Reference Sorbent Research Articles

Alternative sorbents for mercury capture in flue gas from lignite combustion

This paper presents an experimental study of two of alternative sorbents for mercury capture from the lignite combustion flue gas. The sorbents are based on calcium hydroxide and aluminosilicate, using different modifications. A commercially available activated carbon (AC) with bromine impregnation was selected as the reference sorbent. This sorbent is a state-of-the-art solution for mercury removal in industrial combustion facilities. However, its application is costly for power plants because of the market price of the AC and because the presence of carbon in the fly ash can complicate its further use, which gives a strong motivation for exploring new alternatives. Experimental investigation was carried out in a 500 kW pilot-scale bubbling fluidized bed combustor using a lignite with naturally high mercury content. A injection system of our own design and construction was used to supply the sorbents to the flue gas downstream of the combustor at a flow rate in the range of 100–500 mg/m3N of the flue gas. Continuous measurement of mercury concentration was used upstream the sorbent injection and downstream the fabric filter, simultaneously. Different sorbent injection rates and flue gas temperatures at the sorbent injection point were examined.The mercury capture ratio was evaluated considering the Hg balance in the combustor. It was shown that the mercury self-capture by the fly ash in the fluidized bed combustion system varies approximately from 30 to 90 %, depending on the SO2 concentration. The Hg capture ratio for calcium hydroxide was in a range of approximately 15–25 %, while for aluminosilicate it was 25–45 %, determined by the actual conditions of the flue gas and the initial Hg concentration. This is in the range of the reference AC, which typically reaches from 25 – 95%. The increased injection rate of the sorbents was reflected in the Hg capture ratio, but its promotion was observed only in the case of the aluminosilicate sorbent. A correlation of the Hg capture ratio with the flue gas temperature at the injection point was also clearly identified only for the aluminosilicate sorbent, when an increase in the temperature led to increasing in the capture ratio.

Analysis of the energy consumption in solvent regeneration processes using binary amine blends for CO2 capture

Blending two or more amines has recently been recognized as an efficient strategy to formulate competitive sorbents for post-combustion CO2 capture, as it allows to benefit from the advantages of each individual amine. In the present work, we devised four new dual-amine aqueous blends, based on the tertiary amine 2-dimethylamino-2-methyl-1-propanol (2DMA2M1P) mixed with different primary and secondary amines, namely ethanolamine (MEA), benzylamine (BZA), 2-amino-2-methyl-1-propanol (AMP) and diethanolamine (DEA). The CO2 capture and release performance of the formulated blends were experimentally evaluated by measuring CO2 equilibrium solubility, CO2 absorption and desorption rates, and energy consumption during the regeneration process, and results were compared with those obtained under the same operating conditions with 5 M aqueous MEA, the reference sorbent for CO2 capture processes. Moreover, 13C NMR spectroscopy was used to identify and quantify the species formed during the CO2 absorption process to better understand the reaction mechanism in each blend. We found that all formulated blends showed appreciable CO2 capture performance and, most importantly, significantly better desorption performance than conventional MEA. In particular, BZA+2DMA2M1P provided the best capture performance, while AMP+2DMA2M1P showed a faster CO2 desorption rate and lower energy consumption than the other tested blends.

Crosslinked 4-Vinylpyridine Monodisperse Functional Microspheres for Sorption of Ibuprofen and Ketoprofen

Nowadays, ibuprofen and ketoprofen are widely used over-the-counter medications to treat inflammation, fever, or pain. Their high consumption and improper disposal cause them to get into the environment and often pollute surface water. In this study, the new polymeric porous microspheres based on 4-vinylpyridine (4VP) are presented as effective sorbents for ibuprofen and ketoprofen preconcentration and removal. The porous microspheres were obtained via seed swelling polymerization with the use of two types of methacrylate crosslinkers, i.e., trimethylolpropane trimethacrylate (TRIM) and 1,4-dimethacryloiloxybenzene (14DMB). Additionally, as a reference sorbent, a copolymer of styrene and divinylbenzene was obtained. Porous structure investigations showed that the microspheres possess a specific surface area of about 100 m2/g, but noticeable differences were observed in their internal topography depending on the type of crosslinker used. Moreover, the porous structure of dry and swollen microspheres differs significantly. Swollen copolymers reveal the presence of micropores. The 4VP microspheres are characterized by high thermal stability; their initial decomposition temperature is about 300 °C. The performance of the 4VP copolymers as sorbents in aqueous solutions of drugs was evaluated in static and dynamic modes at three pH values of 3, 7, and 11. The highest sorption efficiency was obtained for ibuprofen and ketoprofen in pH 3. Both 4VP copolymers indicate the high sorption capacity in a static sorption as follows: towards ketoprofen of about 40 mg/g whereas towards ibuprofen of about 90 mg/g and 75 mg/g on copolymer crosslinked with trimethylolpropane trimethacrylate and 1,4-dimethacryloiloxybenzene, respectively. The recovery of ibuprofen and ketoprofen after dynamic sorption experiments was higher than 90%.

