Sorbent Performance Research Articles

Manufacture of calcium-based sorbents for high temperature cyclic CO2 capture via a sol–gel process

A CaO sorbent with high reactivity for cyclic high temperature CO2 capture was synthesized using a standard sol–gel process with citric acid as the chelation agent. The cyclic CO2 capture performance of the new sorbent was compared with that of the sorbents derived from commercial micro- and nano-sized CaCO3. The new CaO sorbent achieved a high CO2 capture capacity of 0.51gCO2/gsorbent under mild calcination conditions and retained an acceptable CO2 capture capacity of 0.20gCO2/gsorbent under severe calcination conditions after 20 cycles, much higher than those of the sorbents derived from commercial CaCO3 under the same reaction conditions. In addition, the new sorbent had a very rapid reaction rate at the initial reaction stage, achieving a calcium conversion ratio of 60% within 20s. Microscopic images showed that well-dispersed particles with an average size of about 200nm were formed within the sorbent. The new sorbent also had a better sintering-resistant property than the other sorbents tested during multiple calcination/carbonation cycles.

Adsorption of silver from aqueous solution onto raw vermiculite and manganese oxide-modified vermiculite

In this work, the manganese oxide-modified vermiculite (Mn-MV) was prepared from raw vermiculite (RV) and characterized chemically and morphologically. The adsorption surface of RV was increased about 10 times after the modification due to the increase in negative charge onto the sorbent surface. The adsorption performance of RV and Mn-MV sorbents in the removal of silver (Ag(I)) ions from aqueous solution was examined using batch method. The effects of initial pH of solution, contact time, adsorbent concentration, initial silver ion concentration, modifying agent concentration and temperature of solution on the adsorption efficiency were investigated systemically. The maximum adsorption capacity of RV and Mn-MV sorbents was found as 46.2 and 69.2mgg−1, respectively. The calculated adsorption energy (9.6kJmol−1) from the Dubinin–Radushkevich (D–R) model indicated that the adsorption process onto modified sorbent was taken place mainly by chemical ion exchange. A 95% portion of the Ag(I) ions adsorbed was desorbed successfully from the sorbent surface by using 0.5M 10mL HCl. The Mn-MV sorbent had good reusability performance after 10 adsorption–desorption cycles. The calculated thermodynamic parameters showed that the adsorption of Ag(I) onto Mn-MV sorbent process was feasible, spontaneous and exothermic. The kinetic evaluation also suggested that the adsorption process followed well the pseudo-second-order kinetic model.

Development of low-cost amine-enriched solid sorbent for CO2 capture

CO2 capture amine-enriched solid sorbent using agricultural wastes, such as bagasse, or industrial wastes, such as mullite, as support materials could provide efficient alternative CO2 reduction due to their low cost and ability to shape into many forms. These amine-enriched solid sorbents were prepared by treatment with monoethanolamine (MEA), diethanolamine, piperazine (PZ), 2-(2-aminoethyl-amino) ethanol (AEEA) and mixtures of these amines. The performance of amine-enriched solid sorbents with various amine compositions was studied in a tubular column at 1 atm and an adsorption temperature of 303 K. The CO2 capture capacities of the amine-enriched solid sorbents were determined by gas chromatography at a desorption temperature of 393 K. Amine-enriched solid sorbents in this study exhibited high performance CO2 capture. The MEA-PZ-enriched solid sorbent does have the highest CO2 capture performance of the amine-enriched bagasse support-based sorbents, and the results indicate that PZ is the most effective promoter in this study. The CO2 capture performances of solid sorbents in this study were compared with commercial solid sorbents. This study could lead to the development of low-cost solid sorbents for CO2 capture that can be used in many industrial applications.

