Adsorption Of Organic Molecules Research Articles

Competition between fulvic acid and phosphate-mediated surface properties and transport of titanium dioxide nanoparticles in sand porous media

Fulvic acid (FA) is a series of organic macromolecular compounds with many oxygen-containing functional groups and is easy to complex with nanoparticles (NPs) in the environment, thus affecting the stability and mobility of NPs in the water environment. Therefore, it is necessary to investigate the transport behavior of nano titanium dioxide (nTiO2) particles with FA in the presence of phosphate (P). A series of transport experiments were conducted by using nTiO2 suspended in phosphate background electrolyte with and without the addition of FA passing through water-saturated sand columns. The zeta potentials, hydrodynamic radii, and aggregation kinetics were measured, and the extended Derjaguin-Landau-Verwey-Overbeek (DLVO) theory and two-site kinetic attachment model (TSKAM) were employed to explain the underlying mechanism. The experimental results showed that the presence of FA compressed the transport of nTiO2 in phosphate electrolyte due to formation of larger complex via the adsorption of organic FA molecules onto nTiO2, which can strongly compete with phosphate adsorption, leading to reduced electrostatic repulsive forces between nTiO2 and sand. In the absence of FA at low pH (6.0), transport of individual nTiO2 was increased by low phosphate adsorption in response to increased phosphate levels, and then, transport was decreased with the increased number of cations (Na+) from the phosphate (P ≥ 1.0 mM) electrolyte due to the compressed electric double layer. From the goodness-of-fit of the modeling results, the TSKAM provided a good prediction for the retention and transport of nTiO2 in the copresence of FA and phosphate. The compressed transport of nTiO2 in the copresence of FA and phosphate was distinct from the synergistic transport in the copresence of humic acid.

Catalytic behavior of Li-Al-LDH prepared via mechanochemical and co-precipitation routes for cyanoethylation reaction

It was attempted to get Li-LDH-like compounds containing Li+ and Al3+ in the cationic layer by mechanochemical and co-precipitation methods, starting from nitrates as precursor salts, using for the pH-adjustment either NaOH as inorganic alkali or tetra methyl ammonium hydroxide (TMAH) as an organic one. Using Li+, Al3+ and organic alkali (TMAH), a pure LDH phase is obtained only by co-precipitation method whereas by the mechanochemical method a mixture of pure LDH phase and gibbsite is obtained. This is a step forward in the synthesis of Li-Al-LDH, since the pure phase was usually prepared only from LiOH precursor. The physico-chemical properties of the synthesized solids have been determined using XRD, DRIFT, BET, TG-DTA, and the irreversible adsorption of organic molecules with different pKa values. The catalytic tests performed for the 1,4-addition of ethanol yielding 3-ethoxypropionitrile showed that the gibbsite-unpurified samples led to decreased values of conversion, while higher conversion rates were obtained for the pure LDH phase which had an increased basicity. However, for all investigated solids the selectivity to 3-ethoxypropionitrile product is over 99.9 %. A straight correlation between the number of basic sites and their catalytic activity was evidenced.

An efficient method to quantitatively detect competitive adsorption of DNA on single-walled carbon nanotube surfaces

In this study, we quantitatively detected adsorption and desorption of DNA molecules that competed with sodium cholate (SC) molecules on single-walled carbon nanotubes (SWNTs) by fluorescence spectroscopy. In previous studies, competitive adsorption and/or replacement were studied based on techniques such as near-infrared (NIR) absorbance and photoluminescence (PL) spectroscopy of SWNTs. In those studies, adsorption of organic molecules was detected as spectral changes in SWNTs, but not in organic molecules. In this study, we employed fluorescent-labeled DNA (Fc-DNA) to detect competitive adsorption through quenching of fluorescent dyes that were attached to DNA molecules. Through this approach, the adsorption behaviors of DNA molecules could be directly determined. Hence, we found that Fc-DNA molecules adsorbed on SWNT surfaces that were pre-wrapped with SC when the SC concentration was reduced. However, when SC concentrations recovered after three days of incubation, detachment of Fc-DNA molecules was observed. In addition, our method could be applied to evaluate the adsorption of fluorescent dyes on SWNT surfaces instead of DNA molecules. Hence, our method is effective in studying competitive adsorption of organic molecules on SWNT surfaces. The obtained information is complementary to that obtained from NIR spectroscopy of SWNTs.

