Cooperative Adsorption Research Articles

Cooperative Adsorption: Solvating the Hofmann Elimination of Alkylamines

Cooperative Adsorption: Solvating the Hofmann Elimination of Alkylamines

DNA Binding to the Silica: Cooperative Adsorption in Action.

The adsorption and desorption of nucleic acid to a solid surface is ubiquitous in various research areas like pharmaceutics, nanotechnology, molecular biology, and molecular electronics. In spite of this widespread importance, it is still not well understood how the negatively charged deoxyribonucleic acid (DNA) binds to the negatively charged silica surface in an aqueous solution. In this article, we study the adsorption of DNA to the silica surface using both modeling and experiments and shed light on the complicated binding (DNA to silica) process. The binding agent mediated DNA adsorption was elegantly captured by cooperative Langmuir model. Bulk-depletion experiments were performed to conclude the necessity of a positively charged binding agent for efficient DNA binding, which complements the findings from the model. A profound understanding of DNA binding will help to tune various processes for efficient nucleic acid extraction and purification. However, this work goes beyond the DNA binding and can shed light on other binding agent mediated surface-surface, surface-molecule, molecule-molecule interaction.

Cooperative adsorption of L-tryptophan and sodium ion on a hyper-cross-linked resin: Experimental studies and mathematical modeling

The adsorption separation of L-tryptophan (L-Trp) by the weakly polar hyper-cross-linked resin XDA-200 was studied. First, the adsorption equilibria of different species of L-Trp on the resin were compared. Then, the adsorption isotherms and adsorption kinetics of L-Trp were studied at different pH values. Finally, the dynamic adsorption and separation processes of L-Trp in a packed bed of the resin were studied. The distribution coefficient of L-Trp± between the resin and an aqueous solution of L-Trp (55.69) was found to be markedly larger than that of L-Trp+ (27.53) and L-Trp- (10.42). An adsorption isotherm model depending on pH was established to simulate the adsorption equilibrium data of L-Trp. The cooperative adsorption of sodium ion (Na+) with L-Trp- cannot be ignored when the solution pH is higher than 8.0. Thus, a modified surface diffusion model considering cooperative adsorption of Na+ with L-Trp- was established. The model fitted the kinetic curves for L-Trp adsorption under different pH values satisfactorily. The surface diffusion coefficient of L-Trp first decreased and then increased as pH increased from 3 to 12. In this study, a modified film-surface diffusion model considering cooperative adsorption of Na+ with L-Trp- is proposed. Further, we show that our proposed model can predict the chromatographic peaks of L-Trp, L-glutamic acid (L-Glu), and Na+ satisfactorily.

DFT study of the adsorption of 2,3-epoxypropyltrimethylammonium chloride on montmorillonite surfaces

The hydration expansion of montmorillonite is inhibited by 2,3-epoxypropyltrimethylammonium chloride (NW-1+). The adsorption behaviors of NW-1+ on Na-001, None-001, and internal surfaces of montmorillonite (MMT) in dry and wet environments based on density functional theory (DFT) were analyzed. NW-1+ was stably adsorbed on the surface of MMT-001 as well as between the internal surfaces. The adsorption of NW-1+ on the Na-001 surface and internal surfaces was mainly through electrostatic interaction; however, the adsorption on the None-001 surface was through the combined action of hydrogen bonding and electrostatic attraction. In short, NW-1+ was mainly adsorbed on MMT particles through electrostatic interactions; water and NW-1+ exhibited cooperative adsorption on the surface of MMT, and water bridged NW-1+ and MMT and enhanced their electrostatic interaction and hydrogen bonding.

