Fast Adsorption Research Articles

Corals-inspired magnetic absorbents for fast and efficient removal of microplastics in various water sources.

Microplastics (MPs) as the formidable pollutants with high toxicity and difficult degradation may threaten the aquaculture industry and human health, making it highly necessary to develop the effective removal methods. In this article, Fe3O4 nanoparticles (NPs) were initially fabricated with mesoporous structure, but showing undesirable adsorption efficiencies for the adsorption of MPs (lower than 70%). Inspired by the reefs-rebuilding corals acting as the sinks for various marine pollutants like plastic, Fe3O4 NPs were coated further with adhesive polymerized dopamine (PDA) yielding Fe3O4@PDA absorbents. Unexpectedly, it was discovered that the corals-mimicking absorbents so formed could allow for the removal of MPs with dramatically enhanced efficiencies up to 98.5%, which is over about 30% higher than those of bare Fe3O4 NPs. Herein, the PDA shells might conduct the increased adhesion to MPs, presumably through the formation of hydrogen bonding, π-π stacking, and hydrophobic interactions. A fast (within 20 min) and stable adsorption of MPs can also be expected, in addition to the PDA-improved environmental storage of Fe3O4 NPs. Subsequently, the Fe3O4@PDA adsorbents were utilized to remove MPs from different water sources with high efficiencies, including pure water, suburban streams, village rivers, lake water, inner-city moats, and aquaculture water. Such a magnet-recyclable adsorbent may provide a new way for rapid, effective, and low-cost removal of MPs pollutants from various water systems.

Fabrication and characterization of magnetic mesoporous nanoparticles for efficient determination and magnetic separation of sulfonamides in food samples.

A magnetic, mesoporous core/shell structured Fe3O4@SiO2@mSiO2 nanocomposite was synthesized and employed as a magnetic solid phase extraction (MSPE) sorbent for the determination of trace sulfonamides (SAs) in food samples. The synthesized nanocomposite was characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis, X-ray diffraction, N2 sorption analysis and vibrating sample magnetometry. The results showed that Fe3O4@SiO2@mSiO2 possessed a mesoporous structure with a large surface area. Batch experiments were carried out to investigate the adsorption ability for SAs. Fe3O4@SiO2@mSiO2 showed fast kinetics and high adsorption capacity, and the pseudo-second-order model and Langmuir adsorption isotherm are well fitted with the experimental data, indicating that chemical adsorption might be the rate-limiting step. Moreover, the high adsorption capacity can be maintained for at least 8 runs, indicating excellent stability and reusability. The proposed method exhibited good linearity in the range of 0.2-500 μg L-1, the R2 values of all the analytes were greater than 0.99 and the LODs were all lower than 0.2 μg L-1. Furthermore, real food samples were successfully analyzed with Fe3O4@SiO2@mSiO2 and high recoveries varying from 89.7% and 110.6% were obtained with low relative standard deviations ranging from 1.78% to 6.91%. The Fe3O4@SiO2@mSiO2 magnetic nanocomposite is a promising sorbent for the efficient extraction of SAs from complex food samples.

Simultaneous derivatization and exfoliation of a multilayered Ti3C2Tx MXene into amorphous TiO2 nanosheets for stable K-ion storage.

Two-dimensional transition metal compounds (2D TMCs) have been widely reported in the fields of energy storage and conversion, especially in metal-ion storage. However, most of them are crystalline and lack active sites, and this brings about sluggish ion storage kinetics. In addition, TMCs are generally nonconductors or semiconductors, impeding fast electron transfer at high rates. Herein, we propose a facile one-step route to synthesize amorphous 2D TiO2 with a carbon coating (a-2D-TiO2@C) by simultaneous derivatization and exfoliation of a multilayered Ti3C2Tx MXene. The amorphous structure endows 2D TiO2 with abundant active sites for fast ion adsorption and diffusion, while the carbon coating can facilitate electron transport in an electrode. Owing to these intriguing structural and compositional synergies, a-2D-TiO2@C delivers good cycling stability with a long-term capacity retention of 86% after 2000 cycles at 1.0 A g-1 in K-ion storage. When paired with Prussian blue (KPB) cathodes, it exhibits a high full-cell capacity of 50.8 mA h g-1 at 100 mA g-1 after 140 cycles, which demonstrates its great potential in practical applications. This contribution exploits a new approach for the facile synthesis of a-2D-TMCs and their broad applications in energy storage and conversion.

