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PubMed2005

Enhanced and selective adsorption of mercury ions on chitosan beads grafted with polyacrylamide via surface-initiated atom transfer radical polymerization.

Enhanced and selective removal of mercury ions was achieved with chitosan beads grafted with polyacrylamide (chitosan-g-polyacrylamide) via surface-initiated atom transfer radical polymerization (ATRP). The chitosan-g-polyacrylamide beads were found to have significantly greater adsorption capacities and faster adsorption kinetics for mercury ions than the chitosan beads. At pH 4 and with initial mercury concentrations of 10-200 mg/L, the chitosan-g-polyacrylamide beads can achieve a maximum adsorption capacity of up to 322.6 mg/g (in comparison with 181.8 mg/g for the chitosan beads) and displayed a short adsorption equilibrium time of less than 60 min (compared to more than 15 h for the chitosan beads). Coadsorption experiments with both mercury and lead ions showed that the chitosan-g-polyacrylamide beads had excellent selectivity in the adsorption of mercury ions over lead ions at pH < 6, in contrast to the chitosan beads, which did not show clear selectivity for either of the two metal species. Mechanism study suggested that the enhanced mercury adsorption was due to the many amide groups grafted onto the surfaces of the beads, and the selectivity in mercury adsorption can be attributed to the ability of mercury ions to form covalent bonds with the amide. It was found that adsorbed mercury ions on the chitosan-g-polyacrylamide beads can be effectively desorbed in a perchloric acid solution, and the regenerated beads can be reused almost without any loss of adsorption capacity.

Adsorption↗
PubMed2006

Adsorption of L-lysine on Cu(110): a RAIRS study from UHV to the liquid phase.

The adsorption of L-lysine on a Cu(110) surface has been investigated under UHV conditions from the sublimation of a crystalline phase. The adsorption was characterized by Fourier transform reflection absorption infrared spectroscopy (FT-RAIRS) during exposure and Auger electron spectroscopy (AES). At room temperature, the lysine molecules' adsorption geometry varies as a function of the exposure. At low coverage, the molecules are adsorbed via the oxygen atoms of the deprotonated carboxylate group and the nitrogen atom of the amino group. At high coverage, close to the monolayer, the molecules reorient to be anchored to the surface via one oxygen of a sideways-tilted carboxylate moiety. This first step is followed by the growth of multilayers of nonoriented molecules. In contrast, adsorption on an oxygen-modified copper surface leads to a rather disordered layer. The results are compared with the adsorption carried out on a polycrystalline copper surface after immersion in solutions of lysine at various pH values. The adsorption was monitored by polarization modulation infrared spectroscopy (PM-IRRAS). The chemistry of the adsorbed molecules is function of the starting chemical form of the lysine molecules imposed by the pH of the solution. The combination of the two techniques and various sets of adsorption conditions will give important insight into the adsorption of biomolecules on metal surfaces and the influence of water and surface oxygen.

Adsorption↗
PubMed1989

Effect of anions on adsorption of bile salts by colestipol hydrochloride.

The Langmuir affinity constant and adsorptive capacity for the adsorption of citrate anion or cholate anion by colestipol hydrochloride at pH 7.5, 37 degrees C, were similar. Prior exposure of colestipol hydrochloride to citrate anion caused the adsorption of cholate anion to decrease slightly in comparison to a control utilizing only cholate anion. The concentration of citrate anion was found to be directly related to the decrease in cholate anion adsorption. Simultaneous exposure of colestipol hydrochloride to citrate and cholate anions at pH 7.5, 37 degrees C, resulted in the same adsorption of cholate anion as sequential exposure to citrate anion followed by cholate anion. Sequential exposure of colestipol hydrochloride to simulated gastric fluid and simulated intestinal fluid containing cholate anion resulted in a small decrease in cholate adsorption which was attributed to competition with phosphate anion in simulated intestinal fluid. Pepsin in the simulated gastric fluid did not affect adsorption of cholate anion from simulated intestinal fluid. Preexposure to components of tomato juice and orange juice also slightly reduced the adsorption of cholate anion by colestipol hydrochloride.