Revealing unconventional host\u2013guest complexation at nanostructured interface by surface-enhanced Raman spectroscopy

Interfacial host–guest complexation offers a versatile way to functionalize nanomaterials. However, the complicated interfacial environment and trace amounts of components present at the interface make the study of interfacial complexation very difficult. Herein, taking the advantages of near-single-molecule level sensitivity and molecular fingerprint of surface-enhanced Raman spectroscopy (SERS), we reveal that a cooperative effect between cucurbit[7]uril (CB[7]) and methyl viologen (MV2+2I−) in aggregating Au NPs originates from the cooperative adsorption of halide counter anions I−, MV2+, and CB[7] on Au NPs surface. Moreover, similar SERS peak shifts in the control experiments using CB[n]s but with smaller cavity sizes suggested the occurrence of the same guest complexations among CB[5], CB[6], and CB[7] with MV2+. Hence, an unconventional exclusive complexation model is proposed between CB[7] and MV2+ on the surface of Au NPs, distinct from the well-known 1:1 inclusion complexation model in aqueous solutions. In summary, new insights into the fundamental understanding of host–guest interactions at nanostructured interfaces were obtained by SERS, which might be useful for applications related to host–guest chemistry in engineered nanomaterials.

Experimental and modeling study on adsorption of emerging contaminants onto hyper-crosslinked cellulose

The primary objective of this study was to synthesize a novel hyper-crosslinked cellulosic adsorbent (CLC) by a straightforward one-pot esterification reaction using cellulose and sebacoyl chloride as crosslinker agent. Efficient crosslinking of cellulose was confirmed by FTIR, CPMAS 13C NMR, elemental analysis, TGA, SEM and BET surface area analysis. The CLC material with high content of ester groups was employed to remove paracetamol (PCT) and niflumic acid (NFA) from aqueous solutions in batch adsorption experiments. The mesoporous structure of CLC created upon crosslinking was found to be a determinant in the adsorption behavior of the drugs. Indeed, PCT and NFA adsorption isotherms onto CLC were S-shaped and were adjusted by the Gu–Zhu, Frumkin–Fowler–Guggenheim and Hill–de Boer models. From the GZ isotherm model, the results indicate a cooperative adsorption mechanism leading to the formation of aggregates containing 2.53 and 4.25 molecules of PCT and NFA, respectively. Furthermore, FFG and HdB models reflect that the lateral interactions are attractive in nature for both drugs. The experimental kinetic data were fitted to the pseudo-second-order and intraparticle diffusion models, and the obtained parameters were linked to the aggregates arrangement of the drugs.

Ethylbenzene and toluene interactions with biochar from municipal solid waste in single and dual systems

The present study investigated adsorptive removal of toluene and ethylbenzene from the aqueous media via using biochar derived from municipal solid waste (termed “MSW-BC”) in a single and binary contaminant system at 25–45 °C. The adsorption was evaluated at different pH (3–10), experimental time (up to 24 h), and initial adsorbate concentrations (10–600 μg/L) in single and binary contaminant system. A fixed-bed column experiment was also conducted using MSW-BC (0.25%) and influent concentration of toluene and ethylbenzene (4 mg/L) at 2 mL/min of flow rate. The adsorption of toluene and ethylbenzene on the MSW-BC was mildly dependent on the pH, and the peak adsorption ability (44–47 μg/g) was recorded at a baseline pH of ~8 in mono and dual contaminant system. Langmuir and Hill are the models that match the isotherm results in a single contaminant environment for both toluene (R2 of 0.97 and 0.99, respectively) and ethylbenzene (R2 of 0.99 and 0.99, respectively) adsorption. In the binary system, the isotherm models matched in the order of Langmuir > Hill > Freundlich for toluene, whereas Hill > Freundlich > Langmuir for ethylbenzene. The adsorption in the batch experiment was likely to take place via cooperative and multilayer adsorption onto MSW-BC involving hydrophobic, π- π and n- π attractions, specific interaction such as hydrogen–π and cation–π interactions, and van der Waals interactions. The thermodynamic results indicate exothermic adsorption occurred by physical attractions between toluene and ethylbenzene, and MSW-BC. The breakthrough behavior of toluene and ethylbenzene was successfully described with Yoon-Nelson and Thomas models. The data demonstrate that the low-cost adsorbent derived from the municipal solid waste can be utilized to remove toluene and ethylbenzene in landfill leachate.

Zinc Based Metal-Organic Frameworks as Ofloxacin Adsorbents in Polluted Waters: ZIF-8 vs. Zn3(BTC)2.

