油菜秸秆对多元离子水体系中pb(Ⅱ)的吸附作用与机理

Competitive effects and mechanisms of the biosorption for removal Pb(Ⅱ) by rape straw powders from multi-ion aqueous solutions

通过响应面法Box-Behnken Design(BBD)建立考察离子镉、铜、锌、铬影响油菜秸秆吸附去除铅离子的模型,评估不同质量浓度镉、铜、锌、铬离子对油菜秸秆吸附去除铅离子效率的影响程度;采用红外光谱、电镜扫描、能谱分析技术来分析油菜秸秆在多元离子体系下吸附铅离子的前后状态,初步推断镉、铜、锌、铬4种离子影响油菜秸秆吸附铅离子效能的作用机制.结果表明:多元离子水体系中考察离子镉、铜、锌、铬对油菜秸秆吸附铅离子效率影响模型构建成功(P<0.0001).通过模型分析得出,铜、铬离子较镉、锌离子对铅离子吸附去除具有更强的竞争吸附作用(P<0.0001),对铅离子吸附去除的影响作用强弱排序为:铜>铬>锌>镉.红外光谱显示:多离子水体系中油菜秸秆的—OH、—C=O、—C—O、—C—H、—CH2、酰胺等基团在参与吸附铅、镉、铜、锌、铬离子时呈现出新峰出现、波数位移、吸收峰增强、消失的改变,尤其—CH3基团处新峰的出现可能是导致油菜秸秆对铅离子吸附能力下降的主要原因.能谱分析说明:在多元离子水体系中油菜秸杆完成对目标金属离子吸附的同时,发生了离子交换作用.进一步提示在多离子水体系中油菜秸秆对铅离子仍保持较强的吸附能力,将铜与铬离子的质量浓度控制在低水平是提高油菜秸秆对铅离子去除率的关键因素.

In this study,response Surface Methodology(RSM)based on Box-Behnken Design(BBD)was employed toanalyze the effects of different concentration of cadmium ion,copper ion,zinc ion,chromium ion on the maximumlead-removal rate of rape straw powders in multi-ion designed aqueous solutions.Infrared spectroscopy,scanningelectron microscope and energy dispersive spectrometer were used to characterize the rape straw powders before and afterthe adsorption processes to identify the functional groups and elements which had changed,and therefore,to explore thepossible mechanisms of such competitive biosorption.The results showed that the P values of polynomial mode ofcompetitive biosorption were less than0.0001(α=0.05),which indicated that the models were significant.The cadmiumion,copper ion,zinc ion,chromium ion all showed their competitive effects on the lead ion-biosorption process.Amongthem copper ion and chromium ion were more competitive,they can be sorted by competitiveness as follows:copper ion>chromium ion>zinc ion>cadmium ion.The critical groups such as-OH,-C=O,-C-O,-C-H,-CH2andamide groups,were exhibited by the Fourier transform infrared spectra,the changes of which suggested that these groupsplayed critical roles during the biosorption process.-CH3group appeared to be especial during the biosorption process,by making the lead removal rate decrease.The results of Energy Dispersive Spectrometer revealed potassium and sodiumion exchange during the biosorption process.By conclusion,our study suggested that keeping low concentration of copperand chromium ion in solutions was crucial to improve lead ion removal rate of straw powders in multi-ion aqueoussolutions.