This paper presents the adsorption properties of the o-Al13Co4(100) surface toward molecules involved in the semihydrogenation of acetylene. The energetically favored adsorption sites of H, C2H2, C2H3, and C2H4 are determined thanks to ab initio density functional calculations. The surface model used for this study has been determined previously [Phys. Rev. B 2011, 84, 085411], using an approach combining both experimental observations and density functional theory calculations. We show that although the surface termination layer of o-Al13Co4(100) is a dense Al-rich layer, its adsorption properties are quite different from pure elemental Al surfaces, especially for atomic hydrogen adsorption (exothermic on o-Al13Co4(100) and endothermic on low index Al surfaces). The role of surface and subsurface cobalt atoms is investigated carefully. The electronic donor/acceptor character of subsurface cobalt atoms is shown to influence the adsorption properties. In particular, the subsurface cobalt atoms have a
Adsorption capacity is defined as the volume of gas that can be adsorbed per unit mass of coal at standard pressure. Learn about adsorption isotherms calculations, its concept, Freundlich isotherm & its properties along with freundlich adsorption isotherm calculation.
TY - JOUR. T1 - Protein adsorption mechanisms determine the efficiency of thermally controlled cell adhesion on poly(N -isopropyl acrylamide) brushes. AU - Choi, Sangwook. AU - Choi, Byung Chan. AU - Xue, Changying. AU - Leckband, Deborah E. PY - 2013/1/14. Y1 - 2013/1/14. N2 - This study investigated the impact of the protein adsorption mechanism(s) on the efficiency of thermally controlled cell adhesion and release from poly(N-isopropyl acrylamide) brushes. Large format polymer gradients were used to screen for grafting densities and substrate chemistries that alter both cell adhesion at 37 °C and rapid cell release at 25 °C. In particular, the grafting conditions investigated allowed protein adsorption to the underlying substrate, penetration of the brush only, or adsorption to the outer edge of the film. At an average molecular weight of 30 kDa (degree of polymerization N ∼ 270), the results show that robust protein adsorption to polymer brushes impairs rapid cell release below the lower ...
A new kind of Fe-Si adsorbent was synthesized by iron oxide and diatomite after calcining and hydrothermal process. The influences of the initial Cu2+ concentration, pH and adsorption time on the Cu2+ removal efficiency were discussed. Three adsorption empirical kinetics equations and two thermodynamics equations were used to simulate the adsorption process. The microstructures of newly developed copper removal materials and properties of copper removal are characterized in details by SEM and EDS. Adsorption mechanism of the adsorbent was discussed. The suitable pH value for Cu2+ removal is 5.0 to 6.0 and the adsorption capacity increases with increasing the initial Cu2+ concentration. The adsorption kinetics of the adsorbent could be better described by pseudo second order kinetic model, whereas the adsorption isotherms highly conform to the Freundlich equation. The main crystalline phase of the adsorbent is Fe(SiO3) which can build porous structures conducive to the Cu2+ adsorption ...
Adsorption characteristics of light gases on basalt rock-based zeolite 4A: The adsorption characteristics of light gases on basalt rock-based zeolite 4A (BR zeo
In the mixing process of concrete, the addition of auxiliary cementitious building materials can improve the performance of concrete while saving resources, but due to the compatibility problem of raw materials, there shall occur poor fluidity and abnormal setting etc. for the early-period concrete. For this, based on the adsorption mechanism of water reducer on auxiliary cementitious building materials, this paper carries out the study on the adsorption characteristics of three kinds of polycarboxylate superplasticizer (PCS) on the surface of fly ash, and solves the problem of relationship between the PC dosage/adsorption capacity and particle size of fly ash. The results show that the PC structure has a significant influence on the adsorption capacity, and its adsorption capacity on the surface of fly ash gradually increases and becomes saturated with the increase of its dosage. This study is of great significance for the selection of water reducer and the dosage application ...