Two different zinc-based metal-organic frameworks (MOFs) were investigated to remove one of the most used fluoroquinolone antibiotic, Ofloxacin (OFL), from polluted water. The most common zeolitic imidazolate framework-8 (ZIF-8) and the green Zn(II) and benzene-1,3,5-tri-carboxylate (Zn3(BTC)2) were prepared through a facile synthetic route and characterized by means of Fourier-Transform Infrared (FT-IR) Spectroscopy, X-ray Powder Diffraction (XRPD), and Scanning Electron Microscopy (SEM) analyses. The two MOFs were compared in terms of both adsorption and kinetic aspects under real conditions (tap water, natural pH). Results showed that OFL was adsorbed in remarkable amounts, 95 ± 10 and 25.3 ± 0.8 mg g−1 on ZIF-8 and Zn3(BTC)2, respectively, following different mechanisms. Specifically, a Langmuir model well described the ZIF-8 profile, while for Zn3(BTC)2, cooperative adsorption occurred. Moreover the kinetic results were quite different, pseudo-second-order and sigmoidal, respectively. The suitability of ZIF-8 and Zn3(BTC)2 as adsorbent phases for water depollution was tested on tap water samples spiked with OFL 10 µg L−1. The obtained removal efficiencies, of 88% for ZIF-8 and 72% for Zn3(BTC)2, make these materials promising candidates for removing fluoroquinolone antibiotics (FQs) from polluted waters, notwithstanding their limited reusability in tap water, as demonstrated by in-depth characterization of the two MOFs after usage.

Antibody cooperative adsorption onto AuNPs and its exploitation to force natural killer cells to kill HIV-infected T cells

HIV represents a persistent infection which negatively alters the immune system. New tools to reinvigorate different immune cell populations to impact HIV are needed. Herein, a novel nanotool for the specific enhancement of the natural killer (NK) immune response towards HIV-infected T-cells has been developed. Bispecific Au nanoparticles (BiAb-AuNPs), dually conjugated with IgG anti-HIVgp120 and IgG anti-human CD16 antibodies, were generated by a new controlled, linker-free and cooperative conjugation method promoting the ordered distribution and segregation of antibodies in domains. The cooperatively-adsorbed antibodies fully retained the capabilities to recognize their cognate antigen and were able to significantly enhance cell-to-cell contact between HIV-expressing cells and NK cells. As a consequence, the BiAb-AuNPs triggered a potent cytotoxic response against HIV-infected cells in blood and human tonsil explants. Remarkably, the BiAb-AuNPs were able to significantly reduce latent HIV infection after viral reactivation in a primary cell model of HIV latency. This novel molecularly-targeted strategy using a bispecific nanotool to enhance the immune system represents a new approximation with potential applications beyond HIV.

土壌中における溶質の吸着移動現象の基礎理論 III．協同吸着 · 多層吸着 · 選択係数

土壌中における溶質の吸着移動現象の基礎理論 III．協同吸着 · 多層吸着 · 選択係数

Understanding the relationship between the structural properties of three corrosion inhibitors and their surface protectiveness ability in different environments

All-atom molecular simulations and chemical quantum calculations were used to understand the effect of the environment on the surface adsorption of corrosion inhibitor (CI) molecules. Three CIs abbreviated: TEPA, iTEPA and HC-iTEPA studied in this work, were selected to systematically investigate the influence of the alkyl tail, N-pendant group, imidazoline and benzene rings, on the CIs adsorption behavior. A relationship is provided between their structural properties and their surface protectiveness ability in different environments. Chemical quantum calculations revealed the electron distribution in inhibitors structures, indicating their ability to accept/donate charges from the Fe atoms in vacuum and in water solvation. The quantum molecular parameters in water solvation anticipated higher electron transfer ability of iTEPA in aqueous conditions compared to TEPA and iTEPA, thus, leading to stronger adsorption on iron surface, corroborated by the molecular dynamics (MD) classical simulations. MD simulations showed that nearly 53%, 39%, 59% reduction in adsorption energies was detected for single inhibitor molecule of TEPA, iTEPA, and HC-iTEPA shifting from water to CO2-saline media, respectively. The formation of water double adsorption layer contributed to decreasing the CIs adsorption energies by the larger surface separation distances spotted in the density profiles. Nevertheless, the multi-inhibitors study revealed strong adsorption of TEPA and iTEPA on the iron surface, while HC-iTEPA neglected cooperative adsorption and aggregated as a spherical-like micelle with lower surface coverage propensity. Radial distribution functions g(r) explored the preferential interactions of inhibitor-H2O and inhibitor-CO2 that guided the CIs adsorption conformation. Self-diffusivity coefficients of competing adsorbates with the three CIs were found to be one to two orders of magnitude lower near the interface than in the bulk.

