BDD电极对敌草隆的氧化降解及其影响因素

Electrochemical degradation of diuron via the BDD electrode and the influential factors involved

主要研究了BDD(Boron-Doped Diamond,掺硼金刚石)电极电解产生氧化剂(·OH、SO_4^-·、Cl_2、HClO、ClO^-)对水中典型污染物敌草隆的降解,重点考察了敌草隆初始浓度、电流密度、电极浸没面积和初始pH值对敌草隆降解速率的影响。结果表明:在同种电解质中,BDD电极的氧化降解速率最大,MMO(Mixed Metal Oxides,混合金属氧化物)电极次之,Pt(铂)电极最小;随敌草隆初始浓度增加,氧化降解速率先增加后降低;随电流密度和电极浸没面积增加,敌草隆降解速率增加;在强酸性(pH=3.0)条件下,敌草隆降解速率最大,中性条件下最小。

In this paper,we are going to make an investigation of the electrochemical degradation of diuron by using the borondoped diamond（ BDD,the boron doped diamond） anode,the mixed metal oxides（ MMO,IrO_2-Ta_2O_5/Ti） anode and the Pt anode in phosphate,chloride or sulfate electrolytes. Our investigation has confirmed that,the hydroxyl radical（ ·OH）,sulfate radical（ SO_4^-·）,active chlorine（ Cl_2,HCl O,Cl O-）,and persulfate（ S_2O_2_8^-） should be responsible for the degradation of diuron in the phosphate,chloride,and sulfate electrolytes correspondingly and respectively. Among them,BDD anode has been known for its best performance among the aforementioned three electrolytes,which is followed by MMO and Pt anode. As a kind of non-active anode,the ·OH generated on the surface of BDD anode tends to react directly with the target contaminants with no interaction with the electrode. However,the ·OH generated on the surface of the active anode（ e. g.,MMO and Pt electrode）tends to preferably interact with the electrode surface,so that the MMO and Pt anodes reveal their weaker oxidation capacity than the BDD anode in the phosphate electrolyte,with the pseudo-first order rate being constant in diuron degradation of 0. 059 min-1,0. 015 min^（-1）,0. 009 min^（-1） for BDD,MMO and Pt anode,respectively. In the experiment with the chloride electrolyte,·OH can be observed and found playing a significant role in chlorine generation in the BDD anode,which is different from those of MMO and Pt,with their pseudo-first order rate being constant in diuron degradation,that is,0. 092 min-1,0. 067 min^（-1）,0. 019 min^（-1） for BDD, MMO and Pt anode, respectively. What is more,in the sulfate electrolyte,it would be poosible for the BDD anode to activate the sulfate electrochemically due to its high oxygen evolution potential,whereas the degradation rate of diuron tends to increase with the decrease of the solution pH. Furthermore,we have noticed that the influences of the initial diuron concentration,the current density,the submerged area of the electrodes and the initial solution pH on the diuron degradation situation can also be evaluated with the BDD anode for its better performance on diuron degradation. The results of the above-mentioned experiemnts demonstrate that,when the initial concentration of diuron is increased,the degradation rates with the help of BDD anode tend to increase first and then decrease. On the other hand,not only the degradation rate of diuron,but also the energy consumption tend to increase when the current density and the submerged area of the electrodes tend all to get increased.