Isotherms, Kinetics and Thermodynamic Parameters Studies of New Fuchsin Dye Adsorption on Granular Activated Carbon dye adsorption;adsorption isotherm;adsorption thermodynamics;adsorption kinetics;adsorption equilibrium; Batch adsorption studies including equilibrium, kinetics and thermodynamic parameters for the adsorption of new fuchsin dye using granular activated carbon were investigated with varying the operating variables such as initial concentration, contact time and temperature. Equilibrium adsorption data were fitted into Langmuir, Freundlich, Dubinin-Radushkevich and Temkin isotherms. Adsorption equilibrium was mostly well described by Langmuir Isotherm. From the estimated separation factor of Langmuir ($R_L$ = 0.023), and Freundlich (1/n = 0.198), this process could be employed as an effective treatment for the adsorption of new fuchsin dye. Also based on the adsorption energy (E = 0.002 kJ/mol) from Dubinin-Radushkevich isotherm and the adsorption heat constant (B = 1.920 J/mol) from
The purpose of this study was to elucidate the characteristics and mechanisms of adsorption and desorption for heavy metals by micro and nano-sized biogenic CaCO3 induced by Bacillus subtilis, and the pH effect on adsorption was investigated. The results showed that the adsorption characteristics of Cd2+ and Pb2+ are well described by the Langmuir adsorption isothermal equation, and the maximum adsorption amounts for Cd2+ and Pb2+ were 94.340 and 416.667 mg/g, respectively. The maximum removal efficiencies were 97% for Cd2+, 100% for Pb2+, and the desorption rate was less than 3%. Further experiments indicated that the biogenic CaCO3 could maintain its high adsorption capability for heavy metals within wide pH ranges (3-8). The FTIR and XRD results showed that, after the biogenic CaCO3 adsorbed Cd2+ or Pb2+, it did not produce a new phase, which indicated that biogenic CaCO3 and heavy metal ions are governed by a physical adsorption process, and the high adsorptive capacity of biogenic CaCO3 for Cd2+
This book provides researchers and graduate students with an overview of the latest developments in and applications of adsorption processes for water treatment and purification. In particular, it covers current topics in connection with the modeling and design of adsorption processes, and the synthesis and application of cost-effective adsorbents for the removal of relevant aquatic pollutants. The book describes recent advances and alternatives to improve the performance and efficacy of this water purification technique. In addition, selected chapters are devoted to discussing the reliable modeling and analysis of adsorption data, which are relevant for real-life applications to industrial effluents and groundwater. Overall, the book equips readers with a general perspective of the potential that adsorption processes hold for the removal of emerging water pollutants. It can readily be adopted as part of special courses on environmental engineering, adsorption and water treatment for upper ...
Discharge of untreated industrial wastewater containing heavy metals such as Pb2+ is hazardous to the environment due to their high toxicity. This study reports on the adsorption, desorption, and kinetic study on Pb2+ removal from aqueous solutions using wood/Nano-manganese oxide composite (WB-NMO). The optimum pH, contact time and temperature for adsorption were found to be 5.0, 4 h and 333 K, respectively. Pseudo-second-order kinetics best described the adsorption process with an initial sorption rate of 4.0 mg g min-1, and a half-adsorption time t1/2 of 31.6 min. Best fit for adsorption isotherm was obtained with the Brunauer-Emmett-Teller (BET) model with a maximum adsorption capacity of 213 mg/g for an initial metal concentration of 60 mg/L. Both intra-particle diffusion and film diffusion contribute to the rate-determining step. Desorption experiments with 0.5 mol/L HCl, inferred the reusability of the composite. Adsorption experiment of Pb2+ from industrial wastewater confirmed that the prepared
The competitive adsorption of toluene and n-alkanes at binary solution/silica interfaces was studied at room temperature using IR-visible sum frequency generation vibrational spectroscopy. The Surface coverage of toluene for toluene-pentane, toluene-heptane, and toluene-tetradecane mixtures was measured over the complete mole fraction range from 0 to 1. The competitive adsorption process was reversible, and the toluene coverage only depended oil the bulk mole fraction, not on the history of the system. The estimated molar adsorption free energy of toluene is 3.4 +/- 0.3, 1.8 +/- 0.3, and 0.84 +/- 0.3 kJ/mol higher than pentane, heptane, and tetradecane, respectively. Overall, toluene competes favorably on silica, and the molar adsorption free energy of alkanes increases as the chain length increases. It is consistent with the observed SFG spectra, indicating that the alkanes lie flat on the silica surface.. ...
J Mater Sci. DOI 10.1007/s10853-014-8333-x. Adsorption characteristics of noble metals on the strongly basic anion exchanger Purolite A-400TL. A. Wolowicz • Z. Hubicki. Received: 14 March 2014/Accepted: 16 May 2014. © The Author(s) 2014. This article is published with open access at Springerlink.com. Abstract Ion exchange is an alternative process for uptake of noble metals from aqueous solutions. In the present study, the sorption ofPd(II), Pt(IV), and Au(III) ions from aqueous solution was investigated by using Purolite A-400TL (strongly basic anion exchanger, gel, type I) in a batch adsorption system as a function of time (1 min-4 h). Initial Pd(II) concentration (100-1000 mg/L), beads size (0.425-0.85 mm), rate of phases mixing (0-180 rpm), and temperatures (ambient, 313 K) were taken into account during the Pd(II) sorption process. Moreover, the column flow adsorption study was carried out, and the breakthrough curves were obtained for Pd(II) ions. The equilibrium, kinetic, desorption, ...