Fitting a little-known isotherm equation to S-shaped adsorption equilibrium data

A research topic of current interest concerns the measurement and modeling of adsorption isotherms of water contaminants. The bulk of measured equilibrium isotherms exhibit the convex-upward or favorable curve shape, which can be described by the two-parameter Hill-Langmuir and Freundlich isotherms. An increasing number of recent studies have however reported S-shaped or sigmoidal equilibrium isotherms. Modeling such equilibrium data requires the use of isotherm equations with a highly flexible functional form. This work introduces a little-known isotherm useful for tracking the trajectory of S-shaped equilibrium data. This relatively simple three-parameter isotherm, first proposed by Krishnamurti in 1951, has theoretical merit because it is based on a co-operative adsorption mechanism. It is shown that previously reported S-shaped equilibrium data of water contaminants can be represented by the Krishnamurti isotherm. Specific examples discussed are (1) ammonium ion adsorption by the clay mineral sepiolite, (2) uptake of the antibiotic ciprofloxacin by a magnetic nanosorbent, and (3) fluoride ion removal by a layered double hydroxide adsorbent. Additionally, it is found that a modified form of the Krishnamurti isotherm is superior to its original counterpart. The original and modified Krishnamurti isotherms can be practically very useful to describe S-shaped equilibrium data and for adsorptive process modeling.

Facile immobilization of graphene nanosheets onto PBO fibers via MOF-mediated coagulation strategy: Multifunctional interface with self-healing and ultraviolet-resistance performance

The surface of poly (p-phenylene benzobisoxazole) (PBO) fibers with self-healing and ultraviolet (UV)-resistance performance play the key role in prolonging their service lifespan. Although great advances have been made in the single aspect of above two properties, integration of self-healing and anti-UV performance into the surface of PBO fiber is still a challenge. In this study, the coagulation strategy mediated by metal-organic framework (MOF) is proposed to construct the multifunctional surface of PBO fibers. The spindle-like iron (III)-based MOF (MIL-88B-NH2) nanocrystals are firstly immobilized onto the surface of PBO-COOH through hydrothermal reaction, then serving as the medium layer to further immobilize sufficient graphene oxide (GO) nanosheets. Benefitting from the favorable near-infrared (NIR, 808 nm) photothermal conversion performance of GO nanolayers, the monofilament composite-PBO@Fe-MIL-88B-NH2-GO-TPU (thermoplastic polyurethane) exhibited a stable and high self-healing efficiency (approximately 80%) within five cycle times. Meanwhile, the cooperative adsorption and shielding weaken effects of MOF-GO nanolayers enabled PBO fibers with excellent anti-UV properties that are superior to much reported literatures after 96 h aging time and eventually increased by 75% compared with untreated PBO fiber. In view of the varieties and multifunctionalities of MOFs and carbon nanomaterials, MOF-mediated coagulation strategy would provide guidance for preparing multifunctional composite materials.

Quantitative Protein Corona Composition and Dynamics on Carbon Nanotubes in Biological Environments

AbstractWhen nanoparticles enter biological environments, proteins adsorb to form the “protein corona” which alters nanoparticle biodistribution and toxicity. Herein, we measure protein corona formation on DNA‐functionalized single‐walled carbon nanotubes (ssDNA‐SWCNTs), a nanoparticle used widely for sensing and delivery, in blood plasma and cerebrospinal fluid. We characterize corona composition by mass spectrometry, revealing high‐abundance corona proteins involved in lipid binding, complement activation, and coagulation. We investigate roles of electrostatic and entropic interactions driving selective corona formation. Lastly, we study real‐time protein binding on ssDNA‐SWCNTs, obtaining agreement between enriched proteins binding strongly and depleted proteins binding marginally, while highlighting cooperative adsorption mechanisms. Knowledge of protein corona composition, formation mechanisms, and dynamics informs nanoparticle translation from in vitro design to in vivo application.

