Studies on chelating adsorption properties of novel composite material polyethyleneimine/silica gel for heavy-metal ions

Firstly, the coordination processes of line-type polyethyleneimine with Cu²⁺, Cd²⁺ and Zn²⁺ were studied by using visible light absorption spectroscopy and chelation conductivity titration method, and the structures of the chelates were determined. Afterwards, polyethyleneimine (PEI) was grafted onto the surface of silica gel particles via the coupling effect of γ-chloropropyl trimethoxysilane (CP), and the novel composite adsorption material PEI/SiO₂ with strong adsorption ability towards heavy-metal ions was prepared. The chelating adsorption properties of PEI/SiO₂ for Cu²⁺, Cd²⁺ and Zn²⁺ were researched by both static (batch) and dynamic (flow) methods. The experiment results show that water-soluble polyamine PEI with line-type structure reacts with Cu²⁺, Cd²⁺ and Zn²⁺ easily and quantitatively, and water-soluble chelates with four ligands are formed. The composite material PEI/SiO₂ possesses very strong chelating adsorption ability for heavy-metal ions, and the saturated adsorption amount can reach 25.94 mg g⁻¹ and 50.01 mg g⁻¹ for Cu²⁺ under static and dynamic conditions, respectively. The isothermal adsorption data fit to Langmuir equation, and the adsorption is typical chemical adsorption with monomolecular layer. The adsorbing ability of PEI/SiO₂ towards the three kinds of the ions follows the order of Cu²⁺ > Cd²⁺ > Zn²⁺. The pH value has great influence on the sorption, and at pH 6-7, the adsorption capacity is the greatest. The fact that adsorption capacity increases with temperature rising indicates the adsorbing process of PEI/SiO₂ for metal ions is endothermic. As diluted hydrochloric acid is used as eluent, the adsorbed heavy-metal ions are eluted easily from PEI/SiO₂, and the regeneration and reuse without decreasing sorption for PEI/SiO₂ are demonstrated.     

dsDNA与TiO2 (110)在溶液中相互作用的动力学行为和机制

金红石型TiO2 (110)在DNA传感领域具有广阔的应用前景,然而其与DNA在溶液中相互作用的动力学行为和机制尚不清楚。利用分子动力学模拟,深入研究了双链DNA (dsDNA)在初始时沿轴向平行或垂直于金红石型TiO2 (110)表面时二者在溶液中的相互作用。通过分析dsDNA在吸附后的稳定构型、吸附动力学过程和结构稳定性发现,与一些典型二维纳米材料不同,dsDNA倾向于水平吸附到TiO2 (110)表面。水平吸附不仅使得dsDNA的四种碱基均吸附到TiO2 (110)表面,增加了吸附稳定性,而且不破坏dsDNA的结构稳定性。进而,通过分析dsDNA与TiO2 (110)表面的相互作用能和水分子密度/数量发现,dsDNA的平行吸附可能源于二者之间的短程范德华和长程静电相互作用。此外,纳米级脱湿也增强了dsDNA的吸附。对dsDNA与TiO2 (110)在溶液中的相互作用研究有助于实现TiO2 (110)在DNA传感中的应用。     

CO2 adsorption on branched polyethyleneimine-impregnated mesoporous silica SBA-15

Adsorption of pure CO₂ on SBA-15 impregnated with branched polyethyleneimine (PEI) has been studied. Materials were prepared by impregnating the pore surface of SBA-15 mesoporous silica with different amounts of branched PEI (10, 30, 50 and 70 wt%). Textural properties, elemental analysis and low angle XRD measurements of the prepared samples showed a progressive pore filling of SBA-15 as PEI loading was increased. Pure CO₂ adsorption isotherms on these modified SBA-15 materials were obtained at 45 °C, showing high adsorption efficiency for CO₂ removal at 1 bar. Chemisorption of CO₂ on amino sites of the modified SBA-15 seems to be the main adsorption mechanism. PEI content of impregnated SBA-15 influences the adsorption capacity of the material, being a relevant variable for CO₂ removal by adsorption. Temperature effect on adsorption was also studied in the range 25-75 °C, showing that temperature strongly influences CO₂ adsorption capacity. Adsorption capacity was also tested after regeneration of the PEI-impregnated SBA-15 materials. Our results show that these branched PEI-impregnated materials are very efficient even at low pressure and after several adsorption-regeneration cycles.     

