Adsorption of methyl orange from aqueous solution by composite magnetic microspheres of chitosan and quaternary ammonium chitosan derivative

Novel composite magnetic microspheres containing chitosan and quaternary ammonium chitosan derivative (CHMMs) were prepared by inverse suspension method, and used for the methyl orange (MO) removal from aqueous solutions. The CHMMs were characterized by a scanning electron microscope, a transmission electron microscope, and Fourier transform infrared spectroscopy, respectively. Compared with the chitosan beads, the incorporation of quaternary ammonium chitosan derivative significantly reduced the particle size. The MO adsorption by CHMMs was investigated by batch adsorption experiments. The adsorption kinetics was conformed to the pseudo second-order kinetics equation. The adsorption isotherm followed the Langmuir model better than the Freundlich model and the calculated maximum MO adsorption capacity was 266.6 mg·g^-1 at 293 K. Thermodynamic studies indicated that the MO adsorption was endothermic in nature with the enthalpy change (ΔH°) of 99.44 kJ·mol^-1. The CHMMs had a stable performance for MO adsorption in the pH range of 4-10, but high ionic strength deteriorated the MO removal due to the shielding of the ion exchange interaction. A 1 mol·L^-1 NaCl solution could be used to regenerate the exhausted CHMMs. The proposed CHMMs can be used as an effective adsorbent for dye removal or recovery from the dye wastewater.     

Adsorption behaviors of the aminated chitosan adsorbent

Using inverse suspension technology, a novel aminated chitosan adsorbent with higher adsorption ability for metal cations and metal anions was prepared. Through cross-linking amination reaction, the content of amidocyanogen of aminated chitosan adsorbent was enhanced four times than that of chitosan cross-linked adsorbent. As can be seen from the results, the adsorption ability of the novel aminated chitosan adsorbent for (Nicit)⁻ and Cr(VI) was enhanced remarkably. When the initial concentration of metallic ion was 1,000 mg/L, the adsorption capacity of the novel aminated chitosan adsorbent for nickel citrate and Cr(VI) was up to 30.2 mg/g and 28.7 mg/g, respectively. And the adsorption capacity of the novel aminated chitosan adsorbent for Ni²⁺ was still higher. So the new aminated chitosan adsorbent offers not only a higher uptake for metal cations but also a better adsorption capacity for metal anions.     

Diffusional mass transfer model for the adsorption of food dyes on chitosan films

The adsorption kinetics of erythrosine B and indigo carmine on chitosan films was studied by a diffusional mass transfer model. The experimental curves were obtained in batch system under different conditions of stirring rate (80–200 rpm) and initial dye concentration (20–100 mg L⁻¹). For the model development, external mass transfer and intraparticle diffusion steps were considered and the specific simplifications were based on the system characteristics. The proposed diffusional mass transfer model agreed very well with the experimental curves, indicating that the surface diffusion was the rate limiting step. The external mass transfer coefficient (k_f) was dependent of the operating conditions and ranged from 1.32 × 10⁻⁴ to 2.17 × 10⁻⁴ m s⁻¹. The values of surface diffusion coefficient (D_s) increased with the initial dye concentration and were in the range from 0.41 × 10⁻¹⁴ to 22.90 × 10⁻¹⁴ m² s⁻¹. The Biot number ranged from 17.0 to 478.5, confirming that the intraparticle diffusion due to surface diffusion was the rate limiting step in the adsorption of erythrosine B and indigo carmine on chitosan films.     

胶原蛋白与壳聚糖相容性研究

将胶原蛋白与两种去乙酰度（95％,85％）的壳聚糖分别配成不同质量比的HAc共混溶液,在28℃下测定了共混液的黏度,利用Δb法则比较共混液中两种物质的相容性。结果表明在28℃的HAc溶液中,任何质量比的胶原蛋白和壳聚糖均相容,并且两者相容性不受壳聚糖去乙酰度的影响。     

Electrochemical investigation of conformational rearrangements of polypyrrole deposited on Al alloys

Polypyrrole (PPy) films were electrochemically deposited on AA2024 and AA6082 Al alloys by a two-step galvanostatic procedure: (1) activation in nitric acid and (2) deposition in oxalic acid. Polymeric films were electrochemically characterized through a series of cyclovoltammetric experiments, underlining differences due to the two different substrates. Interesting effects are linked to the presence of copper in AA2024, that extracted from the alloy during the deposition, is included into the polymeric matrix increasing its quality and polymerization yield. Methods and experiments based on Otero's Electrochemically Stimulated Conformational Relaxation model (ESCR) were performed in order to investigate structural changes of the polymer in function of an applied potential. PPy on AA2024 manifests a more complex redox process, involving both cations and anions, as compared to the polymer film on AA6082 that involves only anion interchange.     