Adsorption↗
PubMed1994

Cellulose hydrolysis by the cellulases from Trichoderma reesei: adsorptions of two cellobiohydrolases, two endocellulases and their core proteins on filter paper and their relation to hydrolysis.

Separate binding of several purified cellulolytic components of Trichoderma reesei on to filter paper was studied and concomitant hydrolysis rates evaluated. Enhancement of mass transfer from the bulk liquid to the solid substrate by agitation has two different effects on adsorption depending on the type of enzyme: (i) the fraction of cellobiohydrolase II (CBH II) and endoglucanase III (EG III) bound at equilibrium is increased, whereas (ii) the rate but not the extent of cellobiohydrolase I (CBH I) and endoglucanase I (EG I) adsorption is affected. The adsorption of CBH I core, a component lacking the cellulose-binding domain (CBD), is, however, not significantly influenced by mass transfer. The CBH I interdomain peptide (present in CBH I core b) does not participate in adsorption but enhances stability. The adsorption of CBH I core proteins is a fully reversible process whereas that of the intact CBH I is not. Thus, the interaction of the CBD with filter paper apparently accounts for the mass-transfer-limited binding rate and also for the irreversible adsorption of intact CBH I. Adsorption isotherms at 50 degrees C indicate very similar relative association constants for the intact cellulases (0.24-0.30 l/g of cellulose), but drastically reduced values for CBH I core proteins (0.03 l/g of cellulose). The specific activities of adsorbed CBH I and of its core proteins are identical and a linear relationship between adsorption and rates of hydrolysis is found only for these enzymes. Thus, non-productive binding on to cellulose seems evident in the case of CBH II and EG III but not CBH I.

Adsorption↗
PubMed2000

Peptide interfacial adsorption is kinetically limited by the thermodynamic stability of self association.

We present a study of the adsorption of two peptides at the octane-water interface. The first peptide, Lac21, exists in mixed monomer-tetramer equilibrium in bulk solution with an appreciable monomer concentration. The second peptide, Lac28, exists as a tetramer in solution, with minimal exposed hydrophobic surface. A kinetic limitation to interfacial adsorption exists for Lac28 at moderate to high surface coverage that is not observed for Lac21. We estimate the potential energy barrier for Lac28 adsorption to be 42 kJ/mol and show that this is comparable to the expected free energy barrier for tetramer dissociation. This finding suggests that, at moderate to high surface coverage, adsorption is kinetically limited by the availability of interfacially active monomeric "domains" in the subinterfacial region. We also show how the commonly used empirical equation for protein adsorption dynamics can be used to estimate the potential energy barrier for adsorption. Such an approach is shown to be consistent with a formal description of diffusion-adsorption, provided a large potential energy barrier exists. This work demonstrates that the dynamics of interfacial adsorption depend on protein thermodynamic stability, and hence structure, in a quantifiable way.

Adsorption↗
PubMed2002

Optimization of multistage phenol adsorption by organobentonites: theoretical developments and experimental verification.

Material balance equations were developed for representing phenol adsorption by organobentonites in a countercurrent multistage adsorption process. The developed equations were employed to analyze the adsorption performance of the multistage process. Results of the theoretical analyses using empirical Freundlich adsorption isotherm had shown that the multistage process is more efficient than the single-stage process in terms of phenol removal per unit amount of organobentonite. It was also shown that equal division of the total amount of organobentonite among all adsorption stages yields the best overall phenol removal efficiency for the multistage process in comparison with other organobentonite allocations. The Freundlich adsorption isotherm was confirmed by experimental tests to describe well the phenol adsorption by organobentonites. Results of theoretical performance analyses of the multistage adsorption process were experimentally verified using two- and three-stage test examples.

