Porous Adsorbents Research Articles

Physicochemical synergistic adsorption of CO2 by PEI‐impregnated hierarchical porous polymers

AbstractAmine‐functionalized porous polymers have been considered as a prominent chemical adsorption material for carbon capture and storage (CCS) process, because of their large adsorption capacity and high selectivity. By comparison, the low energy‐consumption for desorption and high recyclability are the advantages of the physical adsorption approach. In this work, an amine‐functionalized hierarchical porous polymer was prepared by HIPE (high internal phase emulsions) template and amine impregnation strategy, and applied as CO2 adsorbent to realize chemical adsorption and physical adsorption simultaneously. First, a hierarchical porous matrix of poly(styrene‐glycidyl methacrylate) was prepared by the HIPE method. The formed meso/micropores in the typical porous polymer matrix could attract CO2 molecules, where the physical adsorption was achieved. Subsequently, PEI (polyethyleneimine) was impregnated into the porous polymer with abundant macropores, and the numerous of amino groups provided the reaction sites, where the chemical adsorption was achieved. As a result, an effective CO2 adsorption material was obtained via controlling the porous structure by changing the volume fraction of dispersive phase, impregnation condition and amine loading. Aided by the chemical adsorption of amino groups, the CO2 adsorption capacity of the obtained adsorbent reached 3.029 mmol/g. Moreover, the CO2 adsorption thermodynamics confirmed the physicochemical synergistic adsorption, and then the Qst reduced to 31–42 kJ/mol and a good cyclic stability was obtained. As conclusion, the porous adsorbent showed a good industrial application prospect. © 2024 Society of Chemical Industry and John Wiley & Sons, Ltd.

One-pot synthesis of highly porous nitrogen and oxygen codoped carbons for solar-driven atmosphere water harvesting

There is significant interest in developing high-performance adsorbents that can harvest water from atmospheric air powered by sunlight. However, The inherent hydrophobicity of porous carbon limits water harvesting capacity. Herein, we report a new class of activated porous carbons (PAK-21) with high water adsorption capacity at moderate to high humidity by solid-phase polymerization of terephthalaldehyde and 2,6-diaminopurine in the presence of KOH under an argon atmosphere at 150 °C for 2 h, and then activated at a high temperature of 700 °C for 1 h. The water harvesting performance surpasses the most common MOFs and porous carbon adsorbents, which benefit from rich surface heterogeneity and highly porous structure. PAK-21 also exhibits fast solar-driven desorption kinetics, ascribing to rapid photothermal responsiveness, hierarchical porosity, and suitable hydrophilicity. Besides, twenty-one adsorption-desorption cycles have been performed to demonstrate its easy regeneration and long-term cyclability. This may pave a new way to modulate the surface functionality and microporous/mesoporous engineering of carbon adsorbents for high-performance solar-driven AWH.

Green Fabrication of Porous Adsorbent with Structural Evolution of Mixed-Dimension Attapulgite Clay for Efficient Removal of Methylene Blue and Sustainable Utilization

Green Fabrication of Porous Adsorbent with Structural Evolution of Mixed-Dimension Attapulgite Clay for Efficient Removal of Methylene Blue and Sustainable Utilization

Preparation of ionic liquid modified graphene composites and their adsorption mechanism of arsenic (V) in aqueous solution.

