Sorbent Selection Research Articles

Experimental research of composite solid sorbents for fresh water production driven by solar energy

Solid sorption air-to-water apparatus driven by solar energy has a great potential for the advantages of being widespread application and efficient in the remote areas with deficit of natural fresh water and electricity supply. Two most important difficulties of the air-to-water apparatus are selection of solid sorbents and the reasonable way for filling the sorbent in the bed. This research focuses on the development of novel composite solid sorbents with high cycle sorption quantity, low desorption temperature, and optimal structure design for filling in the sorption bed. Eight sorbents composite with four matrixes and two salts are studied and compared, and the consolidating Active Carbon Felt (ACF) with LiCl shows the best water uptake performance, and the largest desorption quantity (0.65g/g) at 77°C and 20% relative humidity. Meanwhile, textural properties of consolidated matrixes and composited sorbents are tested by ASAP 2020. Otherwise, the Dubinin–Astakhov (DA) equation based on the Polanyi theory were fitted with the experimental data for the sorption properties of consolidating ACF with CaCl2.

Thermodynamic assessment of the swing adsorption reactor cluster (SARC) concept for post-combustion CO2 capture

This paper presents the novel swing adsorption reactor cluster (SARC) for post combustion CO2 capture. The SARC concept consists of a cluster of bubbling/turbulent multistage fluidized bed reactors which dynamically cycle a solid sorbent between carbonation and regeneration. A synergistic combination of vacuum swing through a vacuum pump and temperature swing through a heat pump is employed to ensure high process efficiency. The base case SARC configuration imposed an energy penalty of 9.64%-points on a conventional coal-fired power plant, which is in line with advanced amine-based absorption processes. Sensitivity analyses showed that significant potential for further improvements (∼1.5%-points) exist through mechanisms such as an increase in the number of reactor stages, further reductions in regeneration pressure and optimization of the cycle length. Additional efficiency improvements can also be traded for increased reactor footprint. However, future sorbent material selection studies especially for this novel process hold the largest potential for further efficiency improvements. The SARC concept is well suited to retrofitting purposes due to limited integration with the steam cycle, and the simple standalone reactor design will simplify future scale-up efforts. The concept is therefore recommended for further study.

Using thermal analysis combined with IR fourier-transform spectroscopy for study and selection of catalysts for removal of organic impurities from water

The suitability of the methods of simultaneous thermal analysis combined with Fourier-transform IR spectroscopy for express investigation and selection of catalysts and sorbents has been demonstrated. Through case studies on reacting aqueous ethanol with carbon and carbon fiber it has been shown that, in the 20–100°C temperature range, ethanol is adsorbed on the carbon material surface, and in the 100–200°C range, it is desorbed. The revealed change in the amount of the ethanol desorbed and the carbon dioxide evolution data indicate that, along with ethanol sorption, oxidation of the adsorbed ethanol occurs.

Molecular simulations of MOF adsorbents and membranes for noble gas separations

Molecular simulations were used to examine noble gas separation performances of MOF adsorbents and membranes. Grand canonical Monte Carlo simulations were combined with equilibrium molecular dynamics to compute adsorption and diffusion of Xe/Kr, Xe/Ar and Xe/Rn mixtures in 115 different MOFs. Several adsorbent evaluation metrics such as selectivity, working capacity, sorbent selection parameter, per cent regenerability were computed for each gas separation to identify the most promising MOFs. Relations between adsorption selectivity and structural properties of MOFs were also investigated to provide structure-property relationships that can serve as a guide for future experimental studies to design better adsorbents. Materials with pore sizes of 4.3–6.8Å, surface areas of 150–1000m2/g and porosities of 0.37–0.58 were found to be the best adsorbent candidates for Xe/Kr, Xe/Ar and Xe/Rn separations. Molecular simulations were then used to model MOFs as membranes for these gas separations. Membrane selectivities and gas permeabilities of 115 different MOFs were computed and a large number of MOFs was identified to outperform traditional polymer and zeolite membranes. MOFs with pore limiting diameters in the range of 3.9–5.7Å were found to be the most promising membrane materials with high selectivities and high gas permeabilities. Our results showed that MOFs have the potential to replace traditional adsorbent and membrane materials in noble gas separation processes.