Study on the effect of NaBr modification on CaO-based sorbent for CO2 capture and SO2 capture

The calcium looping process has been considered as a promising technology for capturing CO2 from the flue gas, but the decay of CaO-based sorbent, which was caused by the sintering process and the poisoning of SO2, was the major obstacle for its application in industry. In this work, NaBr modification was proposed to enhance the cyclic CO2 capture capacity of the CaO-based sorbents, and the effect of SO2 on the cyclic CO2 capture capacity of the NaBr modified CaO-based sorbents was well studied. The enhancing mechanism of cyclic CO2 capture capacity of the modified CaO-based sorbents was analyzed by X-ray diffraction, field emission scanning electron microscopy, N2 physisorption, and fractal dimensions. The result showed that the SO2 in the flue gas inactivated the CO2 capture activity of the sorbents over the cycles, but the NaBr modification not only enhanced the SO2 capture capacity but also improved the cyclic CO2 capture capacity of the sorbents. The specific surface area and BJH cumulative pore volumes of the sorbents decayed rapidly over the repeated cycles, but the fractal dimensions (D) of the NaBr modified sorbents were still larger than that of unmodified reference sorbent. The “NaBr/CaO” captured 15 grams of CO2 per gram of sorbent over the 50 cycles, which was 2.2 times that of “CaO, AR”. Hence, NaBr modification would be a promising strategy to boost the CO2 capture capacity of the CaO-based sorbent in the calcium looping process that contributes to the carbon neutralization scenarios.

A NEW APPROACH TO OBTAIN AEROGELS FOR GAS SAFETY APPLICATIONS

In this study a new approach for aerogel preparation is presented, along with the screening of obtained aerogel towards air decontamination potential. The synthesis method allows the tuning of the porosity degree of the aerogel by changing the amount of the solvent (water), which dictates the physical appearance of the obtained aerogel (compacted or expanded). Experiments have been carried out under dynamic conditions, by using isobutylene (ISB) as model pollutant and activated carbon as a reference sorbent. At low contaminant loading, the obtained aerogels exhibit comparable performance with that observed for activated carbon, otherwise the activated carbon presents the highest performance at higher loadings. The physical appearance of the aerogel appears to influence the ISB removal performance. Influence of gas flowrate and ISB concentration on the performance response is depicted. The obtained results reveal new perspectives in developing and using aerogels (ultralight materials) for the removal of air contaminants in special applications such as those related to gas safety (for example, the gas masks that should assure not only quality, but also comfort).

Amine-Functionalized Metal-Organic Frameworks and Covalent Organic Polymers as Potential Sorbents for Removal of Formaldehyde in Aqueous Phase: Experimental Versus Theoretical Study.

