Narrow Results

The deposition of single Si ad-dimer on the p(2×2) reconstructed Si(100) surface has been simulated by an empirical tight-binding (ETB) method. Using the clean and defective Si surfaces as the deposition substrates, the deposition energies are mapped out around the clean surface and dimer vacancies. From the calculated energy plots, the binding sites and several possible diffusion paths are achieved. It is easy for the ad-dimer to form stable state A1 and metal stable state A2 on the clean surface. The change from A1 to A2 state appears as the rotation of the ad-dimer, which has been observed experimentally. The ad-dimers are found to prefer filling into the missing dimer vacancies. Finally, the diffusion traces of the ad-dimers on the surfaces have been simulated.

The adsorption of oxygen and potassium on the two-phase system: carbide-modified stepped-W(100) surface (CMT) in contact with the solid solution of carbon in bulk tungsten, was investigated by AES and WF measurements. The CMT surface shows metallic behavior judging from its interaction with K. The expected dissociative adsorption of oxygen appears to occur with 1 - θ kinetics, possibly via a molecularly chemisorbed state. The "dispersed phase — two-phase" model is clearly applicable when oxygen adsorbs on the K-pre-covered carbide. The initial sticking coefficient of oxygen increases drastically from the dispersed to the condensed phase, at least four-fold with respect to s₀ on the clean carbide. It is proposed that this two-phase carbon system can be advantageous compared with the bulk carbide since it can easily regenerate the surface if the latter is depleted from carbon.

This paper describes the oxygen adsorption properties on magnesium oxide surface. The results are compared with theoretical adsorption kinetics. Temperature and time dependences of adsorption mechanisms and chemiluminescence are discussed.

We apply a first-principles molecular-dynamics method based on the density functional theory to calculate several initial configurations of an O₂ molecule adsorbed on a Si(001) surface. The bonding processing, adsorption energy, dynamic track, and diffusion coefficient are investigated. The results indicate that the adsorption process may be divided into four stages: physical adsorption, chemical adsorption early stage, chemical adsorption late stage, and the superficial stable state. The Si=O structure, the Si–O–Si surface oxygen-bridge structure, and the Si–O–Si oxygen-bridge structure where oxygen atoms are inserted into the backbonds between the surface and the second layer of silicon atoms in the stable adsorption structures, are beneficial to the formation of the silica tetrahedral structure. We conclude that the remarkable difference between the diffusion coefficients during the physical adsorption stage leads to different diffusion paths, which results in the formation of two concomitant stable structures in the early process of silicon surface oxidation.

The carbon nanotubes grafted methylene blue molecularly imprinted polymers (CNT-MB-MIPs) were prepared by grafting aminated carbon nanotubes (CNTs) and copolymerized in the presence of template molecules methylene blue (MB), functional monomers, crosslinkers, and initiators. The results from structural analyses indicate that CNTs were successfully grafted onto the molecularly imprinted polymers (MIPs). The adsorption experiments showed that the adsorption capacity can be affected by grafting CNTs. The adsorption capacity of CNT-MB-MIPs on MB can reach 2793mgg${}^{-1}$ while the initial concentration of MB was 12gL${}^{-1}$, which was higher than that of MB molecularly imprinted polymers (MB-MIPs). Meanwhile, compared with MB-MIPs, CNT-MB-MIPs had a lower adsorption capacity for iron ions, indicating that CNT-MB-MIPs could inhibit the adsorption of iron ions. Adsorption kinetics study showed that the adsorption mechanism of the polymer for MB was in good agreement with the quasi-second-order kinetics model ($R^2=0.9978$) and the adsorption mechanism for iron ions was also in good agreement with the Bangham kinetics model ($R^2=0.9475$). The adsorption isotherm showed that the adsorption process of the two adsorbents was mainly monolayer chemisorption. The remarkable adsorption capacity of CNT-MB-MIPs may be due to the enlargement of adsorption sites on MIPs surface by CNT-NH₂ grafting. At the same time, it can inhibit the adsorption of iron ions, because part of the carboxyl groups in CNT-MB-MIPs are bonded by CNTs, led to few carboxyl groups sites left for adsorbing iron ions, thereby the complex between carboxyl groups and iron ions were inhibited.

This study was carried out to evaluate the environmental application of functionalized carbon nanotubes through the experimental removal of strontium (II) from water. The aim was to find the optimal condition for the removal of strontium from water under different conditions such as initial concentration of strontium, contact time and neutral pH. The functionalized multi wall carbon nanotubes (f-MWCNT) were characterized by FT-IR and scanning electron microscopy (SEM). The adsorption isotherms were correlated to Freundlich and Langmuir models and it was found that the adsorption data could be fitted better by Langmuir model than Freundlich one. The kinetic data shows that the adsorption describes well with the pseudo-second order kinetic model. Functionalized MWCNT can be used as good adsorbent for the removal of the strontium ions from polluted water according to results.

