Recovery of zero-valent ruthenium from acetic acid waste solution by a combined process of biosorption with bacterial biosorbent fibers and incineration

This study introduces a new process for the recovery of zero-valent ruthenium (Ru) from acetic acid waste solution by a combined process of biosorption with bacterial biosorbent fibers and incineration. As an effective sorbent to bind Ru-acetate complexes, polyethylenimine (PEI)- modified bacterial biosorbent fibers (PBBF) were developed and used for the experiments. The PBBF were prepared by extruding the blended mixture of chitosan-Corynebacterium glutamicum biomass as a fiber, coating the fiber with PEI and cross-linked using glutaraldehyde, consecutively. The role of chitosan in the bacterial biosorbent fiber was binder of the biomass. Batch biosorption studies showed that the maximum Ru uptakes of raw biomass and PBBF were estimated to be 16.0 and 110.5 mg/g, respectively. Kinetic studies showed that PBBF was as fast as powder form of raw biomass. After biosorption, the Ru-acetate complexes ions sorbed biosorbents were incinerated for recover Ru as a metallic form. These biosorbent constituents could be burnt out and at the same time, the sorbed Ru-acetate complexes ions could be reduced to Ru0. X-ray photoelectron spectroscopy (XPS) results indicated that the Ru-acetate complexes ions were able to be reduced into metallic form of zero-valent Ru. X-ray fluorescence spectrometry (XRF) was applied for analysis of impurity metals in the recovered Ru containing ashes. The purity of metallic Ru by means of XRF was 99.79%. The proposed sequential process of biosorption and incineration for recovery of Ru from acetic acid waste solution would contribute to the solution of several problems such as the Ru recovery efficiency, generation of secondary waste, and recover costs and energy.