Development of powerful bacterial biosorbent fibers for recovery of ruthenium and comprehension of the role of bacterial biomass in the fiber

The main purpose of this study is to develop and evaluate the fibrous bacterial biosorbents and to undestand the role of bacterial biomass in functionalizing polyethylenimine (PEI)-coated bacterial biosorbent fiber (PBBF). For this, chitosan fiber (CSF) and chitosan/biomass composite fiber (CSBF) were separately prepared by extruding chitosan solution and chitosan/biomass suspension, respectively. To make PBBF, the CSBF was coated with PEI and then cross-linked by glutaraldehyde. An acetic acid waste solution containing the initial ruthenium concentration of 1822.9 mg/L was used as a model waste solution. Batch sorption studies showed that the maximum Ru uptake of PBBF was 110.5 mg/g, which was 16.5 times higher than that of the commercial ion exchange resin, Lewatit MonoPlus M600. In addition, the thin fiber type of biosorbent showed as fast sorption kinetics as powder form of the raw biomass. Therefore, PBBF was evaluated as a promising biosorbent for recovery of Ru from Ru-containing acetic acid waste solutions. The role of biomass in the fiber was also investigated through sorption experiments and SEM, FTIR and XPS analyses with differently prepared fiber sorbents. In the case that the CSF was made without the biomass, it could not be coated with PEI. Meanwhile, the CSBF could successfully coat with PEI and primary amine groups were significantly increased on the surface of the fiber. Therefore, it can be concluded that the biomass should be essential to make PEI-reinforced chitosan fiber and that the negatively charged carboxyl groups on the biomass give the driving force for binding of cationic polymer PEI.