Molten salts-modified MgO-based adsorbents for intermediate-temperature CO_2 capture: A review

Carbon dioxide(CO2) capture using magnesium oxide(MgO)-based adsorbents at intermediate temperatures has been regarded as a very prospective technology for their relatively high adsorption capacity,low cost, and wide availability. During the past few years, great effort has been devoted to the fabrication of molten salts-modified MgO-based adsorbents. The extraordinary progress achieved by coating with molten salts greatly promotes the CO_2 capture capacity of MgO-based adsorbents. Therefore, we feel it necessary to deliver a timely review on this type of CO_2 capturing materials, which will benefit the researchers working in both academic and industrial areas. In this work, we classified the molten saltsmodified MgO adsorbents into four categories:(1) homogenous molten salt-modified MgO adsorbents,(2) molten salt-modified double salts-based MgO adsorbents,(3) mixed molten salts-modified MgO adsorbents, and(4) molten salts-modified MgO-based mixed oxides adsorbents. This contribution critically reviews the recent developments in the synthetic method, adsorption capacity, reaction kinetics, promotion mechanism, operational conditions and regenerability of the molten salts-modified MgO CO_2 adsorbents. The challenges and prospects in this promising field of molten salts-modified MgO CO_2 adsorbents in real applications are also briefly mentioned.     

Chromatography of beta-glucuronidase from bovine liver. A study of the enzyme binding sites of prepared adsorbents.

beta-Glucuronidase from bovine liver was adsorbed to the adsorbents prepared with CH-Sepharose 4B and either the competitive inhibitor or its analogs such as p-aminophenyl 1-thio-beta-D-glucuronic acid, -glucoside, -galactoside, and N-acetyl glucosaminide. The adsorbed enzyme was eluted at 0.1 or 0.5 M NaCl by a stepwise gradient. Chromatography of the enzyme was also performed by using the adsorbents prepared with Epoxy-activated Sepharose 6B and amine compounds or other compounds. In order to see whether the hydroxyl groups of the sugar parts in the ligand are necessary for the adsorption of the enzyme, chromatography was performed by using the adsorbents prepared with sugar derivatives as the ligand. As a result, it was found that beta-glucuronidase had an affinity for adsorbents prepared with either acetyl derivatives or methoxy derivatives of glycosides and CH-Sepharose 4B. From the results of elution of the enzyme with NaCl from adsorbents having amide bonding, it was clarified that the affinity of the enzyme for adsorbents without glycosides in the ligands correlated with acidity of the amide in the adsorbents. Hydrogen bond chromatography was performed with the prepared adsorbents. The enzyme was adsorbed under a high concentration of ammonium sulfate, and the elution of the adsorbed enzyme from adsorbents was examined by the degradation of salt. The enzyme was most easily eluted from aminoethyl 1-thio-beta-D-glucuronic acid-CH Sepharose 4B at 0.9 M ammonium sulfate and at 0.5 M concentration of the salt with p-aminophenyl 1-thio-beta-D-glucuronic acid-CH Sepharose 4B.(ABSTRACT TRUNCATED AT 250 WORDS)     

Retention characteristics of water‐soluble compounds on water‐holding adsorbents with immobilized zwitterionic copolymers having different ionicities

Three kinds of water‐holding adsorbents with immobilized zwitterionic copolymers having different cationic ionicities were synthesized. To investigate the influence of the charge balance and the ionicity of the cation site, the retention properties of the water‐soluble solutes on the zwitterionic adsorbents were measured by HPLC. These adsorbents had high water contents, and the hydrating water contents depended on the amounts of immobilized copolymer. The retentions of water‐soluble solutes depended on the hydrophilic interaction, and were in the order of logP_o/w (logarithm of octanol–water partition coefficient). This suggests that the partition to the hydration layer was the main retention mechanism on the zwitterionic adsorbents. On the other hand, the electrostatic interaction based on the cation site on the adsorbents was also observed. The electrostatic interaction could be reduced by decreasing the ionicity of the cation sites. These results indicate that the retentions of the water‐soluble solutes on the zwitterionic adsorbents were greatly influenced by the ionicity of the cation sites on the adsorbents.     

