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PubMed2004

Linearity and reversibility of iodide adsorption on sediments from Hanford, Washington under water saturated conditions.

A series of adsorption and desorption experiments were completed to determine the linearity and reversibility of iodide adsorption onto sediment at the Hanford Site in southeastern Washington. Adsorption experiments conducted with Hanford formation sediment and groundwater spiked with dissolved (125)I (as an analog tracer for (129)I) indicated that iodide adsorption was very low (0.2 mL/g) at pH 7.5 and could be represented by a linear isotherm up to a total concentration of 100 mg/L dissolved iodide. The results of desorption experiments revealed that up to 60% of adsorbed iodide was readily desorbed after 14 days by iodide-free groundwater. Because iodide adsorption was considered to be partially reversible, even though small amount of initial iodide is retarded by adsorption at mineral-water interfaces, the weak adsorption affinity results in release of iodide when iodide-free pore waters and uncontaminated groundwaters contact the contaminated sediments in the vadose zone and aquifer systems.

Adsorption↗
PubMed2005

Selective adsorption of p-chloronitrobenzene from aqueous mixture of p-chloronitrobenzene and o-chloronitrobenzene using HZSM-5 zeolite.

The selective adsorption of p-chloronitrobenzene (p-CNB) using zeolite as the adsorbent from an aqueous mixture containing p-CNB and o-chloronitrobenzene (o-CNB) was investigated. The maximum adsorption amounts of p-CNB in HZSM-5 zeolite were found to be approximately 4 molecules per unit cell (mol/uc) at all adsorption temperatures investigated. The maximum adsorption amounts of o-CNB in HZSM-5 zeolite were, however, markedly lower than those of p-CNB at different adsorption temperatures. Diffusion results revealed that the diffusivity of p-CNB at 300K was about 100 times higher than that of o-CNB in HZSM-5 zeolite. The remarkable difference in the adsorption amounts and diffusivities between p-CNB and o-CNB resulted in separation factors of 463.6, 96.8 and 21.9 for p-CNB at 278, 300 and 323 K, respectively, indicating a selective adsorption of p-CNB in HZSM-5 zeolite from the aqueous mixture of p- and o-CNB.

Adsorption↗
PubMed2005

Adsorption-desorption characteristics of phenol and reactive dyes from aqueous solution on mesoporous activated carbon prepared from waste tires.

Liquid-phase adsorption-desorption characteristics and ethanol regeneration efficiency of an activated carbon prepared from waste tires and a commercial activated carbon were investigated. Water vapor adsorption experiments reveal that both activated carbons showed hydrophobic surface characteristics. Adsorption experiments reveal that the prepared activated carbon possessed comparable phenol adsorption capacity as the commercial one but clearly larger adsorption capacity of two reactive dyes, Black 5 and Red 31. It was ascertained that the prepared activated carbon exhibited less irreversible adsorption of phenol and the two dyes than its commercial counterpart. Moreover, ethanol regeneration efficiency of the prepared AC saturated with either dye was higher than that of the commercial AC. Because of its superior liquid-phase adsorption-desorption characteristics as well as higher ethanol regeneration efficiency, the prepared activated carbon is more suitable for wastewater treatment, especially for adsorbing similarly bulky adsorbates.

Adsorption↗
PubMed2005

A study on arsenic adsorption on polymetallic sea nodule in aqueous medium.

A detailed study on As(III) and As(V) adsorption on polymetallic sea nodule in aqueous medium has been reported. Elemental composition of sea nodule comprises primarily, iron, manganese and silicon with trace quantities of aluminium, copper, cobalt and nickel. As(V) adsorption on sea nodule is dependent on pH while As(III) is insensitive to it. Adsorption data broadly follow Langmuir isotherm. Kinetic data follow a pseudo-second-order model for both As(III) and As(V). Arsenic loading on sea nodule is dependent on initial arsenic concentration. Optimum As(III) loading is 0.74 mg/g at 0.34 mg/L and for As(V) it is 0.74 mg/g at 0.78mg/L. As(III) adsorption is broadly independent of ionic environment. Except for PO(4)(3-), As(III) adsorption is not influenced by anions but cations influence it significantly. As(V) adsorption, on the other hand, is influenced by anions and not by cations. Experimental evidence indicates an inner sphere complex for As(III) and partial inner and partial outer sphere complex for As(V). Both As(III) and As(V) adsorptions are marked with very little desorption in the pH range of 2-10. Sea nodule can speciate As(III) and As(V) in groundwater at or above pH 6. Sea nodule was successfully tested as an adsorbent for the removal of arsenic from six contaminated groundwater samples of West Bengal, India, containing arsenic in the range 0.04-0.18mg/L.

