酸热氧化修饰合成MnO_(2)/GAC催化臭氧氧化降解邻氯酚

CATALYTIC OZONATION OF O-CHLOROPHENOL WITH MnO_(2)/GAC SYNTHESIZED VIA ACID-THERMAL OXIDATION MODIFICATION METHOD

通过酸热氧化修饰法在活性炭上负载锰氧化物,制得MnO_(2)/GAC催化剂,并研究其催化臭氧氧化降解邻氯酚的性能。结果表明:在催化剂投加量为0.1 g/L,臭氧浓度为20 mg/L,气体流量为0.5 L/min,初始pH为6的条件下,反应120 min时,邻氯酚的TOC去除率可达到95%,比单纯臭氧氧化提高了55百分点。在一定范围内,增加臭氧浓度和气体流量可以加快反应速率,提高TOC去除率,但通入过量的臭氧反而会降低TOC去除率。探究了无机阴离子对于体系TOC去除率的影响,研究发现:1 mmol/L的NO_(3)^(-)、SO_(4)^(2-)、Cl^(-)对TOC去除率无明显影响,1 mmol/L Br^(-)使体系TOC去除率降低了10%左右。pH是影响体系氧化能力的重要因素,在酸性条件下的TOC去除率远高于碱性条件下,这可能与催化剂表面官能团的作用和反应体系中无机碳的积累有关。此外,提出了催化剂表面羟基存在形式与pH之间的关系,以及不同羟基存在形式下催化臭氧分解产生的活性物种。

MnO_(2)/GAC catalyst was prepared by acid-thermal oxidation modification method loading manganese oxide on activated carbon,and the performance of its catalytic oxidation degrading o-chlorophenol was studied.Results showed that when the catalyst dosage was 0.1 g/L,the ozone concentration was 20 mg/L,the gas flow was 0.5 L/min,and the initial pH was 6,the TOC removal rate of o-chlorophenol reached 95%after 120 min,which was 55%higher than ozonation alone.The reaction rate and TOC removal rate was greater when increasing ozone concentration and gas flow within a certain range,since excessive ozone might lower the TOC removal rate.Effects of different ions on TOC removal rate was studied.No significant difference was noticed on TOC removal rate with the addition of 1 mmol/L NO_(3)^(-),SO_(4)^(2-),Cl^(-),separately.TOC removal was decreased 10%with the addition of 1 mmol/L Br^(-).pH was an important factor affecting the oxidation capacity of the system.Under acidic conditions,TOC removal rate was much higher than in alkaline conditions,which might be related to the behavior of the catalyst surface functional group and the accumulation of inorganic carbon in the system.In addition,the relationship between the form of surface hydroxyl groups on the catalyst and pH was proposed,and the formation pathways of active species under different circumstances were speculated.