Plasticization of chitosan membrane for pervaporation of aqueous ethanol solution

The process of pervaporation in which two components diffuse through a nonporous polymer membrane was modelled when one of the penetrants can exert a plasticization action to the membrane material. Thereat a phenomenological model was employed for describing the plasticization effect on the diffusivities for penetrants in the membrane. The sorption equilibria and permeation fluxes for aqueous ethanol solutions in a chitosan membrane were measured, and the permeation fluxes for water were compared with those predicted by the proposed model. The concentration of sorbed water was linear with its weight fraction (x₄) in the feed solution, whereas the permeation flux of water was. affected by the plasticization action of sorbed water to the polymer. This plasticization effect on the diffusion process can be simulated in terms of the proposed phenomenological model.     

Electrochemical properties of carbon nanotubes-hydrogenase conjugates Langmuir-Blodgett films

We report the preparation of Langmuir-Blodgett (LB) films composed of oxidized carbon nanotubes (CNTs) and hydrogenase (H₂ase) conjugates and their electrochemical properties. Both single-walled (SWNTs) and multi-walled CNTs (MWNTs) were used to form mixed monolayers with H₂ase on the Tris-HCl subphase surfaces. By using the LB method, the CNTs-H₂ase monolayers were transferred onto CaF₂ and indium tin oxide (ITO) electrode surfaces. The LB film modified electrodes showed a couple of waves centered at around −500 mV (versus Ag/AgCl), which corresponding to the redox reaction of [4Fe-4S]^2+/1+ clusters in the H₂ase. The current intensity was enhanced after co-assembly with CNTs. Because of the different diameters of CNTs, this current intensity was proportional to the scan rate (υ) for the electrodes modified with the LB films of pure H₂ase and SWNTs-H₂ase, but to the root of scan rate (υ^1/2) for those modified with the MWNTs-H₂ase LB film. The products of diffusion coefficient and concentration (D^1/2C) increased in the order of pure H₂ase, SWNTs-H₂ase, and MWNTs-H₂ase LB films.     

广谱水溶性壳聚糖的研究进展

拓宽能够溶解壳聚糖的水介质的pH范围,是克服壳聚糖应用和研究受局限的有效途径,因而一直得到人们广泛的关注。作者综述了近年来改善壳聚糖溶解于宽pH范围水溶液的方法,并简要介绍了水溶性壳聚糖的应用研究。     

Sorption of palladium (II) chloride complexes on weakly, intermediate and strongly basic anion exchangers

The precious metals and their alloys are extensively applied in refineries and the chemical and electronic industries as well as in medicine. Their small amounts in nature and extensive exploitation from natural resources are a serious obstacle as far as their application is concerned. High prices of palladium favour its recovery from recyclable materials and industrial wastes. Ion-exchange chromatography is one of the physicochemical methods of noble metal ion recovery. A study was done on the possibility of selective removal of palladium (II) microquantities from the model 0.1-6.0 M HCl, 0.1-0.9 M HCl-0.9 - 0.1 M HNO₃, 1.0 M ZnCl₂ - 0.1 M HCl and 1.0 M AlCl₃-0.1 M HCl systems on weakly, intermediate and strongly basic anion exchangers. The sorption research of Pd (II) on various types of anion exchangers was carried out by means of dynamic and static methods. The working ion-exchange capacities, weight and bed distribution coefficients were calculated from the breakthrough curves of palladium (II) ions. From the static studies the recovery factors of Pd (II) depending on the anion exchanger-solution contact time in the model systems under discussion were determined.     

