Effect Of Coadsorption Research Articles

Low-temperature etching of silicon oxide and silicon nitride with hydrogen fluoride

Etching of high aspect ratio features into alternating SiO2 and SiN layers is an enabling technology for the manufacturing of 3D NAND flash memories. In this paper, we study a low-temperature or cryo plasma etch process, which utilizes HF gas together with other gas additives. Compared with a low-temperature process that uses separate fluorine and hydrogen gases, the etching rate of the SiO2/SiN stack doubles. Both materials etch faster with this so-called second generation cryo etch process. Pure HF plasma enhances the SiN etching rate, while SiO2 requires an additional fluorine source such as PF3 to etch meaningfully. The insertion of H2O plasma steps into the second generation cryo etch process boosts the SiN etching rate by a factor of 2.4, while SiO2 etches only 1.3 times faster. We observe a rate enhancing effect of H2O coadsorption in thermal etching experiments of SiN with HF. Ammonium fluorosilicate (AFS) plays a salient role in etching of SiN with HF with and without plasma. AFS appears weakened in the presence of H2O. Density functional theory calculations confirm the reduction of the bonding energy when NH4F in AFS is replaced by H2O.

Effects of Anion Coadsorption on the Self-Assembly of 11-Acryloylamino Undecanoic Acid on an Au(111) Electrode.

11-acryloylamino undecanoic acid (AAUA) is a versatile polymerizable surfactant that has been applied to coat medical devices, and these applications can benefit from a fundamental understanding of its interaction with a metal substrate. Cyclic voltammetry and in situ scanning tunneling microscopy (STM) were used to examine the adsorption configuration of AAUA molecules on an ordered Au(111) electrode and their mutual interactions, as AAUA was adsorbed from a methanol dosing solution. In addition to the van der Waals force between the aliphatic groups, the hydrogen bonding between the carboxylic acid and acrylamide groups was also important to guide the spatial arrangement of AAUA admolecules on the Au electrode. The -COOH group of AAUA admolecule likely dissociated in neutral media to -COO-, which formed hydrogen bonds with H2PO4 - in phosphate buffer solution (PBS). This interaction between the AAUA admolecules and ions in the electrolyte resulted in different electrochemical characteristics observed in phosphate buffer solution (PBS) and potassium sulfate (K2SO4). Molecular-resolution STM imaging revealed distinctly different AAUA spatial structures on the Au electrode in PBS and K2SO4. Shifting the potential positively to 0.5 V (versus Ag/AgCl) led to lifting of the reconstructed Au(111) to the (1 × 1) phase and the dissolution of the ordered AAUA film, suggesting that the orientation of the AAUA admolecule was altered. The ordered AAUA adlayer could be partially recovered by shifting the potential negatively.

Optimization Strategy for Formaldehyde Removal by Carbon Cathode Electro-Fenton: Enhancement of Formaldehyde and Oxygen Co-adsorption by Rational Nitrogen Doping Types.

This study investigates the effect of N-doped coal-based activated carbon cathode on formaldehyde-oxygen coadsorption. Further investigation investigates the effect of formaldehyde-oxygen coadsorption on H2O2 generation and formaldehyde removal in an electro-Fenton system. Nitrogen doping enhances formaldehyde and oxygen coadsorption by modulating competitive adsorption. Density Functional Theory (DFT) calculations confirm pyrrole nitrogen favors formaldehyde, and graphite nitrogen favors oxygen adsorption. N-doped activated carbon adsorbs 0.36 mg of formaldehyde and 0.1 mg of oxygen in 120 min and removes 82.43% of formaldehyde after electro-Fenton treatment. N-doped activated carbon enhances the synergistic adsorption of formaldehyde and oxygen. In the synergistic adsorption process, the amount of formaldehyde adsorbed is greater than the amount of oxygen adsorbed. This improves the removal efficiency of formaldehyde by electro-Fenton technology. It provides a new method for electro-Fenton removal of organic pollutants.

Controllable construction of a 3D-honeycomb-like porous carbon network as a high-performance cathode for promoting Zn-ion storage capability.

