Gold organic-solution-based

Organic Solution-Based Synthesis of Gold Nanoparticles 33... 

The raw precious metal concentrate is totally dissolved in hydrochloric acid—chlorine solution to form the soluble chloride ions of each of the metals. Silver remains as insoluble silver chloride and can be filtered off. Gold, in the form of [AuClJ, is extracted with, eg, tributyl phosphite or methyl isobutyl ketone. Base metals are also extracted in this step, and are removed from the organic phase by scmbbing with dilute hydrochloric acid (HCl). Iron powder is then used to reduce the gold species and recover them from the organic phase. 

A review of preparative methods for metal sols (colloidal metal particles) suspended in solution is given. The problems involved with the preparation and stabilization of non-aqueous metal colloidal particles are noted. A new method is described for preparing non-aqueous metal sols based on the clustering of solvated metal atoms (from metal vaporization) in cold organic solvents. Gold-acetone colloidal solutions are discussed in detail, especially their preparation, control of particle size (2-9 nm), electrophoresis measurements, electron microscopy, GC-MS, resistivity, and related studies. Particle stabilization involves both electrostatic and steric mechanisms and these are discussed in comparison with aqueous systems. 

The extraction of gold from PGM solutions by dibutyl carbitol is used by Inco,226 whereas extraction by methyl isobutyl ketone is used by Matthey Rustenburg Refiners.224 In both instances, the extraction of the gold immediately precedes the respective extraction steps for palladium described previously. Base-metal anions, such as FeCl4 , which are extracted at high concentrations of aqueous chloride, can be removed by contacting the loaded organic phase with water or dilute hydrochloric acid. Under these conditions, the base-metal chloro anions are converted to the aquated cations, e.g. 

All of the organic solvents, HCl 37% in water and H2O2 30% in water were purchased from Ficher Scintific and used as received. Gold wire was purchased from Sigma-Aldrich Corporatioa The gold content of aqueous solutions was measured by FAA-SpectrAA 55-Varian instrament. Gold powder was synthesized based on the procedure reported by Jeffrey et al. (2003) as described below. 

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