The adsorption of paracetamol and non-steroidal anti-inflammatory drugs (ibuprofen and naproxen) on ordered mesoporous carbons (OMC) and, for comparison, on commercial activated carbon, were investigated in this work. OMC adsorbents were obtained by the soft-templating method and were characterized by low-temperature nitrogen adsorption and scanning electron microscopy (SEM). The effects of contact time and initial concentration of organic adsorbates on the adsorption were studied. The contact time to reach equilibrium for maximum adsorption was 360 min for all the studied adsorbates. The adsorption mechanism was found to fit pseudo-second-order and intra particle-diffusion models. Freundlich, Langmuir and Langmuir-Freundlich isotherm models were used to analyze equilibrium adsorption data. Based on the obtained experimental data, the adsorption isotherm in the applied concentration range for all the studied adsorbates was well represented by the Freundlich-Langmuir model. The adsorption ability of
The ability of commercial activated carbon to adsorb Pb2+ from aqueous solution has been investigated through batch experiments. The adsorption of lead onto commercial activated carbon has been found to depend on adsorbent dose, initial concentration and contact time. The experiments were carried out at natural solution pH. Equilibrium data fitted well with the Langmuir model and Freundlich model with a maximum adsorption capacity of 23.81 mg of Pb/g of commercial activated carbon. The experiments showed that the highest removal rate was 92.42% for Pb2+ under optimal conditions. The sorption of Pb2+ on commercial activated carbon was rapid during the first 30 min and the equilibrium attained within 60 min. The kinetic processes of Pb2+ adsorption on commercial activated carbon were described by applying pseudo-first-order and pseudo-second-order kinetic models. The kinetic data for the adsorption process obeyed a pseudo-second-order kinetic model, suggesting that the adsorption process is ...
Our understanding on how ash particles in volcanic plumes react with coexisting gases and aerosols is still rudimentary, despite the importance of these reactions in influencing the chemistry and dynamics of a plume. In this study, six samples of fine ash (,100 mgrm) from different volcanoes were measured for their specific surface area, as, porosity and water adsorption properties with the aim to provide insights into the capacity of silicate ash particles to react with gases, including water vapour. To do so, we performed high-resolution nitrogen and water vapour adsorption/desorption experiments at 77 K and 303 K, respectively. The nitrogen data indicated as values in the range 1.1-2.1 m2/g, except in one case where a as of 10 m2/g was measured. This high value is attributed to incorporation of hydrothermal phases, such as clay minerals, in the ash surface composition. The data also revealed that the ash samples are essentially non-porous, or have a porosity dominated by macropores with ...
The adsorption characteristics of pure water vapor onto two different types of silica gel at temperatures from (298 to 338) K and at different equilibrium pressures between (500 and 7000) Pa were experimentally studied by a volumetric technique. The thermophysical properties such as the skeletal density, Brunauer-Emmett-Teller surface area, pore size, pore volume, and total porosity of silica gel were determined. The Tóth isotherm model is found to fit all of the experimental data within the experimental errors. The experimental isotherms and the computed enthalpies of adsorption are compared with those of various researchers and found to be consistent with a chiller manufacturers data ...
In this paper, wool carpet dye adsorption properties of nanoporous activated carbon materials (NCMs) prepared from bamboo agro-product is reported. Bamboo cane powder was chemically activated with phosphoric acid at different temperatures (400, 500, and 600 °C) at an impregnation ratio of 1:1. We found that the specific surface area and the total pore volume of NCM increases with temperature giving the highest surface area and pore volume ca. 2130 m2·g−1 and 2.69 cc·g−1 at 600 °C. Owing to superior surface textural properties, bamboo-derived NCM showed excellent adsorption capacity for wool carpet dyes Lanasyn orange (LO) and Lanasyn gray (LG). The adsorption phenomena could be described by Langmuir/Freundlich adsorption isotherm models. The maximum adsorption capacity was ca. 2.60 × 103 and 3.04 × 103 mg·g−1 for LO and LG, respectively. The adsorption followed pseudo second order kinetics with the second order rate constant of 1.24 × 10−3 g·mg−1·min−1 (LO) and 7.69 × 10−4 g·mg
Background: Effective bimolecular adsorption of proteins onto solid matrices is characterized by in-depth understanding of the biophysical features essential to optimize the adsorption performance, Results: The adsorption of bovine serum albumin (BSA) onto anion-exchange Q-sepharose solid particulate support was investigated in batch adsorption experiments, Adsorption kinetics and isotherms were developed as a function of key industrially relevant parameters such as polymer loading, stirring speed, buffer pH, protein concentration and the state of protein dispersion (solid/aqueous) in order to optimize binding performance and adsorption capacity, Experimental results showed that the first order rate constant is higher at higher stirring speed, higher polymer loading, and under alkaline conditions, with a corresponding increase in equilibrium adsorption capacity, Increasing the stirring speed and using aqueous dispersion protein system increased the adsorption rate, but the maximum protein ...
