsorption of different proteins on the PEO grafted surfaces was measured in real time by reflectometry. Furthermore, the change of the zeta-potential of such surfaces resulting from adsorption of the proteins was determined using the streaming potential method. Both the protein adsorption and the zeta-potential were monitored for 1 h after exposure of the protein solution to the surface. The adsorption pattern for a mixture of saliva proteins was compared to those observed for a number of well-defined model-proteins (lysozyme, human serum albumin, beta-lactoglobulin and ovalbumin). The results of the adsorption kinetics and streaming potential measurements indicate that the effect of the PEO layer on protein adsorption primarily depends on the size and the charge of the protein molecules. The saliva proteins are strongly blocked for adsorption, whereas the change in the zeta-potential is larger than for the other proteins (except lysozyme). It is concluded that positively charged protein molecules, having dimensions larger than those of lysozyme, are involved in the initial stage of adsorption from saliva onto a negatively charged surface.

Adsorption↗
PubMed1991

The Vroman effect in tube geometry: the influence of flow on protein adsorption measurements.

The transient adsorption of fibrinogen from plasma (a manifestation of the Vroman effect), due in large part to displacement by trace proteins such as high-molecular-weight kininogen (HK), factor XII, and plasminogen, has traditionally been studied in nonflowing systems in this laboratory. This paper reports new data on adsorption in tubing geometry under laminar flow. Fibrinogen adsorption from human blood plasma and whole blood diluted to varying exents was measured on glass and polyethylene tubing. The presence of flow did not change the nature of the Vroman effect, except that the processes of adsorption and displacement, which are typically diffusion-limited in static systems, were augmented by convective transport. At the highest applied shear rates of 408 and 510 s-1, the initial adsorption rate of fibrinogen was estimated to be 5.0 X 10(-5) cm/s on both surfaces. The intrinsic rate of displacement of fibrinogen (due to the Vroman effect) at high shear rates was about ten times faster from glass than from polyethylene based on data taken 5 min after the experiment started. The rates of fibrinogen adsorption and displacement were not observed to be significantly augmented by the cellular elements of whole blood at dilutions exceeding 20:1. The consistently observed axial dependence of adsorption in static and flow experiments in tubing geometry was investigated. It was concluded that the effect results, under most conditions, from the creation of a concentration boundary layer during the displacement of the equilibrating buffer by the injected protein solution. The possibility of local depletion due to rapid adsorption during injection or the final displacement of the protein solution was concluded to make lesser contributions to axial variations in measured adsorption.

Adsorption↗
PubMed2005

Removal of pesticides from aqueous solution: Quantitative relationship between activated carbon characteristics and adsorption properties.

The adsorption of pesticides (atrazin, atrazin-desethyl and triflusulfuron-methyl) from aqueous solution is performed by activated carbon fibers (ACF) and granular activated carbons (GAC) in static and dynamic reactors, in order to study the co-influence of adsorbent and adsorbate characteristics on the adsorption mechanisms. First, mono-component adsorption equilibrium is carried out in a batch reactor for a wide range of concentrations (from 5 microg 1(-1) to 21.4 mg 1(-1)). Classic models, like Freundlich and Langmuir equations, are applied: the maximum adsorption capacities are high, ranging between 63 and 509 mg g(-1). The comparison of single-solute isotherms tends to confirm the decisive role of the adsorbent properties in the adsorption capacity of pesticides by the activated carbons: the performance of ACF is significantly higher than that of GAC due to a narrower pore size distribution of fibers in the area of micropores. Furthermore, their small diameter (10 microm compared with 1 mm for grains) enables faster adsorption kinetics because of the larger surface area exposed to the fluid. The influence of adsorbate size is also demonstrated. A multiple linear regression enables the co-influence of adsorbent and adsorbate properties to be quantified, a relationship being assessed between Langmuir maximum adsorption capacity and pesticide molecular weight and adsorbent diameter (R2 = 0.90). Secondly, the adsorption of the three pesticides is studied in a dynamic reactor: in this case, the influence of operating conditions (inlet concentration C0, flow velocity U0) is also taken into account. As the initial concentration or flow velocity decreases, the column performance significantly improves. Both operating factors are included in a multiple linear regression (R2 = 0.91) used to predict saturation adsorption capacity, with molecular weight and particle diameter being again designed as influent explicative variables.

Adsorption↗
PubMed2006

Adsorption of divalent copper, zinc, cadmium and lead ions from aqueous solution by waste tea and coffee adsorbents.

