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PubMed2006

Adsorption of Pseudomonas putida on clay minerals and iron oxide.

Adsorption of Pseudomonas putida on minerals including montmorillonite, kaolinite and goethite was studied. The adsorption isotherms of P. putida on the examined minerals conformed to the Langmuir equation. The amount of P. putida adsorbed followed the order: goethite > kaolinite > montmorillonite. A greater extent of P. putida adsorption on minerals was observed in the range of temperature from 15 to 35 degrees C. The adsorption of P. putida on minerals decreased with the increase of pH from 3.0 to 10.0. Magnesium ion was more efficient than sodium ion in promoting P. putida adsorption on minerals. The results suggest that electrostatic interactions play a vital role in P. putida adsorption by soil colloidal factions. The information obtained in this study is of fundamental significance for the understanding of the survival and transport of bacteria in soil systems.

Adsorption↗
PubMed2005

Adsorption of arsenate on soils. Part 1: laboratory batch experiments using 16 Chinese soils with different physiochemical properties.

Laboratory batch experiments were carried out to study the adsorption of arsenate on 16 Chinese soils with different physicochemical properties. Wide differences in arsenate adsorption were observed, and the Jiangxi and Hubei soils were more effective sorbents for arsenate than other soils. The Langmuir one-surface and two-surface equations were used to model the arsenate adsorption data. Except for the Jiangxi and Hubei soils, the Langmuir one-surface equation gave reasonably good fits to the arsenate adsorption data. However, the Langmuir two-surface equation generally provided a better fit than the Langmuir one-surface equation. For soils with relative high organic matter (OM), dissolved organic carbon (DOC) or extractable phosphate, the Langmuir one-surface and two-surface equations described the adsorption isotherms similarly. In contrast, for soils with relatively low contents of OM, DOC or extractable phosphate, the Langmuir two-surface equation gave the better fit to the arsenate adsorption data.

Adsorption↗
PubMed2006

Effect of drug concentration on adsorption of levofloxacin by polyacrylonitrile haemofilters.

We studied an in vitro model of continuous venovenous haemofiltration to determine levofloxacin adsorption by polyacrylonitrile (PAN) filters. Four doses of levofloxacin (5, 25, 50 and 100 mg) were used, resulting in circulating concentrations of levofloxacin at 120 min of 3.56+/-0.14, 15.84+/-2.08, 31.42+/-1.95 and 58.23+/-1.10 mg/L, respectively. Adsorption at 2 h was 0.65+/-0.17, 5.99+/-2.49, 12.30+/-2.34 and 30.13+/-1.32 mg, respectively (P<0.001). From 2h to 4h, increasing the blood pump rate and the ultrafiltration rate had no effect on adsorption. When the concentration was decreased from 3.55+/-0.13 mg/L at 4h to 2.16+/-0.11 mg/L at 5 h by addition of lactated Ringer's solution, adsorption decreased from 0.67+/-0.16 mg to 0.21+/-0.25 mg (P<0.05). These data show that adsorption of levofloxacin by PAN haemofilters is concentration dependent and reversible in vitro and suggest that adsorption by haemofilters is unlikely to affect levofloxacin pharmacokinetics significantly in vivo.

Acrylic Resins↗
PubMed2006

Trypsin immobilization by direct adsorption on metal ion chelated macroporous chitosan-silica gel beads.

Silica gel bead coated with macroporous chitosan layer (CTS-SiO(2)) was prepared, and the metal immobilized affinity chromatographic (IMAC) adsorbents could be obtained by chelating Cu(2+), Zn(2+), Ni(2+) ions, respectively on CTS-SiO(2), and trypsin could be adsorbed on the IMAC adsorbent through metal-protein interaction forces. Batch adsorption experiments show that adsorption capacity for trypsin on these IMAC adsorbent variated with change of pH. The maximal adsorption reached when the solution was in near neutral pH in all three IMAC adsorbents. Adsorption isothermal curve indicated that maximal adsorption capacity could be found in the Cu(2+)-CTS-SiO(2) with the value of 4980+/-125 IUg(-1) of the adsorbent, while the maximal adsorption capacity for trypsin on Zn(2+) and Ni(2+) loaded adsorbent was 3762+/-68 IUg(-1) and 2636+/-53 IUg(-1), respectively. Trypsin immobilized on the IMAC beads could not be desorbed by water, buffer and salt solution if the pH was kept in the range of 5-10, and could be easily desorbed from the IMAC beads by acidic solution and metal chelating species such as EDTA and imidazole. The effect of chelated metal ions species on CTS-SiO(2) beads on the activity and stability of immobilized trypsin was also evaluated and discussed. Trypsin adsorbed on Zn-IMAC beads retained highest amount of activity, about 78% of total activity could be retained. Although the Cu-IMAC showed highest affinity for trypsin, only 25.4% of the calculated activity was found on the beads, while the activity recovery found on Ni-IMAC beads was about 37.1%. A remarkable difference on stability of trypsin immobilized on three kinds of metal ion chelated beads during storage period was also found. Activity of trypsin on Cu-IMAC decreased to 24% of its initial activity after 1-week storage at 4 degrees C, while about 80% activity was retained on both Ni-IMAC and Zn-IMAC beads. Trypsin immobilized on Zn-CTS-SiO(2) could effectively digest BSA revealed by HPLC peptide mapping.