Influence of morphology, porosity and crystal structure of CaCO3 precursors on the CO2 capture performance of CaO-derived sorbents

In this study, several different CaCO3 samples both natural and synthetic, showing diverse physico-chemical characteristics (particle morphology, crystal structure and porosity) were used as precursors of CaO-based sorbents for the capture of CO2. In order to identify the most favorable CaCO3 properties for a high stability and optimal CO2 uptake by CaO-derived sorbents, both series of materials were characterized using the following analytical techniques: X-ray diffraction, N2 adsorption and scanning electron microscopy. Moreover, the main differences in chemical composition, particle morphology and sorbent porosity of the CaO-based materials were correlated to the maximum CO2 uptake and loss-in-capacity after several carbonation/calcination cycles. The results indicate that the crystal structure of CaCO3parent samples strongly affects the physical properties of the calcium oxide formed during the calcination step, significantly influencing the maximum CO2 uptake. The agglomeration of CaO particles after the calcination of the CaCO3 precursors controlled to a certain extent the carbonation rate. However, this factor could not be correlated with the loss of activity of the CaO-derived sorbents in tests carried out over consecutive carbonation/calcination cycles.

Manganese-based regenerable sorbents for high temperature H2S removal

A series of sorbents with different manganese contents have been prepared by co-precipitation method for 850°C regenerative H2S removal. The sulfur capacity increased linearly with the increase of manganese content. The performance of sorbents prepared by co-precipitation of Mn nitrate and Al nitrate appears to be stable over five sulfidation–regeneration cycles. Al2O3 plays an important role in the performance of sorbents and the recovery of elemental sulfur in O2 regeneration. With increasing Mn content in the sorbent, increasing O2 concentration in the regeneration gas or increasing total regeneration gas flow rate, the recovery of elemental sulfur decreased. Elemental sulfur is the only product with SO2 regeneration. The sorbents cannot be completely regenerated with SO2 under the conditions used. The sorbents, however, can be completely regenerated by steam. The main product for steam regeneration is H2S. Steam regeneration results in less sintering than O2 regeneration.

Retention profile and selective separation of 90Y from 89Sr using zirconium-vanadate gel packed column

A low cost and selective method has been developed for the separation of trace concentrations of 90Y3+ from its parent 89Sr2+. The proposed procedure is based upon complete retention of 90Y3+ onto zirconium-vanadate (Zr-V) gel ion exchanger packed column from aqueous solutions containing HCl (1.0 × 10−5mol dm−3). Under these conditions, 89Sr2+ species were not retained onto Zr-V sorbent. The retained 90Y3+ species were then recovered with HCl. The performance of Zr-V sorbent packed column was determined via the height equivalent to the theoretical plates (HETP) and the number of plates (N). Validation of the developed method was checked by calculating the radionuclidic purity in terms of purification factor (Pf = A/A0) and radiochemical purity of the eluted 90Y from the column. Zr-V sorbent packed column offers unique advantages of retention and quantitative separation of 90Y from retention over conventional solid sorbents in rapid and effective separation of trace concentration of 90Y3+ from 89Sr2+ in their aqueous equilibrium media.

An Artificial Estrogen Receptor through Combinatorial Imprinting

Polymeric sorbents targeting endocrine-disrupting estrogen active compounds (EAC) were prepared by terpolymer imprinting using 17β-estradiol (E2) as template. From a group of eight functional monomers representing Brønsted acids, bases, hydrogen-bond donors and acceptors, as well as π-interacting monomers, a terpolymer library that comprises all possible binary combinations of the functional monomers was prepared. Binding tests revealed that imprinted polymers exhibit a markedly higher affinity for E2 compared to nonimprinted polymers (NIPs) or polymers prepared by using single functional monomers. A combination of methacrylic acid (MAA) and p-vinylbenzoic acid offered a particularly promising lead polymer, displaying an imprinting factor of 17 versus 2.4 for a benchmark polymer prepared by using only MAA as functional monomer. The saturation capacities ascribed to imprinted sites were four to five times higher for this polymer compared to previously reported imprinted polymers. NMR titrations and molecular dynamics simulations corroborated these results, indicating an orthogonal preference of the two functional monomers with respect to the E2 3-OH and 17-OH groups. The optimized polymer exhibited a retentivity for EACs that correlates with their inhibitory effect on the natural receptor. By using the optimized molecularly imprinted polymers (MIPs) in a model water-purification system, they were capable of completely removing ppb levels of a small group of EACs from water. This is in contrast to the performance of nonimprinted polymers and well-established sorbents for water purification (e.g., active carbon), which still contained detectable amounts of the compounds after treatment.