Porous materials have been identified as efficient sorbent media to remove volatile organic compounds. To evaluate their potential as adsorbents, the adsorptive removal of formaldehyde (FA) in aqueous environments was investigated using four materials, two water-stable metal-organic frameworks (MOFs) of UiO-66 (U6) and U6-NH2 (U6N) and two covalent organic polymers (COPs) with amine-functionality, CBAP-1-EDA (CE) and CBAP-1-DETA (CD). U6N exhibited the highest removal capacity of 93% (0.56 mg g-1) of the tested materials [e.g., CE (81.1%, 0.53 mg g-1) > CD (67.2%, 0.43 mg g-1) > U6 (66.9%, 0.42 mg g-1)], which was 2 times higher than that of the reference sorbent, activated carbon (AC: 50%, 0.30 mg g-1). The results of Fourier transform infrared and powder X-ray diffraction analyses confirmed the interactions between FA molecules and the amine components of the materials (U6N, CD, and CE). According to density functional theory calculations, the formation of hydrogen bonds between FA molecules and amine components was apparent and was further verified by FA/amine distance (CD: 2.83, CE: 2.88, and U6N: 2.66 Å) along with enthalpy values (CD: -32.4, CE: -45.5, and U6N: -272 kJ mol-1). In case of U6, the major interactions occurred in the metal-clusters (-19.3 kJ mol-1) via electrostatic interactions (distance: 5.49 Å). Furthermore, the sorption by amine-functionalized materials such as U6N is suggested to be dominated by hydrogen bonding which ultimately led to the formation of imine. If the performance of the tested materials is evaluated in terms of partition coefficient, U6N (1153 mg g-1 mM-1) is found as the outperformer in all tested subjects. Regeneration of spent MOFs/COPs was also plausible in the presence of ethanol to maintain their structural integrity even after 10 adsorption-desorption cycles. Overall, the selected MOFs/COPs were seen to have very high removal capacity for hazardous FA molecules in aqueous phase.

Sorption of Highly Hydrophobic Organic Chemicals to Organic Matter Relevant for Fish Bioconcentration Studies.

With regard to a potential underestimation of bioconcentration factors (BCF) in flow-through fish tests, sorption of 11 highly hydrophobic organic chemicals (HOCs) (log KOW 5.5-7.8) from different substance classes was systematically investigated for the first time in the presence of fish feed (FF) and filter residues (FR), the organic matter (OM) most relevant for fish bioconcentration studies. Sorption was investigated in batch-equilibrium experiments by solid-phase microextraction (SPME) resulting in partitioning coefficients of solid-water (Kd), total organic carbon-water (KTOC), and dissolved organic carbon-water (KDOC). Results prove a high affinity of HOCs for FF and FR supporting a significant impact on BCF studies and differing from sorption to Aldrich-humic acid (AHA) utilized as reference sorbent. Sorption is influenced by interactions between HOCs and OM characteristics. For FF, KDOC values were higher than KTOC values. Results help to assess the relevance of interaction of HOCs from different substance classes with OM relevant for BCF studies.

Low-cost sorbents for the removal of acid dyes from aqueous solutions

Abstract Two activated carbons (ACs) derived from apple wood (AWAC) and peach stone (PSAC), and one keratinous material extracted from hydrolyzed wool (WHA) were tested for their adsorption capacity for Acid Red 337 (AR) and 1:2 chromium complex of Acid Blue 349 (AB). A commercial granular activated carbon (GAC) was chosen as reference sorbent. The sorbent characteristics, the dye concentration, the contact time and the working pH were the factors taken into consideration. The SEM images of AWAC and PSAC show different morphologies and pore structures. FTIR spectra of the WHA material did not indicate any drastic disruption of keratin macromolecule. The AR dye exhibited higher uptake as compared with the AB dye for all sorbents. The sorption capacity of the tested materials increased in sequence: AWAC

Synthesis of mesoporous alumina with tunable structural properties

Mesoporous aluminas (MAs) with tunable structural properties including BET surface area, pore volume and pore size were successfully synthesized. The synthesis method was based on a sol–gel process via hydrolysis of aluminium isopropoxide associated with non-ionic block copolymer P123 as the structure-directing template in an acidic aqueous system. The MAs were characterized using thermogravimetry – differential thermal analysis (TG-DTA) for decomposition and mass loss characteristics during calcination, X-ray diffraction (XRD) for bulk crystallinity, transmission electron microscopy (TEM) for nano-scale morphology, selected area electron diffraction (SAED) for local crystallinity and N2 adsorption–desorption techniques for porous structural properties. By tailoring the amount of P123 and HNO3 addition, inorganic aluminium precursor Al(NO3)3 doping ratio and calcination temperature, MAs with controllable structural properties were obtained, leading to regular variations in the surface area (up to 409 m2g−1), pore volume (0.4 cm3g−1 ∼ 2.8 cm3g−1) and pore size (5.0 nm ∼ 33.1 nm). Bovine serum albumin (BSA) was employed to evaluate the adsorption capability of the synthesized MAs. It was found that the structural properties of MA had a crucial effect on the BSA adsorption capability, increasing dramatically with increasing surface area, pore volume and pore size. For the sample MA4P15AlN (surface area 287 m2g−1, pore volume 2.8 cm3g−1 and pore size around 33.1 nm), the BSA adsorption amount reached 182.7 mgg−1 in 2 h, higher than other MA samples as well as a silicon based reference sorbent material, SBA-15 (133.3 mgg−1).