Due to high biocompatibility and tailorable properties, DNA-based nanostructures are widely studied in biosensor and nanomedicine applications. The restriction for using DNA-based nanostructures lie in the purification processes which have low product yield and tedious steps involved. MoS2 nanosheets are chosen to test for its purification efficiency as MoS2 is shown to have discriminating properties between single stranded DNA and double stranded DNA. Adsorption studies of different DNA nanostructures are tested to see the adsorption capacity of MoS2. From the adsorption studies, it has been observed that MoS2 has high affinity to plasmid DNA, so the use of MoS2 as a gene carrier is tested for its delivery performance ...
Batch adsorption experiments were conducted to investigate equilibrium, kinetic and thermodynamics of the sorption of Methylene Blue onto Fly Ash modified with various concentrations of hydrochloric acid (FAHC-4, FAHC-3, FAHC-2 and FAHC-1). Equilibrium data was best described by the Freundlich isotherm model which suggests adsorbents had heterogeneous surfaces therefore multilayer adsorption occurred in all cases. Fly Ash modified with 1M HCl exhibited the highest adsorption capacity (9.8 mg/L) and Fly Ash modified with 4M HCl had the least adsorption capacity (4.4mg/L). Kinetic data was best described by the pseudo-second-order kinetic model which means adsorption processes were controlled by chemisorption. Boyd kinetic model plots revealed that the rate determining step of each sorption process followed the film diffusion mechanism in which adsorbate ions travelled towards the external surfaces of adsorbents due to electrostatic interactions between chemically modified Fly Ash and adsorbate ...
Abstract The adsorption of four substances and their binary mixture is investigated via the terahertz time domain spectroscopy (THz-TDS). The selected unary compound (ethanol, acetone, ethyl acetate, and n-propyl acetate) and binary mixture (solution 1 is composed of ethanol and acetone, and solution 2 is composed of ethyl acetate and n-propyl acetate) exhibit different adsorption behaviors with varied polarities. In comparison with single component, solution 1 shows shorter adsorption equilibrium time, faster adsorption rate, and stronger adsorption capacity, which conform to a synergistic adsorption mechanism, while the competitive behavior is attributed to the slower adsorption in solution 2. In addition, the pseudo-second-order equation with terahertz parameter is used to assess the rate of binary component organics. The present results indicate a further understanding of multicomponent adsorption mechanisms ...
For the first time, we have used a metal oxide-coated quartz crystal microbalance (QCM) to measure Cs+ adsorption onto illuminated and un-illuminated mesoporous TiO2 (m-TiO2) films by microgravimetric means in-situ. In the simplest case, such experiments yield two parameters of interest: K, the Langmuir adsorption coefficient and mmax the maximum mass of adsorbate to form a complete monolayer at the m-TiO2-coated quartz crystal piezoelectric surface. Importantly, we have found that illumination of the m-TiO2 film with ultra bandgap light results in an increase in mmax i.e. illumination allows for greater adsorption of substrate to occur than in the dark. Our studies also show that under illumination, K also increases indicating a higher affinity for surface adsorption. The photoinduced change in mmax and K are thought to be due to an increase in surface bound titanol groups, thus increasing the number of available adsorption sites - and so providing evidence to support the notion of photoinduced ...
TY - JOUR. T1 - Sol-gel synthesis and gas adsorption properties of CuCl modified mesoporous alumina. AU - Wang, Y.. AU - Lin, Y. S.. PY - 1998. Y1 - 1998. M3 - Article. VL - 1. SP - 185. EP - 195. JO - J. Sol-Gel Sci. Tech.. JF - J. Sol-Gel Sci. Tech.. ER - ...
This thesis presents experimental studies of polyelectrolyte adsorption on oppositely charged surfaces, where substrates of both silica and bleached softwood kraft pulp were used. A major aim of this research was to characterise the conformation of adsorbed layers of cationic polyacrylamide (CPAM), in comparison to cationic dextran (Cdextran), and relate this information to the binding capacity of colloidal silica. A second aim in this thesis was to study the kinetics of the sequential adsorption of polyamide epichlorohydrine (PAE) and carboxymethyl cellulose (CMC) on pulp fibres, and to determine the adsorption isotherms for the layer-by-layer deposition of polyelectrolytes on pulp fibres.. The adsorption of CPAM on silica surfaces was studied using stagnation point adsorption reflectometry and quartz crystal microgravimetry to determine its adsorption kinetics as well as the dependencies of polyelectrolyte charge densities, pH, and NaCl concentration on saturation adsorption. The conformation ...
Read "Synthesis, Characterization, and Adsorption Properties of a Graphene Composite Sand (GCS) and Its Application in Remediation of Hg(II) Ions, Water, Air, Soil Pollution" on DeepDyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips.
Fingerprint Dive into the research topics of Control of interpenetration: Via in situ lithium incorporation in MOFs and their gas adsorption properties and selectivity. Together they form a unique fingerprint. ...