The adsorption of the divalent cations of Cu, Zn, Cd and Pb by tea leaves and coffee grounds from aqueous solutions is described. Both adsorbents exhibited strong affinity for these ions which could be described by a simple single-site equilibrium model. For coffee, the order of increasing adsorption equilibrium constant K was Cu < Pb < Zn < Cd, while for tea the opposite order was observed indicating that the adsorption sites on each adsorbent have a different chemical nature. Adsorption decreased at low pH < 4 through competition with H+ for adsorption sites, and for all metals except Cu, at high pH > 10, probably because of anion formation in the case of Zn2+ and also increased leaching of metal-binding soluble materials. The effect of metal ion concentration on the adsorptive equilibria indicated a threshold concentration above which overall adsorption became limited by saturation of the adsorption sites. Competition between two metal ions for the same sites was not observed with Cu(II) and Pb(II), however Zn(II) reacted competitively with Cd(II) binding sites on both tea and coffee. If fresh coffee or tea adsorbents were used, the fraction of metal ion taken up by the adsorbent was diminished by the competitive effects of soluble metal-binding ligands released by the tea or coffee. Experiments with coffee showed that roasting temperature controls the formation of metal ion adsorption sites for this adsorbent.

Adsorption↗
PubMed2000

Adsorption of esters of p-hydroxybenzoic acid by filter membranes: mechanism and effect of formulation and processing parameters.

The adsorption of esters of p-hydroxybenzoic acid (parabens) by filter membranes was studied by a flow-through technique. The hydrophobic effect was the major mechanism of adsorption. Propylparaben was more extensively adsorbed by all the membranes than was methylparaben. Hydrophobic membranes exhibited the greatest degree of adsorption, whereas adsorption was minimal for hydrophilic membranes. The charge of the filter membrane did not affect paraben adsorption. Formulation factors studied included the concentration of paraben, the presence of a tonicity-modifying agent (sodium chloride, mannitol, glycerin), and the presence of a chelating agent (edetate sodium). Paraben adsorption was directly related to paraben concentration. The presence of a tonicity modifier or chelating agent did not alter paraben adsorption to membrane filters. Processing parameters studied included flow rate, temperature, autoclaving, flow interruption, and filter membrane presaturation. Presaturation of the filter membranes for up to 1 hr reduced but did not eliminate paraben adsorption during simulated use. Interrupting the flow of the paraben solution through the filter membrane allowed for additional paraben adsorption and caused the concentration of paraben in the restarted filtrate to be less than 100% of theory.

Adsorption↗
PubMed1992

Adsorption mode of exo- and endo-cellulases from Irpex lacteus (Polyporus tulipiferae) on cellulose with different crystallinities.

The adsorption mode of two highly purified cellulases, exo- and endo-type cellulases, from Irpex lacteus (Polyporus tulipiferae) was investigated by using pure cellulosic materials with different crystallinity as substrates. Adsorption of the two enzymes on the substrates was found to fit the Langmuir-type adsorption isotherm. Maximum amount of adsorbed enzyme obtained from the Langmuir plots showed an inverse correlation to the crystallinity of the substrate with both enzymes, and this value of endo-type cellulase was less dependent on the degree of crystallinity of substrates than that of exo-type cellulase, whose isotherms reached saturation in the range of low enzyme concentrations. The two enzymes showed relatively high affinities for all the substrates and their affinities increased with increasing crystallinity, but this tendency was less marked with endo-type cellulase than with exo-type one. In addition, large negative values of free energy change were observed on the adsorption of both enzymes, and the values became more negative with increasing crystallinity. Consequently, both cellulases showed high adsorption on crystalline cellulose and the adsorption process became smoother with increasing crystallinity. The adsorption of the two types of cellulases was endothermic with an increase in entropy, especially for amorphous cellulose, suggesting the occurrence of water release from the substrates during enzyme adsorption. In addition, the changes in thermodynamic parameters (delta H, delta S, and delta G) in adsorption of exo-type cellulase were larger than in that of endo-type enzyme.

Adsorption↗
PubMed2001

In vitro adsorption of 99Tc(m)-MIBI, 99Tc(m)-tetrofosmin, 99Tc(m)-furifosmin and 99Tc(m)O4- onto tubes.