Adsorption↗
PubMed2006

Low density porous carrier drug adsorption and release study by response surface methodology using different solvents.

Low density porous carriers are widely used in the pharmaceutical applications. Response surface methodology, using 3(2) factorial design was used to study drug adsorption on and its release patterns from microporous polypropylene (Accurel MP 1000) in the absence of additives. Ibuprofen, as model drug, was adsorbed on the polymer by solvent evaporation using two organic solvents methanol (M) and dichloromethane (DCM). The amount of carrier (100 mg) and its particle size range (250-350 microm) were kept invariant while solvent volume (X1) and drug amount (X2) were taken as variables. Drug adsorption pattern depended on the type and amount of solvent used. DSC, XRD, FTIR and TGA, predict crystalline nature and physical form of adsorption. SEM showed the penetration and adsorption of the drug in and on the microporous polymer. Accurel MP 1000 had a pore volume of 1.992 g/cm3 and surface area of 55.9855 m2/g as detected by mercury porosimetery. On drug adsorption, pore volume ranged from 0.413 to 1.198 g/cm3 for methanol and 0.280-0.759 g/cm3 for DCM. Similarly surface area was in the range 38.445-25.497 m2/g for methanol and 18.710-32.528m2/g for DCM. The drug release was investigated in phosphate buffer pH 7.2. All batches showed excellent in vitro floating property. Drug release was partial with recovery to complete dependent on type and volume of solvent. R2 values relating to bulk density, pore volume, surface area and drug release at 60, 120 and 180 min were estimated. Effect of solvent properties shows a positive influence on drug adsorption and release. Release profiles of some batches could be considered as gastroretentive drug delivery system.

Adsorption↗
PubMed2004

Analysis of protein adsorption characteristics to nano-pore silica particles by using confocal laser scanning microscopy.

The effect of average pore size of nano-pore silica particles on protein adsorption characteristics was determined experimentally by the dissociation constant and the adsorption capacity determined from the Langmuir equation. As the average pore size was increased from 2.2 to 45 nm, the BSA adsorption capacity increased from 16.8 to 84.3 mg/g-silica so as the equilibrium constant (from 2.6 to 9.4 mg/ml). Using confocal microscopy with fluorescence labeling, we could visualize the protein adsorption in situ and determine the minimum pore size required for efficient intraparticle adsorption. The confocal microscopy analysis revealed that BSA was adsorbed mainly on the surface of the particles with a smaller pore size, but diffused further into the interstitial surface when it was sufficiently large. It was concluded that for BSA whose Stoke's diameter is ca. 3.55 nm the minimum pore size of about 45 nm or larger was required for a sufficient adsorption capacity.

Adsorption↗
PubMed2004

Nanoscale organization of adsorbed collagen: influence of substrate hydrophobicity and adsorption time.

The adsorption of collagen on polystyrene (PS) and polystyrene oxidized by oxygen plasma discharge (PSox) was studied as a function of time using radiolabeling, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). Radiolabeling and XPS indicated that the initial step of adsorption was faster on PS than on PSox. AFM imaging under water revealed very different supramolecular organization of the adsorbed films depending on time and on the nature of the substrate: PS showed patterns of collagen aggregates at all adsorption times (from 1 min to 24 h); PSox was covered with a smooth layer except at long adsorption times (24 h), for which a mesh of collagen structures was observed. After fast drying, the collagen layer remained continuous and showed a morphology which recalled that observed under water. The mechanical stability of the adsorbed films was assessed under water by scraping with the AFM probe at different loading forces: no perturbations were created on PSox; in contrast, the layer adsorbed on PS was sensitive to scraping, the minimum force required to alter the collagen layer morphology increasing with time. These differences in the film properties were correlated with force measurements upon retraction: multiple adhesion forces were observed with collagen adsorbed on PS samples, whereas such an effect was never observed on PSox. The results show that the amount adsorbed and the organization of the adsorbed film respond differently to the adsorption time and that this is influenced by surface hydrophobicity. The quick initial adsorption on PS, compared to PSox, is thought to leave dangling collagen segments that are responsible for the observed morphology, for adhesion forces, and for lower mechanical resistance of the adsorbed layer.