SAXS cluster structure and properties of sPEEK/PEI composite membranes for DMFC applications

Sulfonated poly(ether ether ketone)/polyethyleneimine (sPEEK/PEI) composite membranes were prepared to reduce the water uptake and methanol permeability of highly sulfonated PEEK membranes (> 65%). Incorporation of small amounts of PEI reduced ionic cluster size via electrostatic complex formation between anionic sulfonic groups of the sPEEK and the cationic amine groups of the PEI, and thus affected membrane properties considerably. Ion cluster size decreased with increasing PEI concentration by small angle X-ray scattering pattern. Addition of 1 wt.% of PEI resulted in reduction of water uptake and methanol permeability by 30% at 60 °C and 85% at room temperature, respectively. The thermal and mechanical stabilities were also enhanced by formation of physical cross-linking induced by electrostatic interactions between acid/base polymers. Although proton conductivity was also reduced by PEI incorporation as a part of the sulfonic acid groups involved in ionic complex formation, its effect on proton conductivity was not as strong as on methanol permeability.     

Raman signatures of strong and weak hydrogen bonds in binary mixtures of phenol with acetonitrile,benzene and orthodichlorobenzene

The present study aims at investigating the effect of hydrogen bonds of phenol in binary mixtures of phenol with three solvents viz. acetonitrile, orthodichlorobenzene and benzene respectively in order of decreasing hydrogen bond strength. Raman spectroscopy in correlation with density functional theory (DFT) calculations has led to a profound understanding of changes in structure, energy, dipole moment and other physical and chemical properties of phenol pertaining to hydrogen bond formation in solution. The spectral variation in wavenumber and linewidth of ring deformation, ring stretching, C≡N stretching and C―H stretching modes have been analyzed in detail. The breaking of self association of phenol in solution and formation of strong or weak hydrogen bonds depending on the nature of the solvent has been discussed by comparing the Raman and DFT results for three different solvents. Copyright © 2016 John Wiley & Sons, Ltd.     

Magnesium silicates - adsorbents of organic compounds

Studies were presented on production of highly dispersed magnesium silicate at a pilote scale. The process of silicate adsorbent production involved precipitation reaction using water glass (sodium metasilicate) solution and appropriate magnesium salt, preceded by an appropriate optimization stage. Samples of best physicochemical parameters were in addition modified (in order to introduce to silica surface of several functional groups) using the dry technique and various amounts of 3-isocyanatepropyltrimethoxysilane, 3-thiocyanatepropyltrimethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane. The so prepared samples were subjected to a comprehensive physicochemical analysis. At the terminal stage of studies attempts were made to adsorb phenol from its aqueous solutions on the surface of unmodified and modified magnesium silicates. Particle size distributions were determined using the ZetaSizer Nano ZS apparatus. In order to define adsorptive properties of studied magnesium silicates isotherms of nitrogen adsorption/desorption on their surfaces were established. Efficiency of phenol adsorption was tested employing analysis of post-adsorption solution.     

Surface modification of the polyethyleneimine layer on silicone oxide film via UV radiation

We herein report a novel method of employing 254 nm of UV radiation (UV) for the modification of a polyethyleneimine (PEI) layer on silicone oxide film. In this study, a PEI layer composed of a 50 mM sodium carbonate solution (pH 8.2) was formed on the surface of a silicone oxide film with spontaneous adsorption. Then, thin film of PEI was patterned by UV radiation. To determine the effect of the UV radiation, fluorescence microscopy, X-ray electron spectroscopy (XPS), and Fourier Transform Infrared spectroscopy (FT-IR) analyses were performed. These results indicated that UV radiation could cause changes in the surface characteristics of the PEI layer. Subsequently, FT-IR analysis showed changes in the chemical composition of the PEI exposed to UV radiation, such as the disappearance of the amine. Based on these results, we can conclude that UV radiation could be used to eliminate the amine group selectively and that this technique could be applied to create a pattern on the surface of a PEI layer.     