Graphene (GR) is a new type of carbon-based material that combines many excellent properties. In order to give full play to the excellent properties of graphene and expand its application scope, this study used ionic liquid SbF6 to modify it and successfully prepared ionic liquid modified graphene composites (H/GR), and studied its adsorption mechanism of arsenic in aqueous solution. By investigating the effects of reaction temperature, reaction time, pH, adsorbent (H/GR) dosage, and humic acid concentration on the removal rate of arsenic in aqueous solution, the experimental results showed that when the reaction temperature was 30°C, reaction time was 1h, pH was 6, H/GR dosage was 0.1g·L-1, and humic acid (HA) concentration was 10mg·L-1, the best arsenic removal effect was achieved with a maximum. The removal rate was 99.4%. The equilibrium adsorption capacity was well modeled by the Langmuir, Freundlich, and Tenkin models at 30°C. The Langmuir adsorption isotherm was the most consistent, with a calculated maximum value of 137.95 mg·g-1, which is higher than most adsorbents in the field. In addition, it was determined that the graphene surface was indeed immobilized with the ionic liquid [Hmim]SbF6 by SEM mapping and EDS energy spectroscopy observation, and the adsorption isotherms and pore size distribution maps of graphene before and after the loading of the ionic liquid were analyzed by BET, which further confirmed a significant increase in the microporosity and porosity of the modified H/GR, and furthermore, it was demonstrated that the arsenic ions are chemically bonded with and indeed adsorbed on the surface of the H/GR by FT-IR and XPS characterization analyses. The results of all experimental data studies indicate that the main mechanism of As(V) removal from water by H/GR is due to electrostatic adsorption, ion exchange, and complexation between the modified graphene itself and the ionic liquid [Hmim]SbF6 itself.

Reservoir characteristics and formation model of Upper Carboniferous bauxite series in eastern Ordos Basin, NW China

Through core observation, thin section identification, X-ray diffraction analysis, scanning electron microscopy, and low-temperature nitrogen adsorption and isothermal adsorption experiments, the lithology and pore characteristics of the Upper Carboniferous bauxite series in eastern Ordos Basin were analyzed to reveal the formation and evolution process of the bauxite reservoirs. A petrological nomenclature and classification scheme for bauxitic rocks based on three units (aluminum hydroxides, iron minerals and clay minerals) is proposed. It is found that bauxitic mudstone is in the form of dense massive and clastic structures, while the (clayey) bauxite is of dense massive, pisolite, oolite, porous soil and clastic structures. Both bauxitic mudstone and bauxite reservoirs develop dissolution pores, intercrystalline pores, and microfractures as the dominant gas storage space, with the porosity less than 10% and mesopores in dominance. The bauxite series in the North China Craton can be divided into five sections, i.e., ferrilite (Shanxi-style iron ore, section A), bauxitic mudstone (section B), bauxite (section C), bauxite mudstone (debris-containing, section D) and dark mudstone-coal section (section E). The burrow/funnel filling, lenticular, layered/massive bauxite deposits occur separately in the karst platforms, gentle slopes and low-lying areas. The karst platforms and gentle slopes are conducive to surface water leaching, with strong karstification, well-developed pores, large reservoir thickness and good physical properties, but poor strata continuity. The low-lying areas have poor physical properties but relatively continuous and stable reservoirs. The gas enrichment in bauxites is jointly controlled by source rock, reservoir rock and fractures. This recognition provides geological basis for the exploration and development of natural gas in the Upper Carboniferous in the study area and similar bauxite systems.

Effect of ultrasound irradiation on the growth of colloidal particles in resorcinol–formaldehyde solutions as precursors to porous adsorbents

Effect of ultrasound irradiation on the growth of colloidal particles in resorcinol–formaldehyde solutions as precursors to porous adsorbents

One Scalable and Stable Metal-Organic Framework for Efficient Separation of CH4/N2 Mixture.

Separating CH4 from coal bed methane is of great importance but challenging. Adsorption-based separation often suffers from low selectivity, poor stability, and difficulty to scale up. Herein, a stable and scalable metal-organic framework [MOF, CoNi(pyz-NH2)] with multiple CH4 binding sites was reported to efficiently separate the CH4/N2 mixture. Due to its suitable pore size and multiple CH4 binding sites, it exhibits excellent CH4/N2 selectivity (16.5) and CH4 uptake (35.9 cm3/g) at 273 K and 1 bar, which is comparable to that of the state-of-the-art MOFs. Theoretical calculations reveal that the high density of open metal sites and polar functional groups in the pores provide strong affinity to CH4 than to N2. Moreover, CoNi(pyz-NH2) displays excellent structural stability and can be scale-up synthesized (22.7 g). This work not only provides an excellent adsorbent but also provides important inspiration for the future design and preparation of porous adsorbents for separations.