Adsorption↗
PubMed2004

Modeling Pb(II) adsorption onto sandy loam soil.

The adsorption of Pb(II) onto hydrous sandy loam soil was investigated with batch equilibrium adsorption experiments. Results show that the amount of Pb(II) adsorbed increases with increasing pH and surface loading. It was demonstrated that the surface acidity of the soil could be determined using electrophoretic mobility measurements. The surface acidity constants, pK(a1)(int) and pK(a2)(int), were 1.57 and 3.43, respectively. A surface complex formation model (SCFM) was employed to describe the adsorption. The intrinsic stability constants, pK(i)(s), for the surface reaction between the Pb species and the ionized soil surface hydroxyl groups were determined from SCFM fitting. The adsorption free energy of Pb2+ and Pb(OH)+ ions ranges from -5.74 to -6.48 kcal/mol and from -9.68 to -10.00 kcal/mol, respectively, for surface loadings between 1.21 x 10(-5) and 2.41 x 10(-4) mol/g. The adsorption binding calculation indicated that the specific chemical interaction is the major mechanism responsible for the adsorption process.

Adsorption↗
PubMed2004

Adsorption of tannic acid, humic acid, and dyes from water using the composite of chitosan and activated clay.

Chitosan is a well-known excellent adsorbent for a number of organics and metal ions, but its mechanical properties and specific gravity should be enhanced for practical operation. In this study, activated clay was added in chitosan slurry to prepare composite beads. The adsorption isotherms and kinetics of two organic acids (tannic acid, humic acid) and two dyes (methylene blue, reactive dye RR222) using composite beads, activated clay, and chitosan beads were compared. With composite beads as an adsorbent, all the isotherms were better fitted by the Freundlich equation. The adsorption capacities with composite beads were generally comparable to those with chitosan beads but much larger than those with activated clay. The pseudo-first-order and pseudo-second-order equations were then screened to describe the adsorption processes. It was shown that the adsorption of larger molecules such as tannic acid (MW, 1700 g mol(-1)), humic acid, and RR222 from water onto composite beads was better described by the pseudo-first-order kinetic model. The rate parameters of the intraparticle diffusion model for adsorption onto such adsorbents were also evaluated and compared to identify the adsorption mechanisms.

Adsorption↗
PubMed2004

Adsorption of lead and mercury by rice husk ash.

An attempt at the use of rice husk ash, an agricultural waste, as an adsorbent for the adsorption of lead and mercury from aqueous water is studied. Studies are carried out as a function of contact times, ionic strength, particle size, and pH. Rice husk ash is found to be a suitable adsorbent for the adsorption of lead and mercury ions. The Bangham equation can be used to express the mechanism for adsorption of lead and mercury ions by rice husk ash. Its adsorption capability and adsorption rate are considerably higher and faster for lead ions than for mercury ions. The finer the rice husk ash particles used, the higher the pH of the solution and the lower the concentration of the supporting electrolyte, potassium nitrate solution, the more lead and mercury ions absorbed on rice husk ash. Equilibrium data obtained have been found to fit both the Langmuir and Freundlich adsorption isotherms.

Adsorption↗
PubMed2004

Nanostructured collagen layers obtained by adsorption and drying.

The supramolecular organization of collagen adsorbed from a 7 microg/ml solution on polystyrene was investigated as a function of the adsorption duration (from 1 min to 24 h) and of the drying conditions (fast drying under a nitrogen flow, slow drying in a water-saturated atmosphere). The morphology of the created surfaces was examined by atomic force microscopy (AFM), while complementary information regarding the adsorbed amount and the organization of the adsorbed layers was obtained using radioassays, X-ray photoelectron spectroscopy (XPS), and wetting measurements. The collagen adsorbed amount increased up to an adsorption duration of 5 h and then leveled off at a value of 0.9 microg/cm2. For samples obtained by fast drying, modeling of the N/C ratios obtained by XPS in terms of thickness and surface coverage, in combination with the adsorbed amount, water contact angle measurements and AFM images, indicated that the adsorbed layer formed a felt starting from 30 min of adsorption, the density and/or the thickness of which increased with the adsorption time. Upon slow drying, the collagen layers formed after adsorption times up to about 2 h underwent a strong reorganization. The obtained nanopatterns were attributed to dewetting, the liquid film being ruptured and adsorbed collagen being displaced by the water meniscus. At higher adsorption times, the organization of the collagen layer was similar to that obtained after fast drying, because the onset of dewetting and/or collagen displacement were prevented by the high density of the collagen felt.

