Study On Preparation And Properties Of Polyethyleneimine-Anionic Cellulose Based Adsorbents

The paper is a part of the12th Five-year Plan of Science and Technology subject "Research on the material of chemical deep processing of novel forest biomass". Cellulose is a kind of important natural polymer but not utilized efficiently. According to the chemical structure and the formation principle of polyampholyte, soluble polyanionic cellulose derivatives and soluble polycationic polyethyleneimine as raw materials, six kind of polyethyleneimine-cellulose derivative adsorbents in this paper were prepared and made to be the basic properties of polyelectrolyte, with further coated to magnetic particles. They are carboxymethyl cellulose-polyethyleneimine (PEI-CMC), magnetic carboxymethyl cellulose-polyethyleneimine (Fe3O4-PEI-CMC), polyethyleneimine-carboxymethyl hydroxyethyl cellulose (PEI-CMHEC) magnetic polyethyleneimine-carboxymethyl hydroxyethyl cellulose (Fe3O4-PEI-CMHEC), polyethyleneimine-cellulose sulfate (PEI-CS) and magnetic polyethyleneimine-cellulose sulfate (Fe3O4-PEI-CS). Synthesis conditions based the yield and the nitrogen content of the adsorbents were optimized via single factor experiments. These obtained adsorbents were characterized by fourier transform infrared spectroscopy (FT-IR), scanning electron microscope(SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and vibrating sample magnetometer (VSM). The adsorption of Cd (Ⅱ), Pb (Ⅱ) and Cu (Ⅱ) ions on adsorbents from aqueous solutions were measured with inductively coupled plasma mass spectrophotometer (ICP-MS) or atomic absorption spectrophotometer (AAS), and the removal of acid black ATT from water were determined by UV spectrophotometer (UV). Various factors affecting the adsorption behavior such as pH, contact time, temperature, initial concentration of metal ions, and desorption were studied. The adsorption kinetics and thermodynamics were also investigated. These studes provide basic data and technical support for the further use of cellulose resource. Six main aspects of research works were performed and are listed as follows, including some obtained novel results.The carboxymethyl cellulose-polyethyleneimine (PEI-CMC) adsorbent was prepared with carboxymethyl cellulose and polyethyleneimine using glutaraldehyde by cross-linking and electrostatic interaction in an aqueous medium. The optimized conditions based the yield and the nitrogen for PEI-CMC prepared were obtained by single factor experiments:the yield and the nitrogen content of PEI-CMC are83%and13%respectively for3h at25℃, When CMC to PEI mass ratio is1:1.5, glutaraldehyde is in an amount of20%. The adsorption kinetics followed the mechanism of the pseudo-second-order equation, and the equilibrium was achieved after about60min. The adsorption equilibrium study exhibited that the Cd (Ⅱ) ion adsorption of PEI-CMC followed a Freundlich isotherm model well than other models, existing homogeneous and heterogeneous surface adsorption.Magnetic carboxymethyl cellulose-polyethyleneimine (Fe3O4-PEI-CMC) adsorbent was synthesized by electrostatic self assembly and cross-linking in this work. First, the Fe3O4-CMC particles were prepared through assembling CMC to the surface of Fe3O4by electrostatic interaction. Second, Fe3O4-CMC and PEI were cross-linked by glutaraldehyde to obtain the Fe3O4-PEI-CMC microspheres. The characterization results indicated that the Fe3O4-PEI-CMC microspheres with active groups such as amino groups, hydroxyl groups and carboxyl groups ranged from10to30nm in size, and the saturation magnetization was55.20emu/g. The Fe3O4-PEI-CMC microspheres showed their potential for the separation of Cd (Ⅱ) ion and acid black ATT dye. The adsorption kinetics all followed the mechanism of the pseudo-second-order equation. The adsorption data obeyed the Langmuir equation with maximum adsorption capacity of69.44mg/g and1016.89mg/g. The Fe3O4-PEI-CMC can be