| In this master dissertation, eucalyptus bark was used for adsorption of Cr(Ⅵ) in wastewater by simple pretreatment with formaldehyde. The structural characteristics of with or without modification of eucalyptus bark for adsorption of Cr(Ⅵ) were investigated.The adsorption capacity was studies with initial concentration of Cr(Ⅵ), pH, adsorbent dosage and reaction temperature by the single factor analysis. It’s showed that initial concentration of Cr(Ⅵ), pH and adsorbent dosage has a significant influence on the adsorption capacity by single factor analysis. To determine the optimal reaction conditions by the response surface design. Analysis of variance showed a high multiple coefficient of determination (R2=0.9875), adjusted determination coefficient (R2Adj=0.9714), and the good second order regression equation. The initial concentration of Cr(Ⅵ) 40.15 mg/L, adsorbent dosing quantity 3.40 g/L and initial reaction pH 2.78, the largest removal rate was 99.998% under the optimum reaction conditions. Langmuir and Freundlich isothermal models well described the adsorption process. Adsorption kinetics studies showed that the adsorption was controlled by multiple factors, dominated by chemical adsorption. The adsorption was found to be spontaneous and endothermic, with △G0< 0, △H0> 0, and △S0> 0. The reaction mechanism was discussed by FTIR and SEM-EDS, the results indicated despite the adsorption process of Cr(Ⅵ) included the REDOX reaction with formaldehyde modified eucalyptus bark, but it still was controlled by adsorption reaction.The adsorption capacity of the formaldehyde modified eucalyptus bark in real environment was studies by the competitive adsorption experiment. The results indicated that Cu(Ⅱ) and Ni(Ⅱ) had a significant role in promoting for the adsorption of Cr(Ⅵ). The formaldehyde modified eucalyptus bark also had a certain adsorption capacity of coexisting metal ions Cu(Ⅱ) and Ni(Ⅱ), which has a certain application value for the practical application of heavy metal in wastewater, such as electroplating waste water. |
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