Interaction Mechanism Between Copper Ions And Electrochemically Active Biofilms Under The Coexistence Of Heavy Metals And Organic Compounds

With the rapid development of industrialization,the direct or indirect emission of heavy metals from industrial sewage has caused serious pollution of the water body ecosystem.Heavy metal ions have made a great threat to human health and environmental safety because of the characteristics of toxicity,biodegradation and bioaccumulation,which has become the one of the most difficult problems of pollution to be solved at present.Bioelectrochemical systems?BES?is a new bioelectrochemical technique.The electrochemically active biofilm?EAB?is used as a biocatalyst to oxidize the organic matter?such as acetate?to accelerate the energy conversion and remove the heavy metal through the metabolic process of the central metabolism.It is generally believed that EAB can degrade organic matter and release electrons to the cathode at the same time,and use them as the final electron acceptor to drive the reduction precipitation of heavy metal ions.However,in these studies,the cathode chamber contains only heavy metals and no organic matter,but in many practical wastewater,heavy metals and organic matter coexist.Therefore,the effect of heavy metal ions on the metabolic process of EAB and the process of extracellular electron transfer and the mechanism of inhibition and the mechanism of EAB in the migration and removal of heavy metal ions are not clear when organic wastewater containing heavy metals is added into the anode chamber.In this study,the effects of EAB on the morphology,electrochemical properties and microbial communities of the anodic biofilm were investigated,and the mechanism of EAB in the migration and removal of heavy metal ions was clarified.It also provides theoretical guidance for anodic treatment of heavy metals in biological electrochemical system.The specific research content and results are as follows:In this study,double chamber BES devices were used to investigate the effects of the increasing concentration of Cu²⁺on the morphology,electrochemical properties and microbial community of biofilms in the anode chamber dominated by electroactive biofilm in the presence of heavy metals and organic compounds.The results showed that when the Cu²⁺concentration was 10 mg L^-1,the voltage continued to decrease and fall to 0,which was due to the toxic effect of heavy metals on the biological anode resulting in the damage of the anodic biofilm,which inhibited the secretion of extracellular cytochrome C.This could adversely affect the power density and voltage output of BES,and limited the degradation of acetic acid and the reduction of heavy metals.When stopping the introduction of Cu²⁺to anodic chamber,the maximum voltage was recovered by 75.1%,and the coulombic efficiency was higher but the removal rate of acetate was lower than that of no Cu²⁺addition before,demonstrating the recovery ability of EABs was stronger than that of nonelectroactive bacteria.In addition,SEM-EDS and XPS indicated that most of the Cu²⁺were adsorbed on the anode surface and were reduced by electroactive bacteria on the anode.Compared with open bioelectrochemical system,electrons can improve the reduction ability of copper ions through the external circuit.Population analysis showed that after the impact of 10 mg L^-11 Cu²⁺in the anode chamber,the content of Geobacter decreased from 44.5%to 32.5%,while the Stenotrophomonas content increased from 0.03%to 37.7%.The changes of microbial community composition in different concentration of Cu²⁺mainly due to the selective impact of high concentration Cu²⁺on microbial communities,which leaded to the emergence of resistant strains.When Cu²⁺were added to the anode chamber,CV found that the biofilm inhibited by heavy metals could restore the activity,meaning that EAB was able to recover after being damaged by heavy metals.The results of this study added to the in-depth analysis of the observed bioanodic inhibition,and provided a new direction for the treatment of organic wastewater containing heavy metals.