reused with less decrease of adsorption capacity through three cyles.The adsorbent of polyethyleneimine-carboxymethyl hydroxyethyl cellulose (PEI-CMHEC) was prepared with glutaraldehyde by cross-linking and electrostatic interaction. The higher percentage of the yield and nitrogen content (about81%and12%) were obtained when the reaction was carried out under optimum conditions (CMHEC to PEI mass ratio:1:1.2, reaction period:2h, reaction temperature:25℃, amount of glutaraldehyde:17%). Characterization results revealed that there are abundant active groups such as amino groups, hydroxyl groups and carboxyl groups on the PEI-CMHEC adsorbent. All of the adsorption kinetics for Cd (Ⅱ), Pb (Ⅱ) and Cu (Ⅱ) ions followed the mechanism of the pseudo-second order equation and the best interpretation for the equilibrium data was given by Langmuir isotherm with monolayer adsorption. The adsorption is exothermic and spontaneous reaction with reduced entropy.The magnetic polyethyleneimine-carboxymethyl hydroxyethyl cellulose (Fe3O4-PEI-CMHEC) was successfully synthesized based on electrostatic interaction, crosslinking using glutaraldehyde and coating to Fe3O4. The results showed that there are abundant active groups such as amino groups, hydroxyl groups and carboxyl groups on the Fe3O4-PEI-CMHEC sorbent. The uptake mechanism was found to be involved mainly in the complex adsorption of metal ions on the adsorbent. The saturation magnetization of Fe3O4-PEI-CMHEC was66.46emu/g. For Cd (Ⅱ), Pb (Ⅱ) and Cu (Ⅱ) ions and acid black ATT dye, the adsorption kinetics followed the mechanism of the pseudo-second order equation, the adsorption data obeyed the Freundlich equation, and the adsorption process is exothermic and spontaneous with reduced entropy. The adsorption capacities for acid black ATT dye are higher when the pH values are in the range of1to8. Fe3O4-PEI-CMHEC can be reused after three times regeneration and be separated from solution with an outer magnetic field. A novel adsorbent based on cellulose sulfate (PEI-CS) was prepared via modifying with polyethyleneimine (PEI) with glutaraldehyde by crosslinking and electrostatic interaction. When the ratio of CS/PEI was1:1.5(m/m) with glutaraldehyde in an amount of17%at25℃for4h, the higher yield (85%) and nitrogen content (11%) of PEI-CS adsorbent were achieved through single factor experiments. Characterization results indicated that PEI-CS contained hydroxyl, amino and acid groups which are involved mainly in the Cd (Ⅱ), Pb (Ⅱ) and Cu (Ⅱ) ions adsorption to complexation. The adsorption processes were all well-described by the pseudosecond-order model. At298,308and318K, Langmuir adsorption isotherms of Cd (Ⅱ), Pb (Ⅱ) and Cu (Ⅱ) ions explained PEI-CS adsorption well, the maximum capacity of Cd (Ⅱ) were100.42,97.34and92.31mg/g, respectively; Pb (Ⅱ),298.07,315.92and316.17mg/g, respectively; Cu (Ⅱ),66.10,64.68and62.34mg/g, respectively. The adsorption processes are exothermic and spontaneous with reduced entropy.Polyethyleneimine-cellulose sulfate (PEI-CS) polymer modified Fe3O4particles (Fe3O4-PEI-CS) was synthesized by crosslinking and electrostatic interaction for removal of Cd (Ⅱ), Pb (Ⅱ) and Cu (Ⅱ) ions and acid black ATT dye. It is shown that the amino groups, hydroxyl groups and Sulfonic acid groups are present and involved in the adsorption process by complexation of metal ions. The saturation magnetization of Fe3O4-PEI-CS was58.82emu/g. For the three metal ions and acid black ATT dye, the adsorption kinetics followed the mechanism of the pseudo-second-order equation, and the equilibrium data fitted well with the Freundlich model which is a heterogeneous adsorption. The adsorption processes for metal ions are exothermic and spontaneous with reduced entropy. The adsorption capacities for acid black ATT dye are higher at pH1-8. The adsorbent could be regenerated effectively and recycled for at least three times with a little loss of adsorption capacity.