Quantitative Protein Corona Composition and Dynamics on Carbon Nanotubes in Biological Environments.

When nanoparticles enter biological environments, proteins adsorb to form the "protein corona" which alters nanoparticle biodistribution and toxicity. Herein, we measure protein corona formation on DNA-functionalized single-walled carbon nanotubes (ssDNA-SWCNTs), a nanoparticle used widely for sensing and delivery, in blood plasma and cerebrospinal fluid. We characterize corona composition by mass spectrometry, revealing high-abundance corona proteins involved in lipid binding, complement activation, and coagulation. We investigate roles of electrostatic and entropic interactions driving selective corona formation. Lastly, we study real-time protein binding on ssDNA-SWCNTs, obtaining agreement between enriched proteins binding strongly and depleted proteins binding marginally, while highlighting cooperative adsorption mechanisms. Knowledge of protein corona composition, formation mechanisms, and dynamics informs nanoparticle translation from in vitro design to in vivo application.

Calorimetric screening of co-operative effects in adsorption of Co(II) on γ-alumina surface in the presence of Co-complexing anions in aqueous solution

The understanding of the mechanism of co-operative adsorption of Co(II) cations and acetate or citrate anions onto γ-Al2O3 from aqueous solutions has been refined on the basis of comparison between the enthalpies of displacement measured in single-solute and bi-solute systems by means of isothermal titration calorimetry. The data processing procedures were adapted to take into account the occurrence of a cobalt-ligand complex in the bulk solution. Considering the bridging role of the adsorbed cobalt cations as a starting point to reproduce the enthalpy of displacement in the cobalt-acetate system, each ligand unit was suggested to bind preferentially to more than one adsorbed metal species and to interact additionally with some electrically neutral binding sites on the oxide surface. In the case of cobalt-citrate couple, the formation of a 1:1 stoichiometry solid-ligand-metal complex and simultaneous adsorption of cobalt cations as bidentate inner-sphere complexes reproduced best the experimental data.

Removal behaviour of NSAIDs from wastewater using a P-functionalised microporous carbon

Diclofenac (DCF), naproxen (NPX) and ibuprofen (IBF) are three of the most commonly used non-steroidal anti-inflammatory drugs (NSAIDs) worldwide. They are widely detected in natural waters due to their persistence in wastewater treatment, and their removal is desirable in future wastewater management worldwide. In this study, “acid catalyst” functionalisation and subsequent carbonisation were adopted to synthesise a P-doped microporous carbonous adsorbent (CScPA) for NSAID removal. The CScPA was evaluated in depth for its adsorption performance (i.e., isotherms, kinetics and thermodynamics of adsorption at lab-scale). The CScPA had a large surface area (791.1 m2/g) and good porosity (0.392 cm3/g), which facilitated a high maximum adsorption capacity of 62.02 mg/g for a NSAID mixture. Thermodynamic data indicated that the adsorption of these NSAIDs was an endothermic process determined by physisorption (low-energy interactions). XPS analysis revealed the specific interactions involved in the adsorption process, including π-π and n-π electron donor-acceptor (EDA) interactions and hydrogen (H-) bonding. The Freundlich isotherm and Elovich kinetic model provided the best fit to the experimental results, which indicated surface heterogeneity (of the CScPA) and cooperative adsorption mechanisms. The adsorption process was shown to have potential to be applied to real wastewater effluent containing NSAIDs at low environmentally relevant concentrations (removal reached > 90% at 10 μg/L). Analysis of different implementation and cost related factors suggested that the CScPA has the potential for use with “real-world” water matrices, offering a sustainable treatment process for pharmaceutical remediation in wastewater.