TY - JOUR. T1 - Nanoscale control of layer thickness for EL devices by mass-controlled layer-by-layer sequential adsorption process. AU - Shiratori, Seimei. AU - Yamada, Masayoshi. AU - Ito, Takahiro. AU - Wang, Tom C.. AU - Rubner, Michael F.. PY - 2000/12/1. Y1 - 2000/12/1. N2 - A mass controlled layer-by-layer sequential adsorption process for polyelectrolytes was newly developed for the fabrication of functional devices using ultra-thin organic film formed by various polymers of different polarity of charge. In this study hydrophobic Ruthenium complex monomer (tris(bipyridyl) ruthenium(II) hexafluorophosphate) was micelle-wrapped with an anionic surfactant, sodium dodecylbenzenesulfonate, and was assembled with PAH (poly (allylamine hydrochloride)), which has the opposite charge, on ITO substrates. With this method, we succeeded in fabricating ultra-thin organic films even when the adsorption material is not polymer but monomer. Moreover it was found that the film thickness of the ...
This thesis presents experimental studies of polyelectrolyte adsorption on oppositely charged surfaces, where substrates of both silica and bleached softwood kraft pulp were used. A major aim of this research was to characterise the conformation of adsorbed layers of cationic polyacrylamide (CPAM), in comparison to cationic dextran (Cdextran), and relate this information to the binding capacity of colloidal silica. A second aim in this thesis was to study the kinetics of the sequential adsorption of polyamide epichlorohydrine (PAE) and carboxymethyl cellulose (CMC) on pulp fibres, and to determine the adsorption isotherms for the layer-by-layer deposition of polyelectrolytes on pulp fibres.. The adsorption of CPAM on silica surfaces was studied using stagnation point adsorption reflectometry and quartz crystal microgravimetry to determine its adsorption kinetics as well as the dependencies of polyelectrolyte charge densities, pH, and NaCl concentration on saturation adsorption. The conformation ...
... The removal of Ni(II) by foam fractionation is brought about by the electrostatic mechanism. From removal and zeta potential measurements, it clearly demonstrates that Ni**2** plus and NiOH** plus ions become associated with the dodecylsulfonate coated (negative charge) N//2 gas bubbles. The optimal Ni(II) to NaDS (molar ratio) is 0. 2. The Ni**2** plus species forms moderately strong complexes with dodecylsulfonate ions.
We use Ca doping during growth of one- and two-monolayer-thick MgO films on Ag(100) to identify the adsorption sites of individual adatoms with scanning tunnelingmicroscopy. For thiswe combine atomic resolution images of the bare MgO layer with images of the adsorbates and the substitutional Ca atoms taken at larger tip-sample distance. For Ho atoms, the adsorption sites depend on MgO thickness. On the monolayer, they are distributed on the O and bridge sites according to the abundance of those sites, 1/3 and 2/3, respectively. On the MgO bilayer, Ho atoms populate almost exclusively the O site. A third species adsorbed on Mg is predicted by density functional theory and can be created by atomic manipulation. Au atoms adsorb on the bridge sites for both MgO thicknesses, while Co and Fe atoms prefer the O sites, again for both thicknesses.. ...
It was found that slow desorption kinetics determine the cyclic working capacity for CO2 and H2O. Furthermore, four different adsorption sites are required to describe the observed complex adsorption behaviour of CO2 and H2O and their cyclic working capacity was determined based on many different carefully designed TGA and PBR breakthrough experiments. The sorption model includes two independent adsorption sites for H2O and CO2 (sites A and B resp.) and another site which can be occupied by both CO2 and H2O, where one component replaces the other (site C). A fourth site (site D) describes the general higher adsorption capacity of the sorbent if H2O and CO2 are fed together to the sorbent ...
Molecularly imprinting (MI) hydrogels for selective adsorption of trypsin are reported. The trypsin imprinted hydrogels were prepared using a polyethylene glycol (PEG)-based dimethacrylate as a crosslinker and anionic functional monomers. The hydrogel prepared without any functional monomers showed significantly low ability to adsorb a variety of proteins. We optimized the concentration and the length of PEG units of the crosslinkers to achieve the complete removal of the template molecule and suitable selective adsorption. Additionally, the functional monomers chosen were anionic since the template, trypsin, is a basic protein. The adsorption tests for proteins, done on the prepared MI gels, indicated that the MI gel prepared with sodium allyl sulfonate (AS) as a functional monomer showed much higher selective adsorption for trypsin, even though a mixture of trypsin and cytochrome c was used as the protein solution. The selective adsorption was more effective in a NaCl solution in which the ...
