超支化聚酰胺改性海藻酸钠微球对Cr(Ⅵ)的吸附

Adsorption of Cr(Ⅵ)by hyperbranched polyamide modified sodium alginate microspheres

采用先制备微球再接枝功能基团的方法,以自制超支化聚酰胺(HA)作为改性剂,用于海藻酸钠(SA)微球表面的胺基化改性,制备HA改性海藻酸钠(HA@SA)微球吸附剂。用FT-IR、EDS、XPS等分析HA@SA微球及其吸附前后结构的变化。通过批次吸附实验研究溶液pH对HA@SA微球吸附Cr(Ⅵ)的影响,进一步研究吸附动力学、吸附等温线和吸附热力学。通过吸附-解吸实验探究HA@SA微球的循环再生能力。结果表明,HA@SA微球对Cr(Ⅵ)吸附的最佳pH为2;用Langmuir模型计算,HA@SA微球对Cr(Ⅵ)的理论最大吸附量可达247.50 mg/g,比SA微球(24.86 mg/g)提高了8.96倍;吸附过程符合准二级动力学和Freundlich等温线模型,表明HA@SA微球对Cr(Ⅵ)的吸附过程是由化学吸附控制的非均相多层吸附,吸热且可自发进行;在8次吸附-解吸循环后,HA@SA微球对Cr(Ⅵ)的吸附能力仍能保留80%以上。

The method of preparing microspheres and then grafting functional groups was adopted.The self-made hyperbranched polyamide(HA)was used as modifier in amination surface modification of sodium al⁃ginate(SA)microspheres.HA modified sodium alginate(HA@SA)microsphere adsorbent was prepared.The structure changes of HA@SA microspheres,before and after its adsorption were analyzed by FT-IR,EDS and XPS.The effects of solution pH on the adsorption of Cr(Ⅵ)by HA@SA microspheres were studied by batch ad⁃sorption experiments.The adsorption kinetics,adsorption isotherms and adsorption thermodynamics were fur⁃ther studied.The reusability of HA@SA microspheres were measured by adsorption-desorption experiments.The results showed that the optimum pH of the adsorption of Cr(Ⅵ)by HA@SA microspheres was 2.Calculat⁃ed by Langmuir model,the theoretical maximum adsorption capacity of Cr(Ⅵ)by HA@SA microspheres was up to 247.50 mg/g,which was 8.96 times higher than that of SA microspheres(24.86 mg/g).The adsorption process conformed to the pseudo-second-order kinetics and the Freundlich isotherm model.It was indicated that the adsorption process of Cr(Ⅵ)by HA@SA microspheres was heterogeneous multi-layer adsorption con⁃trolled by chemical adsorption,endothermic and spontaneous.After 8 adsorption-desorption cycles,the ad⁃sorption capacity of HA@SA microspheres to Cr(Ⅵ)could still retain more than 80%.