Perchlorate Reduction In The Microbial Electrolysis Cell With PANI And Nano-materials Modified Cathode

Perchlorate, as an endocrine disrupting chemical, is an emerging durable contaminant. Perchlorate diffuses rapidly in aquatic environments due to its high stability, good solubility and hard to be adsorbed by mineral substances and activated carbon. In the experiment, microbial electrolysis cell is employed to investigate perchlorate reduction with electrode as alone electron donor. The cathode was modified by electric polymer and nano-material to optimize electrode and study the effect of biocathode on MEC performance.In this study, different nano-materials were synthesized based on spectroscopically pure graphite (SPG) in situ methode. Their electrochemical characteristics and stability have been investigated by Foutier transform infrared spectroscopy (FI-IR), scan electron microscope (SEM), cyclic voltammetry, etc.The study demonstrated that modified electrode is more stable and obtained better electrochemical properties with the doping of graphene (GR) and carbon nanotube (CNT) through cyclic voltammetry. It also demonstrate that perchlorate transfer is mainly controlled by diffusion process and follow the diffusionless. Therefore, three ion exchange mechanisms were involved:1) perchlorate was prone to accumulation near modified surface.2) The doping and de-doping process of perchlorate occurred in the redox potential.3) Perchlorate moved after doping.Compared with PANI modified cathode, the redox peak shift toward negative with the doping of GR and CNT, which is conductive to perchlorate doping/de-doping. There are two main reasons involved:1) The electroconductivity was improved with the doping of GR and CNT, which is facilitate to electron transfer on the surface of electrode; 2) Higher specific surface and rougher surface were achieved with adding of GR and CNT. Meanwhile, smaller peak potential difference was obtained which account for better reversibility and stronger stability.Excellent perchlorate reduction was obtained under various initial concentrations in a non-membrane microbial electrolysis cell (MEC) with modified cathode as sole electron donor. PANI modification could facilitate the formation of biofilm due to its porous structure and good electrocatalytic performance. The hair-like structure, referred as to pili-like, was observed in the suspended sludge in the electrolyte. The result shows that pili was prone to formation under the condition of external electron field as sole electron donor. Analysis of microbial community suggests that perchlorate reduction bacteria community was most consistent with Azospiraoryzae strain DSM 13638 in the subdivision of the class Proteobacteria. Meanwhile, doping GR and CNT could facilitate PCRB acclimation and perchlorate reduction in the MEC due to GR/CNT great conductive property.In the study, the effect of MEC on perchlorate reduction is promoted with adding of GR and CNT. Two reasons were involved:1) The good conductivity of GR and CNT is facilitate to extracellular electron transfer and perchlorate reduction in the MEC; 2) Higher specific surface and rougher surface were obtained with doping of GR and CNT, which is conducive to adsorption of perchlorate and accumulation of perchlorate reduction bacteria. Compared with MEC with PANI-CNT modified cathode, better perchlorate reduction effect was achieved when the cathode were modified with PANI-GR. It is mainly due to higher conductive property and richment of oxygen functional group.