NMR study of the phosphonomethylation reaction on chitosan

N-Phosphonomethylation of chitosan reaction was studied and optimized using different reaction conditions. NMR spectroscopy was an important tool in this work to study this reaction and the α-aminomethylphosphonic acid function introduced onto chitosan was unequivocally characterized by ³¹P and ¹³C NMR analyses. But surprisingly, whatever the reaction conditions used, N-phosphonomethylation reaction of chitosan cannot be dissociated from a side reaction: the N-methylation reaction of chitosan. A mechanism was proposed to explain the formation of this side product.     

A fundamental study of chitosan/PEO electrospinning

A highly deacetylated (97.5%) chitosan in 50% acetic acid was electrospun at moderate temperatures (25-70 °C) in the presence of a low content of polyethylene oxide (10 wt% PEO) to beadless nanofibers of 60-80 nm in diameter. A systematic quantitative analysis of the solution properties such as surface tension, conductivity, viscosity and acid concentration was conducted in order to shed light on the electrospinnability of this polysaccharide. Rheological properties of chitosan and PEO solutions were studied in order to explain how PEO improves the electrospinnability of chitosan. Positive charges on the chitosan molecule and its chain stiffness were considered as the main limiting factors for electrospinability of neat chitosan as compared to PEO, since surface tension and viscosity of the respective solutions were similar. Various blends of chitosan and PEO solutions with different component ratios were prepared (for 4 wt% total polymer content). A significant positive deviation from the additivity rule in the zero shear viscosity of chitosan/PEO blends was observed and believed to be a proof for strong hydrogen bonding between chitosan and PEO chains, making their blends electrospinnable. The impact of temperature and blend composition on the morphology and diameter of electrospun fibers was also investigated. Electrospinning at moderate temperatures (40-70 °C) helped to obtain beadless nanofibers with higher chitosan content. Additionally, it was found that higher chitosan content in the precursor blends led to thinner nanofibers. Increasing chitosan/PEO ratio from 50/50 to 90/10 led to a diameter reduction from 123 to 63 nm. Producing defect free nanofibrous mats from the electrospinning process and with high chitosan content is particularly promising for antibacterial film packaging and filtration applications.     

Properties of chitosan/soy protein blended films with added plasticizing agent as a function of solvent type at acidic pH

Pure and blend films from chitosan (CH) and soy protein isolate (SPI) were produced in varying compositions (CH/SPI 75/25, 50/50, 25/75 w/w) based on the solvent type (acetic and formic acids). Glycerol was used as a plasticizer. The interactions between the two biopolymers was confirmed by FTIR and TGA, indicating miscibility and compatibility. Increasing the amount of soy protein decreased the tensile strength and absorptive properties, but improved the ability of the film to withstand thermal degradation. Blend films cast using acetic acid gave higher hydrophobicity, better internal blend miscibility, and better tensile properties than blend films cast from formic acid.     

Electrochemical synthesis and characterization of new electrodes based on poly‐hematoxylin films

The poly‐hematoxylin films undoped (p‐HX) and doped with strontium (p‐HX‐Sr) were prepared on the platinum electrodes (Pt) using cyclic voltammetry. The influence of experimental parameters, such as: anodic potential and number of voltammetric cycles on the films synthesis was investigated by electrochemical impedance spectroscopy (EIS). The results showed that, the optimal conditions to obtain the poly‐hematoxylin films on platinum electrode from 10^?2 mol L^?1 NaNO₃ solution, were found by recording 10 voltammetric cycles at an anodic potential of 1.5 V. Electrocatalytic activity of the poly‐hematoxylin‐platinum (p‐HX/Pt) and poly‐hematoxylin‐strontium‐platinum (p‐HX‐Sr/Pt) electrodes was tested for electrochemical degradation of benzocaine using UV‐Vis spectrophotometry. Both, the mechanisms of hematoxylin (HX) polymerization, as well as benzocaine degradation were proposed. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Removal of zinc ions from aqueous solution using a cation exchange resin

The present study is concerned with the mass transfer and kinetics study of zinc ions removal from aqueous solution using a cation exchange resin packed in a rotating cylindrical basket reactor. The effect of various experimental parameters on the rate of zinc ion removal, such as initial zinc ion concentration, packed bed rotation speed and temperature has been investigated. In addition to find a suitable equilibrium isotherm and kinetic model for the zinc ion removal in a batch reactor. The experimental isotherm data were analyzed using the Langmuir, Freundlich and D–R equations. The equilibrium data fit well in the Langmuir isotherm. The experimental data were analyzed using four sorption kinetic models, pseudo-first and second-order equations, the Elovich and the intraparticle diffusion model equation, to determine the best fit equation for the biosorption of zinc ions onto purolite C-100 MH resin. Results show that the Elovich equation provides the best correlation for the biosorption process.     