Development of New Potassium Carbonate Sorbent for CO2 Capture under Real Flue Gas Conditions

In this paper, the development of a new potassium carbonateon alumina support sorbent prepared by impregnating K2CO3 with an industrial grade of Al2O3 support was investigated. The CO2 capture capacity was measured using real flue gas with 8% CO2 and 12% H2O in a fixed-bed reactor at a temperature of 65 °C using breakthrough curves. The developed sorbent showed an adsorption capacity of 66.2 mgCO2/(gr sorbent). The stability of sorbent capture capacity was higher than the reference sorbent. The SO2 impurity decreased sorbent capacity about 10%. The free carbon had a small effect on sorbent capacity after 5 cycles. After 5 cycles of adsorption and regeneration, the changes in the pore volume and surface area were 0.020 cm3/gr and 5.5 m2/gr respectively. Small changes occurred in the pore size distribution and surface area of sorbent after 5 cycles.

Preparation of a Low-Cost K2CO3/Al2O3 Sorbent for CO2 Capture at Flue-Gas Operating Conditions

In this study, the efficiency of a low-cost K2CO3/Al2O3 sorbent as a CO2 capture support was investigated. The sorbent was prepared by impregnating K2CO3 on industrial-grade Al2O3. The CO2 capture capacity of the sorbent was calculated from the breakthrough curve of the CO2 adsorption inside a fixed-bed reactor, in the presence of H2O and at an adsorption temperature of 60 °C. An adsorption capacity of 75.4 mg CO2/g of sorbent was obtained. The stability of capture capacity of the sorbent was higher than that of the reference sorbent. The changes in the pore volume and surface area were 0.020 cm3/g and 5.5 m2/g, respectively, after five cycles of adsorption and regeneration. However, there were minor changes in the pore-size distribution and surface area of the sorbent after five cycles. This sorbent can be considered to be used in large-scale applications.

Optimization of CO2 Capture from Flue Gas with Promoted Potassium Carbonate Solutions

The studies aim to develop detergents which show similar reaction kinetics to the reference sorbent 2-aminoethanol (MEA) 30 mass-%. Furthermore the solvent properties and the energy requirement for regeneration can be improved. Apart from the lower desorption enthalpy, it is necessary that the solutions show low corrosiveness, a low vapour pressure, no toxicity and a low degradation rate. These requirements can be achieved by employing carbonate solutions. The challenge is the improvement of the reaction kinetics by using additives which enhance the performance to or above the level of the reference sorbent. In addition to the detergent investigation a detailed understanding of the two-phase system of flue gas and wash solution is required also.

Qualification of the ALKASORB sorbent for the sorption-enhanced water-gas shift process

For the sorption-enhanced water-gas shift (SEWGS) process, a new sorbent material has been qualified in a reactor of 2 m length under conditions close to industrial designs. The sorbent ALKASORB is a potassium-carbonate promoted hydrotalcite-based compound. ALKASORB is shown to have many favourable properties in comparison to the reference sorbent, in particular with respect to mechanical stability. The cyclic capacity of the new compound is substantially higher than the cyclic capacity of the reference sorbent, and it allows a reduction of the steam requirement of 50%. The sorbent has demonstrated catalytic activity for the water-gas shift reaction that is sufficient to omit a separate catalyst. It is demonstrated that the sorbent remains chemically and mechanically stable during operation of at least 2000 adsorption – desorption cycles, even in the presence of H2S in the feed. H2S is shown not to influence CO2 adsorption capacity and is co-captured with the CO2. In contrast to the reference material that showed mechanical degradation during extended adsorption – desorption cycles, the new material is stable and allows to obtain carbon capture levels exceeding 95% more efficiently and more economically since the required size of the vessels will be smaller.

