Modeling of protein adsorption in membrane affinity chromatography

For the design of affinity membranes, protein adsorption in membrane affinity chromatography (MAC) was studied by frontal analysis. According to fast mass transfer, small thickness of affinity membranes and high affinity between the protein and the ligand, an ideal adsorption (IA) model was proposed for MAC and was used together with equilibrium-dispersive (E-D) model to describe the adsorption of bovine serum albumin (BSA) onto cellulose diacetate/polyethyleneimine (CA/PEI) blend membranes with and without Cu2+ chelating. E-D model was found to better describe the initial region of experimental breakthrough curves. The influence of axial dispersion was revealed and it showed the importance of design of the module to homogenously distribute feed solution. IA model was found to be better for the whole experimental breakthrough curve. According to it, the capacity of affinity membranes and the specificity of the interaction are of equal importance for the design of affinity membranes. An optimum feed concentration was also found in the operation of MAC. The discrepancy between experimental optimum feed concentrations and predicted ones from IA model may be due to the ignorance of some experimental effects such as axial dispersion.

A new method for determination of adsorption and desorption coefficients of pesticides with soil column liquid chromatography

The adsorption and desorption coefficients of atrazine, methiocarb and simazine on a sandy loam soil were measured in this study with soil column liquid chromatographic (SCLC) technique. The adsorption and desorption data of all the three pesticides followed Freundlich isotherms revealing the existence of hysteresis. In comparing with other methods, SCLC method showed some characteristics such as rapidity, online and accuracy.

Acid catalyzed synthesis of ordered bifunctionalized mesoporous organosilicas with large pore

Thiol-functionalized mesoporous ethane-silicas with large pore were synthesized by co-condensation of 1,2-bis(trimethoxy-sily)ethane (BTME) with 3-mercaptopropyltrimethoxysilane (MPTMS) using nonionic oligomeric polymer C1H (OCH(2)-CH(2))(10)OH (Brij-76) or poly(alkylene oxide) block copolymer (P123) as surfactant in acidic medium. The results of powder X-ray diffraction (XRD), nitrogen gas adsorption, and transmission electron microscopy (TEM) show that the resultant materials have well-ordered hexagonal mesoscopic structure with uniform pore size distributions. (29)Si MAS NNR, (13)C CP-MAS NMR. FT-IR, and UV Raman spectroscopies confirm the attachment of thiol functionalities in the mesoporous ethane-sificas. The maximum content of the attached thiol group (-SH) in the mesoporous framework is 2.48mmol/g. The ordered mesoporous materials are efficient Hg(2+) adsorbents with almost every -SH site accessible to Hg(2+). In the presence of various kinds of heavy metal ions such as Hg(2+), Cd(2+), Zn(2+), Cu(2+) and Cr(3+), the materials synthesized using poly(alkylene oxide) block cooollxmier (Pluronic 123) g(2+), as surfactant show almost similar affinity to Hg(2+), Cd(2+), and Cr(3+), while the materials synthesized using ofigomeric polymer C(18)H(37)(OCH(2)CH(2))(10)OH (Brij-76) as surfactant exhibit high selectivity to Hg(2+). (C) 2004 Elsevier Inc. All rights reserved.

Dibenzodioxin adsorption on inorganic materials

Dibenzodioxin adsorption/desorption on solid surfaces is an important issue associated with the formation, adsorption, and emission of dioxins. Dibenzodioxin adsorption/desorption behaviors on inorganic materials (amorphous/mesoporous silica, metal oxides, and zeolites) were investigated using in situ FT-IR spectroscopy and thermogravimetric (TG) analysis. Desorption temperatures of adsorbed dibenzodioxin are very different for different kinds of inorganic materials: similar to 200 degrees C for amorphous/mesoporous silica, similar to 230 degrees C for metal oxides, and similar to 450 degrees C for NaY and mordenite zeolites. The adsorption of dibenzodioxin can be grouped into three categories according to the red shifts of the IR band at 1496 cm(-1) of the aromatic ring for the adsorbed dibenzodioxin: a shift of 6 cm-1 for amorphous/mesoporous silica, a shift of 10 cm(-1) for metal oxides, and a shift of 14 cm(-1) for NaY and mordenite, suggesting that the IR shifts are proposed to associated with the strength of the interaction between adsorbed dibenzodioxin and the inorganic materials. It is proposed that the dibenzodioxin adsorption is mainly via the following three interactions: hydrogen bonding with the surface hydroxyl groups on amorphous/mesoporous silica, complexation with Lewis acid sites on metal oxides, and confinement effect of pores of mordenite and NaY with pore size close to the molecular size of dibenzodioxin.

