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Study on the Preparation of Chemically Modified Lawny Grass Cellulose Containing Cyanex272 Adsorbents and Biosorption of Heavy Metals Pb(Ⅱ), Cd(Ⅱ) and Methylene Blue

Author: LvLiLi
Tutor: LuoFang
School: Northeast Normal University
Course: Inorganic Chemistry
Keywords: Lawny grass Citric acid Cyanex272 Heavy metals Methylene blue
CLC: X703
Type: Master's thesis
Year: 2011
Downloads: 87
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Abstract


A series of biomaterial which modified with citric acid and loaded Cyanex272 have been prepared in this paper. Their absorption perform of removal Pb（II）, Cd（II） and methylene blue （MB） from aqueous solution was evaluated in the batch process and the fixed-bed column. The effect of pH, contact time, initial concentration, adsorbents dose and temperature on the adsorption and the regeneration were also investigated. The results of experimental were the followings:The grass sorbents were characterized by SEM and FTIR, confirming that carboxylic groups were introduced onto the grass by modification of citric acid and Cyanex272 was successfully immobilized onto the grass. Cyanex272 played an important role in improving the maximum adsorption and shortened the equilibration time. The optimum pH is in the range of 5.5-6.0 for all adsorbents, H-1CG always had a higher ability to adsorb Pb（II）, Cd（II） and the removal rate could be up to 100%. The kinetic equilibria could be explained as pseudo-second-order. The intraparticle diffusion is not the only rate controlling step. The experimental data fitted the Langmuir-Freundlich best, and the order of maximum capacities onto different adsorbents was 272-1CG > 1CG > 272-RG > RG. Thermodynamic results indicated the adsorption of Cd（II） is spontaneous and endothermic. A selection of 0.1 mol·L-1 HCl was used as the optimum desorption agent. The desorption rates of Pb（II） and Cd（II） were almost 95.1% and 95.2%. The breakthrough point of the columns of 272-1CG to adsorb Pb（II） and Cd（II） are 165 BV and 160 BV, and completely saturated at 330 BV and 335 BV respectively. The elution process was completely in a very small elutent HCl volume.Using the low-cost of lawny grass to remove methylene blue （MB） from aqueous solution was evaluated in the batch process and the fixed-bed column. The MB adsorption capacity onto grass modified with citric acid was 301.1 mg·g-1 biomass, which was almost three times than that of raw grass. The equilibrium could be explained as pseudo-first-order kinetic processes, and equilibrium time was shortened to 20 min （CG） from 40 min （RG）. The adsorption equilibrium followed the Langmuir isotherm model. The desorption rate with 0.1 mol·L-1 HCl was almost 90%. Regenerated CG was reusable with a little decrease （only about 3.38%） in its adsorption capacity during six repeated cycles. In the fixed-bed column, the breakthrough point of CG begins at 183 BV, which was much higher than that of RG （56 BV）. The elution process was completely in a very small elutent HCl volume.

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CLC: > Environmental science, safety science > Processing and comprehensive utilization of waste > General issues > Wastewater treatment and utilization
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