Considerable attention has been focused on the nanoscale carbon black development and application in wastewater treatment. But the CB is a hydrophobic and nonpolar adsorbent, and it has strong adsorption ability to nonpolar organic compounds and poor adherence to heavy metal ions. The nanoscale carbon black modified by appropriate physical and chemical treatments could improve their adsorption capacities for heavy metal ions. In this study, a surface-modified nanoscale carbon black was prepared by oxidizing the carbon black with 65% HNO₃ (B), 0.05 mol⋅L^-1HAc (C), 20% HNO₃+ 1.58% K₂MnO₄ (D) and 50% H₂SO₄ (E), respectively. Batch experiments showed that the adsorption quantities of Cu(II) on the nanoscale carbon black modified by different kind of acids (MCBs) were significantly increased compared with those on the parent one, and the maximum adsorption quantities of Cu(II) were 48.92 mg⋅g^-1 (D), 30.15 mg⋅g^-1 (B), 12.33 mg⋅g^-1 (A), 13.51 mg⋅g^- (C) and 5.47 mg⋅g^-1 (E), respectively. The Langmuir isotherm provided a better fit to the experimental data of the parent one and the MCBs fitted well into Freundlich adsorption isotherm. The adsorption kinetic model of Cu(II) on all sorbents followed pseudo second order model well. It is clear from this work that the nanoscale carbon black modified by 65% HNO₃ (B) and 20% HNO₃+ 1.58% K₂MnO₄ (D) had very good adsorption properties for the metal ions.

The adsorption of Fe(III) ions from aqueous solution by chitosan alpha-ketoglutaric acid (KCTS) and hydroxamated chitosan alpha-ketoglutaric acid (HKCTS) was studied in a batch adsorption system. Experiments were carried out as function of pH, temperature, agitation rate and concentration of Fe(III) ions. The Langmuir and Freundlich adsorption models were applied to describe the equilibrium isotherms and isotherm constants were determined. The Langmuir model agrees very well with experimental data. The pseudo-first-order and second-order kinetic models were used to describe the kinetic data and the rate constants were evaluated. The dynamical data fit well with the second-order kinetic model. The pseudo second-order kinetic model was indicated with the activation energy of 19.61 and 7.98 kJ/mol for KCTS and HKCTS, respectively. It is suggested that the overall rate of Fe(III) adsorption is likely to be controlled by the chemical process. Results also showed that novel chitosan derivatives (KCTS and HKCTS) were favorable adsorbents.

We describe the spectroscopic characterization of a supramolecular trisporphyrin complex that is heterogeneously self-assembled onto mesoporous Al₂O₃ films and can be used as efficient light harvesting complex. The parameters for an efficient complexation process, such as dye loading, are evaluated and discussed. In addition, the heterosupramolecular complex is tested on TiO₂ nanoparticles and the charge transfer process elucidated.

This study presents the synthesis, characterization and toluene sensing properties of copper(II), indium(III) acetate, mono-lutetium(III) acetate and tin(IV) phthalocyanines substituted with 2,6-dimethoxyphenol bioactive groups at the peripheral and non-peripheral positions. The effects of the substituent’s position on the toluene vapor detection capabilities of these compounds were investigated. Adsorption data were analyzed by using first-order and Elovich equations in order to investigate the adsorption kinetics. It was found that the kinetics of the toluene adsorption strongly depends on the position of the substituent groups. Our results showed that the Elovich equation fits the experimental data well for non-peripherally substituted Pc based sensors, while the pseudo first-order model best describes the adsorption data for peripheral substituted Pc based sensors.

Compound (4,4$\prime$ -hex-3-ene-3,4-diyl)bis(4,1-phenylene)bis(oxy)diphthalonitrile 3 was synthesized by the reaction of 4-nitrophthalonitrile 1 and diethylstilbestrol 2 in dry DMF in presence of dry K₂CO₃. New mononuclear phthalocyanines 4-6 were obtained from compound 3 by addition of the corresponding metal salts [Co(OAc)₂ ⋅ 4H₂O, Zn(OAc)₂ ⋅ 2H₂O and Cu(OAc)₂]. The novel compounds were characterized by elemental analysis and FT-IR, UV-vis, ¹H-NMR and MALDI-TOF mass spectroscopy techniques. The effects of four main groups of organic vapors on these novel compounds were studied and discussed. The adsorption kinetics of alkanes ($n$-hexane and $n$-octane), alcohols (methanol and 2-proponal), chlorinated hydrocarbons (dichloromethane and trichloromethane) and amines (diethylamine and triethylamine) on 4-6 were examined using three adsorption kinetic models: the Elovich equation, the pseudo-first-order equations and Ritchie’s equation. Results show that the linear regression analysis with respect to the pseudo-second-order rate equations generates a straight line that best fits the data of adsorption of alcohols and chlorinated hydrocarbons on Pc films. On the other hand, the Elovich equation generates a straight line that best fits the data of adsorption of alkanes and amines.

