A Study On The Oxidative Efficiency Of SZF/H₂O₂/O₃ In Acidic Solution

In this paper,the physical and chemical properties of ozone and its reactions with materials were firstly mentioned to further introduce the application of ozone in water treatment and the existent defects.Based on the research status of ozone advanced oxidation processes and the requirements of industrial application,combined with the properties and application potential of bimetallic composite solid superacid catalyst SO₄^2-/ZrO₂-Fe₂O₃?abbreviated as SZF?,the efficiency of SZF catalyzed H₂O₂/O₃ on the degradation of acetic acid and acetophenone under strong acid conditions?pH <2.0?was investigated.The effects of reaction conditions and anions on the oxidation efficiency of SZF/H₂O₂/O₃ process were also studied.And the reaction mechanism of the process was proposed.Firstly,the oxidation efficiency of SZF/H₂O₂/O₃ for the degradation of acetic acid was studied under acidic condition,and the influence of each operating parameters was investigated.The results showed that SZF/H₂O₂/O₃ had a good effect on the degradation of acetic acid when the pH of solution was 0⁵.0.What's more,when the pH was adjusted to 1.0,the introduction of SZF catalyst had improved the degradation efficiency of acetic acid in H₂O₂/O₃ by 37.1% within 30 minutes.Therefore,the addition of SZF can effectively broaden the working pH range of H₂O₂/O₃.Combined with relevant literatures,the mechanism of this system may be that SZF can react with H₂O₂ to produce a peroxo metallic complex intermediate S-[FeIIIOOH]²⁺,which has the effect of triggering the decomposition of ozone to generate hydroxyl radicals?�OH?.The production amount of �OH can be controlled by the concentration of H₂O₂,the pH value of the solution and the concentration of SZF catalyst.During the reaction,theconcentration of H₂O₂ and SZF should be controlled within a certain range,thus avoiding the useless consumption of �OH.Then,the effects of several common anions on the oxidative efficiency of SZF/H₂O₂/O₃ for the degradation of acetic acid were investigated.It was found that sulfate and nitrate ions had little effect.When the pH of the solution was 3,the removal rate of acetic acid in SZF/H₂O₂/O₃ system was reduced by 7.53% under the same conditions after adding 40 mg�L^-1 H₂PO₄^-.The reason is that,on the one hand,H₂PO₄^-shielded the active reaction center on the SZF surface so that hindering the generation of �OH,and on the other hand,H₂PO₄^- can consuming part of �OH.Cl-,Brare good �OH scavengers,which can quickly consume �OH under strong acid condition,thus reduce the removal rate of acetic acid in SZF/H₂O₂/O₃ system.And Brshowed a stronger inhibitory effect.For F-,due to the higher oxidation potential,the added F-could not cause the inefficient consumption of �OH,so the presence of F-has little effect on the degradation of acetic acid.At last,SZF/O₃ system was used to degrade acetophenone in the simulated wastewater.Under acidic conditions,the removal rate of acetophenone by SZF/O₃ was53.6% higher than that by ozone alone.The mechanism of the process is similar to that of SZF/H₂O₂/O₃ because the ozonation degradation of the aromatic ring substances can be accompanied by the formation of H₂O₂.The catalyst SZF can combine with the generated H₂O₂ to form an active metal peroxo complex and caused the decomposition of the ozone to produce free radicals,thereby degrading the organic contaminants.The removal rate of acetophenone by SZF/O₃ increased with the increase of solution pH.Under the condition of different pH,the addition of SZF could promote the removal of acetophenone by single ozonation,and the stronger the acidity was,the more obvious the lifting effect would be.Under alkaline condition,the degradation rate of acetophenone was the fastest and the time of reaching the end point was the shortest.When the pH of the solution is 1,the apparent rate constant of the degradation reaction of acetophenone by SZF/H₂O₂/O₃ is 6.61�10^-4 s^-1,which is about 7 times of that byozonation alone(0.97�10^-4 s^-1),indicating that acetophenone in the SZF catalytic ozonation process can be degraded more rapidly.In addition,Rct of ozonation and SZF catalyzed ozonation for degradation of acetophenone were 3.55�10^-10 and 24.69�10^-10,respectively,which demonstrates that there were more �OH generated in SZF catalytic ozonation process.Based on the above analysis,it can be confirmed that SZF catalyst can obviously improve the efficiency of H₂O₂/O₃ for the degradation of organic matters,thus effectively expanding the working pH range of H₂O₂/O₃ process.The common anions that exist in water also have effects on the oxidation efficiency of SZF/H₂O₂/O₃ system.These results are significant for the pretreatment of acidic wastewater by ozonation.