Removal Of Cu(II) And Ni(II) From Waste Water By SMFC-SMEC Coupled System

The heavy metal pollution in water has become one of the most important problems in environmental pollution. There are various heavy metal ions in wastewater and Bioelectrochemical Systems(BES), combining the advantages of both microbiology and electrochemistry, is a promising device that can recover resource and remove pollutants(heavy metals) with incomparable advantages than other heavy metals treatment technology. Previous researchers mostly focus on utilizing double-chamber BES to treat wastewater with heavy metals. This research discussed the removal effects of single chamber microbial fuel cell(SMFC), single chamber microbial electrolysis cell(SMEC) and their coupled system on heavy metals Cu(II) and Ni(II).This paper employed SMFC and SMEC to treat wastewater polluted by single heavy metal Cu(II) and Ni(II) for the first time and optimized the treatment conditions metal concentration, initial p H value, external resistor and external voltage. For treating simulated wastewater containing copper with SMFC, the best conditions to reduce copper to deposit were that the maximal tolerated concentration of Cu(II) was 12.5 mg/L, p H was 6.0 and high current density was 500 Ω. There was a similar rules in treating wastewater containing nickel with SMEC that when the maximal tolerated concentration of Ni was 12.5 mg/L, p H was 7.0 and PBS was 100 m M, Ni(II) was easy to remove.Then this research coupled SMFC and SMEC with parallel connnection and this system could remove Cu(II) and Ni(II) effectively. In paralle connection, the effects of number of SMFC and external resistor on output voltage and metal removal rate were explored and the results showed that two SMFCs in parallel connection could improve the electricity output of the syste m and enhance the removal of Ni(II). Compared with when the external resistor was 150 Ω, the removal of Ni(II) increased 51.4% and voltage output increased 58.6%. Similar rules existed when the resistor was big that when the resistor rose from 150 Ω to 300 Ω, the output voltage increased from 0.230 V to 0.300 V and the removal rates of Ni(II) and Cu(II) improved repectively 48.8% and 7.3%. Therefore, raising the number of SMFC and increasing the external resistor could improve the output voltage and removal of heavy metals of coupled system.At last this study analyzed the removal pathways of Cu(II) and Ni(II) in BES and concluded that heavy metals were removed mainly by absorption of materials, microbial adsorption, and bioelectrochemical reduction. The results of SEM-EDS and XPS revealed that the reduzates of Cu(II) and Ni(II) deposited on cathode surface as particles. Results of Illumina high-throughput sequencing showed that Geobacter. sp was the dominant phylum on the anode while it was complex on the cathode. In SMFC, the dominant phyla on the cathode were Proteobacteria and Synergistetes. With the increase of Cu(II) concentration, the microbial community structure on cathode changed obviously and Ochrobactrum sp. and Azospirillum sp.were beneficial to electrogenesis and Cu(II) removal. For the removal of Ni(II), the dominant phyla were Proteobacteria and Bacteroidetes and the genera Ochrobactrum sp., Acetoanaerobium sp., Dokdonella sp. and Azospirillum sp. were beneficial to the reduction of Ni(II). In the end, the interaction between microbe on the anode and cathode was discussed.