Preparation of an activated adsorbent from water treatment plant sludge for phosphate removal from wastewater: optimization, characterization, isotherm, and kinetics studies

Abstract Purifying water for diverse uses is vital, but concerns lie with the sustainability and accessibility of purification materials. As such, this study converted readily available water treatment plant sludge (WTPS) into activated adsorbent for phosphate removal in wastewater. WTPS was activated via thermal activation at 300 °C temperature and chemical activation processes of 3 M acid concentration, 4 h activation time, and 75 °C activation temperature, and then characterized using Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM), Fourier transform infrared, elemental analyzer, and differential scanning calorimetry. SEM and BET analyses revealed a highly porous adsorbent (279.2 m2/g) for efficient adsorption. On top of the activation process, preliminary experiments and numerical optimization using response surface methodology (RSM) were designed and conducted. Through optimizing conditions, it was found that 70 min of contact time, pH 3, 3 g/L adsorbent dose, and 30 mg/L initial phosphate concentration as optimal, yielding 83% removal efficiency. Furthermore, adsorption kinetics and isotherm models were examined and the second-order kinetics and Langmuir isotherm models indicated best fit. Notably, the activated sludge could be regenerated for three cycles before efficiency dropped below 70%. Thus, activated WTPS presents a promising, sustainable, and readily available adsorbent for phosphate removal in wastewater treatment.

Insight into the adsorption behaviors and bioaccessibility of three altered microplastics through three types of advanced oxidation processes

Advanced oxidation processes (AOPs) can significantly alter the structural properties, environmental behaviors and human exposure level of microplastics in aquatic environments. Three typical microplastics (Polyethylene (PE), polypropylene (PP), and polystyrene (PS)) and three AOPs (Heat-K2S2O8 (PDS), UV-H2O2, UV-peracetic acid (PAA)) were adopted to simulate the process when microplastics exposed to the sewage disposal system. 2-Nitrofluorene (2-NFlu) adsorption experiments found the equilibrium time decreased to 24 hours and the capacity increased up to 610 μg g−1, which means the adsorption efficiency has been greatly improved. The fitting results indicate the adsorption mechanism shifted from the partition dominant on pristine microplastic to the physical adsorption (pore filling) dominant. The alteration of specific surface area (21 to 152 m2 g−1), pore volume (0.003 to 0.148 cm3 g−1) and the particle size (123 to 16 μm) of microplastics after AOPs are implying the improvement for pore filling. Besides, the investigation of bioaccessibility is more complex, AOPs alter microplastic with more oxygen-containing functional groups and lower hydrophobicity detected by XPS and water contact angle, those modifications have increased the sorption concentration, especially in the human intestinal tract. Therefore, this indicates the actual exposure of organic compounds loaded in microplastic may be higher than in the pristine microplastic. This study can help to assess the human health risk of microplastic pollution in actual environments.

Probing Structural Transformations and Degradation Mechanisms by Direct Observation in SIFSIX-3-Ni for Direct Air Capture.

Despite global efforts to reduce carbon dioxide (CO2) emissions, continued industrialization threatens to exacerbate climate change. This work investigates methods to capture CO2, with a focus on the SIFSIX-3-Ni metal-organic framework (MOF) as a direct air capture (DAC) sorbent. SIFSIX-3-Ni exhibits promising CO2 adsorption properties but suffers from degradation processes under accelerated aging, which are akin to column regeneration conditions. Herein, we have grown the largest SIFSIX-3-Ni single crystals to date, facilitating single crystal X-ray diffraction analyses that enabled direct observation of the H2O and CO2 dynamics through adsorption and desorption. In addition, a novel space group (I4/mcm) for the SIFSIX-3-Ni is identified, which provided insights into structural transitions within the framework and elucidated water's role in degrading CO2 uptake performance as the material ages. In situ X-ray scattering methods revealed long-range and local structural transformations associated with CO2 adsorption in the framework pores as well as a temperature-dependent desorption mechanism. Pair distribution function analysis revealed a partial decomposition to form nonporous single-layer nanosheets of edge-sharing nickel oxide octahedra upon aging. The formation of these nanosheets is irreversible and reduces the amount of active material for the CO2 sorption. These findings provide crucial insights for the development of efficient and stable DAC sorbents, effectively reducing greenhouse gases, and suggest avenues for enhancing MOF stability under practical DAC conditions.