Use of synthetic adsorbents in preparative normal-phase liquid chromatography

Normal-phase liquid chromatographic separation using polymeric synthetic adsorbents was investigated. The retention behavior of dialkyl phthalates under a hexane-isopropanol eluent system revealed that both polystyrenic and polymethacrylic adsorbents can be used for normal-phase liquid chromatography, and that the polymethacrylic adsorbent has stronger retentivity than the polystyrenic adsorbent. Applicability of these synthetic adsorbents, especially the polymethacrylic adsorbents, was verified by the separation of polyunsaturated fatty acids, schizandrin in Schisandra chinensis fruit, tocopherols and tocotrienols in vegetable oils using a 10-microm adsorbent packed into an HPLC column. Furthermore, the separation was expanded to preparative scale by using polymethacrylic adsorbents with 17- and 31-microm fine grade particle sizes. The effect of loading volume on the retention or separation was also examined, and separation was maintained up to the loading of several grams per liter adsorbent. These results demonstrate that commercially available synthetic adsorbents possess considerable performance as normal-phase chromatographic media for more precise purification of bioactive compounds. including pharmaceuticals and nutraceuticals with scale-up possibilities.     

Development of Composite Adsorbents of Carbon and Intercalated Clay for N2and O2Adsorption: A Preliminary Study

Composite adsorbents of carbon and alumina intercalated montmorillonite were prepared and characterized by adsorption of N₂and O₂at various temperatures. The effects of pyrolysis, temperature, heating rate, subsequent degassing, and doping of cations and anions were investigated. The adsorption capacities of the composite adsorbents developed at higher temperatures (0 and −79°C) are found to be larger than those of normal alumina pillared clays. The experimental results showed that the framework of these adsorbents is made of alumina particles and clay sheets while the pyrolyzed carbon distributes in the space of interlayers and interpillars. The pores between the carbon particles, clay sheets, and alumina pillars are very narrow with very strong adsorption forces, leading to enhanced adsorption capacities at 0 and −79°C. The composite adsorbents exhibit features similar to those of carbonaceous adsorbents. Their pore structures, adsorption capacities, and selectivities to oxygen can be tailored by a controlled degassing procedure. Meanwhile, ions can be doped into the adsorbents to modify their adsorption properties, as usually observed for oxide adsorbents like zeolite and pillared clays. Such flexibility in pore structure tailoring is a potential advantage of the composite adsorbents developed for their adsorption and separation applications.     

Regeneration of Chitosan-Based Adsorbents for Eliminating Dyes from Aqueous Solutions

Chitosan and its derivatives are effective for adsorbing dye molecules from aqueous solutions. However, their use can be limited by environmental concerns on their fate after adsorbent saturation. Desorbing dye molecules and regenerating adsorbents are alternatives to disposing spent adsorbent. In this review, most research topics related to regenerating chitosan-based adsorbents for dye removal are summarized and discussed. Numerous desorption agents, such as acids, alkalis, salts, and organic solvents, have been applied to regenerate chitosan-based adsorbents and recover the adsorbed dye molecules. In addition, the mechanism of desorbing dye molecules from these adsorbents is examined to provide information on selecting methods for recovering chitosan-based adsorbents.     

大孔交联聚苯乙烯吸附树脂的合成及其对叶绿素铜的吸附性能

通过改变苯乙烯-二乙烯苯共聚物的交联度和使用不同结构的二乙烯苯,合成了树脂Ⅰ-Ⅵ,在工业二乙烯苯共聚体系中加入少量丙烯酸甲酯合成了树脂Ⅶ;交联聚苯乙烯经Friedel-Grafts酰化反应在其苯环上引入乙酰基制备了树脂Ⅷ。用物理技术和化学方法表征了树脂的结构。树脂对叶绿素铜的吸附量不仅与其二乙烯苯含量有关,还与二乙烯基的位置(间-,对-)异构有关,树脂骨架极性的增加,不利于树脂对叶绿素铜的吸附。     

New adsorbents from oil shales: Preparation, characterization and U, Th isotope adsorption tests

New activated adsorbents for radionuclides have been produced from Moroccan oil shales by pyrolysis of the natural material at 550 °C flowed by a KMnO₄ activation. The texture and composition of the native rock and the adsorbents were studied before their use in tests for adsorption of radionuclides from standard solutions prepared from uranylnitrate and thorium nitrate in equilibrium with their daughters. The distribution coefficients between solutions containing U, Th and Ra and the adsorbents were evaluated by means of specific activities, measured by g-ray spectrometry. The adsorbents were observed to eliminate U, Th, Ra, Ac and Tl from aqueous solutions. This revised version was published online in August 2006 with corrections to the Cover Date.     

