Biomobilization of silver, gold, and platinum from solid waste materials by HCN-forming microorganisms Biomobilization of silver, gold, and platinum from solid waste materials by HCN-forming microorganisms Abstract Cyanogenic Chromobacterium violaceum, Pseudomonas fluorescens, and P. plecoglossicida were able to mobilize silver, gold, and platinum when grown in the presence of various metalcontaining solids such as gold-containing electronic scrap, silver-containing jewelry waste, or platinum-containing automobile catalytic converters. Five percent of silver was microbially mobilized from powdered jewelry waste as dicyanoargentate after one day, although complete dissolution was obtained when non-biological cyanide leaching was applied. Dicyanoargentate inhibited growth at concentrations of >20 mg/L. Gold was bacterially solubilized from shredded printed circuit boards. Maximum dicyanoaurate concentration corresponded to 68.5% dissolution of the total gold added. Additionally, cyanide-complexed copper was detected during treatment of electronic scrap due to its high copper content of approximately 100 g/kg scrap. However, only small amounts of platinum (0.2%) were mobilized from spent automobile catalytic converter after 10 days probably due to passivation of the surface by an oxide film. In summary, all findings demonstrate the potential of microbial mobilization of metals as cyanide complex from solid materials and represent a novel type of microbial metal mobilization (termed "biocyanidation") which might find industrial application. ABSTRACT Cyanogenic Chromobacterium violaceum, Pseudomonas fluorescens, and P. plecoglossicida were able to mobilize silver, gold, and platinum when grown in the presence of various metalcontaining solids such as gold-containing electronic scrap, silver-containing jewelry waste, or platinum-containing automobile catalytic converters. Five percent of silver was microbially mobilized from powdered jewelry waste as dicyanoargentate after one day, although complete dissolution was obtained when non-biological cyanide leaching was applied. Dicyanoargentate inhibited growth at concentrations of >20 mg/L. Gold was bacterially solubilized from shredded printed circuit boards. Maximum dicyanoaurate concentration corresponded to 68.5% dissolution of the total gold added. Additionally, cyanide-complexed copper was detected during treatment of electronic scrap due to its high copper content of approximately 100 g/kg scrap. However, only small amounts of platinum (0.2%) were mobilized from spent automobile catalytic converter after 10 days probably due to passivation of the surface by an oxide film. In summary, all findings demonstrate the potential of microbial mobilization of metals as cyanide complex from solid materials and represent a novel type of microbial metal mobilization (termed "biocyanidation") which might find industrial application. Biomobilization of silver, gold, and platinum from solid waste materials by HCN-forming microorganisms

Amphiphilic graft copolymers with a thermosensitive PNiPAAm backbone and pH-sensitive hydrophilic poly(2-carboxyethyl-2-oxazoline) graft chains are synthesized. In aqueous solution, stable micelle-like aggregates are formed by increasing the temperature in the pH range 4.5-5.5. The micelles are crosslinked by electron-beam irradiation, yielding stable core-shell nanogels of about 100 nm diameter with reversible thermoand pH-dependent swelling behavior. The temperature sensitivity is provided by a conformational change in the PNiPAAm core, whereas the thickness of the poly(2-carboxyethyl-2-oxazoline) corona depends on pH. The reversible bisensitivity of core-crosslinked nanogels is verifi ed by DLS, while AFM measurements demonstrate the predicted core-shell structures of the aggregates. other sensitivities, that is, pH, light, magnetic fi eld, solvent quality, etc., and their effects on the reversible self-assembly in aqueous solutions or on hydrogel organization.Poly( N -isopropylacrylamide) (PNiPAAm) is the most frequently studied thermosensitive polymer and shows a phase transition in aqueous solutions at a physiological interesting temperature range. [ 2 ] The formation of PNiPAAm-based block copolymers with pH-responsive poly(acrylic acid) (PAA) [ 3 ] or poly( N -acryloylpyrrolidine) [ 1 , 4 ] offered new self-assembly possibilities. In dependence on the applied temperature and pH value, the PNiPAAmblock -PAA copolymers change their hydrophobic and hydrophilic balance and form different types of micelles. [ 3 ] Also random PNiPAAm-co -PAA and PAA-graft -PNiPAAm structures were realized by Chen and Hoffman, [ 5 ] and the temperature-induced phase transition over a wide range of pH values could be demonstrated. Topp et al. [ 6 ] reported on the synthesis of block copolymers of types A-B and A-B-A composed of poly(ethylene glycol) (PEG) and PNiPAAm as well as their micellization behavior. The design of these copolymers is based on the hydrophobic character of PNiPAAm above its lower critical solution temperature 4 5 6 7 8 9 1 0 30 35 40 45 50 55 60 R h (nm) pH 59 nm 44 nm 47 nm 34 nm Δ Δ Δ ΔT 25 °C 50 °C 12 % 100 % Degree of dissociation Δ Δ Δ ΔT

The adsorption of a nonionic amphiphile at the solutiordair interface has been studied by surface secondharmonic generation. The bulk phase transition of micellization was observed by monitoring the surfacereflected nonlinear signal. The concentration dependence ofthe second-harmonic signal could be described in terms of a Langmuir isotherm allowing the determination ofthe free energy of adsorption of the nonionic molecules at the surface. A comparison with experimental data obtained from surface tension measurements suggests a depth-dependent distribution of the surfactant molecules rather than a monolayer-type surface coverage. IntroductionIn aqueous solutions ofnonionic amphiphiles, the critical micelle concentration (cmc) is, in general, determined by measuring the concentration dependence of the interfacial tension (a) against air. Upon plotting u vs log x , with x denoting the mole fraction of the amphiphile in the bulk phase, the break of slope in the aAogx curve identifies the onset of micellization. As further information, the experiment yields the concentration dependence of the

Cyanogenic Chromobacterium violaceum, Pseudomonas fluorescens, and P. plecoglossicida were able to mobilize silver, gold and platinum when grown in the presence of various metal-containing solids such as powdered platinum, platinum-containing automobile catalytic converters, powdered silver, or gold-containing electronic scrap. Five percent of silver was mobilized from powdered jewelry scrap as dicyanoargentate after one day, although 96% was mobilized when non-biological cyanide leaching was applied. Dicyanoargentate proved to inhibit growth at concentrations >20 mg/L. Gold was microbially solubilized from electronic scrap (shredded printed circuit boards). Maximum dicyanoaurate concentration corresponded to a 68.5% dissolution of the total gold added. Additionally, cyanide-complexed copper was detected during treatment of electronic scrap due to its high copper content of approximately 100 g/kg scrap. Small amounts of platinum were mobilized from pure platinum powder after 10 days. The process proved to be very slow. In summary, all findings demonstrate the potential of microbial mobilization of metals as cyanide complex from solid materials and represent a novel type of microbial metal mobilization which might find industrial application.