CO2 capture in natural gas combined cycle with SEWGS. Part B: Economic assessment

This two part-paper investigates the adoption of an innovative CO2 capture concept named SEWGS (sorption enhanced water gas shift) in natural gas combined cycle. In Part A, SEWGS working conditions were optimized in terms of carbon capture ratio as well as CO2 purity and two different sorbent performances were analyzed. Part B presents the economic assessment of investigated SEWGS cases together with three reference cases selected for electricity production: without carbon capture, with post-combustion carbon capture by MEA and with pre-combustion carbon capture by MDEA. Results shows that with reference sorbent performances the calculated cost of CO2 avoided is about 58€/tCO2, which is lower than reference MDEA (64€/tCO2) but higher than MEA (48.5€/tCO2). The adoption of a sorbent with improved performances brings down the cost of CO2 avoided down to 49€/tCO2, which is comparable to post combustion technology. This is a consequence of reforming sections costs which penalizes pre-combustion technologies: specific investment costs for SEWGS cases are 15% higher than MEA. Finally, as far as SEWGS working conditions are concerned, the optimal CO2 capture rate depends on the sorbent cyclic capacity ranging from 90% to 95%, while the selected CO2 purity is 99%. This activity was carried out under the FP7 project CAESAR financed by the EU community.

Improved sorbent for the sorption-enhanced water-gas shift process

Abstract For the sorption-enhanced water-gas shift (SEWGS) process, a new sorbent material has been developed. The sorbent is a potassium-carbonate promoted hydrotalcite-based material. The material has been tested under realistic process conditions in an experimental rig of 2 m length. The cyclic capacity of the material is 27% higher than the cyclic capacity of the reference sorbent, which was used in CACHET, a previous R&D project. Moreover, 36% less steam is required for its regeneration. The sorbent pellets also have a 65% higher crush strength than the reference sorbent. Contrary to the reference material, the novel material does not form notable amounts of MgCO 3 under relevant operating conditions. Due to the absence of this slow CO 2 uptake process, the sorbent remains mechanically stable, the cyclic steady state is reached rapidly, CO 2 slip in the product gas is reduced, and steam requirements are lowered. It is demonstrated that the sorbent remains mechanically stable during operation of at least 1200 adsorption–desorption cycles. With this new, higher density material, carbon capture levels exceeding 95% can be obtained more efficiently and vessels will be smaller.

Selective heavy metals removal from waters by amorphous zirconium phosphate: Behavior and mechanism

Selective removal of heavy metals from water has been of considerable concern for several decades. In the present study, the amorphous zirconium phosphate (ZrP) was synthesized and characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron micrography (SEM), thermogravimetric analysis (TGA) as well as pH-titration experiments. Uptake of heavy metals including lead, cadmium, and zinc onto ZrP was studied by using a polystyrene sulfonic-acid exchanger D-001 as a reference sorbent and Ca 2+ as a competing cation due to its ubiquity in natural or industrial waters. The results indicated that the uptake of heavy metals onto ZrP is essentially an ion-exchange process and dependent upon solution pH. In comparison with D-001, ZrP exhibited more favorable sorption of heavy metals particularly in terms of high selectivity, as indicated by the distribution coefficients of ZrP even several orders higher than D-001 towards heavy metals when calcium ion coexisted at a high level in solution. The Fourier transform-infrared (FT-IR) spectroscopic investigation indicated that the uptake of calcium, cadmium, and zinc ions onto ZrP is only driven by the electrostatic interaction, while that of lead ion is possibly dependent upon the inner-sphere complex formation with ZrP. XPS results further elucidated that ZrP displays different sorption affinity towards heavy metals in the same order as selectivity sequence of Pb 2+>Zn 2+≈Cd 2+>Ca 2+, which can be explained by hard and soft acids and bases (HASB) theory. Moreover, uptake of heavy metals onto ZrP approached to equilibrium quickly and the used ZrP could be readily regenerated for reuse by the dilute HCl solution. Thus, all the results suggest that amorphous ZrP has excellent potential as a sorption material for water treatment.