Role of organic molecules in enabling modern technology

The adsorption of organic molecules on surfaces has played an important role in the development of key technologies available today. These molecules provide unique functionalities and properties to the surface that will not exist otherwise. This article will focus on identifying the role of small organic molecules in applications related to energy, sensing, and electronics. Specifically, the authors explore the use of these molecules in improving biocompatibility, stability, conductivity, and passivation properties of surfaces. The authors aim to provide an understanding of how organic molecules have enabled and promoted modern technologies, and to elucidate the connection that exists between fundamental understanding of molecular adsorption and current applications.

Fabrication of heterocycles-inorganic materials for enhancing corrosion resistance

Abstract Inorganic layers containing magnesium aluminate loaded with N-heterocycles were produced on Mg-3%Al-1%Zn alloy via plasma electrolytic oxidation (PEO) coating followed by organic dip coating. Imidazole (IA) and 2-aminoopyridine (AY) decreased the porosity and microcracks provided an organic coating layer, and thus inhibited magnesium corrosion well in corrosive environment. Organic molecules adsorption may be due to weak interaction between an electron donor from IA or AY having sufficiently low ionization potential and an acceptor, such as the coating surface, having sufficiently high electron affinity or unoccupied molecular orbitals. Quantum chemical parameters such as highest occupied molecular orbital energy (EHOMO), lowest unoccupied molecular orbital energy (ELOMO), and gap energy (∆E), dipole moment (μ), and the fraction of electron (∆N) were calculated using density functional theory. The theoretical and experimental results showed good agreement. Potentiodynamic polarization tests revealed that the inhibition efficiency ηp (%) improved in the following order: PEO coating (99.1%), PEO coating followed by IA (99.4%), and PEO coating followed by AY (99.9%).

Calcareous organic matter coatings sequester siderophores in alkaline soils

Although most studies of organic matter (OM) stabilization in soils have focused on adsorption to aluminosilicate and iron-oxide minerals due to their strong interactions with organic nucleophiles, stabilization within alkaline soils has been empirically correlated with exchangeable Ca. Yet the extent of competing processes within natural soils remains unclear because of inadequate characterization of soil mineralogy and OM distribution within the soil in relation to minerals, particularly in C poor alkaline soils. In this study, we employed bulk and surface-sensitive spectroscopic methods including X-ray diffraction, 57Fe-Mössbauer, and X-ray photoemission spectroscopy (XPS), and transmission electron microscopy (TEM) methods to investigate the minerology and soil organic C and N distribution on individual fine particles within an alkaline soil. Microscopy and XPS analyses demonstrated preferential sorption of Ca-containing OM onto surfaces of Fe-oxides and calcite. This result was unexpected given that the bulk combined amounts of quartz and Fe-containing feldspars of the soil constitute ~90% of total minerals and the surface atomic composition was largely Fe and Al (>10% combined) compared to Ca (4.2%). Soil sorption experiments were conducted with two siderophores, pyoverdine and enterobactin, to evaluate the adsorption of organic molecules with functional groups that strongly and preferentially bind Fe. A greater fraction of pyoverdine was adsorbed compared to enterobactin, which is smaller, less polar, and has a lower aqueous solubility. Using NanoSIMS to map the distribution of isotopically-labeled siderophores, we observed correlations with Ca and Fe, along with strong isotopic dilution with native C, indicating associations with OM coatings rather than with bare mineral surfaces. We propose a mechanism of adsorption by which organics aggregate within alkaline soils via cation bridging, favoring the stabilization of larger molecules with a greater number of nucleophilic functional groups.