Inheriting the energy storage mechanism of supercapacitors and rechargeable ion batteries, zinc ion capacitors (ZICs) greatly increase their energy density at high power without sacrificing their life span. However, sluggish kinetics and insufficient active sites for Zn2+ storage induced by the significant mismatch of charge carriers with limited pore size hinder the efficient Zn2+ storage and smooth application of carbonaceous cathode materials. Herein, a three-dimensional honeycomb-like porous carbon network (HPCN) was fabricated, which can reduce the diffusion barrier for fast kinetics, produce a high-density defect area, effectively increase active sites for charge storage, and generate a high nitrogen-doping content. Benefiting from these advantages, the optimized ZICs bring out a marvelous energy/power density (130 W h kg-1/11.7 kW kg-1) with an ultrahigh reliable cyclability of 97.8% after 50 000 cycles at a high current density of 5 A g-1. Importantly, systematic ex situ characterizations combined with theoretical calculations demonstrate that the outstanding Zn2+ storage capacity is attributed to the synergistic effect of physical co-adsorption of cations and reversible chemisorption. This work presents an attractive strategy for developing advanced carbon cathodes with suitable pores and accelerates the exploration of charge storage mechanisms, which may open a new avenue for practical supercapacitors.

A first principles analysis of potential-dependent structural evolution of active sites in Fe-N-C catalysts.

Fe-N-C (iron-nitrogen-carbon) electrocatalysts have emerged as potential alternatives to precious metal-based materials for the oxygen reduction reaction (ORR). However, the structure of these materials under electrochemical conditions is not well understood, and their poor stability in acidic environments poses a formidable challenge for successful adoption in commercial fuel cells. To provide molecular-level insights into these complex phenomena, we combine periodic density functional theory (DFT) calculations, exhaustive treatment of coadsorption effects for ORR reaction intermediates, including O and OH, and comprehensive analysis of solvation stabilization effects to construct voltage-dependent ab initio thermodynamic phase diagrams that describe the in situ structure of the active sites. These structures are further linked to activity and stability descriptors that can be compared with experimental parameters such as the half-wave potential for ORR and the onset potential for carbon corrosion and CO2 evolution. The results indicate that pyridinic Fe sites at zigzag carbon edges, as well as other edge sites, exhibit high activity for ORR compared to sites in the bulk. However, edges neighboring the active sites are prone to instability via overoxidation and consequent site loss. The results suggest that it could be beneficial to synthesize Fe-N-C catalysts with small sizes and large perimeter edge lengths to enhance ORR activity, while voltage fluctuations should be limited during fuel cell operation to prevent carbon corrosion of overoxidized edges.

Mixture Adsorption in Nanoporous Zeolite and at Its External Surface: In-Pore and Surface Selectivity.

Using toluene, ethylene, and water as gas compounds with different representative molecular interactions, we perform atom-scale simulations for their mixtures to investigate the selectivity of the core nanoporosity and external surface in a prototypical zeolite. As expected, the overall behavior suggests that increasing the pressure of a given component promotes the desorption of the coadsorbing species. However, for water-toluene mixtures, we identify that the pseudohydrogen bonding between water and toluene leads to beneficial coadsorption as toluene adsorption in the low-pressure range promotes water adsorption. Moreover, when the zeolite is completely filled with water, toluene adsorption does not occur due to steric repulsion, and ethylene shows oversolubility as the amount of ethylene per water molecule is significantly larger than in bulk water. The underlying oversolubility mechanism is found to be due to localized ethylene adsorption in the density minima arising from the layering of water in nanoconfinement. Despite these specific effects, the relatively weak coadsorption effects in the zeolite nanoporosity, which are found to be reasonably captured using the ideal adsorbed solution theory, arise from the fact that adsorption of these gases having different molecular sizes occurs in distinct pore regions (channel type, channel intersection). Finally, in contrast to confinement in the nanoporosity, mixture adsorption at the external surface does not show coadsorption effects as it mostly follows the Henry regime. These results show that selectivity is mostly governed by the confinement effects as the external surface leads to a selectivity loss.