外加阴离子吸附剂对复合污染黄土淋洗过程养分淋失的减缓机制(Ⅱ)

化学淋洗法是常用的污染场地修复方法,其经济性、简便性、安全性等指标较其他方法有较大优势。化学淋洗法存在的弊端之一是淋洗过程土壤伴存养分的同步淋失,若能在此瓶颈问题上有所突破,将会大大促进淋洗法场地修复的应用进程。本文研究的目标在于揭示合成秸秆基阴离子吸附剂对养分淋失的减缓机制,采用吸附平衡模式(等温线和动力学)与光谱分析技术(SEM和FT-IR)相结合,力图从微观层面验证宏观研究结果。Langmuir和准二级动力学方程能更好地描述硝酸根和磷酸根的吸附行为,由Langmuir方程计算得出q_m分别为7.507 5和4.194 6 mg·g-1,吸附反应为单层吸附和优惠吸附过程,主要控速步骤为化学吸附。阴离子吸附剂对硝酸根和磷酸根的吸附活化能(298 K)E_a分别为42.25和39.38 kJ·mol-1,吸附反应自发、吸热。纯净水和KOH能够实现阴离子吸附剂的再生,超声辅助和延长解吸时间对于解吸效果略有促进作用。吸附后阴离子吸附剂表面被点状分布的细微颗粒物覆盖,解吸后仅有少量枝状物零星分布。吸附前后FTIR图谱的主要波峰红移或蓝移,证实阴离子吸附剂表面及内部官能团通过静电作用与硝酸根和磷酸根结合。阴离子吸附剂对硝酸根和磷酸根的吸持固定是物理吸附和化学吸附共同作用的结果。     

位阻效应对受阻酚杂化体系阻尼机理的影响

针对尚未解决的受阻酚结构变化与杂化体系阻尼机理间关系的问题,本文采用分子动力学模拟方法构建了三种受阻程度不同的受阻酚/聚合物杂化体系,从理论上探讨了位阻效应对阻尼机理的影响.对体系氢键相互作用、结合能、相对自由体积及扩散系数进行模拟分析表明,位阻效应对受阻酚分子内氢键相互作用有显著的弱化效果,可减少小分子团聚倾向,有利于小分子与聚合物分子间氢键相互作用的形成.但是,过高的位阻对小分子运动有阻碍作用,不利于小分子与聚合物形成强烈的氢键键合,也即不利于杂化体系阻尼性能的提高.因此,如何选择受阻程度适中的受阻酚是制备高阻尼杂化材料的一关键要素.     

Shock Structures in Charge Variable Dusty Plasmas with Effect of Strongly Coupled Dust Particles

A theoretical investigation has been carried out to study the effect of strong electrostatic interaction on the dust acoustic shock structures in strongly coupled dusty plasma with dust charge fluctuations.The fluid approach is employed,in which the strong electrostatic interaction is modeled by effective electrostatic temperature.A Burger-like equation,the coefficients of which are significantly modified by effects of strong coupling and dust charge Ructuation,is derived.It is shown that the combined effects of dust charge Ructuation,the ion/electron temperature,the ion/electron population,and strong coupling effect modify the basic properties of the dust acoustic waves in such a strongly coupled dusty plasma.The results of this work are compared with those observed by some laboratory experiments.     

Dispersibility improvement of gold/iron-oxide composite nanoparticles by polyethylenimine modification

Composite gold/iron-oxide nanoparticles were synthesized by a sonochemical process and their surface then modified with polyethylenimine (PEI). The dispersibility of the composite nanoparticles in acidic solution was improved by the PEI modification. The composite nanoparticles specifically adsorbed sulfur-containing amino acids and could be picked up by an external magnetic field. Thus, composite nanoparticles modified with PEI carry both the ability to bond Au-S and to disperse well in buffer solutions.     

Removal of organic contaminants from aqueous solution by cattle manure compost (CMC) derived activated carbons

The activated carbons (ACs) prepared from cattle manure compost (CMC) with various pore structure and surface chemistry were used to remove phenol and methylene blue (MB) from aqueous solutions. The adsorption equilibrium and kinetics of two organic contaminants onto the ACs were investigated and the schematic models for the adsorptive processes were proposed. The result shows that the removal of functional groups from ACs surface leads to decreasing both rate constants for phenol and MB adsorption. It also causes the decrement of MB adsorption capacity. However, the decrease of surface functional groups was found to result in the increase of phenol adsorption capacity. In our schematic model for adsorptive processes, the presence of acidic functional groups on the surface of carbon is assumed to act as channels for diffusion of adsorbate molecules onto small pores, therefore, promotes the adsorption rate of both phenol and MB. In phenol solution, water molecules firstly adsorb on surface oxygen groups by H-bonding and subsequently form water clusters, which cause partial blockage of the micropores, deduce electrons from the π-electron system of the carbon basal planes, hence, impede or prevent phenol adsorption. On the contrary, in MB solution, the oxygen groups prefer to combine with MB⁺ cations than water molecules, which lead to the increase of MB adsorption capacity.     