A novel needle trap device with single wall carbon nanotubes sol–gel sorbent packed for sampling and analysis of volatile organohalogen compounds in air

This paper describes a new approach that combines needle trap devices (NTDs) with a newly synthesized silanated nano material as sorbent for sampling and analysis of HVOCs in air. The sol–gel technique was used for preparation of the single wall carbon nanotube (SWCNT)/silica composite as sorbent, packed inside a 21-gauge NTD. Application of this method as an exhaustive sampler device was investigated under different laboratory conditions in this study. Predetermined concentrations of each analyte were prepared in a home-made standard chamber, and the effects of experimental parameters, such as temperature, humidity, sampling air flow rate, breakthrough volume and storage time on NTD, and the sorbent performance were investigated. The proposed NTD was used in two different modes and two different injection methods, and an NTD with a side hole, a narrow neck glass liner and syringe pump assisted injection of carrier gas were applied. The NTD packed with SWCNTs/silica composite was compared to the NTD packed with PDMS and also SPME with CAR/PDMS. For four compounds, LOD was 0.001–0.01ngmL−1, LOQ was 0.007–0.03ngmL−1, and the relative standard division for repeatability of method was 2.5–6.7%. The results show that the incorporation of NTD and SWCNTs/silica composite is a reliable and effective approach for the sampling and analysis of HVOCs in air. Coupling this system to GC–MS make it more sensitive and powerful technique.

Hypercrosslinked strong anion‐exchange resin for extraction of acidic pharmaceuticals from environmental water

Two novel high-specific surface area polymeric sorbents (HXLPP-SAXa and HXLPP-SAXb) were synthesised and evaluated as solid-phase extraction sorbents. The novel sorbents under study are based on hypercrosslinked polymer microspheres and designed specifically to offer ion-exchange properties; the specific polymers of interest in the current work have been chemically modified in such a way as to impart a tuneable level of strong anion-exchange character onto the sorbents. The novel sorbents were applied as strong anion-exchange sorbents in solid-phase extraction studies, with the goal being to selectively extract a group of acidic compounds from complex environmental samples in an efficient manner. Out of two HXLPP-SAX resins evaluated in this study, it was found that the sorbent with the lower ion-exchange capacity (HXLPP-SAXa) gave rise to the best overall performance characteristics and, indeed, was found to compare favourably to the solid-phase extraction performance of commercial strong anion-exchange sorbents. When the HXLPP-SAXa sorbent was applied to the solid-phase extraction of environmental water samples, the result showed quantitative and selective extraction of low levels of acidic pharmaceuticals from 500 mL of river water and 100 mL of effluent wastewater.

A Novel Application of Natural Peat for Solid-Phase Extraction of Pyrimethanil, Flumetralin, and Kresoxim-Methyl in Water Using Gas Chromatography-Mass Spectrometry

Natural peat was tested for extraction of pyrimethanil, flumetralin, and krexosim-methyl from water, with analysis using gas chromatography-mass spectrometry (GC-MS) in selected ion monitoring mode (SIM). Experiments were carried out at one fortification level (0.1 μg L−1) and resulted in recoveries in the range 41–96%, with RSD values between 6.8 and 12.6% for natural peat as sorbent. Detection and quantification limits ranged from 0.02 to 0.05 μg L−1 and from 0.07 to 0.1 μg L−1, respectively, for the different pesticides studied. The method developed was linear over the range tested (0.07–4.0 μg L−1), with correlation coefficients ranging from 0.9919 to 0.9989. Comparison between peat and commercial sorbents (C18-bonded silica, ENVI-Carb, Florisil, silica gel, ENVI-Carb/LC-NH2) showed better performance of peat sorbent for flumetralin and kresoxim-methyl.

