微生物絮凝剂去除废水中Cd（Ⅱ）的CCD优化及絮凝机制

应用CCD（中心复合设计）法研究了微生物絮凝剂去除废水中Cd（Ⅱ）的最佳条件组合,并根据傅里叶变换红外光谱与环境扫描电镜分析讨论了絮凝机制。CCD设计以Cd（Ⅱ）去除率为响应值,优化Cd（Ⅱ）初始浓度、MBFGA1投加量、溶液初始pH和反应时间4种因素。方差分析显示,模型F值为11.71,P〈0.0001,相关系数R=0.9154,拟合模型极显著,Cd（Ⅱ）初始浓度、pH和反应时间为显著性因素。在最优化条件下：Cd（Ⅱ）初始浓度23.60 mg/L,MBFGA1投加量27.74 mg/L,pH为9.5,反应时间15.97 min,检测实验Cd（Ⅱ）去除率高于99.5%。傅里叶变换红外光谱图表明,絮凝剂分子上羧基、羟基、磷酸基等官能团参与了絮凝过程,并形成了氢键。结合环境扫描电镜图分析得出,MBFGA1的絮凝机制包括化学反应、吸附架桥、氢键和范德华力结合等作用。

Optimization of cadmium removal using CCD design by microbial flocculants and investigation of flocculation mechanism

In this study,cadmium removal from wastewater was investigated using central composite design（CCD） method,and flocculation mechanism was analyzed by fourier transform infrared（FTIR） spectra coupled with environmental scanning electron micrograph（ESEM）.In CCD method,cadmium removal efficiency was served as response value and initial concentration of Cd（Ⅱ）,MBFGA1 dosing quantity,pH and reaction time were also optimized.Results from the analysis of variance demonstrated that the model was highly significant,in which the Model F value was 11.71 and P value was less than 0.0001,and correlation coefficient was 0.9154.Parameters of initial concentration of Cd（Ⅱ）,pH and reaction time were extremely significant factors.The optimum values of the variables were found to be Cd（Ⅱ） initial concentration of 23.60 mol / L,MBFGA1 dosing quantity of 27.74 mol / L,pH 9.5 and reaction time of 15.97 min,respectively.Under the optimum conditions,it can reach 99.5% of cadmium removal efficiency.FTIR spectra results indicated that carboxyl,hydroxyl and phosphate groups of the microbial flocculants participated in this flocculating process and meanwhile the hydrogen bond was generated.In combined with the results of ESEM,it could be considered that chemical reaction,adsorption bridges,hydrogen bonding and Van der Waals force all contributed to flocculation mechanism.