Adsorption↗
PubMedDate not supplied

Differences in the adsorption behaviour of poly(ethylene oxide) copolymers onto model polystyrene nanoparticles assessed by isothermal titration microcalorimetry correspond to the biological differences.

The adsorption behaviour of a tetrafunctional copolymer of poly (ethylene oxide)-poly (propylene oxide) ethylene diamine (commercially available as Poloxamine 908) and a diblock copolymer of poly (lactic acid)-poly (ethylene oxide) (PLA/PEG 2:5) onto a model colloidal drug carrier (156 nm sized polystyrene latex) is described. The adsorption isotherm, hydrodynamic thickness of the adsorbed layers and enthalpy of the adsorption were assessed. The close similarity in the conformation of the poly (ethylene oxide) (PEO) chains (molecular weight 5,000 Da) in the adsorbed layers of these two copolymers was demonstrated by combining the adsorption data with the adsorbed layer thickness data. In contrast, the results from isothermal titration microcalorimetry indicated a distinct difference in the interaction of the copolymers with the polystyrene colloid surface. Poloxamine 908 adsorption to polystyrene nanoparticles is dominated by an endothermic heat effect, whereas, PLA/PEG 2:5 adsorption is entirely an exothermic process. This difference in adsorption behaviour could provide an explanation for differences in the biodistribution of Poloxamine 908 and PLA/PEG 2:5 coated polystyrene nanoparticles observed in previous studies. A comparison with the interaction enthalpy for several other PEO-containing copolymers onto the same polystyrene colloid was made. The results demonstrate the importance of the nature of the anchoring moiety on the interaction of the adsorbing copolymer with the colloid surface. An endothermic contribution is found when an adsorbing molecule contains a poly (propylene oxide) (PPO) moiety (e.g. Poloxamine 908), whilst the adsorption is exothermic (i.e. enthalpy driven) for PEO copolymers with polylactide (PLA/PEG 2:5) or alkyl moieties.

Adsorption↗
PubMed2001

Adsorption and desorption of mercury by Bangpakong River sediments as influenced by salinities.

Mercury adsorption and desorption by Bangpakong River sediments (pH range 6.8-7.8) of Thailand were investigated at salinity levels of 0, 5, 15 and 30@1000 using a batch equilibration techniques. Using Freundlich isotherm adsorption and desorption data collected represented a nonlinear form. A significant portion (90-99%) of added Hg (2-10 mg L-1) was sorbed by the sediment. Mercury adsorption isotherms or percentage adsorbed were similar among the four salinities tested. In the absence of salinity, Hg adsorption was highly influenced by pH. Whereas in the presence of salinity gradients, Hg(II)-organic complexes predominated over Hg(II)-Cl complexes, neutralizing effect of chloride concentrations and pH on the adsorption phenomena. Organic matter and clay contents of sediment were responsible for the Hg adsorption. Fe and Mn oxides showed negative correlation with the Hg adsorption capacity (r = -0.549 and -0.594 respectively). Increase in Hg desorbed from the sediments occurred only at the 30@1000 salinity level. The Hg adsorption-desorption characteristics of the sediments studied exhibited a very strong irreversible sorption of added inorganic Hg. River sediment such as sediment as shown in this study with significant levels of organic matter and clay have the potential to retain Hg making it less bioavailable and mobile thus reducing potential toxicity to aquatic organisms in the environment.

Adsorption↗
PubMed2003

Removal of reactive dye from wastewater by adsorption using ECH cross-linked chitosan beads as medium.

