| In this study,wheat straw was modified with PEI to enhance its adsorption capacity. As PEI is soluble and can be easily desorbed from wheat straw in adsorbent process, glutaraldehyde(GA) was chosen as crosslinker during the process of PEI modification and epichlorohydrin(ECH) was selected as grafting reagent to modify wheat straw by PEI. The modified wheat straw were characterized by FTIR, elemental analysis, determination of isoelectric point and the results showed that PEI had been successfully coated in surface of wheat straw. Adsorption quantity of NWS for CR, Cu2+, PO43-was found to be 26.15 mg/g, 10mg/g, 5.05m/g, respectively, while in the same experimental conditions, adsorption quantity of GA-MWS for CR was 26.15 mg/g, adsorption quantity of ECH-MWS for Cu2+, PO43- was 35.98 mg/g, 12.07 mg/g.GA-MWS was attained by GA and PEI modification, adsorption property of Conge red by GA-MWS was studied in batch and column mode. The results showed that the maximum adsorption capacity was reached at p H 5.0 and the optimum concentration of adsorbent was 1g/L. Inorganic salt had slightly posoitive effect on CR adsorption. Koble-Corrigan model can describe the adsorption equilibrium behavior very well while the kinetic adsorption process was well fitted by the intra-particle model. Yan model fit the dynamic experimental data very well. The regeneration research showed the CR-loaded GA-MWS was regenerated by 0.1 mol/L Na OH solutions and there was 78% regeneration efficiency while the second and third regeneration efficiency was nearly unchanged. The thermodynamic study revealed that the adsorption process was spontaneous and endothermic.The value of ?S0 suggested the randomness increase in the adsorption system.ECH-MWS was obtained by ECH and PEI modification and adsorption property of Cu2+ and second adsorption of PO43- was carried out in batch and column mode. The suitable adsorption condition was all at nerutral and the dose of adsorbent was 0.8 g/L. Coexist salt had little effect on Cu2+ adaorption while it had negative effect on PO43- adsorption. The isotherm data of both systems were analyzed. The appropriate models for the equilibrium process of Cu2+ and PO43- were Freundlich, Koble-Corrige models and Langmuir, Temkin models, respectively. The kinetic studies indicated that the adsorption of Cu2+ was well fitted by the Double-constant model and the adsorption of PO43- was well fitted by the Elovich model. The dynamic adsorption of Cu2+ and PO43- all fit the Thomas model. Thermodynamic calculations showed that the Cu2+ and PO43- adsorption were all pontaneous, with exothermic process for PO43-and endothermic process for Cu2+. The ECH-MWS loaded Cu2+ was regenerated with 0.1 mol/L HC and there was 65% regeneration efficiency.The adsorption property of PO43- on ECH-MWS was investigated in batch and column mode. The results showed that the appropriate condition was p H at 3.4 while the dose of adsorbent was 0.8 g/L. The study of coexist ions showed that the adsorption of PO43- is sharply reduced when there were coexit ions. The adsorption equilibrium data obey Koble-Corrigan isotherm and the kinetic data were well described by the pseudo-second model. The effects of column heights, flow rate, initial concentration were studied. Thermodynamic study confirmed that the adsorption was spontaneous and exothermal. |
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