Alkali Metal CO2 Sorbents and the Resulting Metal Carbonates: Potential for Process Intensification of Sorption-Enhanced Steam Reforming.

Sorption-enhanced steam reforming (SESR) is an energy and cost efficient approach to produce hydrogen with high purity. SESR makes it economically feasible to use a wide range of feedstocks for hydrogen production such as methane, ethanol, and biomass. Selection of catalysts and sorbents plays a vital role in SESR. This article reviews the recent research aimed at process intensification by the integration of catalysis and chemisorption functions into a single material. Alkali metal ceramic powders, including Li2ZrO3, Li4SiO4 and Na2ZrO3 display characteristics suitable for capturing CO2 at low concentrations (<15% CO2) and high temperatures (>500 °C), and thus are applicable to precombustion technologies such as SESR, as well as postcombustion capture of CO2 from flue gases. This paper reviews the progress made in improving the operational performance of alkali metal ceramics under conditions that simulate power plant and SESR operation, by adopting new methods of sorbent synthesis and doping with additional elements. The paper also discusses the role of carbonates formed after in situ CO2 chemisorption during a steam reforming process in respect of catalysts for tar cracking.

Improving the Efficiency of Coal-Gasification Combined-Cycle Power Plants by Using Natural Chemisorbent for High-Temperature Desulfurization of the Producer Gas

Test results on the selection and optimization of a natural sorbent for high-temperature desulfurization of gases produced by coal gasification at CCPPs are presented. The optimum sorbent-ferromanganese ore of the Askiz deposit-has a high sulfur sorption capacity and selectivity. Technical solutions for applying this sorbent at CCPPs of different capacity are developed and their efficiency is evaluated

Ranking of MOF Adsorbents for CO2 Separations: A Molecular Simulation Study

Identifying materials that can efficiently separate CO2 from natural gas (CO2/CH4), power-plant flue gas (CO2/N2), and petroleum refinery gas streams (CO2/H2) is crucial. We used molecular simulations to examine the adsorption-based separation performances of MOFs in the separations of CO2/CH4, CO2/N2, and CO2/H2 mixtures under different operating conditions. We first compared the results of our molecular simulations with the experimentally available data for the CO2 adsorption and separation performances of various MOFs. Motivated by the good agreement between simulations and experiments, we extended our simulations to 100 different MOF materials. Several adsorbent evaluation metrics including selectivity, working capacity, adsorption figure of merit, sorbent selection parameter, and percentage regenerability were computed for each MOF and for each gas separation. The rankings of the MOFs based on these metrics were examined in detail to understand which parameters play key roles in assessing the gas sep...

Multi-class method for the determination of nitroimidazoles, nitrofurans, and chloramphenicol in chicken muscle and egg by dispersive-solid phase extraction and ultra-high performance liquid chromatography-tandem mass spectrometry

This study describes the development of a multiresidue method for the efficient identification and quantification of nitroimidazoles, nitrofurans, and chloramphenicol in chicken and egg. After derivatization of nitrofuran metabolites, dispersive-solid phase extraction was used for the extraction of target analytes. An optimization strategy involved the selection of sorbents and extraction solutions for dispersive-solid phase extraction in order to achieve acceptably high recoveries and reduce co-extractives in the final extracts. Analytes were determined by ultra-high performance liquid chromatography-tandem mass spectrometry, in one single injection with a chromatographic run time of 7.5min. Mean recoveries ranged from 86.4% to 116.7% and interday precision was lower than 18%. The limits of quantification were between 0.1 and 0.5μg/kg, which were satisfactory to support surveillance monitoring. Finally, the method was applied to real samples, and metabolite of furazolidone, metronidazole and its metabolite, dimetridazole and its metabolite were detected in both chicken and egg samples.