Clamparene: Synthesis, Structure, and Its Application in Spontaneous Formation of 3D Porous Crystals.

Macrocyclic arenes have emerged as pivotal scaffolds in supramolecular chemistry. Despite their significant contributions to molecular recognition and diverse applications, challenges persist in the development of macrocyclic arene-based crystalline materials, particularly in achieving porosity and addressing limitations in adsorption efficiency resulting from the small cavity sizes of existing macrocyclic arenes. In this study, we present the design and synthesis of a novel macrocyclic arene, clamparene (CLP), featuring a rigid backbone, easy synthesis, and a sizable cavity. CLP self-assembles into one-dimensional sub-nanotubes that further organize into a three-dimensional porous framework in the solid state. The crystalline solid of CLP exhibits potential as a porous crystalline adsorbent for various benzene-based contaminants with rapid adsorption kinetics, large uptake amounts, and good recyclability.

Acidified groundnut cake for enhanced bio adsorption of anionic textile dye Reactive Red 195

This study focuses on the improvement of bioremediation of textile dye Reactive Red 195 using agro-industrial waste, groundnut oil cake (GNOC) obtained after oil-pressing. The treatment of GNOC with 1 N H2SO4 had resulted in physiochemical changes on the insoluble porous adsorbent, which improved their adsorption efficiency. The dye removal efficiency increased from 55% to 94% on acidification of GNOC. The raw groundnut oil cake (RGNOC) and acid-treated groundnut oil cake (AGNOC) were characterized using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction, and zeta potential. The rate and efficiency of dye adsorption were examined using adsorption kinetics and isotherm models. The results confirm that acid-treated GNOC eliminates impurities, alter the surface functional groups, and significantly increase porous surface areas of RGNOC. The investigation of key factors such as contact time, initial concentration of dye, static/agitation impact, particle size, and adsorbent dose had significantly influenced adsorption capacity of GNOC. Adsorption of dye fits best into the Langmuir model and equilibrium data of dye on AGNOC was explained by psuedo-second-order reaction with maximum adsorption capacity of 12.65 mg/g. This emphasis AGNOC has a very excellent potential to remove the textile dye Reactive Red dye from industrial effluent.

Removal of low concentration of perchlorate from natural water by quaternized chitosan sphere (CGQS): Efficiency and mechanism research

In this study, an innovative approach utilizing betaine as a raw material was employed to effectively modify the surface of chitosan with quaternary ammonium groups. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectrometer (FTIR) characterization showed that the quaternary ammonium groups on betaine were successfully loaded on the chitosan surface. The effects of dosage, pH, initial perchlorate concentration, temperature and co-existing anions on the removal efficiency of perchlorate were investigated. The saturated adsorption capacity of CGQS was 35.41 mg/g under natural condition. The impact of initial perchlorate concentrations and column flow rates on the column adsorption experiments were investigated, as well as natural water tests. Sterilizing performance experiments of CGQS were carried out innovatively. Under the condition of initial concentration of 0.5 mg/L, 9 BV/h (bed volume per hour), the effluent natural water was up to standard (≤0.07 mg/L) with a treatment capacity of 210 BV/g, and the sterilizing rate of CGQS was up to 97.02%. The proposed adsorption mechanisms involved surface pore adsorption, electrostatic adsorption of quaternary ammonium groups, and ion exchange between chloride and perchlorate ions. The CGQS prepared in this work had great potential for treating trace perchlorate contamination in natural water.

The potential capability of treated perlite for removal of penta chloro nitrobenzene

