Effective Gold Biosorption by Electrospun and Electrosprayed Bio-Composites with Immobilized Lysinibacillus sphaericus CBAM5

Electro-hydrodynamic processing, comprising electrospinning and electrospraying techniques, is a novel technology used in the production of nano- and sub-micro-scale materials with specific properties suitable for environmental remediation processes. Polycaprolactone (PCL) micro-fibrous mats and alginate microcapsules were produced using electrospinning and electrospraying techniques respectively, and Lysinibacillus sphaericus CBAM5, a bacterium capable of metal removal by adsorption and accumulation inside the cell, was immobilized in these matrices. The polymeric structure was able to protect and maintain cell viability and the bio-composite materials were used to capture gold from synthetic water samples. The micro-fibrous membranes with immobilized bacteria were able to remove 93% of the gold after 120 h of inclusion in the aqueous medium. Using a filtration system, an efficiency of 64% was obtained for the removal of the precious metal after 10 cycles of filtration (2 h of exposure to the gold solution). In contrast, the microencapsulated L. sphaericus CBAM5 captured 64% of the gold after 4 h of the assay. Thus, both micro-structured matrices were suitable for the immobilization and protection of L. sphaericus CBAM5 and they showed high efficiencies of gold biosorption. Hence, these bio-composite materials could be used to concentrate gold from industrial wastewaters.

Gold Nanoparticles and Silicate Microsheet Modified Photoanode for Dye Sensitized Solar Cells

Gold nanoparticles and silicate microsheet modified TiO2 photoanode with various decoration amount of gold solution have been successfully synthesized. The gold nanoparticles were prepared using Turkevich method and silicate microsheet was using silica gel. The sample were characterized by XRD, SEM, and FTIR. The DSSC performance were evaluated by photocurrent-voltage measurement. The results show the increasing decoration amount of gold nanoparticles, increase the intensity of diffraction peaks. The gold nanoparticles size is 20-35 nm. Comparing with pristine TiO2 photoanode, the efficiency of DSSC using modified photoanode increase up to 31%.

The Au-Hosting Minerals and Process of Formation of the Carlin-Type Bojitian Deposit, Southwestern China

The recently discovered middle-sized Bojitian Carlin-type Au deposit is located in southwestern Guizhou Province, China, near the well-known Shuiyindong super-large-sized deposit. To improve the understanding on this deposit, here we investigate the minerals that host Au and the occurrence of Au in the deposit, using a combination of microscopic work and electron probe microanalysis (EPMA). Based on the results, the formation of the deposit was addressed. Results indicate that the dominant minerals that host Au include arsenian pyrite and arsenopyrite. Au in the cores of zoned pyrite exists mainly as natural nanoscale Au (Au0), while Au in the rims exists mainly as solid solution Au (Au+), but it likely also exists in the rims as natural nanoscale Au. The framboidal, coarse-grained, and banded pyrite types contain both natural nanoscale Au0 and solid solution Au+. The arsenopyrite is of hydrothermal origin, and Au within the arsenopyrite exists as gold solution Au+. The Bojitian deposit was formed from As-bearing, H2S-rich, low-to-medium-temperature fluids that migrated along faults and other channels. Au that was already present in the strata or source beds migrated with the fluids in the form of Au(HS)− and ore-forming fluids were then formed in the reducing environment. The ore-forming fluids interacted with Fe-rich carbonates to form an abundance of Au-hosting arsenian sulfides.

Preparation of gold-coated sand for ultratrace mercury analysis

In this study, the gold-coated sand was prepared to make gold-trap for mercury analysis at ultra-trace levels. The preparation process was conducted with the etching of sand surface to form silanol groups using a mixture of H2O2/H2SO4 followed by the replacement of the silanol groups by amino groups with aminopropyltriethylsilane. The amino-modified surface is embedded with Au atoms by soaking the amino modified sand in nano gold solution then the Au film is thickened with a mixture of Au(III)+NH2OH.HCl. The gold-coated sand can capture up to 21 μg Hg per 1 g of sorbent. The interferences for the efficiency of mercury sorption such as HNO3, HCl, H2SO4 and temperatureare were investigated. The goldcoated sand was successfully applied for mercury analysis in certified reference materials (DORM-4) by CV-AAS and combustion/thermal decompostion methods.

Synthesis of Gold Nanoparticles by Methanobactin

Methanotrophic physiology is strongly affected by the amount of bioavailable copper, which regulates the enzymes used by methanotrophs to oxidize methane. Methanobactin is a small peptide secreted by methanotrophic bacteria that binds copper outside of the bacterial cell. In this study, gold nanoparticles were firstly synthesized with citrate acid, followed by addition of methanobactin. Then as CuSO4was continuously added to the solution, we found a red shift in the Uv-vis absorption spectra. Meanwhile, for the mixture of methanobactin, 1,4-resorcinol and chlorauric acid, we also found an absorption at 540nm after 1h in dark. We presume that methanobactin has the bioactivity of protecting gold nanoparticles as well as delivering electron for the catalytic synthesis of gold nanoparticles. These molecules then go on to form gold nanoparticles. Gold nanoparticles can be seen with the naked eye, as they turn a gold solution from yellow/gold to a deep cranberry/red. The nanoparticles also display a characteristic absorbance of approximately 540 nm on absorption spectra.