Adsorption↗
PubMed2005

Adsorption of NH3 onto activated carbon prepared from palm shells impregnated with H2SO4.

Adsorption of ammonia (NH3) onto activated carbons prepared from palm shells impregnated with sulfuric acid (H2SO4) was investigated. The effects of activation temperature and acid concentration on pore surface area development were studied. The relatively large micropore surface areas of the palm-shell activated carbons prepared by H2SO4 activation suggest their potential applications in gas adsorption. Adsorption experiments at a fixed temperature showed that the amounts of NH3 adsorbed onto the chemically activated carbons, unlike those prepared by CO2 thermal activation, were not solely dependent on the specific pore surface areas of the adsorbents. Further adsorption tests for a wide range of temperatures suggested combined physisorption and chemisorption of NH3. Desorption tests at the same temperature as adsorption and at an elevated temperature were carried out to confirm the occurrence of chemisorption due to the interaction between NH3 and some oxygen functional groups via hydrogen bonding. The surface functional groups on the adsorbent surface were detected by Fourier transform infrared spectroscopy. The amounts of NH3 adsorbed by chemisorption were correlated with the contents of elemental oxygen present in the adsorbents. Mechanisms for chemical activation and adsorption processes are proposed based on the observed phenomena.

Adsorption↗
PubMed2005

Mesoscopic dynamic Monte Carlo simulations of the adsorption of proteinlike HP chains within laterally constricted spaces.

Two-dimensional dynamic Monte Carlo simulations are applied to the protein-like HP chain model to investigate the influence of lateral confinement of the adsorbed chain on adsorption thermodynamics and the ensemble of accessible chain conformations. The structure of the model makes it possible to enumerate all possible chain conformations and thereby define with precision the relation between adsorption thermodynamics and changes in accessible chain conformations resulting from the adsorption process. Lateral confinement of the adsorbed chain is shown to dramatically reduce the number of accessible energy states and unique chain conformations such that, under certain conditions, adsorption is predicted to actually stabilize the chain against denaturation. Lateral confinement preferentially eliminates expanded conformations of the adsorbed chain, shifting the equilibrium from the unfolded state toward the native state. As a result, the conformational entropy of the adsorbed chain is predicted to be lower than that of the chain free in solution. The protein-like HP chain responds to an increase in the hydrophobicity of the sorbent surface by strongly favoring those conformations that minimize the overall internal energy of the system. As a result, adsorption severely destabilizes the native-state conformation. The ability of our simulation results to provide insights into underlying mechanisms for nonspecific protein adsorption is illustrated through qualitative comparison with activity data for hen egg-white lysozyme adsorbed on silica at different surface concentrations.

Adsorption↗
PubMed2005

Preparation and adsorption properties of monodisperse chitosan-bound Fe3O4 magnetic nanoparticles for removal of Cu(II) ions.

Monodisperse chitosan-bound Fe(3)O(4) nanoparticles were developed as a novel magnetic nano-adsorbent for the removal of heavy metal ions. Chitosan was first carboxymethylated and then covalently bound on the surface of Fe(3)O(4) nanoparticles via carbodiimide activation. Transmission electron microscopy micrographs showed that the chitosan-bound Fe(3)O(4) nanoparticles were monodisperse and had a mean diameter of 13.5 nm. X-ray diffraction patterns indicated that the magnetic nanoparticles were pure Fe(3)O(4) with a spinel structure, and the binding of chitosan did not result in a phase change. The binding of chitosan was also demonstrated by the measurement of zeta potential, and the weight percentage of chitosan bound to Fe(3)O(4) nanoparticles was estimated to be about 4.92 wt%. The chitosan-bound Fe(3)O(4) nanoparticles were shown to be quite efficient for the removal of Cu(II) ions at pH>2. In particular, the adsorption rate was so fast that the equilibrium was achieved within 1 min due to the absence of internal diffusion resistance. The adsorption data obeyed the Langmuir equation with a maximum adsorption capacity of 21.5 mg g(-1) and a Langmuir adsorption equilibrium constant of 0.0165 L mg(-1). The pH and temperature effects revealed that the adsorption capacity increased significantly with increasing pH at pH 2-5, and the adsorption process was exothermic in nature with an enthalpy change of -6.14 kJ mol(-1) at 300-330 K.

Adsorption↗
PubMed2005

Adsorption of lignite-derived humic acids on coal-based mesoporous activated carbons.