Synthesis, characterization, and performance comparison of boron using adsorbents based on N-methyl-D-glucosamine

Using N-methyl-D-glucosamine (NMDG) as the functional monomer, glycidyl methacrylate (GMA) as the connecting monomer, functionalized Fe3O4 nano-particles (NPs) as the support, three adsorbents were prepared including direct polymer GMA-NMDG, magnetic GMA-NMDG polymer (MGN), and boron magnetic ion-imprinted polymer (BMIIP). Based upon the optimization of synthesis conditions, the prepared adsorbents and intermediate products were characterized using Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscope, energy dispersive spectroscopy, X-ray diffraction, vibrating sample magnetometer, and Brunauer–Emmett–Teller to investigate the synthesis process, the morphological structure and the functional properties of the materials. The optimum performances of GMA-NMDG, MGN and BMIIP were obtained in the initial neutral solution (pH of 6.5). Moreover, GMA-NMDG and MGN reached the maximum adsorption capacity at 120 min, whereas BMIIP reached adsorption saturation at 60 min. The pseudo-second-order kinetic model was more suitable for the adsorption of boron using the adsorbents. The maximum adsorption capacity of GMA-NMDG was found to be 43.4 mg·g−1, while those of MGN and BMIIP were 32.5 and 28.3 mg·g−1, respectively. The Langmuir isotherm model was more appropriate to describe the adsorption process. The adsorbents maintained satisfactory adsorption performance within a certain temperature range. Competing ions had little effect on the adsorption of boron, and would be adsorbed simultaneously, due to which, the effect of co-adsorption can be considered. The adsorption capacity of GMA-NMDG was high, while the adsorption selectivity of BMIIP was much better. Furthermore, BMIIP showed good adsorption after five cycles of adsorption and desorption. The comparison of adsorbents showed that GMA-NMDG had the highest adsorption capacity and was suitable for co-adsorption. MGN had a high adsorption capacity, good comprehensive performance and magnetic properties. BMIIP had better adsorption rate, adsorption selectivity and recyclability. Through the optimization of synthesis conditions, the adsorption capacity of the traditional monomer NMDG polymer was increased, and the magnetism was given to facilitate rapid recovery. Combined with the ion imprinting technology, it showed higher boron adsorption selectivity in the presence of competitive ions.

A collaborative diffusion mechanism of multiple atoms during Cu-Ag bimetal surface reconstruction.

The reconstruction of bimetals under reaction conditions is critical for precisely controlling the catalytic performance of bimetallic catalysts. The surface diffusion mechanisms of Cu@Ag nanoparticles before and after CO adsorption were studied in this work. The diffusion patterns with the lowest energy barrier were determined by using ab initio molecular dynamics and meta-dynamics simulations. The effects of nanoparticle size, surface species and CO adsorption were taken into account. We present a mechanism of multiple atom collaborative diffusion during Cu@Ag bimetal reconstruction: surface atoms diffuse outward to form adatoms first, with nearby atoms occupying the original position of the outward diffused atom, and the outward diffusion can accelerate the inward diffusion of nearby surface atoms. The surface diffusion mechanisms of Cu@Ag under a CO atmosphere are different from those of Pd@Au that we previously presented, due to the different diffusion abilities of metal atoms. Our study provides a potential strategy to control the beginning of reconstruction to change the stability of bimetals under reaction conditions.

The role of CO adsorption and CuO formation on the catalyst deactivation during the long-term performance evaluation of methanol steam reforming process for hydrogen production: Comparison of sono-coprecipitation and spray pyrolysis method

In this study, microreactors were coated with catalysts synthesized by two different methods and hydrogen was produced by methanol steam reforming. The structure of the catalysts was characterized by XRD, SEM and EDS analyses in the synthesis, activation and after long-term evaluation stages. The effect of CO adsorption and the structural changes of catalysts on the product stream and conversion were investigated and compared in detail. As a result, it was observed that the catalyst prepared by sono-coprecipitation (SCC) was more active although lost its performance much faster. Considering the performance graphs, SEM/EDS analyses and XRD results, it was revealed that the main reason for the performance decrease of the SPC-reactor (spray pyrolysis coating) was the increase of CO adsorption on the surface. Also, the formation of CuO structures and CO adsorption in the SCC-reactor were responsible for the faster performance decrease.

