| As one of the main pollutants in semi-enclosed spaces in recent years,benzene,ethylbenzene,toluene,and xylenes（BETX）have seriously harmed human physical and mental health.However,the stability of BETX in semi-enclosed spaces makes it difficult for the existing technologies to remove it.As a new oxidant,Chlorine dioxide（Cl O2）has a strong oxidation capacity,wide application,with no side effects,and has been widely used in indoor air purification.In this paper,o-xylene,m-xylene,and p-xylene are taken as the target pollutants.The removal rate of liquid xylene by Cl O2 was tested to study the removal mechanism of gaseous xylene.The removal efficiency of gaseous xylene by Cl O2 was investigated.The byproducts of the reaction were analyzed to deduce the degradation mechanism and reaction pathway and to provide basic theory and data support for the removal of BETX by Cl O2 and the improvement of indoor air quality.The results are as follows:（1）The effects of the reaction time,the concentration of Cl O2,and the temperature of the solution on the removal rate of liquid o-xylene,m-xylene,and p-xylene were studied with high performance liquid chromatography.The results were as follows:Cl O2 and liquid xylene mainly reactes within 5 h.The removal rate of xylene first increases and then decreases with the increase of Cl O2 concentration.The removal rate of 10 mg/L liquid o-xylene,m-xylene,and p-xylene reached a maximum at 0.5 mg/L,5 mg/L,and 12.5 mg/L Cl O2,respectively.The highest o-xylene removal rate at 5 h was 24.56%,40.38%,36.56%,respectively.The removal rates of mixed liquid benzene,toluene,o-xylene,m-xylene,and p-xylene reached a maxium at25 mg/L Cl O2 when the reaction time reached 10 h.The experiment demonstrated that Cl O2 is able to remove liquid xylene.（2）The effects of the reaction time and the concentration of Cl O2 on the removal rate of gaseous o-xylene,m-xylene,and p-xylene were studied with a gas chromatography.Experimental exploration of gaseous o-xylene,m-xylene,and p-xylene removal by Cl O2.The results were as follows:Cl O2 and gaseous xylene mainly reactes within2 h.The removal rate of xylene first increases and then decreases with the increase of Cl O2concentration.The removal rate of 4 mg/m3 gaseous o-xylene,m-xylene,and p-xylene reached a maximum at 8 mg/m3 Cl O2,respectively.The highest o-xylene removal rate at 10 h was64.75%,54.04%,63.04%,respectively.The removal rate of 4 mg/m3 mixed gaseous benzene,toluene,o-xylene,m-xylene,and p-xylene reached a maximum at 50 mg/m3 Cl O2 The highest removal rates of benzene,toluene,o-xylene,m-xylene,and p-xylene in the mixed gas were53.09%,61.70%,58.54%,61.27%,and 60.78%,respectively,when the reaction time reached10 h.The experiment demonstrated that Cl O2 is able to remove liquid xylene.（3）Experimental exploration of the reaction mechanism of the degradation of xylene by Cl O2.The by-products were analyzed using a gas chromatography mass spectrometry.The transition state of the reaction was calculated based on density functional theory.Two possible reaction pathways were found:（1）By the·OH addition reaction,xylene was oxidized to phenol,hydroquinone,and benzoquinone by the addition reaction of hydroxyl radicals,and finally was mineralized to water and carbon dioxide;（2）By the oxidation of·OH radicals,xylene was oxidized to toluene,hydroquinone,and benzoquinone by the oxidation of hydroxyl radicals,and finally was mineralized to water and carbon dioxide... |