Extraction and Separation Properties of Hydrophilic Compounds Using Novel Water-Holding Adsorbents Bonded with a Zwitter-Ionic Polymer

A novel water-holding adsorbent was synthesized by introducing a zwitter-ionic polymer to a hydrophilic methacrylate base resin. The retention abilities of the hydrophilic compounds on the adsorbents with and without cross-link in the zwitter-ionic functional groups were examined. The amount of held water on the non-cross-linked adsorbent was higher than that of the cross-linked one. The extraction efficiencies of the hydrophilic solutes on the adsorbents were evaluated by the solid phase extraction method. These adsorbents showed high affinity for nucleosides and glycosides, and good recoveries for such hydrophilic compounds in the solid-phase extraction were obtained. Furthermore, the retention properties of the hydrophilic solutes on the adsorbents were also evaluated by LC. The hydrophilic solutes were retained on these adsorbents by a partition mode based on a hydrophilic interaction. The retention factors of the hydrophilic solutes showed good correlation to their log P _o/w (logarithm of octanol?Cwater partition coefficient) and good separation based on hydrophilic interaction was obtained for nucleobases and nucleosides.     

Characterization of synthetic adsorbents with fine particle sizes for preparative-scale chromatographic separation

Synthetic adsorbents with fine particle sizes (15-30 microm) were manufactured. These adsorbents are made of poly(styrenedivinylbenzene) and polymethacrylate, and have the same chemical structure as analytical- (5-10 microm) or industrial- (200-600 microm) grade synthetic adsorbents. Both of them have very similar porous structure to those of analytical or industrial sizes, so that they can adsorb compounds of various molecular masses. Chromatographic separation characteristics of newly manufactured fine-particle grades of synthetic adsorbents were evaluated and compared to those of analytical or industrial adsorbents. Reasonable dependency of separation performance on particle size of synthetic adsorbents was obtained. Hydraulic properties of fine-grade adsorbents had also been measured in view of column operations. Furthermore, scalability and applicability of these adsorbents for preparative-scale chromatographic separation of bioactive compounds was evaluated. Separation of soybean isoflavones and tea catechin derivatives had revealed that fine-grade synthetic adsorbents could be well applied with scalability under the same elution conditions used for analytical use. Scalability up to a 22400-fold loading amount was achieved from a small column packed with analytical-grade adsorbent used for method development to a scale-up preparative column packed with fine-grade adsorbent used for preparative purification. These results showed the usefulness of the fine-grade synthetic adsorbents for more precise purification of bioactive compounds, including pharmaceuticals and functional food additives with higher recovery.     

介孔气体吸附剂

介孔二氧化硅经过表面修饰,赋予介孔材料不同的特性,具有很多的潜在用途,是无机材料研究的热点之一。本文综述了近年来以介孔二氧化硅（M41S 和 SBA）为载体设计的气体吸附剂的研究进展。详细讨论了二氧化碳和可挥发性有机物(VOCs)在介孔吸附剂上的吸附过程;介绍了二氧化碳介孔吸附剂的不同制备方法和影响二氧化碳在介孔吸附剂上吸附的因素,以及介孔吸附剂的结构对可挥发性有机物吸附过程的影响。最后,对介孔气体吸附剂的发展进行了展望。     

Polanyi-based models for the adsorption of naphthalene from aqueous solutions onto nonpolar polymeric adsorbents

In this research, naphthalene was adopted as the representative model compound of PAHs, and static adsorption of naphthalene from aqueous solution onto three commercial polymeric adsorbents with different pore structure was investigated. Nonlinear isotherms models, i.e., Freundlich, Langmuir, and Polanyi-Dubinin-Manes (PDM) models were tested to fit experimental data, and the experimental data were found to fit well by the PDM model. Through both isotherm modeling and constructing "characteristic curve," Polanyi theory was useful to describe the adsorption process of naphthalene by polymeric adsorbents, providing evidence that a micropore filling phenomenon was involved during the adsorption process. In addition, a good linear correlation was obtained between the naphthalene adsorption capacities and the micropore volume of adsorbents (Vmicro), whereas no linear relationship was found between the naphthalene adsorption capacities and the specific surface area of adsorbents. Based on the PDM model, the micropore volumes of adsorbents was introduced to normalize the equilibrium adsorbed volume (qv), plots of qv/V(micro) vs adsorption potential density for naphthalene on three different polymeric adsorbents were collapsed to a single correlation curve, which would be of great benefit to predict the adsorption capacity of adsorbent for the purpose of adsorption engineering design.     

