Recent developments in the determination of precious metals. A review

Analyses of the Distribution and Release Processes of Heavy Metal Ions in Surface-modified Silica Gel Systems

“…The distribution processes were analyzed as the intraparticle diffusion, and the diffusion coefficient (D p ) observed in the present systems was compared with that calculated from the theoretical pore and surface diffusion model. We consider that the rate-determining step of the distribution of Au(III) in the Q-TA (pore diameter 5.9 nm) system is the intraparticle diffusion of AuCl 4 . On the other hand, the distribution of Cu(II) into Q-TA was much slower than the intraparticle diffusion.…”

“…Silica gel modified with triamine (QuadraSil-TA, Q-TA) or thiol groups (QuadraSil-MP, Q-MP) was used as a surface-modified silica gel. A single microparticle was injected into an aqueous HAuCl 4 or CuSO 4 solution containing 0.01 M KCl (pH 6), and the distribution rate of the metal ion from water into the microparticle was measured. The rate of release of Au(III) or Cu(II) from Q-TA into water (pH 6) was much smaller than that of the distribution of the metal.…”

Sample Digestion Methods for the Determination of Traces of Precious Metals by Spectrometric Techniques

“…Spectrometric techniques, ultra-violet visible (UV-VIS) spectrophotometry, atomic absorption spectrometry (both flame (FAAS) and graphite furnace (GFAAS) techniques), inductively coupled plasma combined with atomic emission spectrometry (ICP-AES) or mass spectrometry (ICP-MS), are widely applied in the analysis of a variety of samples containing noble metals over a large range of concentrations. [3][4][5][6][7][8][9][10][11][12][13][14] UV-VIS spectrophotometry was historically the first instrumental technique used for the quantification of small amounts of noble metals in various materials. The technique requires a quantitative conversion of the analytes into stable complexes that can act as the basis of spectrophotometric measurements.…”

Simple and Rapid Determination of Trace Amounts of Gold(III), Palladium(II), and Platinum(IV) in Industrial Waste Solutions after Recovery of Noble Metals by Combined Use of GFAAS and Anion-Exchange Separation

“…Usually, any procedure has included the use of a variety of methods of concentration and/or separation prior to the analysis of such waste solutions for noble metals by means of modern and highly sensitive instruments. 3,[6][7][8][9] It has recently been revealed that chromatographic systems 10-16 consisting of a chelate-forming resin or a cellulose anion exchanger and a thiourea solution as an eluant are applicable to the separation of noble metals and base metals in various sample solutions. We have also demonstrated that an anion-exchange method 17 using a common anion-exchange resin and a dilute thiourea solution is more effective than the others, because of much stronger adsorption of the noble metals on the anion-exchange resins.…”

“…Generally, a variety of disposed industrial products containing small amounts of noble metals are first leached in aqua regia, followed by extraction with classical chemical separation methods using inorganic collectors and/or precipitants. [1][2][3][4][5][6][7] This recovery process produces large volumes of waste solutions, which usually contain extremely large amounts of various base metals, ammonium salts, sodium salts, chlorides, nitrates, sulfates, formates, acetates and so on. Contrarily, much smaller amounts of noble metals that are not completely recovered and still remain in the waste solutions are finally collected and removed as their metals by adding into the slightly acidic waste solution a zinc metal plate as a metallic precipitant for a long period of time.…”