How adsorbed H, O, OH, and Cl affect plain adsorption of imidazole on copper

In real environments, metal surfaces are never clean. Even during active dissolution in corrosion, they are likely covered with adsorbed species such as O, OH, H, and Cl. For this reason, we addressed how such species (hereinafter labeled as X(ads)) affect the adsorption bonding of imidazole—used as an archetypal model of azole corrosion inhibitors—on Cu(111). To this end, we performed a systematic high-throughput DFT study by considering over 400 different adsorption configurations, where the effects of coverage, the type of X(ads) species, and the distance between imidazole and X(ads) were scrutinized. Our calculations indicate that O and Cl enhance the adsorption bonding of imidazole, H has almost no effect, whereas OH either diminishes or has a negligible impact on the adsorption of imidazole. The effect of the X(ads) species on the imidazole adsorption usually diminishes with the increasing distance between X(ads) and imidazole and with decreasing X(ads) coverage. Three coadsorption effects of X(ads) on non-dissociative adsorption of imidazole were identified. The first stabilizing effect, operative for O and OH, is due to the hydrogen bond formation with the nearby adsorbed imidazole. The second stabilizing effect, relevant for O and Cl, is due to the X(ads) induced enhancement of the N–Cu bond between the nearby adsorbed imidazole and the surface; this effect enhances with increasing coverage of X(ads). The last effect is related to the X(ads) induced work function change and can be stabilizing (for O and Cl), negligible (for H), or destabilizing (in the case of OH) for adsorption of imidazole and explains why the impact of X(ads) on adsorption bonding of imidazole diminishes with the X(ads) coverage. Finally, if the coverage of X(ads) is too high, then the chemisorption of imidazole is prevented either sterically or due to the unavailability of free surface sites.

PH‐Controlled Switch over Coadsorption and Separation for Mixed Cs+ and Sr2+ by an Acid‐Resistant Potassium Thioantimonate

AbstractSwitchable coadsorption and separation for elimination/partitioning of Cs+ and Sr2+ is achieved by pH‐controlled ion exchange using a potassium thioantimonate K2Sb4S7·2H2O (SbS‐1K) with fantastic pH durability from diluted NaOH (pH 12) to concentrated HCl (3 m). At pH 6, SbS‐1K exhibits ultrafast adsorption kinetics (R ≈ 90% in 2 min for Cs+ and 20 min for Sr2+) and high removal rates (R ≈ 98–99%) at equilibrium for both Cs+ and Sr2+. At pH 2, the Sr2+ adsorption is inhibited by H+ with a great loss in RSr to 11.18%, whereas the RCs remains at 96.99%, contributing to a top‐ranked separation factor SFCs/Sr of 256. The SbS‐1K‐filled ion exchange column can be switched between the eliminating (RCs > 99.91%; RSr > 98.19%) and separating (RCs > 98.99%; RSr ≈ 0±3%) modes for treating continuous flow with a variation from pH 6 to pH 2 or vice versa. The SbS‐1K/PTFE membrane exhibits coadsorption and separation effects for filtration of low concentrated mixed Cs+ and Sr2+ solution (1 ppm for each), even at an ultrafast vacuum filtration speed (30 mL min–1). Combined with easy synthesis and high β/γ irradiation resistance, SbS‐1K represents a new‐concept bifunctional exchanger with discriminating intelligence for equipment innovation.