The adsorption by a coal-based mesoporous activated carbon of humic acids (HAs) isolated from two Polish lignites was studied. For comparison, a commercial Aldrich humic acid was also included into this study. The differences in chemical structure and functional groups of HAs were determined by elemental analysis and infrared spectroscopy DRIFT. Two activated carbons used differed in terms of mesopore volume, mesopore size distribution, and chemical properties of the surface. The kinetics of adsorption of HAs have been discussed using three kinetic models, i.e., the first-order Lagergren model, the pseudo-second-order model, and the intraparticle diffusion model. It was found that the adsorption of HAs from alkaline solution on mesoporous activated carbon proceeds according to the pseudo-second-order model. The correlation coefficients were close to 1. The intraparticle diffusion of HA molecules within the carbon particle was identified to be the rate-limiting step. Comparing the two activated carbons, the carbon with a higher volume of pores with widths of 10-50 nm showed a greater removal efficiency of HA. An increase in the Freundlich adsorption capacity with decreasing carbon content of HA was observed. Among the HAs studied, S-HA shows characteristics indicating the highest contribution of small-size fraction. The S-HA was removed by both activated carbons to the highest extent. The effect of pH solution on the adsorption of HA was examined over the range pH 5.4-12.2. It was found that the extent of adsorption decreased with decreasing pH of the solution.

Adsorption↗
PubMed2005

Multilayer adsorption of amino acids on oxidized cellulose.

The adsorption of amino acids (AA) (glycine, L-alanine, L-proline) on oxidized cellulose (OC) with various carboxyl contents and degrees of crystallinity from aqueous and water/ethanol solutions was studied. It was found that multilayer adsorption occurs in concentrated solutions of AA. It proceeds according to successive mechanisms via adsorption of AA zwitterions onto carboxyls of already adsorbed AA. This leads to formation of chain AA associates in the OC phase. A sharp increase in swelling accompanies multilayer adsorption. It was established that structural characteristics and degree of polymerization of OC are the main factors that affect multilayer adsorption. The distribution of carboxyls in the OC phase also plays an important role. Multilayer adsorption does not proceed in water/ethanol solutions and in the case of the cationic form of AA.

Adsorption↗
PubMed2005

Mechanisms and kinetics of trisodium 2-hydroxy-1,1'-azonaphthalene-3,4',6-trisulfonate adsorption onto chitosan.

Chitosan, a naturally abundant biopolymer, has widely been studied for metal adsorption from various solutions, but the extension of chitosan as an adsorbent to remove organic substances from water and wastewater has seldom been explored. In this study, the adsorption of an azo dye, trisodium 2-hydroxy-1,1'-azonaphthalene-3,4',6-trisulfonate (1), from aqueous solution onto the various degrees of deacetylated chitosan has been investigated. Equilibrium studies have been carried out to determine the capacity of chitosan for dye. The experimental data were analyzed using two isotherm correlations, namely, Langmuir and Freundlich equations. The linear correlation coefficients were determined for each isotherm and the Langmuir provided the best fit. The experimental adsorption isotherms were perfectly reproduced in the simulated data obtained from numerical analysis on the basis of the Langmuir model and the isotherm constants. Adsorption of (1) onto the chitosan flakes was found to be strongly depending on degrees of deacetylation in chitosan and temperatures. Significant amounts of (1) were adsorbed by chitosan 8B (higher degree of deacetylated chitosan), but the adsorption capacity was reduced remarkably with increasing solution temperatures. Thermodynamic parameters such as change in free energy (DeltaG), enthalpy (DeltaH), and entropy (DeltaS) were also determined. In addition, kinetic study indicated that the adsorption process mechanisms were both transport- and attachment-limited.

Adsorption↗
PubMed2005

Effect of alkali metal cations on adsorption of guar gum onto quartz.

The effect of cesium, potassium, sodium, and lithium cations on the adsorption of natural guar gum onto quartz was investigated. The role of these ions was analyzed in terms of their water structure-making or -breaking capabilities. In the presence of structure makers (Na+, Li+) the polymer adsorption density did not change compared to the adsorption levels observed in distilled water. However, in dilute solutions (0.01 N) of structure-breaking cations (Cs+, K+) the adsorption density of guar gum significantly increased, with potassium and cesium producing the same adsorption densities of the polymer. The resulting colloidal aggregation/dispersion equilibria in the quartz-guar gum system were discussed and mechanisms of guar gum-quartz interactions were also suggested. Assuming hydrogen bonding to be the driving adsorption mechanism, it was proposed that guar gum molecules compete with water for silanol surface sites. Structure-breaking cations disturb the interfacial water structure around the quartz particles thus allowing the polymer to more closely approach the quartz surface and interact with the surface groups.

Adsorption↗