Covalent triazine framework with efficient photocatalytic activity in aqueous and solid media

Covalent triazine frameworks (CTFs) have been recently employed for visible light-driven photocatalysis due to their unique optical and electronic properties. However, the usually highly hydrophobic nature of CTFs, which originates from their overall aromatic backbone, leads to limitations of CTFs for applications in aqueous media. In this study, we aim to extend the range of the application media of CTFs and design hybrid material of a CTF and mesoporous silica (SBA-15) for efficient photocatalysis in aqueous medium. A thiophene-containing CTF was directly synthesized in mesopores of SBA-15. Due to the high surface area and the added hydrophilic properties by silica, the hybrid material demonstrated excellent adsorption of organic molecules in water. This leads not only to high photocatalytic performance of the hybrid material for the degradation of organic dyes in water, but also for efficient photocatalysis in solvent-free and solid state. Furthermore, the reusability, stability and easy recovery of the hybrid material offers promising metal-free heterogeneous photocatalyst for broader applications in different reaction media.

Three-Dimensional Mesoporous Covalent Organic Frameworks through Steric Hindrance Engineering.

The development of three-dimensional (3D) covalent organic frameworks (COFs) with large pores and high surface areas is of great importance for various applications. However, it remains a major challenge due to the frequent structural interpenetration and pore collapse after the removal of guest species situated in the pores. Herein, we report for the first time a series of 3D mesoporous COFs through a general method of steric hindrance engineering. By placing methoxy and methyl groups strategically on the monomers, we can obtain non-interpenetrated 3D COFs of diamondoid structures with permanent mesopores (up to 26.5 Å) and high surface areas (>3000 m2 g-1), which are far superior to those of reported conventional COFs with the same topology. This work thus opens a new avenue to create 3D large-pore COFs for potential applications in adsorption and separation of large inorganic, organic, and biological molecules.

Interesting molecule adsorption strategy induced energy band tuning: Boosts 43 times photocatalytic Water splitting ability for commercial TiO2

The photogenerated electron reduction ability and light absorption capacity of photocatalysts are crucial to their photocatalytic hydrogen evolution performance. However, rising the conduction band position will widen the band gap and result in a decrease in light absorption efficiency. Herein, an ultra-simple and novel organic molecule adsorption strategy was carried out on the surface of commercial TiO2 to simultaneously increase the reduction ability of photogenerated electrons and light absorption of commercial TiO2. Then the contradiction mentioned above was perfectly solved by such an interesting strategy. The resultant ethylenediamine adsorbed TiO2 exhibits excellent photocatalytic hydrogen evolution rate, which is 43 times higher than that of commercial TiO2. Effectively, the experimental results and DFT theoretical calculations verified that the adsorbed organic molecule can provide electrons for TiO2. The provided electrons enable the conduction band bend upwards, thus enhance the reduction ability of photogenerated electrons and improve the light absorption ability of TiO2. More interestingly, the provided electrons can also promote the separation efficiency of photogenerated carriers by weakening the attraction of photogenerated holes to photogenerated electrons. Therefore, the efficiency of photocatalytic hydrogen production has been greatly improved. This work opens a new research field to enhance the photocatalytic performance by adsorbing various designed organics on the surface of photocatalysts.

Accordion-like Ti3C2Tx MXene nanosheets as a high-performance solid phase microextraction adsorbent for determination of polycyclic aromatic hydrocarbons using GC-MS.