Adsorption↗
PubMed2005

Adsorptive ozonation of 2-methylisoborneol in natural water with preventing bromate formation.

This paper presents an application of our newly developed adsorptive ozonation process using a high silica zeolite adsorbent (USY) for drinking water treatment. First, the adsorption of 2-methylisoborneol (2-MIB) on USY in a river water/pure water mixture was clarified by a batch-type adsorption experiment. The results showed that 2-MIB was adsorbed on USY; however, almost all of the adsorbed 2-MIB was desorbed over time. The desorption rate was increased with the ratio of river water to pure water, indicating that compounds dissolved in the river water, such as natural organic matter (NOM), prevent the adsorption of 2-MIB on USY. Second, the ability of the river water to consume ozone was confirmed in an experiment using a USY-packed column reactor. The ozone consumption was obviously increased by the presence of USY, indicating that USY-adsorbing compounds dissolved in the river water (probably small size NOM) consumed the ozone. However, the rapid ozone consumption was occurred by 6-8 s in the retention times when 3.14-4.38 mgL(-1) of water dissolved ozone was fed, this rapid ozone consumption lasted no more than these times. This result revealed that the rapid consumption of ozone by the adsorptive compounds in our process could be avoided within a certain retention time (6-8 s; especially for the river water used in this study) when enough concentration of ozone (3.14 mgL(-1) or more; same above) was supplied. We therefore performed a trial in which 2-MIB dissolved in river water was continuously decomposed using a USY-packed column with various ozone concentrations. In the process, the adsorptive compound dissolved in the river water adsorbed and reacted with ozone in the parts of the apparatus upstream of the column, while the adsorption and decomposition of 2-MIB took place in the parts of the apparatus downstream of the column. This resulted in a sufficient 2-MIB decomposition with minimizing bromate ion formation.

Adsorption↗
PubMed2005

Removal of estrone and 17beta-estradiol from water by adsorption.

Endocrine disrupting chemicals (EDCs) are the focus of current environment concern, as they can cause adverse health effects in an intact organism, or its progeny, subsequent to endocrine function. The paper reports on the removal of estrone (E1) and 17beta-estradiol (E2) from water through the use of various adsorbents including granular activated carbon (GAC), chitin, chitosan, ion exchange resin and a carbonaceous adsorbent prepared from industrial waste. The results show that the kinetics of adsorption were adsorbent and compound-dependent, with equilibration being reached within 2 h for a waste-derived carbonaceous adsorbent to 71 h for an ion-exchange resin for E1, and within 7 h for the waste-derived carbonaceous adsorbent to 125 h for GAC for E2. Of all the adsorbents tested, the carbonaceous adsorbent showed the highest adsorption capacity, with a maximum adsorption constant of 87500 ml/g for E1 and 116000 ml/g for E2. The GAC also had a very high adsorption capacity for the two compounds, with a maximum adsorption constant of 9290 ml/g for E1 and 12200 ml/g for E2. The effects of some fundamental environmental parameters including adsorbent concentration, pH, salinity and the presence of humic acid and surfactant on adsorption were studied. The results show that adsorption capacity of activated carbon was decreased with an increase in adsorbent concentration and by the presence of surfactant and humic acid. The results have demonstrated excellent performance of a waste derived adsorbent in removing E1 and E2 from water, and indicated the potential of converting certain solid waste into useful adsorbents for pollution-control purposes.

