氨基功能化双醛淀粉吸附剂的制备及其对Pb(Ⅱ)的吸附行为

Preparation of amino-functionalized dialdehyde starch adsorbent for adsorption of Pb(Ⅱ)ions

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(NH_(2)-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NH_(2)-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NH_(2)-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,NH_(2)-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,NH_(2)-DAS对Pb(Ⅱ)的吸附容量达到165mg/g。NH_(2)-DAS对Pb(Ⅱ)的吸附作用主要是利用其表面—C==N—和—NH_(2)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,NH_(2)-DAS对Pb(Ⅱ)的吸附容量仍然能达到初始吸附容量的84.8%。该NH_(2)-DAS吸附剂在吸附Pb(Ⅱ)方面具有潜在的应用前景。

Amino functionalized dialdehyde starch(NH_(2)-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 NH_(2)-DAS adsorbent were characterized by SEM,EDX,XRD,TGA,FTIR and XPS.The adsorption behavior and adsorption mechanism of NH_(2)-DAS adsorbent toward Pb(Ⅱ)from aqueous solution were studied.The results showed that the adsorption behavior of Pb(Ⅱ)onto NH_(2)-DAS adsorbent could be well described by Langmuir isotherm model and Pseudo-second-order kinetic mode.The NH_(2)-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 NH_(2)-DAS on Pb(Ⅱ)mainly depended on the coordination bonds between—C==N—,—NH_(2) 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 NH_(2)-DAS for Pb(Ⅱ)was still above 84.8%of original adsorption capacity.Therefore,the NH_(2)-DAS adsorbent had potential application prospects in the removal of Pb(Ⅱ)ions from aqueous solution.