Two dimensional accordion-like Ti3C2Tx MXene, where Tx represents surface termination groups such as -OH, -O-, and -F, is synthesized by selective etching of aluminum layers from Ti3AlC2. This manuscript reports on the adsorption of organic molecules from head-space and aqueous environments containing Ti3C2Tx, a representative of the MXene family. Ti3C2Tx coated by gluing method on a stainless steel wire was successfully utilized as a highly sensitive and stable head-space solid-phase microextraction (SPME) fiber. A SPME method with the MXene as the adsorbent combined with gas chromatography with MS detector was used to determine the polycyclic aromatic hydrocarbons (PAHs) in water samples. Low detection limits in the range of 0.2-5ngL-1, wide linearity and good reproducibility (RSD = 4.6 to 7.4% for n= 6) under the optimized extraction conditions was achieved. Finally, the MXene coated fiber was successfully used for the determination of PAHs in real water samples. The relative recoveries for six PAHs are from 91.3-105.0%, which proved the applicability of the method. Also, melamine was selected as a polar analyte and it has been shown that Ti3C2Tx MXene has good capability in extraction of melamine (the extraction recovery for melamine = 80.1%) from aqueous media by dispersive micro solid-phase extraction. Graphical abstractTwo dimensional accordion-like Ti3C2 MXene was synthesized by selective etching of aluminum layers from Ti3AlC2. Ti3C2 MXene was employed as solid phase microextraction fiber coating for the extraction of polycyclic aromatic hydrocarbons from water samples.

Tuning molecular adsorption in SBA-15-type periodic mesoporous organosilicas by systematic variation of their surface polarity.

Surface polarity plays a key role in controlling molecular adsorption at solid-liquid interfaces, with major implications for reactions and separations. In this study, the chemical composition of periodic mesoporous organosilicas (PMOs) was varied by co-condensing Si(OEt)4 with organodisilanes, to create a homologous series of materials with similar surface areas, pore volumes, and hydroxyl contents. Their relative surface polarities, obtained by measuring the fluorescence of a solvatochromic dye, cover a wide range. In this series of PMO materials, EPR spectra of tethered nitroxide radicals show monotonically decreasing mobility as larger fractions of the radicals interact strongly with increasingly non-polar surfaces. The surface properties of the materials also correlate with their affinities for organic molecules dissolved in various solvents. The most polar PMO has negligible affinity for phenol, p-cresol, or furfural when these molecules are dissolved in water. However, stronger solute-surface interactions and favor adsorption as the surface polarity decreases. The trend is reversed for furfural in benzene, where weaker solvent-surface interactions result in higher adsorption on polar surfaces. In DMSO, furfural adsorption is suppressed due to the similar strengths of solute-surface and solvent-surface interactions. Thus, the polarity of the surface relative to the solvent is critical for molecular adsorption. These findings show how adsorption/desorption can be precisely and systematically tuned by appropriate choice of both solvent and surface, and contribute to a predictive strategy for the design of catalytic and separations processes.

In English

A number of multifunctional composite adsorbents based on hydrated zirconium dioxide has been synthesized. The inorganic ion exchanger contained nanosheets of oxidized graphene (GO), the modifier amount was 0.5–7 mass. %. The composites were investigated with methods of transmission electron microscopy and nitrogen adsorption-desorption, macropores were determined using water as a working liquid. It has been found that increasing of GO content depresses microporosity, but meso- and macroporosity grow. Crushing strength reduces exponentially with increase of total pore volume from 0.49 to 0.62 cm 3 g – 1 . Removal of phenol from water containing also inorganic ions was investigated. Adsorption capacity reaches 0.15–0.85 (phenol), 0.5–0.85 (Ca 2+ and Mg 2+ ), 0.005–0.045 (SO 4 2 – ) mmol g – 1 . When the GO content in the composites is 0.5–2 %, this carbon addition improves adsorption of cations and organic molecules comparing with hydrated zirconium dioxide. Further increase in GO amount causes no sufficient effect on adsorption due to decline of specific surface area of the composites. It has been suggested that the optimal content of the modifier, which provides the maximal growth of adsorption capacity, is 2 %. This composite is obtained in a form of large granules (0.3–0.5 mm), their crushing strength is 9 bar. The material was applied to removal of pesticides (acetomipride, carboxine, epoxyconazole and thiamethoxam) from aqueous multicomponent solution under batch conditions. The residual content of carboxine and epoxyconazole, molecules of which contain benzene rings, is lower than the maximal allowable concentration. No deterioration of pesticide uptake has been found after five cycles of adsorption-regeneration.