Adsorption↗
PubMed2006

Selective adsorption of nonionic surfactant on hexagonal mesoporous silicates (HMSs) in the presence of ionic dyes.

Selective adsorption of alkylphenol polyethoxylates (APnEOs) from synthetic textile wastewater was investigated using hexagonal mesoporous silicates (HMSs). HMSs are synthetic silicate that have uniform mesopores, large surface areas and uniform surface functional groups. Five different types of HMSs were synthesized by surfactant-templating methods, and three of them were grafted with organic surface functional groups, i.e., n-octyldimethyl-, 3-aminopropyltriethoxy-, and 3-mercaptopropyl-groups. Titanium-substituted HMS was also made in the same way as HMS. Adsorption capacities and selectivities of these HMSs for APnEOs were investigated in batch adsorption experiments either in single-solute APnEO solutions or in mixed solutions with ionic dyes. Triton X-100 was used as a model APnEO and either Basic Yellow 1 or Acid Blue 45 was used as cationic or anionic dyes, respectively. All the HMSs except 3-aminopropyltriethoxy-grafted HMS had higher adsorption capacities of Triton X-100 than powdered activated carbon. HMS and Ti-HMS had the highest BET surface areas and mesopore volumes measured by the nitrogen adsorption method, and thereby the highest adsorption capacities for Triton X-100. Surface charge was the most important attractive force between HMSs and dyes. FT-IR spectra proved that hydrophilic HMSs adsorbed both Basic Yellow 1 and Acid Blue 45 by hydrogen bonding. Acid-base titration experiments revealed that all the HMSs except 3-aminopropyltriethoxy-grafted HMS were negatively charged at neutral pH, whereas PAC and 3-aminopropyltriethoxy-grafted HMS were positively charged. Due to negative surface charge, the anionic dye (Acid Blue 45) was not adsorbed on the four HMSs, which proves high selectivities of these HMSs for Triton X-100 over Acid Blue 45. On the contrary, a small amount of cationic dye (Basic Yellow 1) was adsorbed on all HMSs, but 3-aminopropyltriethoxy-grafted HMS showed the lowest adsorption capacity for Basic Yellow 1 due to positive surface charge. Unlike other silicate adsorbents, no surface solubilization was observed for all HMSs.

Adsorption↗
PubMed2001

Protein adsorption to polyethylene glycol modified liposomes from fibrinogen solution and from plasma.

Unmodified and polyethylene glycol (PEG) modified neutral and negatively charged liposomes were prepared by freeze-thaw and extrusion followed by chromatographic purification. The effects of PEG molecular weight (PEG 550, 2000, 5000), PEG loading (0-15 mol%), and liposome surface charge on fibrinogen adsorption were quantified using radiolabeling techniques. All adsorption isotherms increased monotonically over the concentration range 0-3 mg/ml and adsorption levels were low. Negatively charged liposomes adsorbed significantly more fibrinogen than neutral liposomes. PEG modification had no effect on fibrinogen adsorption to neutral liposomes. An inverse relationship was found between PEG loading of negatively charged liposomes and fibrinogen adsorption. PEGs of all three molecular weights at a loading of 5 mol% reduced fibrinogen adsorption to negatively charged liposomes. Protein adsorption from diluted plasma (10% normal strength) to four different liposome types (neutral, PEG-neutral, negatively charged, and PEG-negatively charged) was investigated using gel electrophoresis and immunoblotting. The profiles of adsorbed proteins were similar on all four liposome types, but distinctly different from the profile of plasma itself, indicating a partitioning effect of the lipid surfaces. alpha2-macroglobulin and fibronectin were significantly enriched on the liposomes whereas albumin, transferrin, and fibrinogen were depleted compared to plasma. Apolipoprotein AI was a major component of the adsorbed protein layers. The blot of complement protein C3 adsorbed on the liposomes suggested that the complement system was activated.

Adsorption↗
PubMed2003

Competitive interfacial adsorption of blood proteins.