花生壳吸附水中苯酚的热力学与动力学研究

利用废弃的花生壳对水中苯酚进行吸附试验,考察了吸附的最佳条件、吸附热力学和动力学特征.采用Langmuir和Freundlich等温线对平衡数据进行了线性拟合,结果表明,花生壳对苯酚的吸附平衡符合Freundlich等温方程.在298K下,吸附焓变△H=-5.12kJ ·moL^-1,自由能变△G=-4.41 kJ·moL^-1,熵变△S=-2.38J·mo1-1·K-1.表明：该吸附过程为自发进行的放热过程,其动力学行为更好的符合Lagergren准二级动力学模型.     

Infrared and Raman study of the interaction between methyl acetate and phenol derivatives

In previous publications [1–3], we have been concerned with the influence of hydrogen bond formation on the Raman intensity of the carbonyl stretching vibration. It has been shown that hydrogen bond association of simple carbonyl bases (cyclohexanone, acetone, acetophenone) with proton donors such as phenol derivatives, hydrochlorid or hydrobromic acid brings about an intensity increase of the ν_CO Raman band; moreover, the intensity enhancement is linearly related to the enthalpy of complex formation. In the present work, these measurements are extended to the complexes formed between methyl acetate (MeAc) and phenol derivatives.

As suggested by the frequency lowering of the ν_CO vibration and the frequency increase of the ν_CO band, complex formation in solution takes place on the carbonyl function.From NMR [4–5] and UV data [6] it can also be concluded that protonation via hydrogen-bonded attachment occurs in solution predominantly at the carbonyl oxygen atom.Literature data for the thermodynamic quantities referring to esters with hydroxylic compounds are scarce. Consequently in this work, we have determined the equilibrium constants and the enthalpy of formation for complexes between MeAc and phenol derivatives. We also report the absolute intensity of the ν_CO Raman band in the free ester molecule and in the complexes, all measurements been made in a solvent of low polarity : carbontetrachloride.     

Influence of pretreatment methods on adsorption and catalytic characteristics of toluene over heterogeneous palladium based catalysts

The adsorption and catalytic characteristics of heterogeneous palladium based catalyst and its modified catalysts with gases (air and hydrogen) and acidic aqueous solution (HCl) were studied for evaluating the influence of pretreatment methods for toluene. The structural and energetic adsorption properties of the parent and pretreated catalysts were analyzed by means of nitrogen adsorption isotherms and gravimetric methods. The light-off curve and the XPS investigation were used for analyzing the catalytic activity and the surface state of palladium. It was clearly shown from the experimental results that hydrogen pretreated catalysts having metallic surface state exhibited the highest adsorption capacity and catalytic activity compared to that of parent and modified catalysts. The adsorption equilibrium data for toluene were obtained at three different temperatures and correlated successfully with the two-site Langmuir molecular isotherm model (L2m). It was also found that the palladium phase has more adsorption affinity for toluene molecules than the alumina support. The isosteric heat of adsorption calculated by using the Clausius-Clapeyron equation significantly changed with the coverage and the lateral interactions between the adsorbate-adsorbate molecules control the system. Furthermore, comparative analysis of the adsorption energy distribution revealed that the parent and its modified catalysts have different types of surface energetic heterogeneities.     

Amino-containing magnetic nanoemulsions: elaboration and nucleic acid extraction

Amino-containing magnetic colloids were prepared from highly magnetic oil-in-water (O/W) emulsions. The functionalization was performed by controlling the adsorption of polyethyleneimine onto negatively charged magnetic emulsions. The cationic magnetic nanodroplets were characterized in terms of chemical composition, particle size, size distribution, zeta potential and colloidal stability as a function of storage time. These amino-containing magnetic emulsions were assessed as a new tool for nucleic acid extraction and amplification. The adsorption of nucleic acids was mostly controlled by attractive electrostatic interactions. The adsorption efficiency of a model RNA was found to be encouraging and the captured nucleic acid molecules were directly enzymatically amplified in the presence of the magnetic particles without any elution step.     