Pyridyl anchor-assisted photoresponsiveness of 4-(4-diethylaminophenylazo)pyridine on TiO2 surface

The adsorption of organic molecule on metal oxide surfaces via a suitable anchoring group is important to realize various optoelectronic devices and surface switches. In this manuscript, we investigate the pyridyl anchor-assisted molecular adsorption of an azo dye 4-(4-diethylaminophenylazo)pyridine on TiO2 surface and the photoresponsiveness of the pyridyl anchoring-containing dye/TiO2 interfacial structure. The photoisomerization and photocurrent generation of the azo dye are activated on the TiO2 surface via the pyridyl anchor, which are otherwise unavailable when the azo dye is in the free form in the solution. The first-principles calculations elucidate the detailed nanoscopic structure and optoelectronic properties of the different molecule/TiO2 isomers. This manuscript highlights the potentials of the pyridyl anchor to substitute the traditional carboxylate group for the surface photoisomerization and photoresponsive studies, which can benefit various TiO2-incorporated surface switches and optoelectronic devices.

Disordered mesoporous polymer derived N-doped TiO2/Si-O-C-N nanocomposites with nanoscaled heterojunctions towards enhanced adsorption and harnessing of visible light

The mesoporous N-doped TiO2/Si-O-C-N ceramic nanocomposites has been revealed to be a potential candidate towards visible light photocatalytic degradation of organic dyes. The polymer-derived ceramic route was implemented to prepare uniformly distributed in-situ crystallized N-doped TiO2 nanocrystals in a mesoporous amorphous siliconoxycarbonitride matrix. This chemical approach assisted by the hard template pathway resulted in a high surface area (186 m2/g) nanocomposite exhibiting predominantly mesoporous structure with an average pore size of 11 nm. The two-step process involved pyrolysis of the polyhydridomethyilsiloxane impregnated in CMK3 (hard template) under argon generating SiOC-C composites and functionalizing it with titanium n-tetrabutoxide to be pyrolyzed under ammonia to form the titled nanocomposite. Interestingly, pyrolysis in a reactive ammonia atmosphere resulted in the incorporation of nitrogen in the titania lattice while decomposing the template. The Si-O-C-N support on which N-doped TiO2 exhibited superior adsorption of organic dye molecules and photocatalytically active in the visible wavelength. The nanoscaled heterojunctions reduced the recombination rate and the presence of superoxide anions/hydroxyl radicals was found to be responsible for the dye degradation.

The Impact of Salinity on the Interfacial Structuring of an Aromatic Acid at the Calcite/Brine Interface: An Atomistic View on Low Salinity Effect.

This study aims to elucidate the impact of salinity on the interactions governing the adsorption of polar aromatic oil compounds onto calcite. To this end, molecular dynamics simulations were employed to assess adsorption of a model polar organic molecule (deprotonated benzoic acid, benzoate) on the calcite surface in NaCl brines of different concentration levels, namely, deionized water (DW), low-salinity water (LS, 5000 ppm), and sea water (SW; 45,000 ppm). Calcite was found to be completely covered by several well-ordered water layers. The top hydration layer is very compact and prevents direct adsorption of benzoates onto the substrate. Instead, Na+ ions form a distinct positively charged layer by adhering on the calcite substrate through inner-sphere complexion mode. Cl- ions mostly lodge on top of the adsorbed sodium cations, forming a negatively charged layer. The distribution of ions at the calcite/brine interface thus exhibits the features of an electrical double layer, composed of a Stern-like positive layer followed by a negative one. The positive charged layer attracts benzoates toward the surface. As such, the sodium ions attached onto the calcite can act as adsorption sites to connect benzoates to the surface. By increasing the salinity, more Na+ ions adsorb onto the calcite surface, and the density of benzoate molecules at the interface is enhanced as a result of more Na+ bridging ions. The monotonic salinity-dependent adsorption of benzoate molecules on calcite offers a mechanism driving additional oil recovery upon injection of diluted brine into subsurface carbonate reservoirs.