Imine-based covalent organic framework gels for efficient removal of Fe2+ from contaminated water

Aerogels of two imine-based COFs showed fast adsorption uptakes of Fe2+ from contaminated waters. COF-aerogel@Polysulfone composite beads are easily incorporated into water treatment, they are excellent candidates for large-scale preparation.

Novel three-dimensional fibrous covalent organic frameworks constructed via silver amalgam bridging for efficient organic dye adsorption and removal.

The construction of covalent organic frameworks (COFs) with unique structures has great significance in exploring the structure-function relationship and extending their potential applications. Fibrous COFs have demonstrated superior performance in specific application scenarios owing to the distinctive three-dimensional (3D) structure. Herein, we report a facile strategy for the fabrication of 3D COF nanofiber by exploiting silver amalgam as a bridging agent to assemble one-dimensional-extended PA-COF modules into a tubular structure. Dimensions of the obtained 3D COF nanofiber were predicted by DFT calculations, and the nanofiber was endowed with the merits of favorable uniformity and high stability. Due to the enhanced exposure of conjugatable binding sites for dye retention offered by the novel 3D architecture, the PA-COF nanofiber exhibits fast adsorption (within 5 min) and superior adsorption capacity to various organic dyes, e.g., 1717 mg g-1 for methylene blue (MB) and 978.3 mg g-1 for methyl orange (MO). Moreover, the PA-COF nanofiber shows excellent reusability in dye adsorption, which makes it a potential medium for removing dye pollutants from wastewater. This work presents an effective strategy to construct COF materials with unique architecture and potential prospects in the fields of separation and wastewater treatment.

Removal of Methylene Blue by Granitic Residual Soil Supported Nano Zero Valent Iron (Gr-nZVI): Kinetic and Equilibrium Studies

The presence of dyes in water sources that act as contaminants is hazardous to human and animal health. Therefore, this research was conducted on the removal of methylene blue (MB) using granitic residual soil-supported nano zero-valent iron (Gr-nZVI), to examine its potential use as an efficient adsorbent. Batch adsorption experiments were conducted in this study to examine the impact of initial dye concentration, contact time, dosage, pH and temperature effets. Based on the results, it can be inferred that Gr-nZVI (with Kd=0.1 L/g and R2 =1) exhibits superior adsorption of MB at higher metal ion concentrations when compared to granitic residual soil (Gr) (with Kd=0.0588 L/g and R2 =0.9267). The removal percentage of Gr-nZVI was found to be 100%, obtained at 100 mg/L MB ion concentration. Sorption data have been correlated with both Langmuir and Freundlich adsorption models. However, the Langmuir isotherm was the only model that showed a good fit for the adsorption of MB on Gr-nZVI. The mechanistic phases of the process were determined through kinetic energy studies. Kinetic data showed the removal of MB was 100% within 5 min for both Gr-nZVI and Gr. This indicates the very fast adsorption of MB and data followed a pseudo-second order. According to adsorption analysis, Gr demonstrated a higher adsorption capacity for MB removal compared to Gr-nZVI and nZVI. This study also highlights that nZVI does not facilitate MB adsorption, making the composite nZVI unnecessary due to Gr is capable of removing MB on its own.

Preparation of a biochar-lignosulfonate composite material and its adsorption performance for Cu2.