Atomic oxygen adsorption on a pure aluminum terminated Al 9Co2(001) surface is studied by first-principle calculations coupled with STM measurements. Relative adsorption energies of oxygen atoms have been calculated on different surface sites along with the associated STM images. The local electronic structure of the most favourable adsorption site is described. The preferential adsorption site is identified as a bridge type site between the cluster entities exposed at the (001) surface termination. The Al-O bonding between the adsorbate and the substrate presents a covalent character, with s-p hybridization occurring between the states of the adsorbed oxygen atom and the aluminum atoms of the surface. The simulated STM image of the preferential adsorption site is in agreement with experimental observations. This work shows that oxygen adsorption generates important atomic relaxations of the topmost surface layer and that sub-surface cobalt atoms strongly influence the values of the adsorption ...
TY - JOUR. T1 - Adsorption and desorption kinetics for hydrophilic and hydrophobic vapors on activated carbon. AU - Fletcher, A.J.. AU - Yuzak, Y.. AU - Thomas, K.M.. PY - 2006/4. Y1 - 2006/4. N2 - Adsorption dynamics are of fundamental importance in applications of adsorbents in real situations. The adsorption/desorption characteristics of a series of adsorbates, with varying hydrophilic/hydrophobic and structural characteristics, for activated carbon BAX950, were investigated for temperatures in the range 288-323 K. These data provide a comprehensive kinetic study of adsorption/desorption for an activated carbon. The results are discussed in relation to the adsorbent pore structure and functional group concentration, adsorptive structure and adsorption mechanism. The study provides evidence for a compensation effect where activation energy and ln(pre-exponential factor) parameters obtained from the Arrhenius equation exhibit a linear correlation.. AB - Adsorption dynamics are of fundamental ...
In order to shed some light on DNA preservation over time in skeletal remains from a physicochemicalviewpoint, adsorption and desorption of DNA on a well characterized synthetic apatite mimicking boneand dentin biominerals were studied. Batch adsorption experiments have been carried out to determinethe effect of contact time (kinetics), DNA concentration (isotherms) and environmentally relevant factorssuch as temperature, ionic strength and pH on the adsorption behavior. The analogy of the nanocrystallinecarbonated apatite used in this work with biological apatite was first demonstrated by XRD, FTIR, andchemical analyses. Then, DNA adsorption kinetics was fitted with the pseudo-first order, pseudo-secondorder, Elovich, Ritchie and double exponential models. The best results were achieved with the Elovichkinetic model. The adsorption isotherms of partially sheared calf thymus DNA conformed satisfacto-rily to Temkins equation which is often used to describe heterogeneous adsorption behavior ...
A quartz crystal microbalance with dissipation (QCM-D) and an optical reflectometer (OR) have been used to investigate the adsorption behavior of Laponite and Ludox silica nanoparticles at the solid-liquid interface. The adsorption of both Laponite and Ludox silica onto poly(diallyldimethylammonium chloride) (PDADMAC)-coated surfaces over the first few seconds were studied by OR. Both types of nanoparticles adsorbed rapidly and obtained a stable adsorbed amount after only a few minutes. The rate of adsorption for both nanoparticle types was concentration dependent. The maximum adsorption rate of Ludox nanoparticles was found to be approximately five times faster than that for Laponite nanoparticles. The QCM data for the Laponite remained stable after the initial adsorption period at each concentration tested. The observed plateau values for the frequency shifts increased with increasing Laponite particle concentration. The QCM data for the Ludox nanoparticles had a more complex long-time ...
Attapulgite clay also known as palygorskite is a mineral clay which possess good adsorption properties based on its adsorption capacity, porous structure and moderate cation exchange properties. The study investigated the effectiveness of naturally occurring and hydrochloric acid modified attapulgite as adsorbents for Cr (VI) remediation in wastewater. The physical properties of the clay were characterized using a range of techniques. X-ray diffraction confirmed the purity of the clay while BET analysis indicated an increase in surface area from 131.4 to 183.2 m2/g after acid modification. The modified attapulgite was predicted to have an adsorption capacity of 75 mg/g compared to 2.1 mg/g for the naturally occurring attapulgite. The increase in adsorption capacity was attributed to a change in surface area as well as changes in the surface chemistry of the clay. The adsorption isotherms were best described by the Langmuir mono-layer adsorption model while the kinetics fit the Langren first ...