ChemInform Abstract: Halide Removal from Coal‐Derived Syngas: Review and Thermodynamic Considerations

Halide species are one of the most abundant and damaging impurities in syngas derived from coal. Aside from environmental concerns, halides can cause irreversible damage to downstream processes such as particulate filters, catalysts, gas separation membranes, fuel cells and turbines. The current trend towards high-temperature, dry gas cleaning is making solid sorbents increasingly favourable, and sorbent development must take into consideration the chemical, physical, efficiency and economic aspects of sorbent performance. This article reviews the origins of halides in coals, cleaning requirements and efforts to develop solid sorbents for halide removal for gasification processes. Most research effort to date has concerned (1) the performance and optimization of basic sorbents such as calcium and sodium carbonate and (2) determining the tolerances of catalysts, filters, fuel cells and other plant components to halide impurities. In addition, thermodynamic calculations have been used to compare the performance of a large number of potential sorbents examined using criteria such as conversion, speciation, volatility and regenerability. This exercise confirms alkali and alkaline earth carbonates exhibit the greatest halide conversion at the temperatures demanded by various downstream processes, but these species are not regenerable at high temperatures in the same manner as desulfurization sorbents. Although not previously investigated, scope exists for the investigation of barium carbonate for halide sorption. Halide removal is best performed preceding sulfur removal due to the irreversible inhibition of regenerable desulfurization sorbents by halide species. Copyright © 2011 Curtin University of Technology and John Wiley & Sons, Ltd.

ZnO/SBA-15 composites for mid-temperature removal of H2S: Synthesis, performance and regeneration studies

ZnO/SBA-15 composites for mid-temperature H2S removal were prepared by both conventional Incipient Wetness and Two-Solvents impregnation techniques. The composites, differing as to the ZnO loading and the calcination treatment, were characterised by X-ray diffraction, transmission electron microscopy (also in the high resolution mode) and N2 physisorption. Characterisation techniques revealed that zinc oxide was highly dispersed into/over the well-ordered mesoporous channels. In all the composites the mesostructure of the support was still retained together with a high surface area, large pore volume and uniform pore size. The sorbent performance for H2S removal from a H2S/He stream was investigated and compared with a commercial ZnO sorbent. The confinement of the active phase in the SBA-15 structure enhances its ability to interact with hydrogen sulphide, which results in improved performance. Temperature-programmed experiments were carried out for selecting appropriate regeneration conditions. The regenerated sorbent showed a sorption capacity even higher than that of the fresh ones. Such behaviour is maintained in repeated sorption/regeneration cycles.

A comparative study of the effect of clay binders on iron oxide sorbent in the high-temperature removal of hydrogen sulfide

The purpose of this study is to investigate the effect of clay binder, an important additive, on the performance of iron oxide sorbent in high temperature coal gas desulfurization. The four clay binders chosen for the study were kaolinite, diatomite, bentonite and brick clay. The sulfidation–regeneration cycles were conducted in a fixed-bed reactor. XRD, DTA and FTIR, together with texture characterizing techniques, such as mercury porosimetry and nitrogen adsorption, were adopted to characterize the sorbents and raw materials. The results obtained show that sorbents prepared from various clay binders exhibit different breakthrough behaviors. In addition, a correlation between pore volume and sulfur capacity reveals that sorbents with a greater number of pores larger than 200nm (diameter), exhibit higher sulfur capacity. The reason for this is that a greater number of large pores can improve diffusion and provide a larger space for relieving heat impact. However, too many large pores may result in weak strength and very low bulk density, thus a balance between large pores and the density must be achieved. This study also reveals that clay binder can contribute to the modification of a sorbent's texture as gas is released when the mineral structure changes during calcination. In addition, a clay mineral with an active interlayer has been shown to be beneficial in improving the dispersion of active components in the sorbent, because of the existence of an interaction between the mineral and red mud.

Investigation of Porous Silica Supported Mixed-Amine Sorbents for Post-Combustion CO2 Capture

Prospective post-combustion CO2 capture sorbents were prepared by the immobilization of a low-molecular-weight, branched polyethyleneimine (PEI) and 3-(aminopropyl)triethoxysilane (APTES) within a commercially available porous PQ Corporation CS-2129 silica support to investigate (i) CO2 adsorption properties of the supported mixed-amine (PEI+APTES) sorbents in both pure CO2 environments and simulated flue gas conditions, (ii) their thermal and hydrolytic stability over numerous adsorption and desorption cycles, and (iii) their equilibrium and kinetic adsorption behavior. Initial CO2 adsorption–desorption measurements via thermogravimetric analysis (TGA) were conducted in pure CO2 to measure dry, near-equilibrium CO2 adsorption capacities, together in calculating amine efficiencies, which was recognized in being a meaningful criterion in evaluating sorbent performance for selecting the “most favorable” mixed-amine (PEI+APTES) composition. The as-prepared materials containing various weight ratios of PEI to...