The competitive adsorption of blood proteins is of great importance for the treatment of thrombosis using a colloidal drug delivery system. The aim of this study is to investigate competitive adsorption of albumin (BSA) and human immunoglobulin G (HIgG) against fibrinogen (Fb). The competitive adsorption of blood proteins was investigated using interfacial rheology at physiological pH. The influence of bulk concentration, temperature and pH on the interfacial adsorption of protein molecules was determined at the air/aqueous interface. As expected, the results indicated that increase in bulk concentration enhanced the interfacial adsorption. Structure and molecular weight of the protein molecules under investigation had influence on interfacial adsorption leading to a competition at the interface. HIgG is more flexible and surface active molecule than BSA. Thus, HIgG replaced BSA and Fb at the air/aqueous interface. In the presence of Fb, BSA adsorbed rapidly initially and then, was replaced by Fb at the interface. The kinetics of displacement of albumin at the interface was rather slow. In conclusion, the investigation of competitive adsorption of blood proteins may be useful biotechnologically, as it will provide useful information for the production of an antithrombogenic material, which will adsorb albumin rather than Fb.

Adsorption↗
PubMed2001

Affinity chromatography of polyhistidine tagged enzymes. New dextran-coated immobilized metal ion affinity chromatography matrices for prevention of undesired multipoint adsorptions.

New immobilized metal ion affinity chromatography (IMAC) matrices containing a high concentration of metal-chelate moieties and completely coated with inert flexible and hydrophilic dextrans are here proposed to improve the purification of polyhistidine (poly-His) tagged proteins. The purification of an interesting recombinant multimeric enzyme (a thermoresistant beta-galactosidase from Thermus sp. strain T2) has been used to check the performance of these new chromatographic media. IMAC supports with a high concentration (and surface density) of metal chelate groups promote a rapid adsorption of poly-His tagged proteins during IMAC. However, these supports also favor the promotion of undesirable multi-punctual adsorptions and problems may arise for the simple and effective purification of poly-His tagged proteins: (a) more than 30% of the natural proteins contained in crude extracts from E. coli become adsorbed, in addition to our target recombinant protein, on these IMAC supports via multipoint weak adsorptions; (b) the multimeric poly-His tagged enzyme may become adsorbed via several poly-His tags belonging to different subunits. In this way, desorption of the pure enzyme from the support may become quite difficult (e.g., it is not fully desorbed from the support even using 200 mM of imidazole). The coating of these IMAC supports with dextrans greatly reduces these undesired multi-point adsorptions: (i) less than 2% of natural proteins contained in crude extracts are now adsorbed on these novel supports; and (ii) the target multimeric enzyme may be fully desorbed from the support using 60 mM imidazole. In spite of this dramatic reduction of multi-point interactions, this dextran coating hardly affects the rate of the one-point adsorption of poly-His tagged proteins (80% of the rate of adsorption compared to uncoated supports). Therefore, this dextran coating of chromatographic matrices seems to allow the formation of strong one-point adsorptions that involve small areas of the protein and support surface. However, the dextran coating seems to have dramatic effects for the prevention of weak or strong multipoint interactions that should involve a high geometrical congruence between the enzyme and the support surface.

Adsorption↗
PubMed1997

Model discrimination and estimation of the intraparticle mass transfer parameters for the adsorption of bovine serum albumin onto porous adsorbent particles by the use of experimental frontal analysis data.

Experimental data from a chromatographic system involving the adsorption of bovine serum albumin (BSA) onto porous anion-exchange adsorbent particles packed in a column are presented. The parameters that characterize the mass transfer mechanisms of intraparticle diffusion and convection are estimated by fitting the predictions of dynamic mathematical models describing adsorption in column systems having spherical perfusive and purely diffusive adsorbent particles to the experimental breakthrough data obtained from the column adsorption system. Both linear and nonlinear expressions for the equilibrium isotherm are considered. The values of the transport parameters are estimated in the time domain for the nonlinear adsorption models and in the Laplace transform domain for the linear adsorption models. The capabilities of the different models to describe satisfactorily the dynamic behavior of the adsorption system are compared. The dynamic nonlinear adsorption model for purely diffusive particles is found to describe most appropriately the dynamic behavior of the experimental chromatographic system studied in this work.

