| Ozone-based advanced oxidation processes?AOPs-O3?have good application prospects due to its advantages of green,high efficiency and no secondary pollution in water treatment.The decisive factors affecting its application are the development of a reactor,the exploitation of a catalyst and the effect of substrate?such as common anions,etc.?in actual water on its oxidation performance.This article first introduces the basic properties of ozone and its application in water treatment,and then discusses several common ozone advanced oxidation technologies.Therefore,the research content of this article is proposed.This thesis is mainly divided into three parts:the effects of halogens and halogen-containing anions on ozone/hydrogen peroxide?O3/H2O2?and ozone/ultraviolet?O3/UV?systems;magnesium titanate?Mg Ti O3?catalytic ozonation of acetic acid;the effect of common anions in water on the O3/Mg Ti O3 system.O3/H2O2 and O3/UV systems are two relatively mature oxidation technologies in AOPs-O3.Here,acetic acid,the probe of hydroxyl radicals in ozonation was selected as the target pollutant to be degraded,and the effect of halogen and its corresponding oxygen-containing anions on O3/H2O2 and O3/UV systems was investigated at p H 6.0.The results showed that chloride ion had a certain inhibitory effect on O3/H2O2,but almost had no effect on O3/UV system.Hypochlorite ion,chlorite ion,and chlorate ion had no effect on the oxidation efficiency of the two systems.The bromine ion had a remarkably negative effect on the removal of acetic acid in the both systems.When the bromine ion concentration is 0 mg/L,2 mg/L and 5 mg/L,the removal rate of acetic acid is 99.5%,94.1%,64.4%within 30 min in O3/H2O2 system,and 99.5%,94.5%,67.4%in O3/UV system,respectively.It can be seen that bromide ion had a remarkably negative impact on the two systems,which may be related to the quenching effect of hydroxyl radical?·OH?.Therefore,in order to keep the systems at a high oxidation level,the concentration of bromide ions should be controlled below 2mg/L.Iodine ion had a kind of inhibitory effect on the degradation of acetic acid in O3/H2O2 and O3/UV systems,and the inhibitory effect on O3/H2O2 system was more obvious.Iodate had basically no effect on the oxidation efficiency of O3/H2O2 and O3/UV systems.Composite metal oxides tend to have excellent properties than single metal oxides.In this paper,the composite metal oxide of magnesium titanate was used as a catalyst to study the efficiency of ozonation of acetic acid,and the effects of various factors was also investigated.When the initial p H value was 7.0,the dosage of magnesium titanate was 1.0 g/L,the ozone flux was 30.0 mg/min and the reaction time was 30 min,O3/Mg Ti O3 system removed 83.7%of acetic acid,while only 31.1%in ozone system.The results of the chemical oxygen demand?COD?measurement showed that the COD removal rate was 63.8%after adding magnesium titanate,indicating that some intermediate products were formed.The removal of acetic acid by O3/Mg Ti O3 system in tap water was 70.0%,indicating that the background materials had a negative effect on the system,but the effect was not obvious.After five cycles of recycling,the catalyst still had good catalytic activity.The results of ICP-MS analysis showed that the dissolution of Ti and Mg during the first use was0.46 mg/L and 5.14 mg/L,respectively.The above results indicate that the composite oxide has good stability in the process of catalytic ozonation.Free radical quenching experiments confirmed that the system mainly followed the hydroxyl radical mechanism.In order to explore the possibility of the O3/Mg Ti O3 system in practical application,we studied the effect of common anions in water on the system and then,experiments were conducted to treat actual wastewaters.It was found that SO42-,NO3-had no effect on the O3/Mg Ti O3 system;Cl-had a certain inhibitory effect;HCO3-,I-,HPO42-in the range of 0-100 mg/L,the inhibitory effect became more obvious with the concentration increasing.Br-had a significant inhibitory effect on the system.When the concentration of Br-was 1 mg/L,2 mg/L,5 mg/L and 10 mg/L,the removal rates of Ac OH in 30 minutes were 67.1%,64.5%,55.8%and 55.0%,which may be due to the quenching of Br-to·OH.The study found that the removal of COD after adding Mg Ti O3 had a certain improvement compared with O3 alone in an actual wastewaters. |
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