纳米零价铁耦合假单胞菌协同高效降解五氯苯

Integrated zero-valent iron nanoparticles and Pseudomonas sp. strains system enhance degradation of pentachlorobenzene

摘要:

【背景】氯苯类化合物广泛应用于工业化合物的生产，由于其具有高毒性和环境持久性的特点，对人类健康和生态环境造成严重威胁，寻找高效降解这类化合物的新方法成为研究热点。【目的】将纳米零价铁与假单胞菌耦合，探究其在好氧条件下对五氯苯的降解效果和降解机理。【方法】建立纳米零价铁和假单胞菌降解五氯苯的反应体系，通过测定各反应体系中五氯苯及其中间产物的浓度，以及观测细菌的生长状况变化等，分析反应体系的降解效果及其可能的降解机理。【结果】纳米零价铁耦合假单胞菌的反应体系相对于两者的单一体系表现出更好的降解效果，36 h的降解率可达55.4%，反应过程符合伪一级反应动力学，速率常数为0.020 48 h?1。根据GC-MS所测的中间产物推测，该体系的反应机理为纳米零价铁在好氧条件下反应产生羟基自由基，攻击五氯苯使其变为低氯苯类化合物，假单胞菌进一步利用这些低氯苯类化合物；同时，假单胞菌又为纳米零价铁提供附着位点，有效地降低了纳米零价铁的聚集性，提高了反应活性。【结论】研究建立的纳米零价铁耦合假单胞菌反应体系对五氯苯具有较好的降解效果，为含有高氯代苯类等有机污染物的复杂环境的修复提供参考。

Abstract:

[Background] Chlorinated benzenes (CBs) are widely used for the production of many important industrial compounds. High toxicity and environmental persistence of CBs bring serious threats to human health and the environment. Developing new methods for efficiently degrading CBs has become hot topics in this field. [Objective] The objective of this study was to construct a novel synthetic system, containing nanoscale zero-valent iron (NZVI) and Pseudomonas sp. JS100 (JS100), to explore its degradation efficiency of pentachlorobenzene (PeCB) and the potential degradation mechanism under aerobic conditions. [Methods] The NZVI and JS100 reaction system was constructed to degrade PeCB. The concentrations of PeCB and its intermediates in the reaction system were determined periodically by GC-MS. Moreover, the morphology and growth of JS100 were observed. [Results] The NZVI-JS100 reaction system could degrade about 55.4% of PeCB at 36 h. Compared with the single system of NZVI or JS100, it showed better degradation efficiency The reaction process accorded with pseudo-first-order reaction kinetics, and the rate constant was 0.020 48 h–1. Based on the results from GC-MS of the reaction intermediates, the mechanism of PeCB degradation could be rationally hypothesized. At aerobic conditions, hydroxyl radicals were generated from NZVI, and then attacked PeCB, leading to the production of lower chlorinated benzenes. While JS100 used them as nutrient for growth successively. At the same time, it provided multiple attachment sites and reduced the aggregation of NZVI, and thus, improving the efficiency of the NZVI-JS100 system. [Conclusion] The NZVI-JS100 system synthesized in this study exhibited a high degradation efficiency for PeCB. Moreover, NZVI-JS100 system provided an important reference for the remediation of organic pollutants such as higher chlorinated benzenes in complex environments.