Ketoimine modified silica as an adsorbent for gas chromatographic analysis of olefins

New adsorbents for capillary complexation GC have been proposed. The adsorbents contain free ketoimine groups which enable binding copper(II) and chromium(III) chlorides. The adsorbents obtained have been characterised by elemental analysis, differential scanning calorimetry and electron spin resonance. The specific interactions between the adsorbent and adsorbate molecules have been characterised by retention parameters (retention index - I, specific retention volume - Vg, molecular retention index - deltaMe). Attempts were also made at separating mixtures of olefins.     

Synthesis and characterization of superparamagnetic poly(urea-formaldehyde) adsorbents and their use for adsorption of flavonoids from <Emphasis Type="Italic">Glycyrrhiza uralensis</Emphasis> Fisch

Superparamagnetic spherical poly(urea-formaldehyde) (PUF) adsorbents were synthesized and their selective adsorption for licorice flavonoids was investigated in this paper. The magnetite (Fe₃O₄) nanoparticles were prepared by co-precipitation of ferrous and ferric salts. Then the magnetic adsorbents with PUF shell were synthesized by reversed phase suspension polymerization. The spherical adsorbents have an average diameter of 50 μm and exhibit superparamagnetic characteristics. The saturation magnetization of the adsorbents was 15.1 emu/g. The sorption and desorption properties of licorice flavonoids on the adsorbents were studied. The result shows that the adsorbents have high adsorption capacity (about 16.7 mg/g (adsorbent)). The adsorption data of flavonoids generally obeys the Langmuir isotherm equation. The adsorption can reach equilibrium rapidly and depends strongly on the pH of the feed solution. The concentration of licorice flavonoids after desorption can reach 25.12% in the desorbed fraction with 75% ethanol solution, which is higher than the 21.9% of commercial macroporous resin XDA-1. HPLC showed that liquiritin, one of main flavonoids in the licorice, was retained in this fraction, while glycyrrhizic acid (GA) can be almost removed from this fraction.     

树脂填充EVAL纤维吸附剂的制备及其吸附性能表征

采用具有亲水性的乙烯-乙烯醇共聚物(EVAL)作为纤维吸附剂基质材料,粉末型Lewatit阳离子交换树脂CNP80ws为功能材料,采用可控相分离方法,制备了不同表面形态结构的树脂填充EVAL吸附剂.当使用外部液体调控相分离过程时,在纤维的表面形成了粗糙的开孔结构,并且随树脂的填充量提高纤维表面的粗糙度与开孔度有所提高.研究结果表明:树脂填充EVAL纤维吸附剂具有较大的吸附容量与较高的脱附率,其吸附容量不低于53.9mg BSA/g吸附剂(树脂填充量50%).     

Kaolin-Carbon Adsorbents for Carotene Removal of Red Palm Oil

Kaolin-carbon adsorbents were prepared with and without sulfuric acid pretreatment followed by activation-carbonization at 500 degrees C. The total surface area of the resulting kaolin-carbon adsorbents was found to be decreased with the increase in kaolin loading. Sulfuric acid pretreatment of the precursor prior to the carbonization-activation processes resulted in the enhancement of total surface area but reduced the micropore surface area of the resulting adsorbents. At the same time, this improved carotene adsorption capacity from red palm oil. However, recovery of carotene from the carotene-adsorbed adsorbent is only improved when the acid pretreatment of the precursor was done at a high loading percentage of activated carbon. Similarly, the peroxide value (PV) increased. A maximum removal of carotene from red palm oil was obtained at 20% kaolin loading for both adsorbents prepared with and without sulfuric acid pretreatment with about 45 and 65% carotene removal, respectively, from a 30-ppm solution. This indicates that pretreatment with sulfuric acid, prior to the activation-carbonization process, increased the carotene uptake by the resulting adsorbent. However, a further increase in the kaolin loading resulted in the decrease of carotene removal. About 3-4% of carotene adsorbed can be recovered from both types of adsorbents under optimum condition, in which the percentage recovered decreased with the increase in kaolin loading. On the other hand, the PV increased with kaolin loading at around 54-64 mEq/kg for both types of adsorbents. It was also found that carotene uptake by the adsorbents is high if the adsorbent contains a high percentage of activated carbon. Similarly, carotene recovery is high and less oxidation can be observed, as indicated by the lower PV value. Copyright 2001 Academic Press.     

