材料期刊网

研究了柠檬酸改性榴莲壳对水中 Pb(Ⅱ)和Cr(Ⅲ)的吸附效果、动力学与等温吸附特性.通过SEM、FT-IR 和 XPS 表征测试,分析榴莲壳改性前后的特征变化,并探讨榴莲壳的改性和吸附机理.表征分析发现,以 N,N’-羰基二咪唑为活性剂进行榴莲壳表面改性后,在1730和1640 cm－1处分别出现明显的酯羰基和自由羧基吸收峰,且改性后 m (O)/m (C)原子质量比明显增大,说明柠檬酸成功接枝到榴莲壳表面.吸附实验结果表明,榴莲壳经改性后对 Pb(Ⅱ)和 Cr(Ⅲ)的吸附量有明显地提高,分别是未改性榴莲壳的3．15和2．42倍,且当两种金属离子共存时,Pb (Ⅱ)的竞争吸附优于 Cr(Ⅲ).动力学研究显示,改性榴莲壳吸附 Pb(Ⅱ)和 Cr(Ⅲ)在120 min 内达到平衡,实验数据符合准二级动力学模型(R 2＞0．9975).在25℃下,等温吸附过程可采用 Freundlich 模型(R 2＞0．9902)进行拟合.吸附-解吸实验表明,CM-CDI-DRS对 Pb(Ⅱ)进行4次吸附再生循环后仍能保持较高吸附能力.

The adsorption efficiency,isothermal adsorption and kinetics of durian shell modified by citric acid for Pb(Ⅱ)and Cr(Ⅲ)from aqueous solution was investigated.Both modified and unmodified adsorbents were characterized by FT-IR,SEM and XPS,and modification and adsorption mechanism of durian shell was dis-cussed.The results of FT-IR and XPS demonstrated that after modified by citric acid via N,N’-carbonyldiimid-azole as a activator,the new peaks at 1 730 and 1 640 cm-1 were assigned to ester carbonyl groups and carboxyl-ate stretching band on durian shell and the m (O)/m (C)atom mass ratio increased,which indicated the pres-ence of citric acid grafted onto durian shell.Adsorption results showed that,the adsorption capacity of durian shell modified by citric acid for Pb(Ⅱ)and Cr(Ⅲ)were 3.15 and 2.42 times as those of the natural durian shell, respectively.The adsorption of Pb(Ⅱ)on durian shell modified by citric acid exhibited a stronger competitive effect than Cr(Ⅲ)in the aqueous solution with two coexisting anions.The adsorption kinetics data showed that the adsorption equibrium was reached in 120 min for Pb(Ⅱ)and Cr(Ⅲ)and the data of adsorption rate could be described by pseudo-second-order rate model (R 2 >0.9975).At 25 degrees celsius,the isothermal adsorption of Pb(Ⅱ)and Cr(Ⅲ)on durian shell modified by citric acid tended to be fitted well by the Freundlich model (R 2>0.9902).Adsorption-desorption results showed that the CM-CDI-DRS remained high biosorption ability for Pb(Ⅱ)after four-time usage.