Abstract:

Decabromodiphenyl ethane (DBDPE) is the most commonly used brominated flame-retardant. With the widespread detection of DBDPE in various environmental media, environmental pollution control has gained increasing attention. To date, there have been no reports on the application of biochar-loaded nano-zero-valent iron (nZVI/BC) to remove DBDPE from sediments. In this study, nZVI/BC was prepared from sugarcane bagasse by liquid-phase reduction. The kinetic process of nZVI/BC removal from sediment systems by DBDPE was studied, and the mechanism of action was explored, providing a scientific basis and technical support for the use of carbon-based zero-valent iron to remove DBDPE from sediment. It was found that increasing the dosage, moisture content, and reaction temperature, and reducing the initial mass fraction improved the DBDPE removal efficiency. High doses of nZVI/BC provide more adsorption sites and increase the contact area with DBDPE, thereby adsorbing more DBDPE molecules. As the mass fraction of DBDPE increased, the competition between the DBDPE molecules increased, resulting in a decrease in the contact rate between the DBDPE molecules and nZVI/BC particles. A large amount of water can provide more active H, thereby increasing the probability of reaction with DBDPE. The increase in temperature enhanced the molecular motion, contact frequency between nZVI/BC and DBDPE, and reactivity of nZVI. The SEM characterization results showed that the addition of biochar (BC) uniformly dispersed nano-zero-valent iron (nZVI) on the surface of biochar improved the dispersion degree of nZVI and enhanced the reaction activity of nZVI. The FTIR results showed that the stretching vibration of −OH and the bending intensity of −CH₂− on the surface of nZVI/BC decreased after the reaction, the characteristic peak of Fe−CO disappeared, and a stretching vibration peak of C=C appeared. The microporous and mesoporous structures of nZVI/BC, as well as the Fe−O, −OH, −CH₂−, C−O, C−H, C=O, and −COOH groups on the surface, can provide adsorption sites for DBDPE, and the π electrons on the benzene ring structure of DBDPE may interact with the cations on the surface of nZVI/BC to form π-charge interactions. The GC-ECNI-MS detection results indicated that during the degradation of DBDPE by nZVI/BC, octabromodiphenyl ethane may be generated by debromination, and the ECOSAR software predicted the degradation of DBDPE by nZVI/BC, reducing the biological toxicity of the parent organism.

Key words: brominated flame retardant, decabromodiphenyl ethane, biochar, nano-zero-valent iron, sediment, removal mechanism

摘要：

新型溴代阻燃剂十溴二苯乙烷（DBDPE）已经成为目前最常用的溴代阻燃剂。随着DBDPE在各种环境介质中被普遍检测到，其环境污染和治理正引起广泛的关注。迄今为止，生物炭负载零价铁材料（nZVI/BC）去除沉积物中DBDPE的应用尚未见报道。利用甘蔗渣通过液相还原法制备nZVI/BC，研究nZVI/BC去除沉积物体系里DBDPE的动力学过程，并探究其作用机制，为利用碳基零价铁去除沉积物中DBDPE提供了科学依据和技术支持。研究发现增加材料投加量、含水量、反应温度和降低底物初始质量分数，均能提高DBDPE的去除效率。高剂量的nZVI/BC能提供更多的吸附位点，并增大与DBDPE的接触面积，从而吸附更多的DBDPE分子。DBDPE质量分数的增加，将进一步增加DBDPE分子间的竞争反应，导致DBDPE分子与nZVI/BC颗粒的接触率降低。大量的水可以提供更多的活性H，从而提高与DBDPE反应的机会。温度升高，分子运动增强，提高了nZVI/BC与DBDPE的接触频率，也提高了nZVI的反应活性。SEM表征结果显示，生物炭（BC）的加入使纳米零价铁（nZVI）均匀分散在生物炭的表面，改善了nZVI的分散程度，提高了nZVI的反应活性。红外吸收光谱FTIR检测结果表明反应后nZVI/BC表面的−OH的伸缩振动和−CH₂−的弯曲强度均减弱，Fe−CO特征峰消失，并且出现了C=C的伸缩振动峰。nZVI/BC的微孔及介孔结构和表面的Fe−O、−OH、−CH₂−、C−O、C−H、C=O和−COOH等基团均能为DBDPE提供吸附位点，且DBDPE苯环结构上的π电子可能与nZVI/BC表面上的阳离子形成π−电荷相互作用。GC-ECNI-MS检测结果表明DBDPE被nZVI/BC降解过程中可能脱溴生成八溴二苯乙烷，ECOSAR (Ecological Structure Activity Relationships)软件预测nZVI/BC对DBDPE的降解降低了母体的生物毒性。

关键词: 溴代阻燃剂, 十溴二苯乙烷, 生物炭, 纳米零价铁, 沉积物, 去除机制