The effect of edges hydrogenation and adsorption of Co and Mn atoms on spin transport properties of borophene Nanoribbons

The stability and magnetic features of bare (ZBNRs) and hydrogenated zigzag borophene nanoribbons (H-ZBNRs) are studied. The calculations are performed using density functional theory and non-equilibrium Green’s function. The results indicate that by hydrogenating borophene, the stability of nanoribbon increases. The magnetic properties of ZBNRs are affected by the hanging bond ofnanoribbon. ZBNR is a magnetic metal while by t hydrogenation, the magnetic effect is eliminated. The quantum transport properties for borophene nanoribbon at zero and low bias voltages are investigated. By increasing voltage the current increases and at the bias voltage of 0.5 V a current of about 35 µ A is observed. Moreover, the effect of Mn and Co adsorption on the surface of H-ZBNRs is investigated. The results indicate that the non-magnetic structure of H-ZBNRs becomes magnetic by adsorbing Co and Mn atoms. Also, the charge transfer is from Co and Mn atoms to borophene Nanoribbon. Our calculations indicate that the amount of current and the magnetic properties of ZBNRs could be modified by passivated of edge Nanoribbon and the TM atoms, which has a promising application in molecular magnet and Nano-electronic devices.

Structural evolution of MoS2 supported gold nanoclusters under CO oxidation condition and the effect on reaction activity

The understanding of structural evolution of metal nano-catalysts under real reaction condition is crucial for studying the catalytic properties. DFT calculations with van der Waals correction were performed to study the CO oxidation catalytic activity of Au nanoclusters with reconstruction due to CO adsorption. The global minimum structures of bare and MoS2 supported Aun (n = 1–20) nanoclusters, as well as Aun (n = 6, 12, 16 and 19)/MoS2 with different CO coverages, were obtained by minimum hopping algorithm to study the structural evolution. It is noted that three-dimensional Au19 supported on MoS2 transforms into two-dimensional structure for Au19(CO)6/MoS2 and quasi-2D structure for Au19(CO)12/MoS2 with CO coverage increasing. The stability of Aun(CO)m/MoS2 at 300 K was confirmed by ab initio molecular dynamics simulations, and the effect of CO adsorption on nanoclusters diffusion was also observed. Microkinetic analysis results indicated that the MoS2 support and structural reconstruction caused by CO adsorption both have remarkable effect on the CO oxidation activity, and the effect varies with Au nanocluster size.

Simultaneous electrocatalytic hydrogenation of aldehydes and phenol over carbon-supported metals

Electrocatalytic hydrogenation of furfural, benzaldehyde, and phenol was studied on carbon-supported Rh, Ru, Pd, and Cu catalysts. All metals were active for hydrogenation of the carbonyl group in furfural and benzaldehyde, but only Rh/C was active for phenol hydrogenation. The intrinsic activities for furfural and benzaldehyde conversion were Pd/C < Ru/C ≤ Rh/C < Cu/C and Ru/C < Rh/C < Pd/C < Cu/C, respectively. While the trend in furfural hydrogenation remained the same in the presence of phenol, the trend in benzaldehyde hydrogenation in the presence of phenol changed to Rh/C < Ru/C < Pd/C < Cu/C. The Faradaic efficiencies for hydrogenation of both furfural (in the 10–40% range) and benzaldehyde (in the 45–100% range) followed the trend: Cu/C < Rh/C < Ru/C < Pd/C. When phenol and an aldehyde were present in the reactant solution, phenol hydrogenation was suppressed. In contrast, enhancements in the rates of carbonyl reduction were observed for both aldehydes in presence of phenol. Such enhancements depend on both the aldehyde and the metal catalyst. The enhancing factors for hydrogenation of furfural and benzaldehyde were in the 1.5–2 and 2–4 ranges, respectively. We conclude that intermolecular interactions between adsorbed phenol and the aldehydes is a general phenomenon that can potentially enhance the rates of carbonyl hydrogenation. This work highlights co-adsorption effects that pose both challenges and advantages for electrocatalytic reduction of organic compounds.

