Preparation Of Polysaccharide Based Heavy Metal Adsorbent And Applications

With the increasingly serious problems of resources,energy and environment,it is of great significance to develop renewable wood fibers as raw materials and prepare environment-friendly biomass based chemicals for the adsorption of heavy metal ions in water.In this work,cellulose and xylan was modified respectively,which was modified by functional groups and other materials.Sulfonated cellulose gel,magnetic sulfonated cellulose beads and Xylan-functionalized modified microspheres were successfully exploit by using used ionic liquids as solution system.Subsequently,the adsorption ability for Cu²⁺and the mechanism of adsorption process were investigated by a variety of different valid parameters from water solution.The characteristic and configuration were analyzed via different means of representation.The main research contents are expressed as follows:（1）Sulfonated cellulose gel was synthesized in ethanol by sol-gel method.When the mass ratio of adding sulphur trioxide pyridine compounds to cellulose was 1:1,reaction temperature were 80℃and the reaction time was 45 min,the WPG of SCG was best.The maximum adsorption capacities was 32.745 mg/g for the initial concentration of100 mg/L（p H=6）for 60 min at 25℃.The pseudo-second-order model and Freundlich isotherm model could fit better.Characterization analysis results showed that the hydrogen bond between cellulose macromolecules was damaged and SO₃-Py was grafted successfully in the process of ionic liquid dissolution.SCG had rough surface structure,which was conducive to adsorption.（2）The magnetic sulfonated porous cellulose beads（MSCB）were successfully synthesized by adding SO₃-Py and Fe₃O₄ nanoparticles.The optimum conditions for preparation of MSCB were obtained by preliminary experiments.When the Cu²⁺initial concentration was 100 mg/L,p H was 6,the mass of MSCB was 50 mg and the reaction time was 60 min,the maximum uptake capacities was 87.64 mg/g.Moreover,Fe₃O₄ nanoparticles could crosslink cellulose,which consequently had magnetic responsiveness and recyclability.The repetition adsorption efficiency was still kept to above 84%.The pseudo-second-order model could fit adsorption kinetics better and the isotherm models of adsorption followed Temkin pattern,which confirming that chemical uptake is dominated of adsorption mechanisms.Characterization analysis results showed that the hydrogen bond between cellulose macromolecules was damaged in the process of ionic liquid dissolution.The SO₃-Py and Fe₃O₄ nanoparticles were successfully introduced to improve the internal contact area and the mechanical strength of the microspheres.（3）Two kinds of xylan-based functional modified microspheres were prepared by droplet method with xylan as raw material and[BMIM]Cl as solvent system.When the Cu²⁺initial concentration was 100 mg/L,p H was 6,the maximum uptake capacities SXB and MSXB were 26.71 and 43.82 mg/g in 150 and 90 min respectively.The pseudo-second-order model and Freundlich isotherm model could describe the adsorption mechanisms,which confirming that chemical uptake is dominated of adsorption.Characterization analysis results showed the two kinds of microspheres prepared by the droplet method presented complete globules with particle size distribution ranging from 1.5 mm to 2 mm.Moreover,composite porous structure was formed inside the sphere to improve the reaction contact area and adsorption capacity.