Abstract Perlite is an example of clayey type geologic mineral. Perlite is a cheap and abundant adsorbent and it can be used for versatile applications in food, pharmacy and chemistry industries. Perlite was chosen for the removal of penta chloro nitrobenzene (PCNB) pesticide. This pesticide is used for the control of fungi species in farming commonly. Adsorbent surface area and pore volumes were determined as 288.15 m2/g and 78.24 cm3/g (BET method). The characteristics of the adsorbent were furnished by evaluating the SEM and FTIR images. The adsorption equilibrium was reached in 80 min. Initial adsorbate concentration and pH of the medium were also investigated from this point of view. The experimental data were evaluated with proper isotherm models such as Langmuir, Freundlich and Halsey. Langmuir and Freundlich isotherms give the best results. Monolayer capacity was found as 238.095 mg/g. The kinetic mechanisms of the phenomon was analyzed by employing the pseudo first and second order models. Pseudo first order kinetic results were better than the second one with the higher regression coefficients and close experimental and calculated uptake values. Those values were found as 0.615 and 0.6587 mg/g for 1 μg/mL aqueous pesticide solution. Activation energy was found approximately 5094 J/mol which was shown a physisorption mechanism of the adsorption. Activation energy is also employed for interpreting the sticking probability factor. The thermodynamic of adsorption were also evaluated and found as −2.385 J/g at the room temperature. The negative Gibbs energy shows the feasibility and spontaneous nature of PCNB removal on perlite.

Amorphization of natural ilmenite for production of a potential porous adsorbent towards crystal violet dye removal from aqueous environment

In this work, amorphization of ilmenite mineral was obtained by solid NaOH alkaline fusion at 550 oC. The material was tested as an adsorbent towards crystal violet (CV) removal from an aqueous matrix. Several techniques, such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), and N2 adsorption/desorption isotherms (BET) were used to characterize the material, and revealed an amorphous structure with superior surface area (88.84 m² g-1) compared to raw sample (5.90 m² g-1). These intrinsic characteristics resulted in a satisfactory adsorption capacity, reaching 133 mg g-1 at a temperature of 328 K. Kinetic studies on the adsorption process indicated that the equilibrium condition was reached within 50 min, being well represented by the Avrami model. The thermodynamic study revealed that the CV adsorption onto ilmenite is spontaneous, endothermic, and favorable. The amorphized material maintains the same adsorptive performance after three reuse cycles. Therefore, the amorphization route proposed in this work was satisfactory for producing a porous adsorbent from the ilmenite mineral, with potential use for wastewater treatment.

New discovery of extremely high adsorption of environmental DNA on cuttlefish bone pyrolysis derivative via large pore structure and carbon film

Environmental DNA (eDNA) carrying antibiotic resistance gene (ARG) has attracted a great deal of attention because of its threat to the ecology and human health. Traditional porous adsorbents, such as microporous biochar and natural mineral, are low-effective in removing eDNA from sewage. This study used cuttlefish-bone (CB), a fishery waste, as an anticipated material to adsorb a model compound of eDNA from herring sperm (hsDNA). An interesting result was firstly observed that extremely high DNA adsorption on cuttlefish-bone pyrolysis derivative (CCB) was up to 88.7 mg/g, 3–10 folds higher than that of most other adsorbents in the existing literatures, which was attributed to the carbon film and large pores. To achieve an adsorption rate of 75 %, hsDNA adsorption took 96 h on CB but only 24 h on CCB, which was attributed to the fluent channel of CCB. The ligand exchange, Ca2+ bridge and π-π interaction were identified as dominated adsorption mechanisms, based on FTIR and phosphate competition experiments. This study exploited a high-efficient, environmentally friendly, and low-cost adsorbent for treating ARG-contaminated soil and water.

Elimination of Pharmaceutical Compounds from Aqueous Solution through Novel Functionalized Pitch-Based Porous Adsorbents: Kinetic, Isotherm, Thermodynamic Studies and Mechanism Analysis.

The long-term presence of PPCPs in the aqueous environment poses a potentially significant threat to human life and physical health and the safety of the water environment. In our previous work, we investigated low-cost pitch-based HCP adsorbents with an excellent adsorption capacity and magnetic responsiveness through a simple one-step Friedel-Crafts reaction. In this work, we further investigated the adsorption behavior of the prepared pitch-based adsorbents onto three PPCP molecules (DFS, AMP, and antipyrine) in detail. The maximum adsorption capacity of P-MPHCP for DFS was 444.93 mg g-1. The adsorption equilibrium and kinetic processes were well described through the Langmuir model and the proposed secondary kinetic model. The negative changes in Gibbs free energy and enthalpy reflected that the adsorption of HCPs onto PPCPs was a spontaneous exothermic process. The recoverability results showed that the adsorption of MPHCP and P-MPHCP onto DFS remained above 95% after 10 adsorption-desorption cycles. The present work further demonstrates that these pitch-based adsorbents can be used for multiple applications, which have a very extensive practical application prospect.