Asphaltene-induced spontaneous emulsification: Effects of interfacial co-adsorption and viscoelasticity

Asphaltenes are a class of high molecular weight aromatic compounds found in crude oil. They adsorb onto toluene-water interfaces and induce a spontaneous emulsification phenomenon, whereby stable water-in-oil emulsions form without the need of an external energy input. This work aims to control and understand the factors affecting spontaneous droplet formation in the presence of asphaltene adsorption. This is particularly useful for crude oil refining, where the presence of a stable emulsion hampers the efficiency of downstream processing operations. We explore the effect of the addition of copolymers designed as crude oil flow improvers as a means to control the extent of emulsion formation. We find that the polymers competitively adsorb onto the toluene-water interface and diminish spontaneous emulsification. We also conduct fluorescence microscopy experiments and measurements of the interfacial energy to determine the mechanism of spontaneous emulsification in asphaltene systems. We conclude that an emulsion forms via the diffusion of molecular water into the oil phase and subsequent binding with asphaltene aggregates, leading to the nucleation of micrometer-sized water droplets. We find that the polymer forms complexes with the dissolved asphaltenes, possibly hampering the ability of diffused water to bind to the asphaltenes and reducing the extent of spontaneous emulsification. Finally, we investigate the role of interfacial shear and dilatational viscoelasticity to better understand which fundamental interfacial properties are important in the emulsification of asphaltene-laden systems. We find that the rate of formation of an interfacial microstructural network is inversely correlated with the extent and rate of spontaneous emulsification.

Controlling dye coverage instead of addition of organic acid to reduce dye aggregation in dye-sensitized solar cells

The photo-generated electron injection yield of dye-sensitized solar cells (DSSCs) based on donor-acceptor conjugated dyes is lowered by the aggregation of surface adsorbed organic dyes that pose a low-photoenergy conversion efficiency. Coadsorbates used to prevent the aggregation cause to decompose or detach the dye molecules anchored on the TiO2 surface. In this study, the effect of coadsorption of organic acid and organic dyes on photovoltaic performances was systematically scrutinized by means of adsorption isotherms and photovoltaic measurements. Our laboratory synthesized {0 1 0}-faceted TiO2 (PA TiO2) and P25 TiO2 were used as mesoporous nanocrystals, D149 organic dye was used as a sensitizer and cheno-deoxycholic acid, CDA, was used as a coadsorbate. The coadsorption of CDA reduces the adsorption parameters, maximum adsorption density (Qm) and adsorption constant (Kad), and the reduction depended on the type of TiO2. The photovoltaic performance indicates that the D149 dye has the best dye coverage at around 70% for the effective photovoltaic energy conversion. The coadsorption of CDA increased the photovoltaic performances of DSSCs based on P25 TiO2 but, CDA decreased the photovoltaic performances of DSSCs based on PA TiO2 due to the reduction of the dye coverage below 70%. The results suggest that the coadsorption of organic acids is not necessary if the particular TiO2 can maintain its coverage at the best coverage. Thus, the requirement of coadsorbates to reduce the dye aggregation depends on the type of TiO2 used in DSSCs.

Thermal Behaviour of Synovene and Oleamide in Oil Adsorbed on Steel

Oleamide and Synovene lubricant additives when mixed together show a clear co-operative effect leading to friction and wear reduction. Sum Frequency Generation vibrational spectroscopy has been used to record in situ spectra of these additives with the aim of understanding the behaviour of these molecules when adsorbed on steel immersed in a model base oil at pre-selected temperatures. The spectra of the individual components and of mixtures have been recorded up to 130 °C. Individual spectra from both molecules have been distinguished using per-deuterated oleamide. The temperature at which maximum ordered adsorption of pure Synovene molecules occurs drops from ~ 130 to ~ 70 °C in the mixture with oleamide. Our results show that co-adsorption occurs, which causes a change in net polar orientation of the oleamide component suggesting the hydrocarbon chains of the oleamide molecules reverse their polar orientation when Synovene is present. The net effect of co-adsorption and change in orientation as well as conformation of the two molecules could explain the reduction of friction and wear observed at the metal–metal interface.

