Papers by Author: P. Yong

Abstract: Over the past 30 years the literature has burgeoned with bioremediation approaches to heavy metal removal from wastes. The price of base and precious metals has dramatically increased. With the resurgence of nuclear energy uranium has become a strategic resource. Other ‘non-carbon energy’ technologies are driven by the need to reduce CO2 emissions. The ‘New Biohydrometallurgy’ we describe unites these drivers by the concept of conversion of wastes into new materials for environmental applications. The new materials, fashioned, bottom-up, into nanomaterials under biocontrol, can be termed ‘Functional Bionanomaterials’. This new discipline, encompassing waste treatment along with nanocatalysis or other applications, can be summarized as ‘Environmental Bionanotechnology’. Several case histories illustrate the scope and potential of this concept.

Abstract: This study describes biofilm formation as a non line-of-sight coating method on support materials such as polyurethane foam, porous glass, polypropylene (PP) and titanium alloy, using a Serratia sp., which can manufacture extracellular nanoscale scaffolded hydroxyapatite (HA) crystals via enzymatic cleavage of glycerol 2-phosphate (G2P) in the presence of CaCl2. Various microscopies and non-invasive magnetic resonance imaging were used to visualize the biofilm coating on the support surface. A novel micromanipulation technique was used to estimate the adhesive strength of native and HA-mineralized biofilms. The biofilm with HA was up to forty times stronger than that without HA. A coating of nano-HA (> 80 m) onto a biofilm-Ti disc was achieved.

Abstract: Nanoparticles of palladium were obtained with the help of hydrogen-oxidising, metal- reducing bacteria and used for the production of electricity in a proton exchange membrane (PEM) fuel cell. Earlier works have shown that palladised cells of Escherichia coli and Desulfovibrio desulfuricans (Bio-PdE.coli and Bio-PdD.desulfuricans, respectively) appeared similar by electron microscopy and were comparably active in a chemical test reaction. When tested in a PEM fuel cell they produced 0.018 and 0.108 W, respectively. Electron paramagnetic resonance analysis of Bio-PdE.coli mixed with activated carbon showed paramagnetic activity. However, Bio-PdD.desulfuricans under the same conditions quenched the intrinsic EPR signal. This quenching is indicative of the magnetic properties of the particles. The magnetic behaviour of Pd nanoparticles was theoretically predicted for particles between 10 and 20 nm in diameter and can be experimentally confirmed by EPR measurements.

Abstract: Bio-manufacturing of nano-scale palladium was achieved using bacterial cells. Highly active Pd-catalyst (Bio-Pd) produced by an E. coli mutant gave power output in a fuel cell. Up to ~115% of the maximum power generation was achieved by electrodes of Bio-Pd catalysts from Escherichia coli, compared to that from a commercial-Pd electrode (~0.099 W). A bio-precious-metals (Bio-PM) catalyst made directly from an industrial reprocessing solution by the E. coli was also made into fuel cell electrodes and ~0.06W of maximum power generation was observed.

Abstract: Nano-scale palladium was bio-manufactured via enzymatically-mediated deposition of Pd(II) from solution. The bio-accumulated metal palladium crystals were processed and applied onto carbon paper and tested as anodes in a proton exchange membrane (PEM) fuel cell for power production. Up to 85% and 31% of the maximum power generation was achieved by Bio-Pd catalysts made using two strains of bacteria, compared to commercial fuel cell grade Pt catalyst. Therefore, it is feasible to use bio-synthesized catalysts in fuel cells for electricity production.

Abstract: Palladized biomass of typical Gram negative bacteria (Desulfovibrio desulfuricans and Escherichia coli) is well documented as a potentially useful catalyst for reduction of metallic species such as Cr(VI). This bionanocatalyst can be sourced from Pd-waste and scrap leachates via biocrystallization. A major industrial application of precious metal catalysts is in hydrogenation and hydrogenolysis reactions whereby, respectively, H is added across unsaturated bonds and halogen substituents can be removed from aromatic rings. Gram positive bacteria have not been evaluated previously as potential supported Pd-bionanocatalysts. We compare the activity of ‘Bio-Pd(0)’ supported on the fundamentally different Gram negative (Desulfovibrio) and Gram positive (Bacillus) bacterial surfaces, and evaluate the activity of the two types of ‘Bio-Pd(0)‘ in a standard reference reaction, the hydrogenation of itaconic acid, against a commercially available catalyst (5% Pd on carbon). The results show that the bionanocatalysts have a similar activity to the commercial material and biomanufacturing from waste sources may be an economic alternative to conventional processing for catalyst production as precious metal prices continue to rise.