Preparation Of Amino Functionalized Cellulose Porous Beads And Their Adsorption Performances

Porous beads have attracted enormous attention in the field of adsorption and separation due to their high specific surface area,high porosity,tunable morphology and porous architecture,and adjustable surface chemistry.The highly porous structure of porous beads not only endows them with large specific surface area,but also provides channels for the mass transfer of guest molecules,which is conducive to the enrichment and mass transfer of adsorbate.Therefore,porous beads are ideal adsorption material.In recent years,with the development of green chemistry,the preparation of porous beads from low-cost,green,non-toxic,and biodegradable cellulose attracted enormous attention by researchers.However,there are still many shortcomings in the emerging porous cellulose beads,such as small specific surface area,weak mechanical strength,and complex preparation process.To overcome above problems,this thesis achieved the synchronously control of the hierarchical porous architecture and surface chemistry of cellulose porous beads via combined epichlorohydrin pre-crosslinking strategy with polyethyleneimine(PEI)grafted modification,and the amino functionalized cellulose porous beads(PCB-PEI)were prepared successfully.At the same time,the influence of the amount of pre-crosslinking agent on the porous structure of cellulose beads and the physicochemical properties of the PCB-PEI were investigated.Furthermore,taking organic dyes as the contaminants models,the adsorption performance and adsorption mechanism of the PCB-PEI were systematically studied,and their potential for intelligent separation of mixed dyes was also discussed.And the feasibility of its application in the treatment of real printing and dyeing wastewater was further explored.The detailed research contents and results are as follows:(1)The preparation and physicochemical properties of amino functionalized cellulose porous beads:Based on the phase separation method to prepare cellulose porous beads,a simple pre-crosslinking strategy was introduced to effectively control the surface morphology and internal porous structure of the porous beads,and combined with glutaraldehyde chemical cross-linking method to graft PEI onto cellulose beads,the amino functionalized cellulose porous beads were prepared successfully.SEM analysis showed that the pre-crosslinking treatment produced abundant pores on the external surface of cellulose porous beads.With the increased of crosslinking agent dosage from 0.5 to 2 g,the average pore size on the external surface increased from 0.88 to 3.20 μm,and the inner pore size also increased from 0.81 μm to 2.11 μm.And the obtained PCB-PEI exhibited a 3D hierarchical porous structure.The surface area was 100.61 m2/g,the porosity was 94.27%,and the amino content was as high as 1.91 mmol/g.Benefiting from the constructed double cross-linking network architecture via ECH pre-crosslinking combined with glutaraldehyde graft crosslinking,the PCB-PEI exhibited significantly improved mechanical strength,elasticity,and recoverability.Under 50%compression strain,the compressive strength of PCB-PEI reached 202 kPa.After 10 cycles of compression,the compressive strength still maintains at 94.5 kPa,and the shape recovery percentage was 84.1%.(2)The adsorption properties of amino functionalized cellulose porous beads for dyes:Taking the anionic dyes methyl blue(MB)and rose bengal(RB)as contaminants models,the effects of initial dye concentrations,contact time,temperature,and initial pH were systematically investigated.The results showed that the PCB-PEI possess excellent adsorption performance and reusability.The maximum adsorption capacities for MB and RB were 1550.55 and 467.95 mg/g,respectively.After 8 adsorption-desorption cycles,the adsorption capacities of PCB-PEI for MB and RB still maintained more than 97%and 86%of original values,respectively.Further studies showed that electrostatic interaction was dominant in the adsorption process,and there were multiple interactions such as hydrogen bond interaction,Van Der Waals force and π-π stacking.In addition,combined with cationic dyes rhodamine B(RdB)and malachite green(MG),the intelligent separation effect of PCB-PEI on MB/RdB,RB/RdB,MB/MG and RB/MG mixed dyes was studied.These results showed that PCB-PEI had highly selectivity for adsorption of MB and RB,and the separation efficiency of four mixed dyes reached above 99%.To explore the practical application potential of PCB-PEI,the purification effect of PCB-PEI on silk printing and polyester interlining dyeing wastewater was investigated,respectively.The COD of the wastewater was reduced by 78.6%and 79.3%respectively,and the chroma was reduced by 97.5%,and the decolorization effect was outstanding.In this thesis,the method of combined pre-crosslinking with PEI grafting was used to successfully prepare amino functionalized cellulose porous beads with both surface pores and amino groups.The hierarchical porous architecture and surface functionalization of cellulose porous beads were simultaneously controlled.Based on the double cross-linking network,PCB-PEI exhibited excellent mechanical properties,elasticity,and recoverability.At the same time,PCB-PEI exhibited excellent adsorption properties and reusability for removal of anionic dyes.This work provides a novel method to achieve the synchronously regulation of surface functionalization and hierarchical porous structure of cellulose porous beads and provides a novel material with great application prospects for the effective removal of organic dyes from printing and dyeing wastewater.