A thermodynamic study of the removal of HCl and H2S from syngas

Advanced integrated-gasification combinedcycle (IGCC) and integrated-gasification fuel cell (IFGC) systems require high-temperature sorbents that are capable of removing hydrogen chloride and hydrogen sulfide from coal derived gases to very low levels. HCl and H2S are highly reactive, corrosive, and toxic gases that must be removed to meet stringent environmental regulations, to protect power generation equipment and to control the emissions of contaminants. The thermodynamic behavior of 13 sorbents for the removal of HCl and H2S under various conditions including: initial toxic gas concentration (1–10000 ppm), operating pressure (0.1–11 Mpa), temperature (300 K–1500 K), and the presence of H2O were investigated. The correlation between HCl and H2S was also examined. Thermodynamic calculations were carried out for the reactions of the 13 sorbents using a FactSage 5.2 software package based on free energy minimization. The sorbents, Na2CO3, NaHCO3, K2CO3, and CaO are capable of completely removing chlorine at high temperatures (up to ∼1240 K) and at high pressures. Water vapor did not have any significant effects on the dechlorination capability of the sorbents. Nine of the sorbents namely; Cu2O, Na2CO3, NaHCO3, K2CO3, CaO, ZnO, MnO, FeO, and PbO, were determined to have great potential as desulfurization sorbents. Cu2O and ZnO had the best performance in terms of the optimum operating temperature. The addition of water vapor to the reactant gas produces a slightly detrimental effect on most of the sorbents, but FeO exhibited the worst performance with a reduction in the maximum operating temperature of about 428 K. The dechlorination performance of the alkali sorbents was not affected by the presence of H2S in the reactions. However, the desulfurization capability of some sorbents was greatly affected by the presence of HCl. Particularly, the performance of Cu2O was significantly reduced when HCl was present, but the performance of FeO improved remarkably. The thermodynamic results gathered are valuable for the developments of better sorbents.

Manganese Doping of Magnetic Iron Oxide Nanoparticles: Tailoring Surface Reactivity for a Regenerable Heavy Metal Sorbent

A method for tuning the analyte affinity of magnetic, inorganic nanostructured sorbents for heavy metal contaminants is described. The manganese-doped iron oxide nanoparticle sorbents have a remarkably high affinity compared to the precursor material. Sorbent affinity can be tuned toward an analyte of interest simply by adjustment of the dopant quantity. The results show that following the Mn doping process there is a large increase in affinity and capacity for heavy metals (i.e., Co, Ni, Zn, As, Ag, Cd, Hg, and Tl). Capacity measurements were carried out for the removal of cadmium from river water and showed significantly higher loading than the relevant commercial sorbents tested for comparison. The reduction in Cd concentration from 100 ppb spiked river water to 1 ppb (less than the EPA drinking water limit of 5 ppb for Cd) was achieved following treatment with the Mn-doped iron oxide nanoparticles. The Mn-doped iron oxide nanoparticles were able to load ~1 ppm of Cd followed by complete stripping and recovery of the Cd with a mild acid wash. The Cd loading and stripping is shown to be consistent through multiple cycles with no loss of sorbent performance.

Synthesis and strong heavy-metal ion sorption of copolymer microparticles from phenylenediamine and its sulfonate