Adsorption↗
PubMed1999

Boronate affinity adsorption of RNA: possible role of conformational changes.

Batch equilibrium adsorption isotherm determination is used to characterize the adsorption of mixed yeast RNA on agarose-immobilized m-aminophenylboronic acid. It is shown that the affinity-enhancing influence of divalent cations depends strongly on the precise nature of the cation used, with barium being far more effective than the conventionally-used magnesium. This adsorption-promoting influence of barium is suggested to arise primarily from ionic influences on the structure and rigidity of the RNA molecule, as the adsorption of ribose-based small molecules is not similarly affected. The substitution of barium for the standard magnesium counterion does not greatly promote the adsorption of DNA, implying that the effect is specific to RNA and may be useful in boronate-based RNA separations. RNA adsorption isotherms exhibit sharp transitions as functions of temperature, and these transitions occur at different temperatures with Mg2+ and with Ba2+. Adsorption affinity and capacity were found to increase markedly at lower temperatures, suggestive of an enthalpically favored interaction process. The stoichiometric displacement parameter, Z, in Ba2+ buffer is three times the value in Mg2+ buffer, and is close to unity.

Adsorption↗
PubMed2003

A new insight into the adsorption of bovine serum albumin onto porous polyethylene membrane by zeta potential measurements, FTIR analyses, and AFM observations.

The mode of adsorption of bovine serum albumin (BSA) on porous polyethylene (PE) membrane was studied as a function of time and concentration, which may contribute to the surface coverage. An improved physical model for adsorption is initiated based on the results of the adsorptional and desorptional measurements, FTIR analysis, and AFM observations as well as streaming potential measurements. The results obtained indicate that the adsorptional mode depend on both time and concentration. It is shown that a critical concentration (about 1000 ppm here) exists in the adsorptional process. Below this concentration, the adsorption seems to be conducted in a normal side-on way but time elapse gives rise to greater conformational change than concentration increase; above this concentration, the aggregation of protein molecular plays a decisive role and the adsorption is in an aggregation way, which is similar to end-on, but a relative large gap between the adsorbed molecules exists due to aggregation. This conclusion is general and can be expected to apply in other globular protein-hydrophobic porous surface systems.

Adsorption↗
PubMed2003

Mechanisms and kinetics of humic acid adsorption onto chitosan-coated granules.

Chitosan, a naturally abundant biopolymer, has widely been studied for metal adsorption from various aqueous solutions, but the extension of chitosan as an adsorbent to remove humic substances from water has seldom been explored. In this study, chitosan was coated on the surface of polyethyleneterephthalate (PET) granules through a dip and phase inversion process and was examined for humic acid removal in a series of batch adsorption experiments. Scanning electron microscopic (SEM) images showed that the PET granules were uniformly covered with a layer of chitosan and the chitosan layer possessed numerous open pores on the surface. Zeta potential study indicated that the chitosan-coated granules had positive zeta potentials at pH < 6.6 and negative zeta potentials at pH > 6.6. Adsorption of humic acid onto the chitosan-coated granules was found to be strongly pH-dependent. Significant amounts of humic acid were adsorbed under acidic and neutral pH conditions, but the adsorption capacity was reduced remarkably with increasing solution pH values. The adsorption isothermal data under various initial humic acid concentrations (at the same solution pH value) can be adequately modeled by the Langmuir and Freundlich models. X-ray photoelectron spectroscopy (XPS) revealed that the amino groups of the chitosan layer were protonated due to humic acid adsorption, suggesting the formation of organic complex between the protonated amino groups and humic acid. Kinetic study indicated that the adsorption process was transport-limited at low solution pH values, but became both transport- and attachment-limited at high solution pH values.

Adsorption↗
PubMed2001

Equilibrium and kinetics of metal ion adsorption onto a commercial H-type granular activated carbon: experimental and modeling studies.