Electrochemical synthesis of poly(o-anisidine)/chitosan composite on platinum and mild steel electrodes

In this study, poly(o-anisidine)/chitosan composite film was electrochemically synthesized on the platinum and mild steel electrodes. Electrochemical synthesis of the composite film was carried out by cyclic voltammetry technique. The synthesized composite film was characterized by FT-IR, UV–Vis, cyclic voltammetry, SEM and TGA. The SEM micrographs showed that the composite film homogeneously covered the surfaces of platinum and mild steel electrodes. The TGA results proved that the composite film does not degrade until 648 °C while the poly(o-anisidine) film is decomposed between 190 and 432 °C. Also, electrochemical studies showed that poly(o-anisidine) and the composite films have good stability and electroactivity.     

Exchange of counter anions in electropolymerized polyaniline films

Mobile counter anion exchange of electropolymerized polyaniline (PANI) films with the anions in acid solutions has been investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), scanning electron microscopy, Raman, UV-vis, and fluorescence spectra. The studied acids include camphorsulfonic acid, p-toluene sulfonic acid, HCl, HClO₄, H₂SO₄ and H₃PO₄. In two cases of small and large counter ions of PANI films, CV tests have been performed alternately three times in each of two electrolytes containing organic or inorganic acid. The investigation of electrochemical and spectrophotometric measurements reveals that large counter anions can be easily replaced by the small anions; and the reverse exchange also occurs, but shows very low efficiency. This indicates that the achieved anion exchange in both cases leads to the remarkable alteration in electrochemical behavior and electrical conductance of PANI films. This implies counter anions, whatever the original or redoping ones, play an important role in the electrical, electrochemical, even optical properties of PANI. However, the polymer morphology does not be changed after exchange tests. This allows us to point out a ‘morphology-memory’ effect which is very significant for the development and application of PANI films with the same morphology and different properties.     

壳聚糖季铵盐及其复合物的研究进展

壳聚糖季铵盐及其复合物是一种很有应用前景的材料,作者综述了壳聚糖季铵盐及其复合物在载基因、载药、抗菌创伤材料、抗凝血材料、水处理材料等领域的研究进展。     

Morphological and structural study of plasma deposited fluorocarbon films at different thicknesses

The growth of fluorocarbon thin films has been obtained by continuous and modulated r.f. plasmas fed with C₂F₄. The kinetics surface morphology of the coatings has been investigated and analyzed on films of various thicknesses. Such a study has allowed the evolution of structures in size and shape to be followed. Specifically, it has been observed that modulated plasmas with the proper duty cycles (⩽7%) lead to the formation of micrometer-long ribbon-shaped nanostructures. The precursors of the ribbons are nuclei that align into a spiral-mimic. Highly nanostructured films with an optimal thickness and ribbon density exhibit a super-water repellent surface with contact angles up to 170°. The surface roughness and smoothing of fluorocarbon films are strongly affected by the modulated and continuous plasmas, respectively.     

Novel chitosan/polyvinyl alcohol/talc composite for adsorption of heavy metals and dyes from aqueous solution

ABSTRACT

In this study, adsorption capability of chitosan/polyvinyl alcohol/talc composite (CPTC) in removal of Congo red, Methyl orange, Pb²⁺, and Cr⁶⁺ was evaluated. CPTC was characterized using Fourier transfer infrared spectroscopy, field emission scanning electron microscope, X-ray diffraction, thermogravimetric analysis, and weight loss test. Flocculation was the main phenomena in Congo red removal for 100 mg/L and in Methyl orange for <100 mg/L. The removal amounts of Pb²⁺ and Cr⁶⁺ were 96% and close to 100% up to 200 mg/L, and 88% and 92% at 400 mg/L, respectively. Langmuir model demonstrated better results in describing the heavy metals removal. Moreover, it was found that kinetics followed a pseudo-second-order equation.     

壳聚糖多糖膜的性能与应用研究

综述了壳聚糖多糖膜的性质、制备、性能及应用等方面的研究进展。