Two-dimensional hexagonal boron nitride is a fascinating nanomaterial with a broad range of potential applications. However, further development of this nanomaterial is hampered because of its poor functionality and low processability. One of the efficient strategies for improving the processability of two-dimensional hexagonal boron nitride is the covalent functionalization of this nanomaterial. In this study, we report on a straightforward approach for functionalization of two-dimensional hexagonal boron nitride by lithium cyclopentadienyl and its application for water treatment. Cyclopentadienyl-functionalized boron nitride was characterized by different spectroscopy and microscopy methods as well as thermal and BET analysis. The synthesized nanomaterial was able to efficiently remove methylene blue from water in a short time. Adsorption capacity of this nanomaterial was as high as 476.3mg/g, which was superior to the nonfunctionalized boron nitride. Our results showed that cyclopentadienyl-functionalized boron nitride is a promising candidate for the removal of cationic pollutants from water.

Micro/mesoporous materials are low-cost functional materials with the potential for CO₂ adsorption. Modifying micro/mesoporous materials is significant for enhancing CO₂ adsorption and their high-value utilization. Herein, the micro/mesoporous material of composite molecular sieve ZSM-5/MCM-48 (ZM) was synthesized by a two-step crystallization method using cetyltrimethylammonium bromide as a template, tetraethyl orthosilicate as a silicon source and ZSM-5 seed as part of silicon aluminum source. Tetraethylenepentamine (TEPA) and polyethyleneimine (PEI) were used as impregnation modifiers to modify ZM with amine groups. The results showed that with the increase of amine loadings, both ZM-T60 (Impregnated with TEPA) and ZM-P60 (Impregnated with PEI) functionalized adsorbents exhibited the best adsorption capacities of $4.97\mathrm{\text{mmol}}\cdot {\mathrm{\text{g}}}^{-1}$ and $3.28\mathrm{\text{mmol}}\cdot {\mathrm{\text{g}}}^{-1}$ at 60, respectively, when the loading of ZM sample was 60%. The adsorption kinetic analysis showed that the adsorption of CO₂ by ZM-T60 and ZM-P60 was a chemisorption-dominated process accompanied by physical adsorption. After 10 adsorption/desorption cycles, the CO₂ adsorption capacity of ZM-T60 and ZM-P60 decreased by 8.7% and 2.6%, respectively. This work demonstrates that impregnation modification of the composite molecular sieve to achieve efficient CO₂ adsorption has practical application significance.

The environmental impact of untreated dye effluent is a concern due to potential mutagenic and allergic effects. This study aims to develop a cost-effective selenium-doped biochar as an adsorbent material to remove acid red (AR) and crystal violet (CV) dyes from water. Selenium nanoparticles (SeNPs) were produced using chemical and biological synthesis methods. The SEM, EDX, XRD, FTIR, and BET surface analysis methods were used to characterize the biochar and selenium-doped biochar (Se-AC and BSe-AC) samples. Surface modification with SeNPs resulted in an increase in surface area to 14.560m²/g for Se-AC and 85.456m²/g for BSe-AC. Different adsorption isotherms (Langmuir, Freundlich, and Temkin) and adsorption kinetic models (pseudo-firstorder, pseudo-secondorder, and intra-particle diffusion kinetics) were investigated to understand the adsorption patterns of biochar, Se-AC, and BSe-AC. The maximum adsorption capacities of biochar, Se-AC, and BSe-AC for AR and CV dye were found to be between 0.48mgg${}^{-1}$ and 7.51mgg${}^{-1}$, 2.31mgg${}^{-1}$ and 7.86mgg${}^{-1}$, and 6.88mgg${}^{-1}$ and 9.09mgg${}^{-1}$, respectively, at 313K. The obtained negative $\mathrm{\Delta }{G}^{\circ }$ indicates effective adsorption, while a positive $\mathrm{\Delta }{H}^{\circ }$ suggests an endothermic reaction for both dyes. BSe-AC is an eco-friendly alternative to biochar for removing AR and CV.

Compound (4,4′-hex-3-ene-3,4-diyl)bis(4,1-phenylene)bis(oxy)diphthalonitrile 3 was synthesized by the reaction of 4-nitrophthalonitrile 1 and diethylstilbestrol 2 in dry DMF in presence of dry K₂CO₃. New mononuclear phthalocyanines 4–6 were obtained from compound 3 by addition of the corresponding metal salts [Co(OAc)₂ · 4H₂O, Zn(OAc)₂ · 2H₂O and Cu(OAc)₂]. The novel compounds were characterized by elemental analysis and FT-IR, UV-vis, 1H-NMR and MALDI-TOF mass spectroscopy techniques. The effects of four main groups of organic vapors on these novel compounds were studied and discussed. The adsorption kinetics of alkanes (n-hexane and n-octane), alcohols (methanol and 2-proponal), chlorinated hydrocarbons (dichloromethane and trichloromethane) and amines (diethylamine and triethylamine) on 4–6 were examined using three adsorption kinetic models: the Elovich equation, the pseudo-first-order equations and Ritchie’s equation. Results show that the linear regression analysis with respect to the pseudo-second-order rate equations generates a straight line that best fits the data of adsorption of alcohols and chlorinated hydrocarbons on Pc films. On the other hand, the Elovich equation generates a straight line that best fits the data of adsorption of alkanes and amines.