Systematic studies on metal ion adsorption equilibrium and kinetics by a commercial H-type granular activated carbon were carried out. Titration of the carbon showed that the surface charge density decreased with an increasing pH. Higher copper adsorption was obtained with increasing solution pH and ionic strength. Metal removal was in the descending order: Cu2+ > Zn2+ approximately Co2+. Copper removal was not affected by addition of zinc or cobalt, while copper can reduce both zinc and cobalt removal. Kinetic experiments demonstrated that the copper adsorption rapidly occurred in the first 30-60 min and reached the complete removal in 3-5 h. Removal of zinc and cobalt was slightly slower than that of copper. It was found that the mass transfer is important in the metal adsorption rate. The surface complex formation model was used successfully to describe the surface change density, as well as the single- and multi-species metal adsorption equilibrium. The copper removal was due to adsorption of Cu2+, CuOH+, and CuCl+, while the zinc and cobalt uptake was due to the formation of surface metal complexes of SOM2+ and SOMOH+ (M = Zn and Co). It was found that the diffusion-control model well described the adsorption kinetics with various metal ions and pH values. Finally sensitivity analysis on the kinetic model's parameters was carried out.

Adsorption↗
PubMed2002

Cadmium adsorption on goethite-coated sand in the presence of humic acid.

Heat was employed to coat crystalline goethite onto a quartz sand surface so that the adsorbent properties of the coating could be utilized. The adsorption characteristics of cadmium and humic acid onto goethite-coated sand were examined. Results show that the goethite-coated sand surface had a higher specific surface area and more mesopores than the uncoated sand. The adsorption of both cadmium and humic acid was highly pH-dependent: cadmium adsorption increased with pH, but humic acid adsorption decreased as pH increased. The presence of humic acid resulted in increasing cadmium adsorption in a specific pH range. The order of reacting humic acid with cadmium was found to have a noticeable effect on the final adsorption capacity. The adsorption capacity of cadmium for humic acid that is adsorbed onto goethite-coated sand before reacting with a cadmium system, exceeds that of humic acid that is mixed with cadmium ions before goethite-coated sand is added.

Adsorption↗
PubMed2003

Role of cell surface components on Cu2+ adsorption by Pseudomonas putida 5-x isolated from electroplating effluent.

A gram-negative bacterium Pseudomonas putida 5-x with high Cu2+ accumulating capability was isolated from electroplating effluent in Kwun Tong, Hong Kong. The pretreated cells without superficial layer-capsule, isolated cell envelopes and the separated peptidoglycan layer materials were obtained from fresh P. putida 5-x cells, their Cu2+ adsorption capacities and properties were compared with that of the fresh cells. Pretreatment by 0.1 mol L(-1) HCl enhanced Cu2+ adsorption capacity due to the degradation of cell superficial layer-capsule of P. putida 5-x cells. Isolated cell envelopes possessed five times more Cu2+ adsorption capacity than that of fresh intact cell. The Cu2+ adsorption of separated peptidoglycan layer materials indicated that the peptidoglycan layer only played 10-15% part of the Cu2+ adsorption capacity, and implied other cell surface components such as outer membrane or inner membrane might play an important role in such high Cu2+ binding of the cell envelopes. The adsorption process of fresh cells, pretreated cells and cell envelopes of P. putida 5-x could be described with Freundlich isotherm, while the adsorption of Cu2+ by separated peptidoglycan layer materials was better described with Langmuir isotherm.

Adsorption↗
PubMed2003

Removal of Cu(II) from aqueous solutions by adsorption process with anatase-type titanium dioxide.

The experiment was performed in the reactor with suspended anatase-type titanium dioxide particles. The adsorption amount increased rapidly with an increasing pH value from pH 2 to 5 and remained constant over pH 5. The adsorption amount of Cu(2+) increased with temperature from 15 degrees C to 40 degrees C. The adsorption equilibrium constant (K(ads)) was 0.854 and adsorption isotherm of Cu(2+) adsorption on titanium dioxide was more suitable in Langmuir adsorption isotherm than in Freundlich isotherm. The adsorption rate was rapid with an increasing number of UV lamps of 254 nm.

Adsorption↗