Study On Preparation Of Hydrazine-modified Cellulose-g-poly Methyl Acrylate And Application In Adsorption For Heavy Metal Ions

In recent years,cellulose based adsorbent has been a research focus of biomass adsorbent for heavy metal ions.Cellulose based adsorbent has extensive application potentiality for adsorbing heavy metal ions as it displaying excellent adsorption capacity,mechanical property and regeneration.In this paper,hydrazinolyzed cellulose-graft-polymethyl acrylate(Cell-g-PMA-HZ)has been prepared by ceric salt-initiated graft polymerization of methyl acrylate from microcrystalline cellulose surface and subsequent hydrazinolysis with hydrazine hydrate.In order to increase the content of chelating group,the effect of reaction conditions on graft yield were discussed.The successful synthesis was confirmed by Fourier-transform infrared spectroscopy,13C-NMR,elemental analysis,scanning electron microscopy and thermogravimetric analysis.Adsorption behavior of Cell-g-PMA-HZ for Cu(?),Ni(?),Pb(?)and Cd(?)were studied through batch static adsorption processes and column chromatography methods.Experimental results indicated that,using microcrystalline cellulose with 0.5g,initiator(CAN)with 0.0558g,monomer of MA with 2mL,reaction temperature of 35?and reaction time of 3h,cellulose-graft-polymethyl acrylate(Cell-g-PMA)with graft yield of 326%was prepared.While molar ratio of MA in Cell-g-PMA of 326%graft yield to hydrazine was adjusted as 1:60 and reaction temperature as well as reaction time was set as 55? and 3h,respectively,hydrazinolyzed cellulose-graft-polymethyl acrylate(Cell-g-PMA-HZ)was achieved with maximum nitrogen content of 20.81%.Adsorption experimental results showed that,graft yield,initial pH,contact time,temperature would influence adsorption capacity of Cell-g-PMA-HZ.When graft yield of Cell-g-PMA was 326%,the adsorption capacity of Cell-g-PMA-HZ to Cu(?)was the highest.The optimum pH value of Cell-g-PMA-HZ adsorbent for Cu(?),Ni(?),Pb(?),Cd(?)ions was between 4.0-5.0.Kinetic adsorption for Cu(?),Ni(?),Pb(?)and Cd(?)ions can be explained by pseudo-second-order and adsorption isotherms of Cu(?),Ni(?)and Cd(?)ions fit well with Langmuir isotherm model,from which maximum adsorption capacity(qm)can be derived as 229.36mg g-1 for Cu(?),173.91 mg g-1 for Ni(?)and 235.85 mg g-1 for Cd(?)at 28?,while isotherm of Pb(II)adsorption fits well with Freundlich isotherm model and equilibrium adsorption capacity(qe)can be measured as 249.89 mg g-1.Further thermodynamic investigation indicated that adsorption of Cu(?),Ni(?)and Pb(II)by adsorbent Cell-g-PMA-HZ was exothermic and demonstrared an entropy reduction process under studied conditions.On the other hand,thermodynamics of Cd(?)indicated that the adsorption process was endothermic and denoted an entropy increase process.The results of dynamic adsorption experiments proved that,adsorption of Cu(?),Ni(?),Pb(?),Cd(?)ions on Cell-g-PMA-HZ was relatively fast,which can be completely eluted with 20mL HCl of Imol L"1.Consecutive adsorption-desorption experiments showed that after 6 recycling,adsorbent maintained more than 80%of its initial adsorption capacity,verifying that Cell-g-PMA-HZ is reusable with satisfactory adsorption capacity.