The feasibility of the removal of reactive dye from wastewater using a novel adsorbent, ECH cross-linked chitosan beads, as medium was examined. The effect of the pH and the initial concentration of the dye (RR222) solution on the adsorption capacity of the ECH cross-linked chitosan beads were also investigated. It was found that the initial dye concentration and the pH of the solution significantly affected the adsorption capacity. An increase in initial dye concentration results in the increase of adsorption capacity while an acidic pH was found to be favorable for the adsorption of dye. It was also found that the equilibrium adsorption of RR222 could be adequately described by using the Langmuir model (r2 > or = 0.999). Moreover, results showed that the adsorption rate of RR222 onto ECH cross-linked chitosan beads could be described by using the second-order kinetic model, suggesting that chemical sorption instead of mass transfer was the rate-limiting step for the adsorption process. The maximum monolayer adsorption capacity obtained from the Langmuir model was extremely high as compared to the data reported in literature; 2252 g/kg at 30 degrees C with a pH of 3.0. Therefore, ECH cross-linked chitosan beads could be a feasible medium for the removal of reactive dye from wastewater and potentially an alternative for the decolorization of wastewater.

Adsorption↗
PubMed1980

Bile salt adsorption ability of dietary fiber from named varieties of carrot at different developmental ages.

The adsorption of bile salts to fiber has been measured using fiber prepared from different varieties of carrot at different developmental ages. We investigated the carrot varieties Altrinchan and Chantenay and used the bile salts deoxycholate and glycocholate. The method used to measure adsorption distinguished between true adsorption and apparent adsorption due to bile salts trapped within the interstices of the fiber matrix. Adsorption ability was influenced by the developmental age of the carrot but not by variety. Adsorption ability was at a maximum when the carrot fresh weight was at a maximum. The adsorption ability measured was true adsorption and was not dependent on the water holding capacity of the fiber. Deoxycholate was better adsorbed than glycocholate and the results suggest that the developmental age of a fiber source could be important when formulating diets designed to influence bile salt metabolism.

Adsorption↗
PubMed1977

Adsorption characteristics of volatile anesthetics on activated carbons and performance of carbon canisters.

The adsorption characteristics, such as the adsorption capacity, the nature of the mass transfer zone, and heats of adsorption, are important for evaluating the performances of carbon canisters for removal of waste anesthetic vapors. The adsorption capacities and the natures of the mass transfer zones were measured for halothane, methoxyflurane, enflurane, isoflurane, and trichloroethylene on Witcarb 965 activated carbon. In addition, adsorption capacities and heats of adsorption for nitrous oxide, cyclopropane and oxygen were measured on the same carbon. The data indicate that high adsorption capacities of dilute anesthetic vapors on this activated carbon permit the use of carbon canisters for removal of these volatile anesthetics from mixtures with oxygen or nitrous oxide. In contrast, high concentrations of anesthetics such as nitrous oxide and cyclopropane cannot be removed economically by disposable canisters. A simplified procedure using the "characteristic curve" concept and "LUB/equilibrium section theory" for approximate prediction of the adsorption capacities and evaluation of the performance of a canister is outlined.

Adsorption↗
PubMed2006

Volatile organic compound (VOC) adsorption on material: influence of gas phase concentration, relative humidity and VOC type.

UNLABELLED: This paper presents the results of a factorial experiment design analysis to investigate volatile organic compounds (VOC) adsorption on a ceiling tile. The impacts of three factors, VOC gas phase concentration, relative humidity, and VOC type, as single parameters and as a combination, on adsorption have been investigated. Cyclohexane, toluene, ethyl acetate, isopropyl alcohol and methanol were the five VOCs used in this study. A factor significant level was determined through evaluating its F value and comparing it with the critical value of F distribution at 95% confidence level. It was found that: (i) neither the relative humidity and gas phase concentration nor any interaction effect between them had significant impacts on toluene adsorption on the ceiling tile; (ii) the adsorption isotherm appeared to be linear for the non-polar compounds and non-linear for the semi-polar and polar compounds; (iii) no significant impact of relative humidity on adsorption was observed for most VOC compounds except for methanol; and (iv) the ceiling tile had the highest adsorption capacity toward the polar compounds, followed by the aromatic compounds and aliphatic compounds. In addition, the statistical analysis regarding the experimental results of toluene as a single compound or as a part of a mixture showed that toluene adsorption capacity on the ceiling tile as a single compound was higher than as a part of a mixture. PRACTICAL IMPLICATIONS: Building materials and furnishings may act as source and sink of VOCs in the indoor environment. In this study, a factorial experiment design analysis technique was used to show the impact of three factors, VOC gas phase concentration, relative humidity, and VOC type, as single parameters and as a combination, on the adsorption process (sink effect). The aim was to better understand the interaction between these parameters and to verify the common assumptions made in the model development and measurement of indoor air quality.