A sensitive multi-residue method for the determination of 35 micropollutants including pharmaceuticals, iodinated contrast media and pesticides in water

A sensitive, multi-residue method using solid-phase extraction followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) was developed to determine a representative group of 35 analytes, including corrosion inhibitors, pesticides and pharmaceuticals such as analgesic and anti-inflammatory drugs, five iodinated contrast media, β-blockers and some of their metabolites and transformation products in water samples. Few other methods are capable of determining such a broad range of contrast media together with other analytes. We studied the parameters affecting the extraction of the target analytes, including sorbent selection and extraction conditions, their chromatographic separation (mobile phase composition and column) and detection conditions using two ionisation sources: electrospray ionisation (ESI) and atmospheric pressure chemical ionisation (APCI). In order to correct matrix effects, a total of 20 surrogate/internal standards were used. ESI was found to have better sensitivity than APCI. Recoveries ranging from 79 to 134% for tap water and 66 to 144% for surface water were obtained. Intra-day precision, calculated as relative standard deviation, was below 34% for tap water and below 21% for surface water, groundwater and effluent wastewater. Method quantification limits (MQL) were in the low ng L(-1) range, except for the contrast agents iomeprol, amidotrizoic acid and iohexol (22, 25.5 and 17.9ngL(-1), respectively). Finally, the method was applied to the analysis of 56 real water samples as part of the validation procedure. All of the compounds were detected in at least some of the water samples analysed. Graphical Abstract Multi-residue method for the determination of micropollutants including pharmaceuticals, iodinated contrast media and pesticides in waters by LC-MS/MS.

Sorption of chlorophenols on microporous minerals: mechanism and influence of metal cations, solution pH, and humic acid.

Sorption of 2-chlorophenol (2-CP), 2,4-dichlorophenol (2,4-DCP), and 2,4,6-trichlorophenol (2,4,6-TCP) on a range of dealuminated zeolites were investigated to understand the mechanism of their sorption on microporous minerals, while the influence of common metal cations, solution pH, and humic acid was also studied. Sorption of chlorophenols was found to increase with the hydrophobicity of the sorbates and that of the microporous minerals, indicating the important role of hydrophobic interactions, while sorption was also stronger in the micropores of narrower sizes because of greater enhancement of the dispersion interactions. The presence of metal cations could enhance chlorophenol sorption due to the additional electrostatic attraction between metal cations exchanged into the mineral micropores and the chlorophenolates, and this effect was apparent on the mineral sorbent with a high density of surface cations (2.62 sites/nm(2)) in its micropores. Under circum-neutral or acidic conditions, neutral chlorophenol molecules adsorbed into the hydrophobic micropores through displacing the "loosely bound" water molecules, while their sorption was negligible under moderately alkaline conditions due to electrostatic repulsion between the negatively charged zeolite framework and anionic chlorophenolates. The influence of humic acid on sorption of chlorophenols on dealuminated Y zeolites suggests that its molecules did not block the micropores but created a secondary sorption sites by forming a "coating layer" on the external surface of the zeolites. These mechanistic insights could help better understand the interactions of ionizable chlorophenols and metal cations in mineral micropores and guide the selection and design of reusable microporous mineral sorbents for sorptive removal of chlorophenols from aqueous stream.

Enhanced Carbon Dioxide Capture from Landfill Gas Using Bifunctionalized Benzimidazole-Linked Polymers.