Biochar was prepared using peanut shells as raw materials, and then composite amino-functionalized lignosulfonate was used to prepare a biochar/lignosulfonate adsorbent (BC-CLS). The morphology and structure of BC-CLS were characterized using FT-IR, SEM, zeta potential, and XPS. The adsorption performance of BC-CLS was evaluated by batch adsorption experiments and dynamic adsorption experiments (adsorption column flow adsorption). The results showed that BC-CLS adsorbent exhibited significant adsorption performance for Cu2+, including a short equilibrium time (50 min), fast adsorption rate (11 mg g-1 min-1), and high static saturation adsorption capacity (354 mg g-1). Dynamic adsorption experiments indicated that the maximum adsorption capacity of BC-CLS adsorbent was approximately 280 mg g-1, with a removal rate of over 99% after five cycles, meeting the wastewater discharge standard (less than 1 mg L-1). The results demonstrated that the adsorption capacity of BC-CLS adsorbent for Cu2+ was controlled by multiple adsorption mechanisms, including electrostatic attraction, precipitation, and metal ion complexation. Additionally, under pH = 5 conditions, using a 40 mg per L Cu2+ solution, the adsorption performance of BC-CLS adsorbent remained above 60% after five adsorption-desorption experiments, indicating good cycling stability of BC-CLS adsorbent.

Chemically robust functionalized covalent organic framework for the highly efficient and selective separation of bromine.

Effective sequestration of bromine holds great promise for the chemical industry's safe expansion, environmental preservation, and public health. However, attaining this goal is still challenging due to the serious drawbacks of existing adsorbents such as limited capacity, low retention efficiency, and sluggish uptake kinetics. Herein, we report a strategy-driven systematic study aimed at significantly enhancing multiple host-guest interactions to obtain functionalized covalent-organic frameworks for the efficient sequestration of bromine. Results showed that the presence of specific quantities of selective binding sites of the porous frameworks afford stronger host-guest interactions and therefore higher bromine adsorption capacities. The developed framework exhibits high bromine sorption capacity of up to 5.16 g g-1 in the vapor phase and 8.79 g g-1 in the aqueous phase under static adsorption conditions with fast kinetics, large distribution coefficient (Kd ∼105 mL g-1), high retention efficiency and reusability. Moreover, the adsorbent is able to sequestrate trace bromine (from 13 ppm to below 4 ppm) from aqueous medium with fast adsorption kinetics (86.3% within less than 3 h) and demonstrates the selective extraction of bromine over iodine under both static and dynamic conditions. These results were further utilized to demonstrate recycling-selective and highly efficient bromine capture from a real-water system, exhibiting excellent scalability and affordability, as exemplified using COF membranes in a continuous flow-through process.

Optimization of reaction variables in the sol-gel synthesis of Ni0.5Zn0.5Fe2O4 nanoparticles as a very fast adsorbent of methylene blue

An optimization study for the sol-gel synthesis of Ni0.5Zn0.5Fe2O4 nanoparticles and their performance for the adsorptive removal of the methylene blue (MB) dye was reported. The as-produced samples and their associated calcined corresponding ones in the range of 400–800 °C were systematically characterized for their structure and microstructure using different techniques. For the expected best candidate for the MB removal, the pure NiZn nanoferrite (optimized parameters: Fuel=Urea; pH=5; [Fe3+]:0.025 M; Total nitrate to fuel molar ratio=8/6.66) consists of ultrasmall nanocrystals with an average crystallite size of ∼4 nm. For the optimization study of adsorptive removal of the MB dye by selected ultrasmall NiZn ferrite nanoparticles, various critical physicochemical parameters were varied. Regarding the effect of calcination temperature, it was demonstrated that the nanoferrite calcined at 500 °C showed the best removal efficiency of MB (for instance ∼43% and ∼72%, for the as-prepared and the nanoferrite calcined at 500 °C, respectively). For the selected nanoparticles, the removal efficiency was found to increase in a monotonous manner in the pH range of 4–11. This increase was faster with pH values higher than the pHPZC (∼8). For instance, it is ∼10% for pH∼4, ∼18% for pH∼8 and ∼62% for pH∼11. Whereas, the uptake capacity of the dye onto the produced nanoparticles was found to decrease and increase, respectively, with the increase in the dosage and in the MB concentration. Whatever the dye concentration, almost of the removable amount of the dye takes place in the first 30 s. The very fast adsorption rate observed in the initial stage was mainly attributed to the external surface properties of the ferrite nanoparticles. Additionally, for an industrial, economic and environmental purposes, the reusability efficiency of the nanoparticles was tested. The nanoadsorbent was stable for up to five adsorption–desorption–regeneration–reuse consecutive cycles without obvious decrease in the removal efficiency for dyes.