Combined effect of ultrasound and nanoclay on adsorption of phenol

Sorption of phenol onto organophilic bentonite (nanoclay) by ultrasonic irradiation was investigated. Tetrabutyl ammonium chloride (TBAC), N-acetyl-N,N,N trimethyl ammonium bromide (CTAB) and hexadecyl trimethyl ammonium chloride (HDTMA) were used as intercalating agents. Nanoclay was synthesized using sonication technique. TBAC modified nanoclay shows amorphous exfoliated nature, while CTAB and HDTMA modified nanoclay shows intercalating crystalline nature, which was revealed by XRD gram. Further FTIR reveals the presence of NH(2) and (CH(2))(n) groups onto clay platelet. Due to sonication, adsorption equilibrium was achieved within short period of time (10 min). It was found that intraparticle diffusion resistance has overcome due to sonication. The experimental data obtained obeys both Freundlich isotherm model and Langmuir adsorption isotherm model. HDTMA modified nanoclay shows higher parameter values.     

Bionanodot monolayer array fabrication for nonvolatile memory application

A polyelectrolyte thin film which was simply spin-coated on a substrate showed the high-density adsorption of bionanodot-accommodated ferritins through electrostatic interaction. Solution pH adjustment facilitated the control of adsorption density to a value grater than 80% of the theoretical maximum density. The formed polyelectrolyte film was very thin and vulnerable like protein, therefore, only the array with densely adsorbed bionanodot was left on the substrate after organic component removal. The floating nanodot gate type MOS capacitor fabricated with this bionanodot array showed a memory effect, and no negative influences of polymer such as carrier trapping on the capacitance-voltage characteristics was observed.     

Electrostatic interaction of macroparticles in a plasma in the strong screening regime

We have studied the electrostatic interaction of spherical particles in an equilibrium plasma or an electrolyte in the moderate and strong screening regimes when the macroparticle size is comparable with or much larger than the Debye screening radius. We have developed an approximate theory of the electrostatic interaction of macroparticles in the case of constant potentials of their surfaces in the weak or moderate screening regimes. In this theory, the charges of macroparticles with a fixed spacing between them are determined using vacuum capacitive coefficients, which are corrected taking into account the plasma screening effects. The force of interaction with the resultant charges is calculated based on the solution of the problem of interaction in a homogeneous dielectric (vacuum) and is multiplied by the plasma factor. We have also obtained an approximate solution to the problem in the strong screening regime. Comparison with the exact solution has demonstrated high accuracy of the proposed methods of calculation.     

精确计算TATB分子间相互作用能并重新认识其作用本质

TATB炸药的钝感性质与其分子间强烈的相互作用密切相关，目前尚难以用实验方法直接准确地测定其分子间相互作用能。已发表的理论研究工作受当时计算方法和条件限制，计算结果误差较大、充满矛盾。本文用B3PW91-D3BJ/def2-TZVPP方法优化了TATB二聚体可能存在的六种构型的几何结构并作振动频率分析，发现仅有三种稳定构型，即氢键构型A，堆叠构型B和C，用MP2/def2-TZVPP方法重新优化了这三种构型的几何结构参数，并用于CCSD(T)/CBS方法计算，得到分子间相互作用能分别为A: -6.20，B: -15.45，C: -15.65 kcal/mol，CCSD(T)/CBS计算中发现构型B和C的高级校正项大约是分子间相互作用能的50%，是MP2方法不可能准确预测TATB二聚体堆叠构型分子间相互作用能的原因；本文还用新一代能量分解方法ALMO-EDA分析了TATB分子间相互作用本质，发现对于堆叠构型B和C，除了色散作用之外，静电吸引对决定TATB二聚体中的几何结构十分重要，TATB高能炸药良好的钝感性质起源于其分子间较强静电吸引的驱动和定向，使之形成稳定的堆叠结构，其稳定性来源于色散和静电的协同作用。