Degradation mechanism of saliferous compounding heavy metals-organic wastewater by manganese and iron cycling in the microbial fuel cell

Abstract

With the rapid development of industry and agriculture, the heavy metal ions and organic matter pollution coexistence systems become increasingly common, aggravating environmental damage and endangering water safety. Therefore, an urgent need to find a general method to achieve the typical removal of two pollutants or promote the removal of one to improve another degradation, solving the related pollution problems. Meanwhile, the related research microorganism’s salt and heavy metal tolerance is lower, limiting the related research. Therefore, the study makes the deep-sea sediment as the strain source, obtaining the low-valence manganese-oxidizing functional bacteria (OMF) with salt-tolerant and heavy metal-tolerant characteristics, constructing the closed-circuit microbial fuel cell (MFC), carried out the degradation mechanism of saliferous compounding heavy metals-organic wastewater by manganese and iron cycling processes. The results showed that under the salt content conditions of 3%, pH = 6, external resistance of 510 Ω, Mn2+ concentration of 11 g/L, Mn2+:Fe2+ = 1:0.3 and OMF (Rhodococcus erythropolis: Microbacterium kitamiense: Dietzia = 1:2:1) inoculation amount of 20%. The maximum removal rates of organic pollutants (400 mg/L), Cu2+ (250 mg/L), Co2+ (150 mg/L) and Ni2+ (200 mg/L) were 94.72%, 91.23%, 99.89% and 99.97%, respectively. Realizing the heavy metal ions and organic matter pollution coexisting systems purification. The manganese-iron cycle mediated by oxidized low-valent manganese functional bacteria has a dual effect on the pollutant’s degradation process through MFC. Firstly, the synergistic redox cycle transformation of iron and manganese promoted the production of OH and accelerated the degradation of organic matter. Secondly, the ferromanganese oxidation products and bio-nanowires enhance material oxidation and electron transfer, improving the organic pollution oxidation and heavy metal ions fixation efficiency. This study provides a new idea for the heavy metal ions and organic matter pollution coexisting systems remediation and MFC degradation efficiency optimization.