Tuning the binding affinity of small gases and their selective uptake by porous adsorbents are vital for effective CO2 removal from gas mixtures for environmental protection and fuel upgrading. In this study, an amine-functionalized benzimidazole-linked polymer (BILP-6-NH2) was synthesized by a combination of pre- and postsynthetic modification techniques in two steps. Presynthetic incorporation of nitro groups resulted in stoichiometric functionalization (1 nitro/phenyl) in addition to noninvasive functionalization, where more than 80% of the surface area maintained compared to BILP-6. Experimental studies presented enhanced CO2 uptake and CO2/CH4 selectivity in BILP-6-NH2 compared to BILP-6, which are governed by the synergetic effect of benzimidazole and amine moieties. DFT calculations were used to understand the interaction modes of CO2 with BILP-6-NH2 and confirmed the efficacy of amine groups. Encouraged by the enhanced uptake and selectivity in BILP-6-NH2, we have evaluated its performance in landfill gas separation under vacuum swing adsorption (VSA) settings, which resulted in very promising working capacity and sorbent selection parameters outperforming most of the best solid adsorbent in the literature.

Development of natural sorbent based micro-solid-phase extraction for determination of phthalate esters in milk samples

In the present study, a natural sorbent based micro-solid phase extraction (μ-SPE) was developed for determination of phthalate esters in milk samples. For the first time, an efficient and cost effective natural material (seed powder of Moringa oleifera) was employed as sorbent in μ-SPE. The sorbent was found to be naturally enriched with variety of functional groups and having a network of interconnected fibers. This method of extraction integrates different steps such as removal of proteins and fatty stuff, extraction and pre-concentration of target analytes into a single step. Thirteen phthalate esters were selected as target compounds for the development and evaluation of method. Some key parameters affecting the extraction efficiency were optimized, including selection of membrane, selection and amount of sorbent, extraction time, desorption solvent, volume of desorption solvent, desorption time and effect of salt addition. Under the optimum conditions, very good linearity was achieved for all the analytes with coefficient of determinations (R2) ranging between 0.9768 and 0.9977. The limits of detection ranged from 0.01 to 1.2 μg L−1. Proposed method showed satisfactory reproducibility with relative standard deviations ranging from 3.6% to 10.2% (n = 7). Finally, the developed method was applied to tetra pack and bottled milk samples for the determination of phthalate esters. The performance of natural sorbent based μ-SPE was better or comparable to the methods reported in the literature.

A novel methodology for assessing the environmental sustainability of ionic liquids used for CO2 capture.

Ionic liquids (ILs) have been proposed as suitable sorbents for CO2 capture because of their high CO2 absorption capacity, thermal stability, negligible vapour pressure and physico-chemical tunability. However, the environmental implications of ILs are currently largely unknown because of a lack of data. The issue is further complicated by their complex chemical structures and numerous precursors for which environmental data are scarce or non-existent. In an attempt to address this issue, this paper presents a new methodology for estimating life cycle environmental impacts of novel ILs, with the aim of aiding synthesis and selection of more sustainable CO2 sorbents. The methodology consists of four main steps: (1) selection of an appropriate IL and synthesis route; (2) construction of a life cycle tree; (3) life cycle assessment; and (4) recommendations for improvements. The application of the methodology is illustrated using trihexyltetradecylphosphonium 1,2,4-triazolide ([P66614][124Triz]), a promising IL for CO2 capture currently under development. Following the above steps, the paper demonstrates how the data obtained from laboratory synthesis of the IL can be scaled up to industrial production to estimate life cycle impacts and identify environmental hotspots. In this particular case, the main hotspots are the precursors used in the synthesis of the IL. Comparison of impacts with monoethanolamine (MEA), currently the most widely-used CO2 sorbent, suggests that [P66614][124Triz] has much higher impacts than MEA, including global warming potential. However, human toxicity potential is significantly higher for MEA. Therefore, the proposed methodology can be used to optimise the design of ILs and to guide selection of more sustainable CO2 sorbents. Although the focus is on ILs, the methodology is generic and can be applied to other chemicals under development.