Pd3Ag(111) as a Model System for Hydrogen Separation Membranes: Combined Effects of CO Adsorption and Surface Termination on the Activation of Molecular Hydrogen

The co-adsorption of hydrogen and carbon monoxide on Pd3Ag(111) alloy surfaces has been studied as a model system for Pd-Ag alloys in membrane and catalysis applications using periodic density functional theory calculations (PW91-GGA). We explored the effects of Pd–Ag surface composition, since segregation of silver towards and away from the surface has been suggested to explain the experimentally observed changes in H2 activation, CO inhibition and reactivity. We found that CO pre-adsorbed on the surface weakens the adsorption of H on Pd3Ag(111) alloy surfaces irrespective of whether the surface termination corresponds to the bulk Pd3Ag composition, or is purely Pd-terminated. A higher coverage of H with CO present is obtained for the Pd-terminated surface; this surface also exhibits a larger range of chemical potentials for co-adsorbed hydrogen and CO. The barrier for H2 activation increases with increasing CO coverage, but the surface composition has the largest impact on H2 activation at intermediate CO coverage. The results imply that Pd-based membranes with typically ~ 23 wt% Ag are less prone to CO poisoning if the surface becomes Pd-terminated.

Effect of CO adsorption on properties of transition metal doped porphyrin: A DFT and TD-DFT study

The structural, electronic and optical properties of transition metal doped porphyrin (TM@P; TM = Mn, Co, Fe, Cu, Ni, Zn) as well as the effect of CO adsorption on TM@P properties have been investigated using the density functional theory (DFT). The presented results include adsorption energies, bond lengths, electronic configurations, magnetic moments, density of states, frontier molecular orbitals, and UV-Vis. spectra. Our calculation results show that, the CO molecule favors to be adsorbed on TM-doped Porphyrin with its carbon head. The most energetically stable adsorption of CO is reported for Fe doped Porphyrin. The interaction between CO molecules with TM@P is attributed to donation-back donation as well as charge transfer mechanisms. Mn, Co and Fe-doped porphyrins have visible active nature which may be affected by CO adsorption, whereas, Ni, Cu and Zn-doped porphyrins have UV active nature which not affected by CO adsorption. These results may be meaningful for CO removal and detection.

The synergistic effect and microscopic mechanism of co-adsorption of three emerging contaminants and copper ion on gemini surfactant modified montmorillonite

Montmorillonite (G-Mt) modified by a gemini quaternary ammonium cationic surfactant (Propyl bis (hexadecyl dimethyl ammonium) chloride, 16-3-16) was used to remove emerging contaminants (ECs) (such as 1H-Benzotriazole (BTA), 5-Methyl-1H-benzotriazole (TTA) and 1-Hydroxybenzotriazole (HOBT)) and Cu2+ from wastewater. Based on the adsorption of the above three ECs in our previous studies, single adsorption of Cu2+ and the simultaneous adsorption of three ECs with Cu2+ on G-Mt were also investigated. G-Mt showed much lower adsorption amount on Cu2+ comparing with original montmorillonite (Ca-Mt) in single adsorption system due to the difficulty of ion-exchange property of G-Mt. In co-adsorption system, three organic pollutants and Cu2+ played a synergistic effect and the adsorption capacity of G-Mt on them increased, the influence sequence of Cu2+ on the adsorption of three ECs or the effect of ECs on the adsorption of Cu2+ both followed as: TTA > BTA > HOBT. The results of FT-IR, EDS and XPS revealed that the complex of Cu2+ and ECs were adsorbed onto G-Mt via forming complexes and hydrophobic interaction in co-adsorption system. The pH experiment showed that the optimum pH of the co-adsorption of ECs and Cu2+ on G-Mt was 5. Molecular dynamics (MD) simulations showed that three ECs or ECs combining with Cu2+ were dominantly adsorbed in the interlayer space of G-Mt, which resulted in the arrangement manner of 16-3-16 between the layer of G-Mt before and after adsorption of three organic pollutants was different. Furthermore, by quantitatively analyzing electrostatic potential (ESP) distribution, average local ionization energy (ALIE) distribution and their minimum points on three ECs molecules surfaces, Multiwfn program has been applied to probe the microscopic mechanism. The synergistic effect of co-adsorption will promote enrichment of copper ions and ECs to remove them more efficiently in polluted waters.