Decoration of carbohydrate nanocomposite with silver nanoparticles for highly efficient adsorption of methylene blue and antimicrobial against human pathogens

The current study aims to prepare carbohydrate nanocomposite based on 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) oxidized cellulose nanofibers (CNFs) /chitosan chloride (Ch) decorated with silver nanoparticles (Ag-NPs) and designed as (TEMPO/CNF/Ch/Ag-NPs) that was investigated as antimicrobial materials and applied as efficient sorbent. CNF was prepared from cellulose through TEMPO oxidation-mechanical defibrillation technique. Anionic CNF and Ch were ironically interacted to prepare novel sustainable ionic nanofibers films. Ag-NPs having approximately 20 nm were prepared in situ to decorate the ionic fibers. The effects of experimental parameters including media pH (3.0–8.0), contact time (10–120 min), and initial methylene blue (MB) concentration (50–800 ppm) on the adsorption behavior of MB onto nanocomposite films were evaluated. The results exhibited similar and fast adsorption kinetic, as illustrated by the pseudo-second-order model. The adsorption results were best suited by the Langmuir isotherm model, and the maximum adsorption capacity for the TEMPO/CNF/Ch and TEMPO/CNF/Ch/Ag-NPs nanocomposite was 369 and 432 mg/g, respectively, at the optimized media pH of 7 with a contact time of 60 min at 88 to 90 mg/g of MB. In kinetic studies, the pseudo-second-order model for nanocomposite films provided the best fit (R2 = 0.98), than pseudo-first-order model (R2 = 0.82 and 0.77). The TEMPO/CNF/Ch and TEMPO/CNF/Ch/Ag-NPs nanocomposite retains 73 and 69% of its initial adsorption performance towards MB after five consecutive runs. The formed nanocomposite showed excellent efficacy against Escherichia coli (14.3 ± 0.57 mm), followed by Candida albicans (12 ± 1 mm), Staphylococcus aureus (11.3 ± 1.15 mm), and Streptococcus mutans (10.6 ± 1.15 mm), and their antimicrobial activity was enhanced by the incorporation of Ag-NPs. The formed nanocomposite might find applications in industrial and biomedical fields.

A water compatible magnetic molecularly imprinted nanocomposite for the class-selective enrichment of quinoxaline-1,4-dioxides in environmental water.

In this work, a novel water compatible core-shell magnetic molecularly imprinted nanocomposite (Fe3O4-COOH@MIPs) was synthesized in an acetonitrile-water reaction system by adopting carboxyl group-functionalized Fe3O4 nanoparticles as the magnetic core, olaquindox as the template molecule and acrylamide as the functional monomer. The resulting Fe3O4-COOH@MIPs was characterized and applied as an adsorbent for magnetic solid-phase extraction (MSPE) of three quinoline-1,4-dioxides (QdNOs). The Fe3O4-COOH@MIPs possessed strong magnetic responsiveness, fast adsorption equilibrium rate (equilibrium within 5 min) and excellent selectivity. By coupling Fe3O4-COOH@MIPs based MSPE with high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS), good linearity (R2 ≥ 0.9985) and low limits of detection (0.83-5.0 ng L-1) for QdNOs were obtained. Finally, the proposed method was applied to determine trace QdNOs in environmental water samples, and the recoveries were in the range of 68.08-99.88% with RSD less than 12.5%.

Microporous Nitrogen-Doped Activated Biochars Derived from Corn: Use of Husk Waste and Urea for CO2 Capture

The increase in anthropogenic activity over time has led to an exponential increase in greenhouse gas emissions, especially CO2. Profitable technologies for CO2 capture and separation are conspicuous, and porous biochars derived from biomass waste can be a useful solution. Herein, we produced activated nitrogen-doped biochars for CO2 capture from corn husk waste, urea and K2CO3, named N-Bio-X (X = 600, 700, and 800 °C). N-Bio-X exhibited microporosity and different nitrogen contents and thus played an important role in the adsorption of CO2. N-Bio-700 exhibited the highest CO2 adsorption capacity, fastest adsorption kinetics and excellent stability after multiple adsorption-desorption cycles. N-Bio-600 showed excellent CO2/N2 selectivity, induced by nitrogen sites, particularly pyridinic and graphitic nitrogen. The cost-effectiveness of the raw material, coupled with its high adsorption capacity, rapid kinetics, and stable properties, provided highly promising N-doped biochars for practical implementation in CO2 capture and separations in postcombustion processes.