Aramid as potential solid Sorbent for CO2 capture

The escalating level of green house gases and in particular CO2 emissions is an issue of major concern because of its link to potential climate change. CO2 capture and sequestration (CCS) is a promising strategy to control CO2 emission in the atmosphere. In sorption-based CO2 separation technologies, sorbent selection is very crucial. In order to mitigate the CO2 emissions, solid aramid sorbent was synthesized by a facile one pot polyamidation reaction between melamine and terephthaloyl chloride in 1,4-dioxane as the reaction medium. Aramid was probed using Fourier transform Infrared spectroscopy (FTIR), X-ray diffraction, thermogravimetric analysis, Brunauer-Emmett-Teller surface area and pore size analysis, field emission scanning electron microscopy and CO2 adsorption measurements. CO2 adsorption capacity of aramid was determined at temperatures of 273 and 298 K at a pressure of 1 bar. The polymeric material displayed the highest CO2 uptake equal to 2.01 cm3/g at 273 K relative to 1.46 cm3/g at 298 K and at 1 bar respectively. The results revealed that aramid is capable of capturing CO2, thus acting as a promising CO2 scavenger in severe environment.

Computational screening of MOFs for C2H6/C2H4 and C2H6/CH4 separations

Metal organic frameworks (MOFs) are promising nanoporous materials in gas separation applications due to their tunable pore sizes, large surface areas, high porosities, good thermal and mechanical stabilities. In this study, large-scale computational screening of 278 different MOFs was performed for separation of C2H6/C2H4 and C2H6/CH4 mixtures using molecular simulations. This is the largest number of MOFs screened in the literature for these two gas separations. We first compared simulated gas adsorption data with the experimental measurements to validate the accuracy of our computational approach. Molecular simulations were then used to estimate adsorption selectivity, working capacity and sorbent selection parameter of MOFs for C2H6/C2H4 and C2H6/CH4 separations. Results showed that there is a significant number of MOFs predicted to exhibit significantly higher adsorption selectivities and working capacities compared to zeolites. Membrane selectivities of MOFs that show the highest adsorption selectivities were also calculated and compared with selectivities and gas permeabilities of zeolite and polymer membranes. Results show that MOFs can be strong alternatives to traditional membranes for C2H6/C2H4 separations.

Trends in the control of NOx and SOx combustion emissions: Implications to the design of fluidised bed combustion operations

This paper attempts to review the implications of the sulphur oxides (SOx), nitrogen oxides (NOx) and nitrous oxide (N2O) emissions to the design of fluidised bed combustion (FBC) operations. The review focuses on how the knowledge of SOx and NOx emissions trends can be applied to influence the design of FBC operations. The effects of the emission trends of these noxious gases on the design operations for FBC such as temperature control, nozzle designs, sorbent selection design, air supply and control designs were reviewed. The implications of SOx, N2O and NOx emissions on the design of FBC systems rest primarily on the need to design the operational conditions of the system. The design for the precise location of the fuel feeding ports, secondary air feeding ports, limestone feeding ports and a prescribed size and quantity of sorbents to feed into the system was found to be crucial for reduction of these emissions. The emissions also have an impact on the design of the distributor plate of the system; reduction of the emissions necessitates good fluidisation and well-regulated temperature within the system. The review therefore concludes that there is a close nexus between the design and operation of FBC systems with NOx, N2O and SOx emissions.

Identifying Highly Selective Metal Organic Frameworks for CH4/H2 Separations Using Computational Tools

The large number of metal organic frameworks (MOFs) represents both an opportunity and a challenge for identification of materials exhibiting promising properties in gas separations. We used molecular simulations to screen 250 different MOF structures in order to examine their adsorption-based CH4/H2 separation performances. Adsorption selectivity, working capacity, sorbent selection parameter, and regenerability of MOFs were calculated and compared with those of traditional nanoporous materials. The accuracy of simple models that can predict adsorption selectivity of MOFs based on structural properties of materials was discussed. With the use of molecular dynamics, gas diffusivities were computed in the MOFs which were identified as the top performing materials for adsorption-based CH4/H2 separation. Membrane selectivities of these MOFs were predicted to discuss kinetic separation performances of materials. Results showed that there is a significant number of MOFs that exhibit extraordinarily large adsor...