Adsorption of radiopharmaceuticals onto disposable syringes has been reported to amount to levels of almost 50%. Data on adsorption of radiopharmaceuticals onto materials used for in vitro studies are extremely limited. We assessed the extent of adsorption of 99Tc(m) hexakis(2-methoxyisobutylisonitrile) (99Tc(m)-MIBI), 99Tc(m)-tetrofosmin, 99Tc(m)-furifosmin and 99Tc(m)O4 onto tubes used for in vitro measurement of cellular uptake of these radiopharmaceuticals. The influence on adsorption of different incubation media, temperature and time of incubation was evaluated. Total (not corrected for adsorption) uptake was compared with corrected, net cellular uptake in SK-BR-3, MCF-7 and liposarcoma cell lines. Values of adsorption ranging from 0.94+/-0.13% to 7.07+/-0.46% were found. The extent of adsorption of all the radiopharmaceuticals varied with the type of incubation medium and the incubation temperature. With 99Tc(m)-furifosmin, adsorption was dependent on the incubation time as well on the incubation temperature and some of the incubation media investigated. Our findings indicate that systematic investigations to evaluate the adsorption of radiopharmaceuticals onto materials used during in vitro studies of cellular uptake should be considered a mandatory aspect of quality control.

Adsorption↗
PubMed2006

Interfacial energetics of globular-blood protein adsorption to a hydrophobic interface from aqueous-buffer solution.

Adsorption isotherms of nine globular proteins with molecular weight (MW) spanning 10-1000 kDa confirm that interfacial energetics of protein adsorption to a hydrophobic solid/aqueous-buffer (solid-liquid, SL) interface are not fundamentally different than adsorption to the water-air (liquid-vapour, LV) interface. Adsorption dynamics dampen to a steady-state (equilibrium) within a 1 h observation time and protein adsorption appears to be reversible, following expectations of Gibbs' adsorption isotherm. Adsorption isotherms constructed from concentration-dependent advancing contact angles theta(a) of buffered-protein solutions on methyl-terminated, self-assembled monolayer surfaces show that maximum advancing spreading pressure, Pi(a)max, falls within a relatively narrow 10 < Pi(a)max < 20 mN m(-1) band characteristic of all proteins studied, mirroring results obtained at the LV surface. Furthermore, Pi(a) isotherms exhibited a 'Traube-rule-like' progression in MW similar to the ordering observed at the LV surface wherein molar concentrations required to reach a specified spreading pressure Pi(a) decreased with increasing MW. Finally, neither Gibbs' surface excess quantities [Gamma(sl)-Gamma(sv)] nor Gamma(lv) varied significantly with protein MW. The ratio {[Gamma(sl)-Gamma(sv)]/Gamma(lv)} approximately 1, implying both that Gamma(sv) approximately 0 and chemical activity of protein at SL and LV surfaces was identical. These results are collectively interpreted to mean that water controls protein adsorption to hydrophobic surfaces and that the mechanism of protein adsorption can be understood from this perspective for a diverse set of proteins with very different composition.

Adsorption↗
PubMed1998

Variability of mitomycin C adsorption by activated charcoal.

A saline suspension of mitomycin C adsorbed on activated charcoal and administered intraperitoneally has been reported to be safe and effective in the treatment of gastric carcinoma. Activated charcoal specifically targets tumour and lymph-node tissues and the sustained higher local drug concentration is thought to be beneficial. The charcoal particles used in these suspensions have varied in size from > 147 microm to < 20 nm in diameter, but no data have been published to show how this might affect drug adsorption and delivery. Any variability in drug adsorption could pose a serious clinical risk for drugs with a narrow therapeutic index. We have, therefore, investigated the adsorption of mitomycin C on activated charcoal in-vitro. Activated charcoal was ground and sieved to yield four size-fractions between 180 and 53 microm. Adsorption isotherms (n > or = 3) were constructed and applied to the Freundlich model with 0-l00 microg mL(-1) mitomycin C measured by HPLC with detection at 365 nm. Adsorption of mitomycin C by activated charcoal varied by a factor of three under identical conditions at room temperature (21 degrees C) and at 37 degrees C. The specific adsorption (microg mitomycin C (mg activated charcoal)(-1)) was generally higher at 37 degrees C than at room temperature. The variability of mitomycin C adsorption was greatly reduced by addition of the surface-active agent polyvinylpyrollidone, used to determine that adsorption of mitomycin C was independent of activated charcoal particle size. The characteristics of adsorption of mitomycin C by activated charcoal are complex and should be thoroughly investigated to discover the critical controlling factors before submitting the suspensions for further clinical evaluation.