Leveraging Diffusion Kinetics to Reverse Propane/Propylene Adsorption in Zeolitic Imidazolate Framework-8.

The separation challenge posed by propylene/propane mixtures arises from their nearly identical molecular sizes and physicochemical properties. Metal-organic frameworks (MOFs) have demonstrated potential in addressing this challenge through the precision tailoring of pore sizes and surface chemistry. However, introducing modifications at the molecular level remains a considerable hurdle. This work presents an approach to reversibly tune the propylene/propane adsorption preference in zeolitic imidazolate framework-8 (ZIF-8) by manipulating the particle size and gas flow rate. Systematically increasing the ZIF-8 crystals from 9 to 224 μm restricts propane diffusion, thereby reversing its preferential adsorption over propylene. Furthermore, raising the gas flow rate of mixed propylene/propane shifts the rate-determining breakthrough step from thermodynamic equilibrium to kinetics, again reversing the adsorption preference in a particular ZIF-8 sample. We propose "dynamic selectivity (Sd(t))" as a concept that incorporates both thermodynamic and kinetic factors to elucidate these unexpected findings. Moreover, the driving force equation, grounded on the concept of Sd(t), has improved the precision and stability of the computational simulation for fixed-bed adsorption processes. This work underscores the potential of diffusion-based modulation, implemented through manageable external changes, as a viable strategy to optimize separation performance in porous adsorbent materials.

Development of amine-pillar[5]arene modified porous silica for CO2 adsorption, and CO2/CH4, CO2/N2 separation

Solid amine adsorbents with macrocycle are emerging as promising candidate for efficient CO2 adsorption due to their abundance of active sites, inherent cavities, and ease of encapsulation. Herein, a novel amine­pillar[5]arene functionalized porous silica adsorbent (EDA-P5S) was synthesized to investigate CO2 adsorption, the adsorption process of CO2 was executed using a fixed-bed (FD-2000) reactor. The dynamic adsorption capacities of EDA-P5S were 7.62 (0.46) and 7.72 (0.41) mmol/g for CO2/CH4 and CO2/N2, respectively, both the gas mixtures showed high separation selectivity. Subsequent research indicated that its porous structure facilitated the dispersion of amines and increased the exposure of active sites, thereby enhancing CO2 adsorption. Furthermore, the in-situ FTIR, 13C NMR spectra, and computational results collectively confirmed that the CO2 adsorption mechanism on EDA-P5S was consistent with the zwitterion mechanism. This work may provide a useful strategy for CO2 solid amine porous adsorbents to obtain high-purity CO2 by selectively removing CO2 from CH4 or N2.

Design of Porous Carbon Adsorbents from Ethylene Glycol for Selective CO2 Adsorption

AbstractThe production of affordable advanced porous materials is necessary for applications involving the capture of CO2. This study aimed to investigate the use of inexpensive liquid precursors in the production of CO2 sorbents. Porous precursors were produced through solvothermal processing of ethylene glycol via dehydration using sulfuric acid. Various pyrolysis and activation techniques were utilized on a carbon precursor to examine how different heat treatment methods affect surface chemical properties and the behavior of static CO2 adsorption at temperatures of 273 K, 298 K, and 313 K. Out of the studied carbons, the urea‐treated pyrolyzed sample exhibited a CO2 uptake capacity of 0.93 mmol g−1 at a pressure of 0.15 bar and a temperature of 298 K. This carbon exhibited a remarkable CO2/N2 selectivity of 46, mainly due to its microporosity and a nitrogen content of 8.3 atomic percent. Moreover, the investigation of adsorption and chemical properties unveiled that nonoxidized sulfur exhibits favorable effects on CO2 adsorption, particularly at the temperature of 298 K. This study provides evidence that liquid precursors can be effectively employed to generate porous doped functional carbons or precursors using solvothermal conditions.