CO adsorption and correlation between CO surface coverage and activity/selectivity of preferential CO oxidation over supported Ag catalyst: an in situ FTIR study

In situ IR measurements for CO adsorption and preferential CO oxidation in H-2-rich gases over Ag/SiO2 catalysts are presented in this paper. CO adsorbed on the Ag/SiO2 pretreated with oxygen shows a band centered around 2169 cm(-1), which is assigned to CO linearly bonded to Ag+ sites. The amount of adsorbed CO on the silver particles ( manifested by an IR band at 2169 cm(-1)) depends strongly on the CO partial pressure and the temperature. The steady-state coverage on the Ag surface is shown to be significantly below saturation, and the oxidation of CO with surface oxygen species is probably via a non-competitive Langmuir Hinshelwood mechanism on the silver catalyst which occurs in the high-rate branch on a surface covered with CO below saturation. A low reactant concentration on the Ag surface indicates that the reaction order with respect to Pco is positive, and the selectivity towards CO2 decreases with the decrease of Pco. On the other hand, the decrease of the selectivity with the reaction temperature also reflects the higher apparent activation energy for H-2 oxidation than that for CO oxidation.

CO hydrogenation to light alkenes over Mn/Fe catalysts prepared by coprecipitation and sol-gel methods

CO hydrogenation to light alkenes was carried out on manganese promoted iron catalysts prepared by coprecipitation and sol-gel techniques. Addition of manganese in the range of 1-4 mol.% by means of coprecipitation could improve notably the percentage of C-2 (=) similar to C-4 (=) in the products, but it was not so efficient when the sol-gel method was employed. XRD and H-2-TPR measurements showed that the catalyst samples giving high C-2 (=) similar to C-4 (=) yields possessed ultra. ne particles in the form of pure alpha-(Fe1-xMnx)(2)O-3, and high quality in lowering the reduction temperature of the iron oxide. Furthermore, these samples displayed deep extent of carburization and different surface procedures to the others in the tests of Temperature Programmed Surface Carburization (TPSC). The different surface procedures of these samples were considered to have close relationship with the evolving of surface oxygen. It was also suggested that for the catalysts with high C-2 (=) similar to C-4 (=) yields, the turnover rate of the active site could be kept at a relatively high level due to the improved reducing and carburizing capabilities. Consequently, there would be a large number of sites for CO adsorption/dissociation and an enhanced carburization environment on the catalyst surface, so that the process of hydrogenation could be suppressed relatively to a low level. As a result, the percentage of the light alkenes in the products could be raised.

Study of adsorption of methylene blue and new methylene blue in liquid-solid interface by slab optical waveguide spectroscopy

A slab optical waveguide (SOWG) has been used for study of adsorption of both methylene blue (MB) and new methylene blue (NMB) in liquid-solid interface. Adsorption characteristics of MB and NMB on both bare SOWG and silanized SOWG by octadecyltrichlorosilane (ODS) were compared. Effect of pH on adsorption on MB and NMB was investigated. Binding rate constant analysis showed that both MB and NMB on bare SOWG demonstrates larger association constants than those on ODS-SOWG. Interactions of NIB and NMB on bare SOWG and ODS-SOWG were analyzed by molecular mechanics calculation method. The binding energy change was in the following order: ENMB-bare > EMB-bare > ENMB-ODS > EMB-ODS. (c) 2004 Elsevier B.V. All rights reserved.