Adsorption↗
PubMed1988

Activation thermodynamics of virus adsorption to solids.

The kinetics of bacteriophage MS2, T2, and f2 adsorption to powdered nitrocellulose and disrupted Seitz S1 filters at pH 7 were determined as a function of temperature. Data from these studies were combined with data produced in a previous study on MS2 adsorption to clay by Stagg et al. (Appl. Environ. Microbiol. 33:385-391, 1977). These workers studied the adsorption of MS2 to bentonite clay as a function of temperature. Data from both this previous study and the current one were used to calculate the thermodynamic parameters of virus adsorption. The results show that adsorption of bacteriophages to the solids tested is a physical process (energy of activation, less than 40 kcal [168 J]/mol) rather than a chemical process (energy of activation, greater than 40 kcal/mol). The free energy of activation showed a high negative correlation (r = -0.904, r2 = 0.817) with the percentage of virus adsorption to the solids tested. The energy of activation was highly negatively correlated with the percentage of virus adsorption to nitrocellulose and clay (r = -0.913, r2 = 0.834) but poorly correlated with the percentage of virus adsorption to disrupted Seitz S1 filters (r = -0.348, r2 = 0.121). In general, under conditions in which the percentage of virus adsorption was low, the energy of activation, the free energy of activation, and the entropy of activation were high. Increasing the percentage of virus adsorbed by changing the adsorbing conditions or changing the adsorbing solid decreased the energy of activation, the free energy of activation, and the entropy of activation.

Adsorption↗
PubMed1983

Influence of physicochemical parameters on adsorption of Actinomyces viscosus to hydroxyapatite surfaces.

Adsorption of Actinomyces viscosus strains T14V and T14AV to saliva-treated and untreated hydroxyapatite (HA) under various environmental conditions was studied. Strain T14V adsorption to saliva-treated HA was not influenced by pH, whereas strain T14AV adsorbed in higher numbers under acidic conditions. The addition of cations inhibited adsorption of strains T14V and T14AV to saliva-treated HA. Strain T14V possessed a greater affinity for hydrophobic gels than did strain T14AV, but incorporation of non-ionic detergents, which inhibit hydrophobic interactions, did not influence adsorption of strain T14V to saliva-treated HA. Adsorption of strain T14V to saliva-treated HA increased in the presence of an anionic detergent; however, strain T14AV adsorption was not affected. Strain T14V adsorption decreased in the presence of a cationic detergent, whereas strain T14AV adsorption increased. Collectively, these data suggest that electrostatic interactions, but not hydrophobic interactions, are of major importance in the adsorption of strain T14V to saliva-treated HA.

Actinomyces↗
PubMed1993

Glucagon adsorption on polymer surfaces with alpha-helical and extended beta-strand conformations: a computational approach.

The adsorption of glucagon with alpha-helical and extended beta-strand conformations on polymer surfaces was investigated using a computer simulation approach. An X-ray crystallographic structure of glucagon was employed in the study of the alpha-helical glucagon adsorption. The X-ray structure was then modified to simulate an extended beta-strand structure in the study of the beta-strand glucagon adsorption. Totally, 1632 different adsorption orientations of glucagon with each conformation were examined on polystyrene, polypropylene, polyethylene, poly(hydroxyethyl methacrylate) and poly(vinyl alcohol) surfaces. The calculation of the average adsorption energies among different orientations did not reveal any marked difference between the two conformations. However, when the lowest-energy orientations were compared, the adsorption energy of the extended beta-strand glucagon was always much lower than that of the alpha-helical glucagon, indicating that the adsorption of extended beta-strand glucagon was more energy favorable. The lower adsorption energy for the extended beta-strand glucagon than for the alpha-helical glucagon appeared to be contributed by the lower interaction potential energy of the former conformation. A greater number of the surface atoms in the extended beta-strand glucagon than in the alpha-helical glucagon was also observed. Fourier transform infrared spectroscopic (FTIR) studies in the literature showed conformational changes in adsorption of various larger proteins. Our study appears to provide a theoretical insight for the results from the FTIR studies.

Adsorption↗
PubMed2005

Kinetics of protein adsorption and desorption on surfaces with grafted polymers.

