Abstract:

Amino functionalized dialdehyde starch (NH₂-DAS) was successfully synthesized by Schiff base reaction of DAS with hydrazine hydrate. During the preparation process, dialdehyde starch (DAS) was firstly prepared using starch as raw material and NaIO₄ as oxidant. The morphology, element distribution, thermal stability and surface chemical property of the NH₂-DAS adsorbent were characterized by SEM, EDX, XRD, TGA, FTIR and XPS. The adsorption behavior and adsorption mechanism of NH₂-DAS adsorbent toward Pb(‍Ⅱ) from aqueous solution were studied. The results showed that the adsorption behavior of Pb(‍Ⅱ) onto NH₂-DAS adsorbent could be well described by Langmuir isotherm model and Pseudo-second-order kinetic mode. The NH₂-DAS exhibited a high adsorption capacity of 165mg/g toward Pb(‍Ⅱ) at adsorption temperature of 45℃, pH=5.5 and the adsorption time of 240min. The adsorption of NH₂-DAS on Pb(‍Ⅱ) mainly depended on the coordination bonds between—C\stackrel{}{̿}N—, —NH₂ groups and Pb(‍Ⅱ) ions. The adsorption process was a spontaneous, endothermic and entropy increase process. After five times of regeneration test, the adsorption capacity of NH₂-DAS for Pb(‍Ⅱ) was still above 84.8% of original adsorption capacity. Therefore, the NH₂-DAS adsorbent had potential application prospects in the removal of Pb(‍Ⅱ) ions from aqueous solution.

Key words: dialdehyde starch, adsorbent, lead(Ⅱ) ions, adsorption mechanism

摘要：

以淀粉为原料，高碘酸钠为氧化剂，制备出双醛淀粉（DAS），然后与水合肼反应制备了氨基功能化双醛淀粉吸附剂（NH₂-DAS）。采用扫描电子显微镜、能量色散X射线光谱仪、X射线衍射仪、热重分析仪和X射线光电子能谱等表征手段对NH₂-DAS的形貌、元素组成、热稳定性和表面化学性质进行了分析。详细研究了NH₂-DAS吸附剂对水溶液中Pb(Ⅱ)离子的吸附行为和吸附机理。结果表明，NH₂-DAS对Pb(Ⅱ)的吸附符合Langmuir等温吸附模型和准二级吸附动力学模型。当吸附温度为45℃、pH为5.5、吸附时间为240min时，NH₂-DAS对Pb(Ⅱ)的吸附容量达到165mg/g。NH₂-DAS对Pb(Ⅱ)的吸附作用主要是利用其表面—C\stackrel{}{̿}N—和—NH₂与Pb(Ⅱ)的配位螯合作用实现的，且为自发、吸热的熵增过程。经过5次再生利用后，NH₂-DAS对Pb(Ⅱ)的吸附容量仍然能达到初始吸附容量的84.8%。该NH₂-DAS吸附剂在吸附Pb(Ⅱ)方面具有潜在的应用前景。

关键词: 双醛淀粉, 吸附剂, 铅离子, 吸附机理