Preparation of nitrogen self-doped hierarchical porous carbon with rapid-freezing support for cooperative pollutant adsorption and catalytic oxidation of persulfate

Herein, we report a method to synthesize nitrogen self-doped hierarchical porous carbon materials derived from chitosan. This method uses potassium hydroxide (KOH) activation and rapid-freezing technology. The catalyst (CA-900Q 1–1) obtained after rapid-freezing and KOH activation treatment show excellent persulfate activation ability. It can remove 20 mg bisphenol A (BPA) within 10 min better than traditional metal oxidate and nanomaterials. In the aquatic environment, CA-900Q 1–1 has a high resistance to inorganic anions. CA-900Q 1–1, possessing a high proportion of graphitic nitrogen, provides a sufficient number of active sites for persulfate activation. In addition, the catalyst yielded sizeable specific surface areas (SSAs) (1756.1 m2/g) and a hierarchical pore structure, which helps to improve the mass transfer in the carbon framework. The efficient adsorption of pollutants by the catalyst shortens the time required for target organic molecules to migrate to the catalyst surface and hierarchical pore structure. Furthermore, the catalyst has excellent electrical conductivity (R = 1.73 Ω), which enables pollutants adsorbed on the catalyst surface to transfer electrons to the persulfate through the N-doped sp2-hybrid carbon network faster.

High-efficiency adsorption of tetracycline by cooperation of carbon and iron in a magnetic Fe/porous carbon hybrid with effective Fenton regeneration

Highly efficient removal of tetracycline (TC) has been achieved by cooperative adsorption of carbon and iron in a magnetic Fe/porous carbon hybrid (MagFePC) derived from MIL-101(Fe). The optimum hybrid material MagFePC-700 (obtained from MIL-101(Fe) carbonization at 700 °C had a good adsorption capacity for TC at a wide range of pH, and the highest adsorption capacity was up to 1301.24 mg g−1 at a pH of around 7, which was 6 times higher than that of activated carbon. In addition to TC, it also showed high adsorption capacity (>800 mg g−1) for oxytetracycline, chlortetracycline hydrochloride, and tetracycline hydrochloride. The porous carbon in MagFePC-700 was rich inmeso-andmicropores, which were conducive to the transport and enrichment of TC molecules. Especially, the Fe nanoparticles in the hybrid were found to contribute greatly to the adsorption, which were both the active site of adsorption and the active site of Fenton reaction. A multi-cycle experiment revealed that the MagFePC material was regenerated well through Fenton reaction, and the regeneration conditions were mild without adjusting the pH. Taken it all together, MagFePC-700 is a green and recyclable adsorbent for the removal of antibiotics from water owing to its high adsorption capacity, easy separation, and good reuse performance.

Enhanced Thermal Conductivity in a Diamine-Appended Metal-Organic Framework as a Result of Cooperative CO2 Adsorption.

Diamine-appended variants of the metal-organic framework M2(dobpdc) (M = Mg, Mn, Fe, Co, Zn; dobpdc4- = 4,4'-dioxidobiphenyl-3,3'-dicarboxylate) exhibit exceptional CO2 capture properties owing to a unique cooperative adsorption mechanism, and thus hold promise for use in the development of energy- and cost-efficient CO2 separations. Understanding the nature of thermal transport in these materials is essential for such practical applications, however, as temperature rises resulting from exothermic CO2 uptake could potentially offset the energy savings offered by such cooperative adsorbents. Here, molecular dynamics (MD) simulations are employed in investigating thermal transport in bare and e-2-appended Zn2(dobpdc) (e-2 = N-ethylethylenediamine), both with and without CO2 as a guest. In the absence of CO2, the appended diamines function to enhance thermal conductivity in the ab-plane of e-2-Zn2(dobpdc) relative to the bare framework, as a result of noncovalent interactions between adjacent diamines that provide additional heat transfer pathways across the pore channel. Upon introduction of CO2, the thermal conductivity along the pore channel (the c-axis) increases due to the cooperative formation of metal-bound ammonium carbamates, which serve to create additional heat transfer pathways. In contrast, the thermal conductivity of the bare framework remains unchanged in the presence of zinc-bound CO2 but decreases in the presence of additional adsorbed CO2.