Advanced Materials Research Vol. 825

Abstract: In this study, we developed Alamine-336-impregnated alginate capsule (Alamine-336-AC) by using a simple method. Alamine-336 was used as a model solvent extractant because it has good selectivity toward gold. Alamine-336-AC was prepared at different ratios of A (mixture of 1% CaCl₂ and 2.5% carboxymethyl cellulose) and B (Alamine-336) solutions. A comparative study revealed that the ratio of 9:1 (A:B) was the best condition for fabricating Alamine-336-AC. Microscope images revealed that Alamine-336 was well dispersed in the Alamine-336-AC. The maximum of gold uptake by Alamine-336-AC was 284.1 mg/g, which was about 5 times higher than those of Pt and Pd. Kinetics of adsorption was also investigated.

Abstract: Nowadays, metal nanoparticles have attracted a great scientific interest due to their unique optoelectronic and physicochemical properties with applications in diverse areas such as molecular diagnostics and drug delivery, electronics, catalysis or sensing. The development of techniques for the controlled synthesis of nanoparticles of well defined size, shape and composition has become a big challenge. Development of reliable and eco-friendly processes for synthesis of metallic nanoparticles is an important step in the field of applied nanotechnology. The use of biological systems as factories to produce nanoparticles is one way to achieve this objective. This study reports the synthesis of different metallic nanoparticles (gold, silver and platinum) through reduction of metal precursors by the extract of orange peel. It also demonstrates that particle size and shape could be controlled by varying parameters such as pH.

Abstract: The main purpose of this work 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.

Abstract: 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.

Abstract: An anionic biosorbent was derived from an industrial fermentation biowate, Corynebacterium glutamicum, by being cross-linked with polyethylenimine (PEI). A fiber form of the biosorbent was used to examine its potentiality of removing anionic metals such as As (V), Cr (VI) and Mn (VII) in aqueous system. As (V) and Cr (VI) were efficiently removed by the biosorbent through anionic adsorption mechanism. Sulfate ion seriously inhibited adsorption of the anionic metals through competitive inhibition with respect to the binding site of the biosorbent. In the case of Mn (VII), its removal mechanism by the biosorbent was not anionic adsorption. Mn (VII) was completely removed in aqueous phase, meanwhile, Mn (II) appeared and increased in proportion to the Mn (VII) depletion. As a result, adsorption coupled reduction was chosen as the mechanism of Mn (VII) removal by the biosorbent. In conclusion, the anionic biosorbent could be used to remove various anionic metals from aqueous solution through anionic adsorption or reduction mechanism.