电絮凝处理补给水中有机物的动力学分析及响应面优化

Kinetic Analysis and Response Surface Optimization of Electroflocculation Treatment of Organics in Make-up Water

锅炉补给水中有机物的去除问题一直困扰着电厂化学工作者。采用电絮凝去除补给水中的有机物,并对其动力学过程进行研究,探讨电絮凝过程中板间距(0.5、1.0、1.5、2.0、2.5、3.0cm)、pH(3、5、7、9、11)和电流密度(5、10、20、50、70、100A·m^(-2))对反应动力学速率常数的影响,通过Box-Behnken设计建立二次数学模型,以给水中代表性有机物腐植酸的去除率为响应值,分析上述3个因素的影响程度;通过对数学模型进行方差分析,优选出最佳方案并进行验证试验,同时对絮凝体进行扫描电镜(scanningelectron microscopy,SEM)分析。结果表明,电絮凝去除腐植酸过程符合一级反应动力学,动力学常数为0.04154min;增大板间距(如2.0cm)、酸性条件(如pH=3)和较大电流密度(如100A·m^(-2))均会增大速率常数;二次数学模型能较好反映电絮凝去除腐植酸过程,相关系数为0.9618;在最佳条件下腐植酸去除率为96.53%。SEM分析表明,电絮凝反应产生疏松的絮凝体吸附了腐植酸,为去除锅炉补给水中的有机物提供了一种新的思路。

The issue of organics removal in boiler make-up water remains an undissolved problem for power plant chemists.In this work,electroflocculation was used to remove the organics in make-up water,and the dynamic process of removal process was studied.The influence of factors,such as plate spacing(0.5,1.0,1.5,2.0,2.5,3.0 cm),pH(3,5,7,9,11)and current density(5,10,20,50,70,100 A·m^(-2))on the reaction kinetic rate constant was studied.A quadratic mathematical model was established through Box-Behnken design(BBD).The removal efficiency of humic acid,which is the representative organics in the feed water,was selected as the response value to analyze the influence of above three factors.Through the variance analysis of mathematical model,the experimental parameters were optimized and verified via test.The morphology of flocs was analyzed by scanning electron microscopy(SEM).The results show the process of removing humic acid by electroflocculation agreed with the first-order reaction kinetics,and the kinetic constant is 0.04154 min.The increase of the plate spacing(such as 2.0 cm),acidic conditions(such as pH=3)and current density(such as 100 A·m^(-2))will increase the kinetic constant.The quadratic mathematical model can better describe the humic acid remove process by electroflocculation,and the correlation coefficient is 0.9618.The maximum removal efficiency of humic acid was 96.53%.SEM analysis showed that the humic acid was adsorbed by porous flocs generated by the electroflocculation.This paper provides a new solution for organics removing in the boiler feed water.