Use of Microwave Radiation for Activating Carbon from Rice Husk Using ZnCl2 Activator

Activated carbon is one of the most commonly used adsorbents in a variety of separation processes because it is inexpensive, and also the design and principal of application are quite simple. The ability of activated carbon as an adsorbent is related to its large surface area and pore volume, varying pore structure, and diverse surface reactivity. The use of microwave radiation can further improve the efficiency of activated carbon adsorption. Micro-waves can affect the pore texture and surface of the activated carbon, but rarely do both practitioners and researchers control these variables influencing the relationship between features and performance of biomass-based activated carbon as an adsorbent at the time of manufacture from the initial stage (carbonation) to carbon application active (e.g., adsorption of heavy metals, surfactants, and organic molecules). This study aims to synthesize activated carbon from rice husk, which has the efficiency and capacity of adsorption of heavy metals such as Pb and activator organic molecules used is ZnCl2 30% and microwave radiation. This research has succeeded in making activated carbon using the ZnCl2 activator and microwave radiation. The time and power of microwave radiation that provides the highest efficiency in the carbon activation process for Pb ion adsorbate, were 7 minutes and 800 W. For phenol adsorbate was 5 minutes at 800 W. The highest efficiency time and concentration of adsorption for Pb ion adsorbate were 40 minutes at 60 ppm while for phenol adsorbate were 5 hours at 100 ppm. The adsorption efficiency for Pb cation adsorbate was 99.57%. While for phenol adsorbate is 81.05%. Characterization with FTIR, SEM-EDX, and SAA showed a C-Cl bond, the pores were visible, and an increased surface area of activated carbon was 36.9 times the surface area of carbon and the pores formed were mesoporous.

Use of Microwave Radiation for Activating Carbon from Rice Husk Using ZnCl2 Activator

Activated carbon is one of the most commonly used adsorbents in a variety of separation processes because it is inexpensive, and also the design and principal of application are quite simple. The ability of activated carbon as an adsorbent is related to its large surface area and pore volume, varying pore structure, and diverse surface reactivity. The use of microwave radiation can further improve the efficiency of activated carbon adsorption. Micro-waves can affect the pore texture and surface of the activated carbon, but rarely do both practitioners and researchers control these variables influencing the relationship between features and performance of biomass-based activated carbon as an adsorbent at the time of manufacture from the initial stage (carbonation) to carbon application active (e.g., adsorption of heavy metals, surfactants, and organic molecules). This study aims to synthesize activated carbon from rice husk, which has the efficiency and capacity of adsorption of heavy metals such as Pb and activator organic molecules used is ZnCl2 30% and microwave radiation. This research has succeeded in making activated carbon using the ZnCl2 activator and microwave radiation. The time and power of microwave radiation that provides the highest efficiency in the carbon activation process for Pb ion adsorbate, were 7 minutes and 800 W. For phenol adsorbate was 5 minutes at 800 W. The highest efficiency time and concentration of adsorption for Pb ion adsorbate were 40 minutes at 60 ppm while for phenol adsorbate were 5 hours at 100 ppm. The adsorption efficiency for Pb cation adsorbate was 99.57%. While for phenol adsorbate is 81.05%. Characterization with FTIR, SEM-EDX, and SAA showed a C-Cl bond, the pores were visible, and an increased surface area of activated carbon was 36.9 times the surface area of carbon and the pores formed were mesoporous.

