Synthesis Of Biogenic Manganese Oxide And Its Application For Heavy Metals Removal

Manganese oxidizing bacteria is a type of phylogenetical microbe which can oxidizes soluble Mn2+ into insoluble Mn3+/Mn4+ oxides.Nowadays,there are plenty of reports about pure cultured manganese oxidizing bacteria(MnOB),but rare work concerned on the manganese oxidizing consortium.In terms of application,manganese oxidizing consortium was more suitable than pure cultured MnOB.This work was performed to obtain an acclimated microbial consortium from the marine sediments and conduct the 16 S rRNA gene sequencing of microbial consortium.Then the growth and Mn2+ oxidation performance of microbial consortium in various conditions was investigated.The results showed that a significantly shift has taken place during the acclimation process.In the phylum level,the relative abundance of Proteobacteria firstly decrease from 56.72% to 35.1%,and then increase again to 76.12%.When the initial concentration of Mn2+ was up to 5 mM,the consortium could still oxidize manganese ion.Metal ions had different effects on Mn2+ oxidation performance of community and Zn2+,Co2+ and Cd2+ restrained the Mn2+ oxidation capacity to varying degree,but Fe3+ could accelerate the rate of Mn2+ oxidation.pH 7.0 and the salinity below 3.5% are suitable for growth and Mn2+ oxidation of community.The characterization results showed that the BioMnOX was amorphous with specific surface area of 31-41 m2 g-1.In order to study the heavy metals removal efficiency which performed in bioreactor by manganese oxidizing consortium,we firstly studied the heavy metals removal by BioMnOX only.Element mapping and N2 adsorption/desorption curves indicated that it contains C,O,N,Mn and Fe elements,and with specific surface area of 81.426 m2 g-1.Then BioMnOX was used to adsorb various heavy metals,and the results showed that BioMnOX have stronger affinity for Pb2+ over other metal ions.The results of FTIR and exciation-emission matrix fluoscence spectra indicated that the amide group,hydroxyl group,tryptophan protein-like molecules and aromatic protein-like molecules on BioMnOX surface plays an important role in adsorption of Pb2+.The adsorption of Pb2+ on BioMnOX could be approximated favorably by pseudo-secondorder model and Langmuir model,and the maximum adsorption capacity of Pb2+ was 507.61 mg g-1.The adsorption was spontaneous of monolayer adsorption and exothermic process.It also suggested that the chemisorption was main process in the adsorption of Pb2+.Finally,we attempted to enrich MnOB in bioreactor and produce BioMn OX in situ to remove Mn2+.We built the biological aerated filter(BAF)bioreactor and moving bed biofilm reactor(MBBR)to remove Mn2+.The results showed that the removal efficiency of Mn2+ by BAF was unstable.The falling biofilm has a bad effluent quality.However,the MBBR kept the removal of Mn2+ and the removal efficiency of Mn2+ was up to 86.53% when the influent Mn2+ concentration was 5.5 mg L-1.Therefore,the MBBR is more suitable for enriching MnOB and produce BioMnOX in situ.