微生物光电化学池去除硝酸盐氮:以PANI/TiO2-NTs为光阳极

Removal of Nitrate Nitrogen by Microbial Photoelectrochemical Cell:PANI/TiO2-NTs as a Photoanode

利用微生物光电化学池(MPEC)去除污染物是一种经济高效环保的方法.本实验在制备获得聚苯胺/二氧化钛纳米管阵列(PANI/TiO2-NTs)复合光电极的基础上,构建了由PANI/TiO2-NTs光阳极和生物阴极组成的MPEC系统,并对其去除硝酸盐氮(NO3^--N)的性能进行研究.结果表明,PANI负载时间为80 s时,PANI/TiO2-NTs电极光电性能最佳,相比于TiO2-NTs电极光电流密度增大约一倍,PANI的修饰有效提高了光能利用率.构建的MPEC系统能在无外加电压的条件下利用光能驱动实现自养反硝化脱氮,NO3^--N的生物降解符合准一级反应动力学方程.光响应电流密度越大,系统反硝化脱氮性能越好,NO3^--N初始浓度为25 mg·L^-1时,当光响应电流密度从0.17 mA·cm^-2增加至0.67 mA·cm^-2,平均反硝化速率从0.83 mg·(L·h)^-1增大到2.83 mg·(L·h)^-1.对生物阴极微生物膜进行了高通量测序,发现Pseudomonas所占比例最大(27.37%)为优势菌属.分析认为PANI/TiO2-NTs光阳极产生的光生电子通过外电路传递到阴极,Pseudomonas、Alishewanella和Flavobacterium等具有自养反硝化能力和电化学活性的微生物可直接利用电极上的电子作为唯一的电子供体进行自养反硝化脱氮.

The use of microbial photoelectrochemical cells(MPECs)for the removal of contaminants is a cost-effective and environment-friendly method.Based on the preparation of polyaniline/titanium dioxide nanotube array(PANI/TiO2-NTs)composite photoelectrodes,an MPEC system comprising PANI/TiO2-NTs photoanode and biocathode was constructed and the removal performance of nitrate nitrogen(NO3^--N)was studied.The experimental results showed that the PANI/TiO2-NT electrode exhibited the best photoelectric performance when the PANI loading time was 80 s.Compared with the TiO2-NTs electrode,the photocurrent density doubled.The light-driven MPEC system could realize autotrophic denitrification without an external voltage.The biodegradation of NO3^--N conformed to the pseudo first-order kinetics.The higher the photoresponse current density,the better the denitrification performance of the system.When the initial concentration of NO3^--N was 25 mg·L^-1 and the photoresponse current density increased from 0.17 mA·cm^-2 to 0.67 mA·cm^-2,the average denitrification rate increased from 0.83 mg·(L·h)^-1 to 2.83 mg·(L·h)^-1.High-throughput sequencing of the biocathode microbial membranes revealed that Pseudomonas(27.37%)was the dominant bacteria.It was considered that the photogenerated electrons generated by the PANI/TiO2-NTs photoanode were transmitted to the cathode through an external circuit.Pseudomonas and other microorganisms with autotrophic denitrification and electrochemical activity directly used the electrons on the electrode as the sole electron donors for autotrophic denitrification reaction.