Cadmium (Cd) concentration in soil solution and its bioavailability is controlled by sorption-desorption reactions. The objective of this research was to compare Cd adsorption behavior in six calcareous and four acid soils. Soil samples were equilibrated with 0.01 M Ca(NO3)2 containing 25 to 3200 mg Cd L−1. Results showed that the tendency for adsorption was high at low Cd concentrations (0-400 mg L-1), but decreased as the Cd increased (400-3200 mg L-1). Among five equations evaluated, Freundlich, Langmuir, and Gunary equations best described Cd adsorption in both calcareous and acid soils as indicated by high values for coefficient of determination (R2) and low values for standard error of estimate (SE). Stepwise regression equations between constants of the best-fitted models and soil properties revealed that cation exchange capacity (CEC) and clay content were the most important soil properties affecting Cd adsorption behavior in calcareous soils, whereas in acid soils Cd adsorption was mainly
Oxygen and carbon monoxide adsorption studies were carried out in ultra high vacuum on vapor deposited polycrystalline platinum films with a |111| fiber axis and on monocrystalline (111) palladium films. The techniques of Auger electron spectroscopy (AES), electron loss spectroscopy (ELS) and thermal desorption spectroscopy (TDS) were used. A new form of electron diffraction pattern, namely Kikuchi rings, was also observed from these films. Oxygen adsorption studies on the Pt films showed the existence of two forms of adsorbed oxygen. TDS of carbon monoxide adsorbates showed only one peak and resulted in the development of a new loss line in the ELS spectrum. Electron beam irradiation decomposed the adsorbed CO resulting in a shape change for the carbon Auger line. The rate of reaction for carbon monoxide oxidation was found to be temperature dependent, thereby supporting the Langmuir-Hinshelwood mechanism for CO oxidation. Transmission electron microscope (TEM) replica studies of vapor deposited (111)
Sulphate adsorption and desorption can delay the response in soil acidity against changes in acid input. Here we evaluate the use of an extended Freundlich equation for predictions of pH-dependent SO4 adsorption and desorption in low-ionic strength soil systems. Five B horizons from Spodosols were subjected to batch equilibrations at low ionic strength at different pHs and dissolved SO4 concentrations. The proton coadsorption stoichiometry (eta), i.e. the number of H+ ions co-adsorbed for every adsorbed SO42- ion, was close to 2 in four of five soils. This enabled the use of a Freundlich equation that involved only two adjustable parameters (the Freundlich coefficient K-F and the non-ideality parameter m). With this model a satisfactory fit was obtained when only two data points were used for calibration. The root-mean square errors of log adsorbed SO4 ranged from 0.006 to 0.052. The model improves the possibility to consider SO4 adsorption/desorption processes correctly in dynamic soil ...
TY - JOUR. T1 - Optimization of adsorption isotherm types for desiccant air-conditioning applications. AU - Sultan, Muhammad. AU - Miyazaki, Takahiko. AU - Koyama, Shigeru. PY - 2018/6. Y1 - 2018/6. N2 - The present study investigates five kinds of adsorbents for desiccant air-conditioning (DAC) applications. Each adsorbent yield distinctive water vapor adsorption isotherm that can be categorized as type-I, type-II, type-III, type-V, and type-linear on the basis of the International Union of Pure and Applied Chemistry (IUPAC) classification. Ideal DAC cycle is evaluated for the air-conditioning (AC) applications, and steady-state moisture cycled (MCSS) is estimated by means of adsorption isobars. Results showed that the adsorbent enabling type-linear adsorption isotherm gives maximum MCSS for industrial AC processes of matches manufacturing/drying/storage, rubber dipped goods storage and photo studio drying room. However, adsorbent enabling type-V adsorption isotherm is found the optimum ...
adsorption experimental methods to study the micropore types and pore structures and their effects on the methane adsorption capacity of organic-rich shales found in the Fenggang block in northern Guizhou Province. The results indicate that the microscopic surface porosity of the lower Cambrian Niutitang Formation ranges from 2.88% to 5.34%, with an average value of 3.86%. Based on nitrogen adsorption methods, the range of the average pore size distribution is 4.6-9.491 nm, with an average value of 6.68 nm. All of the samples exhibit significant unimodal distributions. The main pore size is less than 10 nm, and these pores account for most of the mesopore volume, which is generally consistent with the NMR results. The methane adsorption capacity of the shale samples gradually increases in the range of 0-8 MPa at 30°C and reaches a maximum at approximately 10 MPa. Positive correlations were found between the gas content and specific surface area, total pore volume, and micropore volume. These ...
TY - JOUR. T1 - Effect of surface strain on oxygen adsorption on Zr (0 0 0 1) surface. AU - Wang, X.. AU - Khafizov, M.. AU - Szlufarska, I.. PY - 2014/1/1. Y1 - 2014/1/1. N2 - The effect of surface strain on oxygen adsorption on Zr (0 0 0 1) surface is investigated by density functional theory (DFT) calculations. It is demonstrated that both surface strain and interactions between oxygen adsorbates influence the adsorption process. Oxygen binding to zirconium becomes stronger as the strain changes from compressive to tensile. When oxygen coverage is low and the oxygen interactions are negligible, surface face-centered cubic sites are the most stable for O binding. At high coverage and under compression, octahedral sites between second and third Zr layers become most favorable because the interactions between adsorbates are weakened by positive charge screening. Calculations with both single-layer adsorption model and multiple-layer adsorption model demonstrate that compressive strain at the ...