The kinetics of protein adsorption are studied using a generalized diffusion approach which shows that the time-determining step in the adsorption is the crossing of the kinetic barrier presented by the polymers and already adsorbed proteins. The potential of mean-force between the adsorbing protein and the polymer-protein surface changes as a function of time due to the deformation of the polymer layers as the proteins adsorb. Furthermore, the range and strength of the repulsive interaction felt by the approaching proteins increases with grafted polymer molecular weight and surface coverage. The effect of molecular weight on the kinetics is very complex and different than its role on the equilibrium adsorption isotherms. The very large kinetic barriers make the timescale for the adsorption process very long and the computational effort increases with time, thus, an approximate kinetic approach is developed. The kinetic theory is based on the knowledge that the time-determining step is crossing the potential-of-mean-force barrier. Kinetic equations for two states (adsorbed and bulk) are written where the kinetic coefficients are the product of the Boltzmann factor for the free energy of adsorption (desorption) multiplied by a preexponential factor determined from a Kramers-like theory. The predictions from the kinetic approach are in excellent quantitative agreement with the full diffusion equation solutions demonstrating that the two most important physical processes are the crossing of the barrier and the changes in the barrier with time due to the deformation of the polymer layer as the proteins adsorb/desorb. The kinetic coefficients can be calculated a priori allowing for systematic calculations over very long timescales. It is found that, in many cases where the equilibrium adsorption shows a finite value, the kinetics of the process is so slow that the experimental system will show no adsorption. This effect is particularly important at high grafted polymer surface coverage. The construction of guidelines for molecular weight/surface coverage necessary for kinetic prevention of protein adsorption in a desired timescale is shown. The time-dependent desorption is also studied by modeling how adsorbed proteins leave the surface when in contact with a pure water solution. It is found that the kinetics of desorption are very slow and depend in a nonmonotonic way in the polymer chain length. When the polymer layer thickness is shorter than the size of the protein, increasing polymer chain length, at fixed surface coverage, makes the desorption process faster. For polymer layers with thickness larger than the protein size, increases in molecular weight results in a longer time for desorption. This is due to the grafted polymers trapping the adsorbed proteins and slowing down the desorption process. These results offer a possible explanation to some experimental data on adsorption. Limitations and extension of the developed approaches for practical applications are discussed.

Adsorption↗
PubMed2006

Characterization of Pb, Cu, and Cd adsorption on particulate organic matter in soil.

Evidence exists for significant metal enrichment in particulate organic matter (POM) compared to other soil constituents, but the relevant mechanisms are poorly understood. In the present study, adsorption of the heavy metals Pb, Cu, and Cd on a loamy soil and on POM separated from this soil was investigated. The adsorption kinetic data can be well described with a pseudo-second order model, whereas the equilibrium data are well fitted by a Langmuir model. Adsorption isotherms and kinetics data, in addition to the influence of pH on metal adsorption, showed that POM had a much higher adsorption capacity for Pb, Cu, and Cd compared to the whole soil. Ionic strength effects on metal adsorption, Fourier transform infrared spectroscopy, x-ray absorption spectroscopy x-ray absorption spectroscopy including x-ray absorption near-edge structure and extended x-ray absorption fine-structure spectroscopy were employed to elucidate the adsorption mechanisms. The results suggested that Pb and Cu adsorption on POM was mainly through inner-sphere complexes with carboxyl and hydroxyl groups. Cadmium was possibly adsorbed via outer-sphere complexation, indicated by the influence of ionic strength on Cd adsorption.

Adsorption↗
PubMedDate not supplied

Contrasting nitrate adsorption in Andisols of two coffee plantations in Costa Rica.

Fertilizer use in coffee plantations is a suspected cause of rising ground water nitrate concentrations in the ground water-dependent Central Valley of Costa Rica. Nitrate adsorption was evaluated beneath two coffee (Coffea arabica L.) plantations in the Central Valley. Previous work at one site had identified unsaturated zone nitrate retardation relative to a tritium tracer. Differences in nitrate adsorption were assessed in cores to 4 m depth in Andisols at this and one other plantation using differences in KCl- and water-extractable nitrate as an index. Significant adsorption was confirmed at the site of the previous tracer test, but not at the second site. Anion exchange capacity, X-ray diffraction data, extractable Al and Si, and soil pH in NaF corroborated that differences in adsorption characteristics were related to subtle differences in clay mineralogy. Soils at the site with significant nitrate adsorption showed an Al-rich allophane clay content compared with a more weathered, Si-rich allophane and halloysite clay mineral content at the site with negligible adsorption. At the site with significant nitrate adsorption, nitrate occupied less than 10% of the total anion adsorption capacity, suggesting that adsorption may provide long-term potential for mitigation or delay of nitrate leaching. Evaluation of nitrate sorption potential of soil at local and landscape scales would be useful in development of nitrogen management practices to reduce nitrate leaching to ground water.

