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自20世纪60年代,多溴联苯醚(PBDEs)被广泛用作聚氨酯塑料、纺织品、家用电器以及建筑材料中的阻燃剂[1]。PBDEs有一个共同的结构,都是由两个苯环与一个氧原子相连。依据苯环上溴原子取代数目和位置的不同,PBDEs有10个同系物组,209种同系物。PBDEs商用产品通常包括五溴联苯醚、八溴联苯醚和十溴联苯醚产品,其中十溴联苯醚产品是被使用最多的商用阻燃剂[2]。
PBDEs具有长距离迁移性和环境持久性等特性,2009年,联合国环境规划署的《斯德哥尔摩公约》将PBDEs列入持久性有机污染物(POPs)名单[3]。PBDEs通过多种途径进入环境,在土壤、大气、水环境中均已检测到PBDEs[4-6]。通过食物链富集,PBDEs蓄积在生物内[7],对生物具有生殖、神经、免疫和内分泌等多种毒性[8-9]。在209种同系物中,十溴联苯醚BDE209是主要的污染物,在多数环境样本中占PBDEs总量的80%以上[10-11],因此对BDE209污染环境的修复研究刻不容缓。
目前对于PBDEs的修复研究主要有生物、化学和物理技术,其中零价铁还原降解卤代有机物是一种高效快速且经济可行的治理技术,该技术主要通过直接电子转移实现卤代有机物的降解[12]。近几年,研究者发现,相比零价铁,纳米零价铁的比表面积更大、反应活性更高、还原能力更强[13-14]。但单一的纳米零价铁还原存在着容易团聚、表面生成氧化物后易失活等问题,难以实现卤代有机物的快速降解。因此提高纳米零价铁活性和避免团聚是亟待解决的问题。
本文采用铁镍双金属复合材料并以硅藻土为载体,通过液相还原法将纳米铁与镍负载在硅藻土上,合成了硅藻土@多巴胺@Fe/Ni纳米颗粒,减少纳米零价铁团聚现象的发生,且硅藻土无毒并对环境有一定的改良效果,研究其对BDE209的降解性能,明确最佳降解条件,并分析其降解产物和降解途径,为PBDEs污染环境修复提供科学依据。
铁镍双金属复合材料的制备及对BDE209的降解
Preparation of Fe/Ni bimetallic composites for degradation of BDE209
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摘要: 以多巴胺(PDA)改性硅藻土为载体,采用液相还原法制备铁镍双金属复合材料(硅藻土@PDA@Fe/Ni)并进行了表征,研究了不同制备条件下复合材料对BDE209的去除效果,获得最佳制备条件,分析了不同用量、污染物初始浓度和pH条件下复合材料对BDE209的去除效果,通过分析不同反应时间后的降解产物,明确降解途径。结果表明,Fe/Ni双金属复合材料的最佳制备条件为硅藻土-PDA比例为1:1.1,负载体和纳米Fe的质量比为1:2,Ni的比例为5%。复合材料用量为12 g·L−1、初始浓度5 mg·L−1、溶液pH为5时,BDE209的去除率较高,为99.23%。降解初期高溴联苯醚产生,降解后期低溴联苯醚出现,同时体系中Br−的产生量与BDE209的降解同步,表明Fe/Ni双金属复合材料降解BDE209的途径是逐步脱溴。降解结束后,溶液中Fe2+、Fe3+和Ni2+浓度低于污水综合排放标准限值,有效避免了二次污染问题。Abstract: Fe/Ni bimetallic composites (diatomite@PDA@Fe/Ni) were prepared by liquid phase reduction method with dopamine (PDA) modified diatomite as a carrier and characterized. The removal effects of composite materials on BDE209 under different conditions of preparation were analyzes, and the optimum preparation conditions were obtained. Under different conditions of dosage, initial concentration of pollutants and pH, the removal effects were also analyzed. Through the analysis of the degradation products of different reaction time, the degradation pathway was clarified. The results showed that the optimum preparation conditions of Fe/Ni bimetallic composites were as follows: 1:1.1 of the ratio of diatomite to PDA, 1:2 of the mass ratio of the carrier to nano-iron, and 5% of the proportion of Ni in the composites. When the dosage of composite material was 12 g·L−1, the initial concentration was 5 mg·L−1, and the pH of solution was 5, the removal rate of BDE209 was high (99.23%). Highly brominated polybrominated diphenyl ethers were produced in the initial stage of degradation and low brominated polybrominated diphenyl ethers appeared in the later stage. At the same time, the production of Br− in the system was synchronized with the degradation of BDE209, indicating that the degradation of BDE209 by Fe/Ni bimetallic composites was gradual debromination. After the degradation, the concentrations of Fe2+, Fe3+ and Ni2+ in the solution were lower than the limits of the integrated wastewater discharge standard, which effectively avoided the secondary pollution.
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Key words:
- zero-valent iron /
- bimetallic /
- polybrominated diphenyl ethers /
- degradation
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