Removal of VOCs at trace concentration levels from humid air by Microwave Swing Adsorption, kinetics and proper sorbent selection

Microwave Swing Adsorption, MWSA, is already established as an alternative way of heating and regenerating solids efficiently in adsorption operations. When zeolites are used for MWSA applications it becomes necessary to tailor the zeolite properties towards microwave heating while at the same time aiming to obtain the highest adsorption capacity and selectivity. These objectives may in some cases be contradictory. In this paper the adsorption of binary mixtures of n-hexane (500ppm) and water (15,000ppm) in air, together with the regeneration of the sorbents using microwaves is studied for three commercial, faujasite Y type zeolites: NaY, HY and DAY. In the Henry regime for adsorption of low concentrations of n-hexane, the Na exchanged zeolite shows the higher affinity for the n-hexane. However, when the binary mixtures are considered DAY zeolite, with higher Si/Al ratio, is more selective towards the adsorption of the alkane. During microwave heating of zeolites, the water adsorbed, the mobile cations of the zeolite framework and the hydroxyl groups on the surface of the zeolite contribute to the absorption of microwave energy. Both heating and desorption are considerably faster using MW, compared to conventional heating. The DAY zeolite with a Si/Al=40 has been found excellent candidate material for MWSA of n-hexane in binary mixtures with water, since it combines good adsorption capacity and efficient interaction with microwaves.

Mixed-bed affinity chromatography: principles and methods.

Mixed-bed chromatography is far from being a well-established technology within the panoply of bioseparation tools. Composed of an assembly of distinct sorbents that are mixed in a single bed, they have been mostly developed in the last decade for the reduction of dynamic concentration range where they allowed discovering many low-copy proteins within very complex proteomes. Other interesting preparative applications of mixed-bed chromatography have since been developed. In this chapter the basic concepts first and then detailed application recipes are described for (1) the reduction of protein dynamic concentration range, (2) the removal of impurity traces at the last stage of a biopurification process, and (3) the selection and use of sorbents as mixed bed in protein purification.

Highly Selective CO2 Capture by Triazine-Based Benzimidazole-Linked Polymers

Triazine-based benzimidazole-linked polymers (TBILPs), TBILP-1 and TBILP-2, were synthesized by condensation reaction of 2,4,6-tris(4-formylphenyl)-1,3,5-triazine (TFPT) with 1,2,4,5-benzenetetraamine tetrachloride (BTA) and 2,3,6,7,14,15-hexaaminotriptycene (HATT), respectively. The Ar sorption isotherms at 87 K revealed high surface areas for TBILP-1 (330 m2 g–1) and TBILP-2 (1080 m2 g–1). TBILP-2 adsorbed significantly high CO2 (5.19 mmol g–1/228 mg g–1) at 1 bar and 273 K. Initial slope selectivity calculations demonstrated that TBILP-1 has very high selectivity for CO2 over N2 (63) at 298 K, outperforming all triazine-based porous organic polymers reported to date. On the other hand, the larger surface area of TBILP-2 leads to relatively lower selectivity for CO2/N2 (40) and CO2/CH4 (7) at 298 K. TBILPs showed moderate isosteric heats of adsorption for CO2: TBILP-1 (35 kJ mol–1) and TBILP-2 (29 kJ mol–1) enabling high and reversible CO2 uptake at ambient temperature. In addition, TBILPs displayed promising working capacity, regenerability, and sorbent selection parameter values for CO2 capture from gas mixtures under vacuum swing adsorption (VSA) and pressure swing adsorption (PSA) conditions.