Zn-Fe LDHs改性石英砂生物膜体系对BDE-47的去除效果与机理

REMOVAL EFFICIENCY AND MECHANISM OF BDE-47 BY THE ZN-FE LDHS MODIFIED QUARTZ SAND-BIOFILM SYSTEM

文章以四溴联苯醚(BDE-47)为目标污染物,利用共沉淀法制备Zn-Fe LDHs覆膜改性石英砂基质,在好氧、厌氧及两者交替条件下,研究腐败希瓦氏菌CN32(Shewanella putrefaciens CN32)在LDHs改性基质上生物膜形成过程及其对培养液中BDE-47的去除效果;通过监测反应体系中Fe^(2+)和H_(2)O_(2)浓度变化探讨BDE-47的生物及非生物去除机制。结果表明,LDHs改性不影响石英砂基质表面生物膜的形成,但在好氧条件下,Zn-Fe LDHs石英砂改性基质对CN32电子传递链活性存在一定抑制作用,而在厌氧条件下,LDHs改性会影响基质生物膜胞外聚合物(EPS)组成特性,使多糖占比升高。无论在好氧还是厌氧条件下,基质生物膜反应体系中EPS总浓度均显著高于纯菌CN32体系;且在好氧与交替条件下,基质生物膜的形成均显著提高反应体系中BDE-47的去除效果(约25%)。在交替条件下,前3次循环(72h内)BDE-47的去除以基质吸附为主;72h后,生物膜吸附与生物降解共同发挥作用,且LDHs改性基质在后期上升潜力更大。研究报道了LDHs改性基质生物膜形成特性及其对水相中PBDEs去除的潜力,为强化人工湿地中PBDEs生物降解提供新思路。

In this paper,Zn-Fe layered double hydroxides(LDHs)modified quartz sand was prepared by coprecipitation method and cultivated with inoculation of Shewanella putrefaciens CN32 under aerobic,anaerobic and alternating conditions,to examine the biofilm formation process on LDHs modified matrix and its removal efficiency of BDE-47 as the target pollutant.The biotic and abiotic removal mechanisms of BDE-47 were further explored by monitoring variations of Fe^(2+)and H_(2)O_(2) concentrations in the reaction systems.The results showed that LDHs coating would not affect the formation of biofilm on the surface of the modified quartz sand,but Zn-Fe LDHs modified matrix showed certain inhibitory effects on electron transport system activity of CN32 under aerobic condition,while the composition of extracellular polymer substance(EPS)of matrix biofilm changed with an increase in the proportion of polysaccharide under anaerobic condition.Total concentrations of EPS in the matrix biofilm reaction systems were significantly higher than those in the pure CN32 system under both aerobic and anaerobic conditions.The formation of matrix biofilm significantly improved the removal efficiency of BDE-47 in the reaction system(about 25%)under aerobic and anaerobic alternating condition.Under the alternating condition,the removal of BDE-47 in the first three cycles(within 72h)depended mainly on matrix adsorption;while 72h later,biofilm adsorption and biodegradation contributed jointly,and LDHs modified matrix exhibited greater boosting potential in the later stage.This study firstly demonstrated the biofilm formation characteristics of LDHs modified matrix and its potential for the removal of PBDEs from the aqueous phase,and provided new ideas for enhancing the biodegradation of PBDEs in constructed wetlands.