| Br- exists widely in the natural water. Generally, its concentration is between 0.01-1.00mg/L. Br- is not toxic, but during the disinfection,it will be oxidized by the strong oxidizing disinfectant or the intermediate product, to produce the BrO3-, which is considered as a potential 2B carcinogen.Due to its unique advantage, electrochemical disinfection, as a new pattern of disinfection technology, shows stronger developing potential in drinking water disinfection treatment. However, electrochemical technology owned strong ability of ?OH, can react with organic and inorganic substances, forming the DBPs. Currently, the research of DBPs mainly focuses on the formation of organic DBPs, but little was known about inorganic DBPs, especially bromine inorganic DBPs.In this study, the electrochemical disinfection of drinking water containing bromide was conducted using the BDD electrode, Ti/Ru O2-Ir O2-Ti O2, Ti/Pt and Ti/Ru O2-Ir O2-Ti O2 anodes, respectively. The formation mechanism of bromate during electrolysis was studied. The main conclusions in the paper are follows:1.Under the condition of C0（Br-） = 1.00mg/L, current density = 100 m A/cm2, p H = 7,electrode distance = 1.5cm, all four electrodes can form BrO3-; BDD anode produced the highest concentration of BrO3-, followed by Ti/Pt anode,Ti/Ru O2-Pt anode and Ti/Ru O2-Ir O2-Ti O2 anode.2. The current density and C0（Br-）was positively correlated with the formation of BrO3-. Namely, the greater C0（Br-） and current density, the higher the concentration BrO3-. However, the greater current density would cause side reaction of electrode, which reduces current efficiency. The smaller electrode spacing, the more favorable for the formation of BrO3-.Compared with acidic and alkaline conditions, BrO3- were more likely to be formed in neutral environment.3. The research has been screened out the best process conditions with orthogonal method using the concentration of bromate to evaluate. The results revealed that C0（Br-） ã€p H〠current density and electrode spacing were the factors which influence the value of bromate, among them p H was the most significant factor. The optimum experimental conditions of four electrodes are follows: C0（Br-） of 0.5 mg/L, p H of 7, current density of 50 m A/cm2, electrode spacing of 2 cm.4. Under the best condition of C0（Br-） is 0.5 mg/L, p H of 7, current density of 50 m A/cm2, electrode spacing is 2cm, four electrodes have good electrochemical sterilization effect. BDD anode has the best sterilization effect. At the same time, the concentration of BrO3- was 0.042 mg/L. After 2h, other three electrodes during the electrolysis sterilization efficiency were above 95%. The concentration of BrO3- was 0.018, 0.042 and 0.026mg/L. When the concentration of BrO3- was 0.01mg/L of GB5749-2006 regulations the electrolysis sterilization efficiency was 68%.5. By means of electrochemical cyclic voltammetry scanning of anodes and RNO faded experiment, it is concluded that during the electrochemical oxidation of Br-, Ti/Pt electrode electrochemical had not only direct oxidation, but also indirect oxidation by producing active intermediate material ·OH; BDDelectrode, Ti/Ru O2-Pt electrode and Ti/Ru O2-Ir O2-Ti O2 electrode are oxidized by generating oxidation（forced the OH）. BDD electrode has a higher ability to form OH. This is why Br O4- occurs in the BDD electrode.6. From the perspective of thermodynamics, whether in acidic or alkaline condition, Br- can be oxidized by ?OH, and the end product is BrO3-. If the electrode has a strong capacity of forced the ?OH, it may eventually be oxidized Br O4-. The hydroxyl radical oxidation mechanism was preliminary issued.7. From the perspective of experiment, bromine was conserved in aqueous solution. During the electrolysis, bromine was not lost, but in other valence of bromine present in the water. Along with the growth of the electrolytic time, Brwas on the decline. The declining rate of BDD electrode was the fastest. Active bromine and BrO3- all took on a growth trend. The formation rate of BrO3- was higher than active bromine. It is likely that, Br O4- can be formed with the BDD electrode, because of its strong capacity of forced the ·OH. |
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