还原-氧化协同强化机械化学降解十溴联苯醚的研究

Decabromodiphenyl ether (BDE209) is a new persistent organic pollutant with great resistance to the oxidative degradation and extremely low water solubility. The common treatment methods either have a low degradation efficiency or must carry out in organic solvent, leading to serious secondary pollution. Mechanochemical reduction technology is recognized as a promising technology for the disposal of solid wastes containing halogenated pollutants, but it suffers from a problem of the accumulation of highly toxic less halogenated products. According to the molecular characteristics of BDE209, this proposal designs a new mechanochemical reduction and subsequent oxidation relay system, which consists of ball milling as treatment technique, metal oxide as dehalogenation reagent and persulfate as oxidant. During the mechanochemical process, metal oxide can induce the reduction of BDE209 to less brominated congeners, which show a higher reactivity toward oxidizing radicals,while the instantaneously high temperature because of the high-energy ball-milling can activate persulfate to produce sulfate free radicals, which then efficiently oxidize less brominated congeners, leading to a full debromination and deep mineralization. By investigating the recutive and oxidative degradation process and mechanism of BDE209 and the related polybrominated diphenyl ethers (PBDEs) in the obtained system, a new mechanochemical method is proposed for effectively degrading BDE209. The key-point of this work is the combination of the reduction of highly brominated PBDE and the subsequent oxidation of lower brominated congeners. This relay strategy will provide much valuable information in the field of pollutant control chemistry. The goal of this work is the development of a simple and feasible method for the large scale treatment of PBDEs, and the obtained results will provide many environmental benefits.

十溴联苯醚（BDE209）是一种难于氧化降解的有毒有机污染物，水溶性很差。常规方法对其处理时，或效果差，或需要在有机溶剂中进行，二次污染相当严重。机械化学还原脱卤法适合固相反应，但易积累高毒性低卤代产物。本项目根据BDE209的分子结构特点，采用机械球磨法，以金属氧化物为脱卤剂、过硫酸盐为氧化剂，构建一个还原-氧化接力强化机械化学反应新体系；研究BDE209及相关多溴联苯醚的还原与氧化降解过程及机理，提出一种机械化学还原-氧化接力降解新方法。本方法先利用机械力活化脱卤剂将BDE209还原为低溴联苯醚，再利用球磨产生的机械热将过硫酸盐活化分解为硫酸根自由基，接力氧化与矿化低溴联苯醚中间产物。本项目的核心是将高溴联苯醚的还原脱溴与低溴联苯醚的氧化分解有机结合，实现BDE209的彻底去除，能丰富污染控制化学的基础理论；目标是建立一种操作简便且能规模化处置多溴联苯醚的新体系，将产生重大的环境效益。

以十溴联苯醚（BDE209）为代表的多溴联苯醚（PBDEs）是一类应用广泛的添加型阻燃剂。由于BDE209具有强生物毒性、持久性和稳定性，被列入持久性有机污染物（POPs），因此，对其进行无害化处置备受关注。机械化学法是一种较有前景的非焚烧技术处理POPs固废的技术。针对高浓度溴代阻燃剂固废难深度矿化和脱溴的处置难题，本项目根据“高溴代联苯醚易还原，而低溴代联苯醚相对易氧化”的特点，提出了机械化学还原-氧化接力处置PBDEs的思路，首先建立了三个机械化学氧化体系：① 以过硫酸盐为氧化剂，利用机械球磨作用将其活化分解为硫酸根自由基，反应3 h，BDE209的脱溴率达98.3%。② 选择商用MnO2为氧化性磨剂，利用机械球磨作用活化其表面金属离子还原及晶格氧的释放，促使BDE209高效氧化降解，反应2h，。③以NaBiO3为磨剂，基于Bi5+的强氧化性及机械作用可加速NaBiO3表面晶格氧释放的特点，建立了NaBiO3高效降解溴代阻燃剂四溴双酚A的体系选择。接着，开发了两个二元磨剂还原-氧化接力降解BDE209的体系：① 采用Bi2O3和Fe为共磨剂，在机械作用下，利用零价铁预还原BDE209为低溴联苯醚，再利用Bi2O3释放的晶格氧氧化低溴联苯醚，建立了机械化学还原-氧化协同降解体系。② 采用TiO2和SiO2为共磨剂，发现二者对BDE209的降解和脱溴存在协同增强作用，在常温常压下，球磨2 h，即可实现BDE209的深度脱溴。结合降解中间产物分析和反应活性物种鉴定，阐明了BDE209在各降解体系中的降解反应历程和机制。本项目取得的研究结果不仅具有重要的科学意义，而且具有显著的环境效益和社会效益。.在国家自然课基金的资助下，本项目已发表10篇学术论文（其中9篇标注了基金），申报国家发明专利3项，其中1项已授权。综上所述，本项目执行良好，已实现预期目标。