| The properties of ozone and its application in water treatment were reviewed in this article.The emphasis of discussion focused on the current research and application of advanced oxidation process based on ozone.On the basis of the current situation of water treatment and the problems faced by ozone oxidation technology,the research purposes and main tasks in this was presented.The content of dissertation mainly includes three parts:(1)degradation of acetic acid by Mn2+/H2O2/O3 process under acidic circumstance;(2)mechanism of degradation of acetic acid by Mn2+/H2O2/O3 process under acidic circumstance;(3)effect of common anions on oxidation efficiency of Mn2+/H2O2/O3 oxidation system.The oxidation efficiency of O3,H2O2/O3,Mn2+/O3,Mn2+/H2O2 and Mn2+/H2O2/O3 for acetic acid degradation were compared at initial pH value of 1.0.The results showed that only Mn2+/H2O2/O3 had high efficiency on the oxidation of acetic acid,and the removal rate of acetic acid was 45.8% in 20 min.Acetic acid could be completely degraded by adding H2O2 and prolonging the reaction time.It was found that Mn2+/H2O2/O3 system could effectively degrade acetic acid as long as the concentrations of manganese and H2O2 were kept suitable valuses for any concentration of acetic acid in any acid solution.In addition,the oxidation efficiency of Mn2+/H2O2/O3 oxidation system increased with the increase of pH.The optimized process results showed that the low concentration of manganese ion was beneficial to the improvement of the system of oxidation efficiency,and high manganese ion concentration would reduce its oxidation efficiency.Considering the utilization of H2O2,H2O2 concentration had a appropriate value for a certain acid wastewater.For an acidic wastewater under specific conditions,the system has a best Mn2+/H2O2 ratio,for example,the optimum value was 140 whenpH was 2.0 and the initial concentration of acetic acid was 100 mg/L.In addition,H2O2 added in a batch way was also conducive to increase the utilization of hydrogen peroxide.The mechanism of Mn2+/H2O2/O3 oxidation process was studied.It was found that Mn2+/C2H2O4/O3 had similar degradation efficiency in acetic acid degradation(oxalic acid is reducible and ozone inert).This result showed that H2O2 might play a role of reductant in this process.When the hydroxyl radical scavenger t-butanol was added,it was found that there was no negative effect on the degradation of acetophenone,suggesting no the mechanism of hydroxyl radical.Combined with the literature,the main mechanism of the oxidation system might be the intermediate state of active manganese ions.Therefore,the effect of adding sodium pyrophosphate(scavenger for Mn3+)on the oxidation efficiency was investigated.The results showed that sodium pyrophosphate had inhibitory effect on the system,indicating that the possible active intermediates might be trivalent manganese ions.UV-visible scanning spectroscopy results showed that the system really has Mn3+production.Based on the experimental results and the oxidation mechanism of Mn3+in the latest literature,the mechanism of manganese ion valence cycling was proposed,and its highly active ions were trivalent manganese ions.The concentration of dissolved ozone remained a very low value within 10 min every experiment,and it would increase rapidly at the end of the experiment,which indirectly proved that ozone played an important role in this process.Considering the practical application,the effect of common anions on the oxidation efficiency of the system was studied.The results showed that NO3-and SO42-had no effect on Mn2+/H2O2/O3 oxidation system.Cl-and Br-had significant inhibitory effect on the system.Both F-and phosphate had little effect on the oxidation process.The above results have good guiding significance for the effective pretreatment or resource reuse of acidic wastewater. |
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