方铁锰矿型生物源Mn_(2)O_(3)转化阿特拉津的ROS作用分析

Role of ROS in the transformation of atrazine by biogenic Mn_(2)O_(3)

生物源锰氧化物具有表面活性高、比表面积大和酸性位点多等特点,常被用于催化分解环境中难降解的有机污染物.阿特拉津作为全球消耗量最大的除草剂之一,经过长期使用和环境积累,已造成全球范围的土壤和水资源污染.目前,关于锰氧化物转化阿特拉津的研究主要集中在化学源锰氧化物,而生物源锰氧化物的转化研究尚处在起步阶段.在本研究中,首先利用Mn(Ⅱ)氧化细菌Providencia manganoxydans LLDRA6制备了生物源锰氧化物,对其进行了X射线粉末衍射(XRD)以判断锰氧化物类型;进一步对其转化阿特拉津过程中的五种活性氧(O_(2)^(·−)、·OH、^(1)O_(2)、H_(2)O_(2)和NO)的含量进行了测定;最后通过自由基淬灭试验和电子顺磁共振(EPR)分析了不同自由基对阿特拉津转化的影响.结果表明,LLDRA6产生的锰氧化物为方铁锰矿型生物源Mn_(2)O_(3)(Bio-Mn_(2)O_(3)),并且具有较强的阿特拉津转化能力.在Bio-Mn_(2)O_(3)转化阿特拉津过程中,经化学法检测到有明显的O2^(·−)、·OH和NO产生,但未检测到^(1)O_(2)和H_(2)O_(2).自由基淬灭和EPR分析发现,O2^(·−)不能有效转化阿特拉津,而^(1)O_(2)和·OH发挥了转化阿特拉津的作用,其中^(1)O_(2)是Bio-Mn_(2)O_(3)转化阿特拉津时起主要作用的自由基.

Biogenic manganese oxides generally exhibit the traits of large specific surface area and high surface activity,which can be used to decompose the recalcitrant organic pollutants in the environment.As one of top ranked herbicides consumed in the world,atrazine has resulted in a globally environmental contamination after the long-term use.At present,the researches regarding the transformation of atrazine by manganese oxides commonly focus on chemogenic manganese oxides.In contrast,the topic in regards to the transformation of atrazine by biogenic manganese oxides remains to be investigated.In this work,we firstly employed the Mn(Ⅱ)-oxidizing bacterium,Providencia manganoxydans LLDRA6,to prepare biogenic manganese oxides,and conducted the X-ray diffraction(XRD)test to determine their crystalline structure.Then,five different reactive oxygen species(O_(2)^(·−)、·OH、^(1)O_(2)、H_(2)O_(2) and NO)were tested for their concentrations in the transformation process of atrazine by biogenic manganese oxides.Finally,the roles of these free radicals played in the atrazine degradation were evaluated by radical quenching and electron paramagnetic resonance(EPR)tests.The results show that,the manganese oxides produced by LLDRA6 were bixbyite-type Mn_(2)O_(3)(Bio-Mn_(2)O_(3)),and they possessed a strong ability to transform atrazine;During the transformation of atrazine by Bio-Mn_(2)O_(3),O_(2)^(·−),·OH and NO were readily detected by chemical assays,but ^(1)O_(2) and H_(2)O_(2) cannot be detected by chemical assays;O2^(·−)could not effectively transform atrazine,while ^(1)O_(2) and·OH were able to effectively transform atrazine,in which ^(1)O_(2) played a major role in the transformation of atrazine by Bio-Mn_(2)O_(3).