Use of new generation poly(styrene-divinylbenzene) resins for gas-phase trapping-thermal desorption: Application to the retention of seven volatile organic compounds

Two new generation polymeric resins, Bond Elut ENV (styrene-divinylbenzene) from Varian and LiChrolut EN (ethylvinylbenzene-divinylbenzene) from Merck, commonly used in liquid–solid-phase extraction (SPE) were evaluated as sorbents for gas-phase sampling followed by thermal desorption and compared to Tenax TA, a reference sorbent in this kind of applications. The three resins were tested against seven volatile organic compounds (VOCs): 1-octene, ethylbenzene, ( p-, m-, o-)xylenes, styrene and 1,4-dichlorobenzene. Elution curves for all compounds were determined at temperatures from 120 to 180 °C, and from such curves, different parameters, such as retention factor ( k), distribution coefficient ( K), height equivalent to a theoretical plate ( H), asymmetry factor ( F a) and breakthrough volume ( V B) were calculated and extrapolated at room (25 °C) and desorption (220 °C) temperatures in order to estimate breakthrough and elution volumes. In average, retention in LiChrolut EN is 10 and 200 times stronger than in Bond Elut ENV and Tenax TA, respectively, but its chromatographic behavior is rather poor giving quite asymmetric elution profiles ( F a > 1.8 at 120 °C). Bond Elut ENV exhibited the best chromatographic behavior, with H values two or five times lower than those of LiChrolut EN or Tenax TA. An additional advantage of the new sorbents is that retention decreases with T much faster than it does in Tenax (8 or 20 times for Bond Elut ENV or LiChrolut EN). Modeling has finally shown that beds with 60–80 (for Bond Elut ENV) or 300–400 (for LiChrolut EN) times less of sorbent have the same retention properties than standard Tenax TA tubes and similar (LiChrolut EN) or five to six times smaller (Bond Elut ENV) elution volumes. These predictions have been experimentally confirmed.

Enhanced removal of p-chloroaniline from aqueous solution by a carboxylated polymeric sorbent

In the present study a carboxylated styrene-divinylbenzene (St-DVB) polymeric sorbent (CSPS) was prepared for enhanced removal of p-chloroaniline from aqueous solution. A commercial styrene-divinylbenzene polymeric sorbent Amberlite XAD-4 was selected as the reference sorbent to evaluate the performance of CSPS. Characterization of CSPS was determined by infrared spectroscopy and pore size distribution. A p-chloroaniline sorption enhancement on CSPS at capacity about twice of Amberlite XAD-4 was observed, which was mainly attributed to the carboxyl group added on the polymeric matrix. Different pH-dependent sorption property of p-chloroaniline onto XAD-4 and CSPS was observed partly due to the role of carboxyl group. Sorption isotherm of p-chloroaniline on CSPS could be represented by Freundlich model reasonably, and that on XAD-4 was more suitable for Langmuir model. Kinetic studies demonstrated that the uptake of p-chloroaniline on CSPS and XAD-4 followed the pseudo-second order model. Moreover, breakthrough curves on CSPS further demonstrated its better performance towards p-chloroaniline removal from aqueous solution. Complete regeneration of the spent sorbent CSPS was achieved by dilute hydrochloric acid for its repeated use, implying its potential application in associated chemical wastewater treatments.

Optimisation of sorbent trapping and thermal desorption–gas chromatography–mass spectrometric conditions for sampling and analysis of hydrogen cyanide in air

Among the chemicals belonging to the schedules of the Chemical Weapons Convention (CWC), sampling and analysis of highly volatile compounds such as hydrogen cyanide (HCN) require special consideration. The latter is present in numerous old chemical weapons that are stockpiled awaiting destruction in Northeastern France: thus, sampling on stockpile area and subsequent verification of HCN levels is compulsory to ensure safety of workers on these areas. The ability of several commercial sorbents to trap hydrogen cyanide at various concentration levels and in various humidity conditions, was evaluated. Furthermore, thermal desorption of the corresponding samples, followed by analysis by gas chromatography-mass spectrometry was also optimised. Carbosieve S-III, a molecular sieve possessing a very high specific area, proved the most efficient sorbent for HCN sampling in all conditions tested. Conversely, the presented results show that Tenax, albeit generally considered as the reference sorbent for air monitoring and analysis of CWC-related chemicals, is not suitable for HCN trapping.