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In this study, cadmium sulfide nanoparticles (CdS NPs) were prepared, characterized and used as a new adsorbent for simultaneous removal of Pb(II) and Cu(II) ions from aqueous solutions. Using a batch adsorption method, the effects of solution pH, contact time, adsorbent dose, and temperature were studied and optimized. Removal efficiencies, higher than 98% were obtained for both the metal ions at the optimum conditions. The adsorption process was rapid, as equilibrium was achieved within 15 min. The kinetic and isotherm experiment data could be well described with the pseudo-second order kinetic model and the Freundlich isotherm model. The maximum adsorption capacities for Pb(II) and Cu(II) ions were 200 mg/g and 166.7 mg/g, respectively. The thermodynamics of adsorption process such as changes in standard free energy, enthalpy and entropy were also discussed. This study revealed that CdS NPs are effective adsorbent for rapid removal of Pb(II) and Cu(II) ions from aqueous solutions.
TY - JOUR. T1 - A Review on Adsorption of Cationic Dyes using Activated Carbon. AU - Corda, Nikita Chrishel. AU - Kini, M. Srinivas. PY - 2018/1/9. Y1 - 2018/1/9. N2 - In this article efficiency of activated carbon as a potent adsorbent of cationic dyes has been reviewed. Non-biodegradable nature of pollutants and their removal in the present generation is a great challenge. Therefore, extensive study on adsorption of these classes of pollutants from water bodies is being carried out. Methylene blue (majorly) a dye seen in the effluent streams of textile, printing, paper industries along with some of the commonly used cationic dyes in process industries and their sorption on activated carbon are reviewed here. High cost of commercially activated carbon which is a limitation to its extensive use have paved way for study of adsorption by naturally obtained and extracted activated carbon from agricultural wastes and various other sources. The purpose of this review paper is to summarize the ...
Abstract: Hydrophobic-hydrophilic macroporous polydivinylbenzene/polyacrylethylenediamine interpenetrating polymer networks (PDVB/PAEMIPN) were prepared by the sequential suspension polymerization method. These were composed of two networks, of which one was hydrophobic (PDVB) and the other was hydrophilic (PAEM). The objective of this work was to study the adsorption thermodynamics and adsorption kinetics of this hydrophobic-hydrophilic IPN. The focus was on adsorption isotherms of vanillin at different temperatures, and these fit well into the Freundlich adsorption isotherm. The isosteric adsorption enthalpy, adsorption Gibbs free energies and the adsorption entropy could be calculated according to thermodynamic functions. The hydrophobic PDVB in the PDVB/PAEM IPN resin adsorbs through hydrophobic interaction while the hydrophilic PAEM adsorbs by hydrogen bonding. The adsorption kinetic data was fitted to the Lagergren pseudo second order rate equation. Intraparticle diffusion was the rate ...
Cr (VI) as an extremely soluble and highly toxic ion is present in effluents of industries and imposes severe health-related problems. The current study aimed to provide information on Cr (VI) adsorption potential of fire clay as an abundant, cost-effective and untried material. Batch adsorption trials of Cr (VI) were performed to investigate the effects of pH, contact time, initial metal ion concentration and the adsorbent dosage. Langmuir, Freundlich and Dubinin-Radushkevich isotherm models were used to evaluate the equilibrium data at 20°C and regression coefficients were derived. Moreover, adsorption kinetics was analyzed using the pseudo-first-order and the pseudo-second-order kinetic models. Maximum chromium removal was found at pH 2.0. A kinetic study yielded an optimum equilibrium time of 90 minutes with an adsorbent dose of 2.5 g/50 mL. Results suggested that the equilibrium adsorption described by the Freundlich model. The kinetic data of the sorption showed that the pseudo second-order
Sorption-based Joule-Thomson (JT) cryocoolers often operate with pure gases. A sorption-based compressor has many benefits; however, it is limited by the pressure ratios it can provide. Using a mixed-refrigerant (MR) instead of a pure refrigerant in JT cryocoolers allows working at much lower pressures. Therefore, it is desired to use MRs in sorption-based cryocoolers in order to reduce one of its main limitations. The adsorption of mixed gases is usually investigated under steady conditions, mainly for storage and separation processes. However, the process in a sorption compressor goes through various temperatures, pressures and adsorption concentrations; therefore, it differs from the common mixed gases adsorption applications. In order to simulate the sorption process in a compressor a numerical analysis for mixed gases is developed, based on pure gas adsorption characteristics. The pure gas adsorption properties have been measured for four gases (nitrogen, methane, ethane, and propane) with ...
Article Adsorption mechanism of As(V) and As(III) on Fe-Mn binary oxides in synthetic and real water matrices. A series of Fe-Mn binary oxides with different Fe:Mn ratios (1:1, 3:1, 6:1, 9:1) were synthesized to investigate the optimal Fe:Mn ratio fo...