Structural and energetic properties of carbosils hydrothermally treated in the classical autoclave or the microwave reactor

Carbon/silica adsorbents (carbosils) prepared by pyrolysis of CH₂Cl₂ at 823 K and the reaction time from 0.5 to 6 h on the mesoporous silica gel surface (Si-60, Merck, granule size 0.2–0.5 mm) and then hydrothermally treated at 473 K with steam or liquid water by using the classical autoclave with traditional heating way or in the microwave reactor were studied by means of TG, adsorption and Q-TG methods. Changes in the structural characteristics of hybrid adsorbents before and after hydrothermal treatment were analyzed on the basis of nitrogen adsorption. Thermal properties of initial and modified samples as well as concentration of carbon deposit were studied using thermogravimetry (TG) in the range of 293–1273 K. The adsorbed water layers were investigated by means of thermodesorption of water under the quasi-isothermal conditions (Q-TG) in the range of 293–573 K. Concentration of weakly and strongly adsorbed water and the surface free energy on the interphase of adsorbent/water were calculated. It was stated that hydrothermal treatment in the microwave reactor, contrary to that in the classical autoclave, allows to obtain adsorbents with noticeably higher values of total pore volume in relation to the initial adsorbents and in majority with a higher specific surface area. Application of microwave energy allows to obtain adsorbents with lower values of surface free energy in relation to the initial adsorbents and those modified in the autoclave.     

半焦吸附剂烟气脱硫脱硝性能

采用廉价半焦为原料,经硝酸氧化和高温热处理改性后,负载金属氧化物制备半焦吸附剂,考察吸附剂的脱硫脱硝性能和再生性能,并利用BET、TEM和TPD等手段研究影响半焦吸附剂性能的内在因素.结果表明,当烟气组成为NO-O2-N2时,吸附剂具有良好的脱硝性能,失活吸附剂经水洗再生后,脱硝活性恢复较好;当烟气组成为SO2-O2-...     

Removal of Phenol by Using Montmorillonite,Clinoptilolite and Hydrotalcite

This work is to study the removal of phenol from aqueous solutions by adsorption using three different adsorbents, clinoptilolite, montmorillonite, and hydrotalcite (HT). Except for montmorillonite, the other adsorbents were treated. Clinoptilolite was modified using cetyltrimethylammonium bromide (CTAB) and hydrotalcite was calcined by heating to 550C. Adsorption isotherms of phenol on all of the mentioned adsorbents was determined by using the batch equilibration technique and indicated that, the adsorption behavior could be modelled by using the Modified Freundlich equation. The differences observed in the isotherms were explained by the variations in adsorbent-adsorbate interactions under the effects of the different surface structures of adsorbents and the pH dependent ionization behavior of phenol. Calcined hydrotalcite (HTC) was found to be the best among the studied adsorbents since it can adsorb 52% of phenol from a solution containing initially 1 g/L phenol for the 1/100 adsorbent solution ratio while the others can adsorb only 8% of phenol for the same concentration and adsorbent solution ratio.     

吸附法脱除废气中羰基硫的研究进展

羰基硫(COS)广泛存在于黄磷尾气、电石炉尾气等矿热冶炼废气中,但因其结构较稳定,极性和酸性较弱难以直接脱除.本文综述了吸附法脱除COS常用的吸附剂以及吸附剂改性方法,对负载改性所涉及的活性组分进行详细介绍,并分析影响吸附效果的主要因素及吸附机理,对比不同吸附剂的再生方式及再生效果.最后,分析吸附法脱除COS存在的不足...