Clay minerals for the removal of pharmaceuticals: Initial investigations of their adsorption properties in real wastewater effluents

The adsorption of pharmaceutical products (PPs) onto kaolinite and raw and sodium-exchanged montmorillonite was investigated in real wastewater effluents (WWE). The important role of the charge state of the PPs in controlling the adsorption extent was highlighted. Whereas cationic PPs were mostly adsorbed through cation exchange, the adsorption of neutral and anionic PPs appeared to be controlled by the nature of compensating inorganic cations and/or the simultaneous adsorption of organic moieties onto clay minerals. In raw WWE, the concentration of PPs is indeed far lower than the concentration of other organic molecules. Among the adsorbents tested, kaolinite displayed the lowest adsorption capacity of both PPs and other organic molecules, compared to raw montmorillonite which presented the highest adsorption capacity. The sodium-exchanged montmorillonite displayed intermediate adsorption properties, highlighting the key role of divalent inorganic cations in the adsorption of non-cationic PPs and other organic molecules. Hence, raw montmorillonite appears to be the most promising adsorbent for further investigations aiming to test the practicability of a clay-based adsorbent for the removal of organic contaminants, such as PPs, in WWE.

Synthesis of MOR Zeolite/Magnetite Composite via Seed Assisted Method.

MOR zeolite is an effective adsorbent for separating organic molecules from various solutions owing to its large windows of 0)65 × 0)70 nm and its relatively high silica-alumina ratio which provides higher hydrophobicity. Fine powdery MOR zeolite is desirable for adsorption of organic molecules considering its larger surface area; however, fine particles are difficult to remove from solutions after treatment. Intensification of magnetic susceptibility through combination with magnetic particles ensure quick and easy removal of fine adsorbents by magnetic force. Meanwhile, seed assisted method is a powerful technique to direct and accelerate zeolite synthesis by adding seed crystals into the precursor sol prior to hydrothermal synthesis. In this work, we selected magnetite as the magnetic particle and propose the hydrothermal synthesis of MOR zeolite/magnetite composite via seed assisted method for the first time. MOR zeolite/magnetite composite with high MOR zeolite crystallinity was obtained by synthesizing for only 6 hours at 463 K when adding seed crystals, while no sign of crystallization was observed even after 24 hours in their absence. In addition, pre-milling of seed crystals together with magnetite was found to be effective to incorporate magnetite into MOR zeolite during crystallization and to decrease the primary crystal size of the crystallized MOR zeolite.

Tannin-derived micro-mesoporous carbons prepared by one-step activation with potassium oxalate and CO2

Micro-mesoporous carbons (MMCs) were successfully prepared using natural polyphenolic compounds, condensed tannins, and glyoxal, a nontoxic aldehyde, in lieu of synthetic phenolic compounds like formaldehyde and resorcinol as carbon precursors. Such MMCs were fabricated by a soft-templating strategy under mild conditions. Porosity development was achieved by varying the amount of potassium oxalate as an in-situ activator coupled with one-step CO2 activation at 700 °C. This strategy allowed for the enhancement of microporosity as well as retention of the uniform mesoporous structure of the carbons. The CO2 uptakes of 5.2 mmol/g at 0 °C and 3.6 mmol/g at 25 °C were achieved at 1 bar pressure for the tannin-derived activated MMC sample with a surface area of 1192 m2/g, a volume of fine micropores (sizes below 1 nm) of 0.33 cm3/g, and a mesopore volume of 0.49 cm3/g. This study opens new opportunities for a facile and green synthesis of MMCs from less toxic precursors with tailored porosity by synergistic effects of chemical and physical activation. The resulting MMCs exhibit the potential applicability not only as CO2 sorbents but also in other environmental applications such as adsorption of organic volatile compounds and dye molecules, which require slightly larger pores.