Strong heavy-metal-ion sorbents based on copolymer microparticles with many functional groups including amino, imino and sulfonic groups were synthesized by a chemical oxidative polymerization of m-phenylenediamine (mPD) and p-sulfonic-m-phenylenediamine (SPD) in pure water. The sorbent performance has been investigated with regard to mPD/SPD ratio, functional group densities, metal ion species, and sorption conditions. It is found that mPD/SPD (95/5) copolymer microparticles demonstrate the maximal yield, maximal electrical conductivity, maximal Pb(II) and Cr(VI) (mainly as HCrO4−) adsorbability, but the minimal Cu(II) adsorbability, while mPD/SPD (50/50) copolymer microparticles demonstrate the maximal Hg(II) adsorbability, suggesting that the polymers are real copolymers rather than a mixture of both homopolymers. The sorption rate of the metal ions steadily rises in the order of Cr(VI) ≪ Hg(II) ≪ Pb(II), the adsorbance rises in the order of Cu(II) ≪ Pb(II) < Cr(VI) ≪ Hg(II), whereas the adsorptivity rises in the order of Cu(II) ≪ Cr(VI) < Pb(II) < Hg(II). In particular, the mPD/SPD (95/5) copolymer microparticles reach adsorption equilibrium within 3 min, achieving an initial Pb(II) adsorption rate of up to 509.5 g g−1 h−1. The microparticles are simultaneously strong, rapid, sustainable sorbent towards Pb(II), Hg(II), and Cr(VI). The HCrO4− sorption is endothermic and enhanced by properly elevating the temperature. The pH of the ion solutions declines after the sorption, implying that the sorption includes the replacement of H+ by the ions. The microparticles also exhibit good selectivity for Hg(II) and Pb(II) over Cu(II) ions, possessing the highest selective adsorptivity of up to 99.9%. The sorption mechanism of the ions onto the microparticles was analyzed.

Surfactant promoted solid amine sorbents for CO2capture

A new strategy to improve the CO2 capture performance of solid amine sorbents has been developed based on the balance of CO2 kinetic diffusion and thermodynamic sorption. The CO2-neutral surfactant was introduced into polyethyleneimine (PEI) to create extra CO2 transfer pathways, facilitating CO2 diffusion into the deeper PEI films. Consequently, the sorbents offered increased amount of reactive sites and higher utilization efficiency of amine groups, leading to a dramatically enhanced CO2 dynamic capacity and total capacity. Due to the facilitating diffusion, the sorbents could work at room temperature with very good performance. At 30 °C the surfactant-promoted sorbents had the CO2 capture capacity as high as 142 mg g−1 and their amine utilization was over 50%, which are the highest values ever reported for the PEI loaded sorbents working at this temperature. The surfactant-promoted sorbents also exhibited much better sorption kinetics and regeneration performance. In addition to advancing the support or amine, the present study provides another cost-efficient and general approach to design high performance CO2 solid sorbents and may have a major impact on the advance of current carbon capture and storage technologies.

Impact of impregnation pressure on desulfurization performance of Zn-based sorbents supported on semi-coke

High-pressure impregnation, a new preparation method for sorbents to remove H 2S from hot coal gas, is introduced in this paper. Semi-coke (SC) and ZnO is selected as the support and active component of sorbent, respectively. The sorbent preparation process includes high-pressure impregnation, filtration, ovendry and calcination. The aim of this research is to primarily study the effects of the impregnation pressure on physical properties and desulfurization ability of the sorbent. The desulfurization experiment was carried out in a fixed-bed reactor at 500°C and a simulated coal gas used in this work was composed of CO (33 vol%), H 2 (39 vol%), H 2S (300 ppm in volume), and N 2(balance). Experimental results show that the pore structure of the SC support can be improved effectively and ZnO active component can be uniformly dispersed on the support, with the small particle size of 10-500 nm. Sorbents prepared using high-pressure impregnation have better desulfurization capacity and their active components have higher utilization rate. P20-ZnSC sorbent, obtained by high-pressure impregnation at 20 atm, has the best desulfurization ability with a sulfur capacity of 7.54 g S/100g sorbent and a breakthrough time of 44 h. Its desulfurization precision and efficiency of removing H 2S from the middle temperature gases can reach <1 ppm and > 99.7%, respectively, before sorbent breakthrough.

Efficient CO2 sorbents based on silica foam with ultra-large mesopores

A series of high-capacity, amine impregnated sorbents based on a cost-effective silica foam with ultra-large mesopores is reported. The sorbents exhibit fast CO2 capture kinetics, high adsorption capacity (of up to 5.8 mmol g−1 under 1 atm of dry CO2), as well as good stability over multiple adsorption–desorption cycles. A simple theoretical analysis is provided relating the support structure to sorbent performance.