Adsorption↗
PubMed1987

The effects of surface chemistry and coagulation factors on fibrinogen adsorption from plasma.

Fibrinogen adsorption from plasma exhibits an unusual displacement phenomenon (the Vroman effect) in that decreases in adsorption occur after longer contact time or as the plasma concentration increases. Fibrinogen adsorption and the displacement effect were found to depend markedly on the nature of the surface, the time and temperature of adsorption, and to a lesser extent on certain contact activation factors. Displacement still occurred from plasmas lacking kininogens, factor IX, and prekallikrein, and from plasma that had been treated with BaSO4 to remove factors II, VII, IX, and X. Furthermore, displacement was also observed from fibrinogen solutions to which either albumin or hemoglobin had been added. In addition, competitive adsorption of binary protein mixtures was also shown to depend strongly on surface type. It therefore appears that fibrinogen adsorption from plasma is subject to similar if not identical competitive processes that occur in simpler protein mixtures. The final adsorption then reflects the influence of all the proteins in plasma, each competing for the limited number of adsorption sites according to the fundamental physical properties of surface activity and mass concentration.

Adsorption↗
PubMed1979

Comparative adsorption of human enteroviruses, simian rotavirus, and selected bacteriophages to soils.

Virus adsorption to soils is considered to be the most important factor in removing viruses after land treatment of wastewater. Most of the studies on virus adsorption to soils have utilized poliovirus as the model system. In the present study, comparative adsorption of a number of different types and strains of human enteroviruses and bacteriophages to nine different soil types was studied. Under the experimental conditions of this study, greater than 90% of all viruses adsorbed to a sandy loam soil except echovirus types 1, 12, and 29 and a simian rotavirus (SA-11), which adsorbed to a considerably lower degree. A great deal of variability was observed between adsorption of different strains of echovirus type 1, indicating that viral adsorption to soils is highly strain dependent. Of the five phages studied, f2 and phi X174 adsorbed the least. In addition to being dependent on type and strain of virus, adsorption was found to be influenced also by type of soil. Thus, soils having a saturated pH of less than 5 were generally good adsorbers. From these results, it appears that no one enterovirus or coliphage can be used as the sole model for determining the adsorptive behavior of viruses to soils and that no single soil can be used as the model for determining viral adsorptive capacity of all soil types.

Adsorption↗
PubMed1975

Adsorption of typhus rickettsiae to ghosts of sheep erythrocytes.

Rickettsia prowazeki will adsorb to ghosts derived from sheep erythrocytes by hypotonic lysis. Adsorption to ghosts, as to intact erythrocytes, is dependent on the metabolism of the rickettsiae. KCN and 0 C inhibit adsorption. Fluoride, while inhibiting hemolysis, has no effect on adsorption to ghosts or intact erythrocytes. The adsorption of rickettsiae to ghosts does not lead to lysis, in that fluorescent albumin can be retained by the ghost after adsorption. Both inside-out and right-side-out vesicles formed from the ghost are equally capable of adsorption, indicating that the receptor is stable during the process of vesiculation and is not localized to one aspect of the cell membrane. Adsorption to ghosts is slower and displays less affinity than to the intact erythrocyte. The ghost system will be useful in characterizing the membrane receptor for rickettsia and in establishing assays for adsorption to other cells.