Development of new effective activated carbon supported alkaline adsorbent used for removal phenolic compounds

Phenolic (phenol) compounds are the major contaminates in wastewater, which can have a considerable negative influence on the environment and health of human. Adsorption is an efficient process that is widely applied in order to eliminate phenol in wastewater. In recent, Adsorption process has acquired a lot of attentiveness owing to its relative moderate operating conditions. However, adsorption process needs considerable ameliorations in terms of adsorbent modification, process type, productivity, and conversion rate. This work studies the development of a fast and effective adsorption process in a fixed bed adsorption column (FBAC) in order to reach safe and continuous elimination of phenolic compounds. Several adsorption parameters (reaction temperature, adsorbent bed height, feed flow rate and kind of adsorbent) were studied to achieve the highest removal of phenolic compounds. The adsorption process was conducted in the presence of two type of adsorbents (activated carbon (AC), and KOH/AC), 73% and 94% of phenol elimination were attained, respectively, at 10 cm bed height, 1 ml/s feed flow rate, and 75 °C reaction temperature. The adsorbents activity was investigated after six consecutive adsorption cycles at the best process conditions, and the adsorbents show high stability in terms of phenolic compounds adsorption. After that, the spent adsorbents were regenerated by utilizing various solvents (methanol, ethanol and iso-octane), and the results show that iso- octane achieved highest regeneration efficiency. The adsorption process was implemented in the adsorption column that the performance is possibly to be adjusted at an industrial scale since it can be scaled up predictably.

UiO66-based molecularly imprinted polymers with water-compatible deep eutectic solvent as functional monomer for purification of lysozyme from egg white.

Protein-templated molecularly imprinted polymers have limitations such as poor mass transfer, slow recognition kinetics, and difficulties in isolation and purification due to their large molecular sizes, complex structures, and flexible conformations. To address these limitations and obtain lysozyme (Lyz)-imprinted polymers, a molecularly imprinted polymer (UiO66@DES-MIPs) was prepared for the first timeby using Lyz as a template molecule, a metal-organic framework (UiO66-NH2) as a matrix, and a water-compatible deep eutectic solvent (DES) as a functional monomer. The introduction of UiO66-NH2 by the solvothermal method with a large specific surface area and favorable stability and resistance to environmental disturbances into the MIPs can reduce the "embedding" phenomenon and acquire a higher binding capacity and fast mass transfer. In addition, a water-soluble binary DES (1:2 molar ratio of choline chloride to 1,3 dimethylurea) prepared by a hydrothermal method as a functional monomer generates multiple forces with Lyz, increasing the hydrophilicity of UiO66@DES-MIPs and contributing to the formation and stabilization of the imprinted sites. Consequently, UiO66@DES-MIPs exhibited good selectivity, water compatibility, and fast adsorption equilibrium (the adsorption equilibrated at 243.87 ± 4.88mgg-1 in 90min). Besides, reusability experiments indicated that the UiO66@DES-MIPs could be recycled six times without obvious loss of adsorption capacity. The imprinting factor of UiO66@DES-MIPs is 3.67. The isolation and purification of Lyz from egg white confirmed the practicability of UiO66@DES-MIPs. The high adsorption capacity and specific recognition make this polymer a promising candidate for the isolation and purification of biological macromolecules.