Adsorption↗
PubMed2006

Development of chitosan-based granular adsorbents for enhanced and selective adsorption performance in heavy metal removal.

Novel chitosan-based granular adsorbents were developed for enhanced and selective separation of heavy metal ions. The research included the synthesis of chitosan hydrogel beads, the cross-linking of the hydrogel beads with ethylene glycol diglycidyl ether (EGDE) in a conventional and a novel amine-shielded method, the functionalization of the chitosan beads through surface grafting of polyacrylamide via a surfaceinitiated atom transfer radical polymerization (ATRP) method, and the examination of the adsorption performance of the various types of chitosan beads in the removal of heavy metal ions. It was found that chitosan beads were effective in heavy metal adsorption, the conventional cross-linking method improved the acidic stability of the beads but reduced their adsorption capacity, the novel amine-shielded cross-linking method retained the good adsorption capacity while it improved the acidic stability of the beads, and the grafting of polyacrylamide on chitosan beads not only enhanced the adsorption capacity but also provided the beads with excellent selectivity for mercury over lead ions. XPS analyses indicated that the adsorption of metal ions on chitosan beads was mainly attributed to the amine groups of chitosan, the novel amine-shielded cross-linking method preserved most of the amine groups from being consumed by the cross-linking process and hence improved the adsorption capacity of the cross-linked chitosan beads, and the many amide groups from the polyacrylamide grafted on the chitosan beads increased the adsorption capacity and also made possible selective adsorption of mercury ions because the amide groups can form covalent bonds with mercury ions.

Adsorption↗
PubMed1999

The phenomenon of salivary protein adsorption onto Streptococcus mitis ATCC 903 cells.

It is thought that salivary proteins on bacterial cells have some influence on the adhesion of oral bacteria onto the surface of oral tissues and on bacterial aggregation. Initially, this study sought to examine the phenomenon of salivary protein adsorption to the surface of Streptococcus mitis ATCC 903 using 3H-labeled salivary proteins. We investigated the effects of hydrophobic level and lectin-ligand binding on adsorption of salivary proteins, and also the influence of cell surface components on adsorption. The results showed that the adsorption of salivary proteins was clearly reduced by the presence of Tween 20, LiCl, NaSCN, Hexadecane and some sugars. The adsorption was also affected by the pH level, and protease treatment or heat treatment of cells also decreased the volume of adsorbed proteins. Although the adsorption of proteins onto heat-treated cells was dramatically reduced by the presence of LiCl and NaSCN, the presence of sugars had little influence on this adsorption. These findings suggest that the main adsorption of salivary proteins is due to hydrophobic factors, and the heat-sensitive surface components of the cells had some relation to lectin-ligand binding. Therefore, it appears important to study the adsorption of salivary proteins onto cells since the salivary proteins on bacterial cells play an important role in their adherence to the saliva-coated oral tissues and bacterial aggregation.

Adsorption↗
PubMedDate not supplied

Coating charcoal with polyacrylate-polymethacrylate copolymer for haemoperfusion. III: The effect of the coat thickness on the adsorptioncapacity of the coated charcoal and its adsorptivity to small and middle size molecules.

In this study, the effect of the coat thickness of polyacrylate-polymethacrylate copolymer on the adsorption capacity of activated charcoal to methylene blue as a model marker was investigated by constructing both Langmuir and Freundlich isotherms. It was found that the coat thickness significantly affected the adsorption coefficient of the coated charcoal to methylene blue as is reflected by the attractive forces between the adsorbent and the adsorbate. This effect is understandable as the membrane will act as a barrier between the adsorbent and the adsorbate. The coat thickness also had some effect on the adsorption capacity of activated charcoal but not as much as it affected the adsorption coefficient. The data followed the Freundlich isotherm more closely than the Langmuir equation. The effect of the coat thickness on the adsorption of selected drugs of different molecular size was also investigated using theophylline, paracetamol, sodium phenobarbital, creatinine and vitamin B12 as model drugs. The results showed that the adsorption patterns of theophylline, paracetamol and sodium phenobarbital were more or less similar. The apparent coating thickness did not affect the extent of adsorption of these model drugs and there was little effect on the adsorption rate especially during the first 15 min. The adsorption of vitamin B12 and creatinine showed completely different patterns which are discussed in detail.

Acrylic Resins↗