Adsorption↗
PubMed1981

Role of surface fimbriae (fibrils) in the adsorption of Actinomyces species to saliva-treated hydroxyapatite surfaces.

We studied the adsorption, morphological, and serological characteristics of selected Actinomyces and related species. Evaluation of uranyl acetate-stained cells by electron microscopy revealed wide variations among strains in the frequency of surface fimbriae. These variations did not always correlate with the percent adsorption to saliva-treated hydroxyapatite of the various Actinomyces strains. However, two strains of Rothia dentocariosa possessing no surface fimbriae and five strains of A. israelii possessing very few surface fimbriae exhibited feeble adsorption to saliva-treated hydroxyapatite. Although the calculated number of adsorption sites on saliva-treated hydroxypatite did not vary widely among the strains tested, significant differences were observed in the affinities calculated for some species or serotypes. The mean affinities for strains of A. viscosus serotype 2 and A. naeslundii serotype 3 were similar, and these strains adsorbed well to saliva-treated hydroxyapatite. The mean adsorption and affinity for the A. naeslundii strain serotype 1 and all strains of A. israelii tested were significantly less than those determined for the A. viscosus serotype 2 or A. naeslundii serotype 3 strains. Adsorption inhibition activity of antiserum to strain T14V, previously shown to be solely related to antibodies in immune serum directed against the VA1 fimbria (fibril) antigen, was removed by preadsorption of the antiserum with most A. viscosus and A. naelundii strains, but not with A. israelii strains. This suggests some cross-reactivity among strains of A. viscosus and A. naeslundii but not A. israelii. Adsorption to saliva-treated hydroxyapatite of all A. viscosus and A. naeslundii strains tested was strongly inhibited by fimbriae isolated from A. viscosus strain T14V. Collectively, these data suggest that the adsorption of certain A. viscosus and A. naeslundii strains is mediated by surface fimbriae, many of which appear serologically cross-reactive with strain T14V fimbriae.

Actinomyces↗
PubMed1973

Rickettsial hemolysis: effect of metabolic inhibitors upon hemolysis and adsorption.

The hemolysis of sheep red blood cells by typhus rickettsiae is initiated by a temperature-sensitive adsorption process that is dependent on the energy-generating metabolism of the rickettsaie but not that of the erythrocyte. Adsorption is followed by events dependent on the metabolism of both the rickettsaie and red blood cells. At 34 C the adsorption step is complete after about 4 min, at lower temperatures the time required for adsorption is increased. At 0 C no adsorption occurred. The addition of cyanide inhibited the catabolism of glutamate by the rickettsiae and, consequently, both adsorption and the subsequent steps in hemolysis. The starvation of the rickettsiae for glutamate also prevented adsorption. Fluoride had no demonstrable effect on rickettsial metabolism nor the adsorption step but inhibited glycolysis in the erythrocytes and the hemolysis of the erythrocytes by rickettsiae.

Adsorption↗
PubMed1982

Adsorption of the tailed mycoplasma virus L3 to cell membranes.

The adsorption properties of the tailed bacteriophage L3 to Acholeplasma laidlawii cells were studied. Adsorption followed a biphasic curve. Reversibility and virus heterogeneity were not sufficient to explain the break in the adsorption curve. Binding studies showed that each colony-forming unit could bind about 350 virions. The electrostatic nature of L3 adsorption was indicated by the effect of cations, pH, and temperature on the adsorption rate constant. L3 adsorption appeared to have a requirement for Ca2+, which could not be replaced by the mono- and divalent cations examined. Ethylene glycol-bis(beta-aminoethyl ether)-N,N-tetraacetic acid inhibition of adsorption was totally reversed by added Ca2+. The effects of EDTA, proteases, and lectins on absorption indicated that membrane proteins are the L3 receptors. The model for L3 adsorption is a multivalent one involving lateral diffusion of adsorbed virions and receptor proteins.

Acholeplasma laidlawii↗