Installation of synergetic binding sites in β-Cyclodextrin-Bipyridine ionic liquid based magnetic sorbent for simultaneous removal of anionic PFAS and Cr (Ⅵ) in water matrix

Herein, we develop a versatile strategy for developing a Fe3O4-NH-β-CD-BP ILs based sorbent by installing synergistic bonding sites for simultaneous removal of per- and polyfluoroalkyl substances (PFASs) and heavy metals from contaminated water. This sorbent with its quaternary ammonium cation achieved remarkable removal efficiency (∼99 %)for both short and long chain anionic PFASs in pure water as compared to previous β-CD based materials. Moreover, when subjected to a challenging metal salt matrix, the adsorbents revealed that long-chain PFASs primarily relied on electrostatic and hydrophobic interactions, while short-chain PFASs depended solely on electrostatic attractions. The results indicate that the sorbent exhibits outstanding adsorption capacities for PFCAs, PFSAs and Cr (VI) coupled with fast adsorption kinetics featuring equilibrium times 5, 4 and 2 h, respectively. The simultaneous removal of PFOA, PFOS and Cr (VI) in multi-component systems (electroplating plant wastewater) was also determined due to their dual sites rendered by cationic and β-CD groups. The adsorption of PFCAs and Cr (VI) was significantly influenced by the initial pH compared to the sorption of PFSAs. Additionally, the viologen based sorbent also showed better photocatalytic hydrogen evolution activity. In summary, these results revealed the outstanding adsorption capacity and convenient regeneration process make the adsorbent as a promising candidate for efficient and rapid removal of PFASs from other pollutants.

A novel scalable polycationic melamine sponge-based filtration matrix for continuous ultrafast adsorption of anionic pollutants

Effective capturing of anionic pollutants from wastewater under industrial operating conditions, which requires high processing flux and fast adsorption rate remains a challenge. Here, a commercially available melamine sponge (MS) with reticulated 3D macroporous structures was covalently modified with positively charged moieties using a single step functionalization under mild conditions. The developed novel polycationic melamine sponge (MS+) was formed by a nucleophilic addition reaction between glycidyltrimethylammonium chloride (GMTA) and MS, followed by a self-propagation of GMTA. The produced MS+ possessed strong electrostatic interactions with different anions such as Rose Bengal (RB) and phosphates (P) under a wide pH range (3–11). The MS+ exhibited promoted static adsorption efficiencies of 400 mg g−1 (P) and 600 mg g−1 (RB), within 5 min and 60 s, respectively. Furthermore, the MS+ showed high stability and recyclability for up to 15 cycles of uses, and the recycling process was environmentally friendly by using 1 M NaCl as a releasing solution. Benefiting from fast flow through the macroporous MS+ and highly positive charged skeleton, the MS+ was applied for rapid dynamic enrichment process of P from real manure wastewater with an enrichment factor of 4.4. Utilization of the MS+ as the substrate brings additional advantages such as low cost, availability, and flexibility to fit into existing filtration devices. The developed MS+ could be expanded for enrichments of other anionic species from various polluted water sources.

Three-dimensional hydrangea-like layered double hydroxide anchoring hollow metal organic-framework for efficient adsorption of 2, 4-dichlorophenoxyacetic acid

In this work, a facile approach to create a layered double hydroxide@hollow zeolitic imidazolate framework-8 nanocomposites (LDH@HZIF-8) was performed for the removal of 2, 4-dichlorophenoxyacetic acid (2,4-D) in food samples. This novel material inherits the advantages of pristine metal-organic frameworks. Additionally, it possesses a hierarchical pore structure, a hollow cavity, a large specific surface area (624.09 m2 g−1), and improved dispersity of ZIF-8. The potential of LDH@HZIF-8 as an adsorbent for removing 2,4-D from food samples was investigated. Our findings revealed a significant maximum adsorption capacity of 178.6 mg g−1 at 25 °C, along with fast adsorption kinetics within 20 min. The adsorption process was well described by the pseudo-second-order kinetics and Langmuir model. Furthermore, thermodynamic data indicated that the adsorption process was exothermic in nature. This novel composite effectively addresses the issues associated with sluggish mass transfer of target molecules/ions and a shortage of active sites. Moreover, LDH@HZIF-8 offers spacious cavities and channels that are capable of accommodating the desired substances.

Understanding fast adsorption in single-solute breakthrough curves

To design efficient adsorption separations and select high-performing materials, understanding the relationship between adsorption equilibria and the movement of solute waves along the fluid is critical. While approximate-analytical methods are useful to combat nonlinearities in the differential equations and efficiently investigate the myriad of materials, their utility is limited by the lack of a clear physical interpretation and mathematical relationship to well-established models. In this work, we show that the two popular methods can be understood with regular perturbation theory and boundary layer theory in small ɛ, where a dilute solute travels from fluid to solid much faster than along the column. We consider conditions associated with a popular experimental technique used to characterize solute wave movement, where the column is initially at steady state and the fluid concentrations exiting, or breaking through, are time-monitored in response to a step change in inlet concentration. Our transformations and asymptotic analyses illustrate the time scales associated with popular techniques. We generalize their applicability to equilibria possessing inflection points while considering both adsorption and desorption modes. We use numerical simulations to estimate convergence orders of asymptotic approximations of breakthrough concentrations. For the leading-order approximation of regular perturbation theory, rarefaction waves possess positive convergence orders, depending on the extent of nonlinearity, while shock waves do not. Boundary-layer theory affords a more accurate approximation of the breakthrough curve than a shock wave, without guaranteeing a positive convergence order. This lack of positive convergence order is likely due to the evolution of the boundary layer, as illustrated with numerical simulations. An improved understanding of fast adsorption sets the stage for more realistic selection of high-performing materials and design configurations from thousands of available candidates.

Synergy tetraethylenepentamine and diethanolamine impregnated within silica nanotubes derived from natural halloysite for efficient CO2 capture

Amine-impregnated porous solid adsorbents are promising commercial CO2 capture adsorbents for CO2 mitigation due to relatively large CO2 capacity and high CO2 selectivity. However, the intrinsic viscosity and aggregation of the polyamine leads to low amine efficiency and greatly limits its further development. In this work, a facile and efficient approach was carried out to manipulate the porosity of natural halloysite (HNTs) support with hollow tubular structure and impregnate mixed-polyamines, i.e., both tetraethylenepentamine (TEPA) and diethanolamine (DEA) to synergistically enhance CO2 adsorption capacity, fast adsorption kinetics and thermal/chemical stability compared to the individual supported TEPA and DEA. The effects of the blend amount for TEPA and DEA, adsorption temperature and CO2 partial pressure on CO2 adsorption capacity and adsorption kinetics were specifically discussed. Due to the auxiliary effect of DEA, the chemical reaction between non-hydroxylated TEPA and CO2 was altered thus improving amine efficiency and the agglomeration layer between protonated TEPA molecules and carbamate, which existed due to electrostatic interaction when TEPA was loaded alone, was loosened thus improving amine efficiency and adsorption kinetics. Therefore, the maximum CO2 adsorption capacity of MHNTs loaded with 20 wt% TEPA and 20 wt% DEA was 3.25 mmol/g at 75 °C in the flow of 40 vol% N2/60 vol% CO2. Compared with loading individual TEPA with multiple amino groups on MHNTs, individual DEA with hydroxyl groups could increase the utilization efficiency of the amino groups of TEPA and ultimately obtain excellent CO2 capture capacity and adsorption kinetics. The experimental results show that the adsorbents obtained in this study using mixed amine impregnated silica nanotubes derived from natural minerals have a promising application in practical CO2 capture and separation processes.

Enhancing Cytochrome C Recognition and Adsorption through Epitope-Imprinted Mesoporous Silica with a Tailored Pore Size.

We have reported the synthesis of epitope-imprinted mesoporous silica (EIMS) with an average pore size of 6.2 nm, which is similar to the geometrical size of the target protein, cytochrome C (Cyt c, 2.6 × 3.2 × 3.3 nm3), showing great recognition and large-scale adsorption performance. The characteristic fragment of Cyt c was used as a template and docked onto the surface of C16MIMCl micelles via multiple interactions. Nitrogen adsorption-desorption and transmission electron microscopy confirmed the successful preparation of EIMS. Due to the ordered pore structure, larger pore size, and high specific surface area, the prepared EIMS show superior specificity (IF = 3.8), excellent selectivity toward Cyt c, high adsorption capacity (249.6 mg g-1), and fast adsorption equilibrium (10 min). This study demonstrates the potential application of EIMS with a controllable pore size for high-effective and large-scale separation of Cyt c, providing a new approach for effective biomacromolecular recognition.