Recovery of silver from silver chloride residues

A new chemical process for recovering silver metal from waste silver chloride residues is described. The silver chloride is digested in an oxidizing mixture before complexation with ammonia. High-purity free silver metal is precipitated from solution by the addition of ascorbic acid as the reducing agent.     

Closed-loop recirculating manifold for matrix isolation in flow injection flame atomic absorption spectrometry. Analysis of silver electrolysis solutions

Two flow injection procedures have been investigated for the determination of some elements in silver electrolysis solutions, for which the problem of the formation of silver acetylide needs to be addressed. A single line manifold was found to give acceptable results for limited time periods, but for prolonged operation it was necessary to remove the silver. This was achieved with a recirculating reactor in which the silver was precipitated as the chloride and retained on a filter of nylon fibers. Good recoveries of copper, iron, nickel and zinc from solutions containing up to 100 g/l. silver were obtained with over 95% of the silver retained on the filter. The filter was regenerated rapidly by flushing with ammonia solution.     

Electrolytic determination of nanomolar concentrations of silver in solution with a piezoelectric quartz crystal

Silver in solution is determined in situ by the frequency change of a piezoelectric quartz crystal on electrodeposition on the electrode of the crystal. The electrolyte solution flows through a cell containing the platinum-plated electrode (cathode) of the quartz crystal, a coiled platinum-wire anode and a silver—silver(I) chloride reference electrode, and is electrolyzed at —0.2 V vs. $\text{Ag}\text{AgCl}$. The frequency change is proportional to the silver concentration in the range 10^-5–5 × 10^-7 M after electrodeposition for 5 min, and in the range 10^-8–10^-9 M by recycling 20 ml of the solution over the electrodes for 3 h.     

Plasmonic photocatalytic system using silver chloride/silver nanostructures under visible light

Plasmonic photocatalytic nanostructured system was investigated on silver chloride/silver nanoparticles under visible light. Silver chloride/silver nanoparticles were readily prepared using dispersing agent and light irradiation. The d-spacing analysis, high resolution-transmission electron microscopy, X-ray diffraction analysis and diffuse-reflectance spectroscopy demonstrated that silver nanoparticles were introduced on the surface of silver chloride nanoparticles and then silver chloride/silver nanostructured photocatalytic materials were successfully synthesized. The as-synthesized plasmonic photocatalysts exhibited the enhanced photocatalytic performance over nitrogen-doped titania nanomaterials. The improved catalytic activity was originated from the enhanced adsorption for visible light, electron–hole separation, and the formation of chloride atoms in silver chloride/silver nanostructured materials.     

Electrodeposition and anodic stripping of silver on single carbon fibers

Silver is deposited electrolytically on carbon fibers from acetate buffer at pH 4.6 in the potential range from ?0.3 to ?0.8 V vs. SCE. Chronoamperometric and cyclic voltammetric measurements confirm that the mecanism of deposition is nucleation; the rate is higher than that at large circular glassy carbon electrodes. The silver deposits are more stable, especially with respect to oxidation by air, than are similar deposits of mercury. Preliminary results on codeposition of silver and mercury are reported.     

Electrolytically generated silver(II) as a coulometric titrant

The use of electrolytically generated silver(II) as a coulometric titrant has been studied. Difficulties arising from the current efficiency for generation of silver (II) at a platinum or gold electrode and from the reduction of silver(II) by water, have been overcome. The precautions necessary for accurate titrations of oxalic acid, cerium(III), arsenic(III) and vanadium(IV) by amperometric or potentiometric methods are detailed. Manganese and chromium could not be determined directly. Substances which reduce nitric acid could be determined if care was taken.     

Electrolytic methoxylation of halognofurans

-Halogenofurans are electrolytically methoxylated in two ways in the presence of sulfuric acid electrolyte, methoxyl groups either adding at the 2 and 5 positions in the furan ring or replacing a ring halogen atom. The following are methoxylated: 2-bromo-, 2-iodofuran, 5-chloro-, 5-bromo-, and 5-iodofurfural, ethyl 5-bromopyromucate. Derivatives of 2, 2, 5-trimethoxy-2, 5-dihydrofuran are prepared, giving on hydrolysis-aldehydo- and-ketoacrylic acids.Total anode polarization graphs are obtained in order to study the electrolytic methoxylation reaction mechanism.Furfural and 2-acetylfuran methoxylate, but only after first undergoing conversion to the dimethylacetal [1, 2].Electrolytic methoxylation of furan derivatives using sulfuric acid as electrolyte was first applied to methoxylation of a pyromucic ester, which, as referred to above, is not methylated using ammonium bromide.     

Application of platinum gauze activated by hydrogen to the adsorption separation of silver traces and their determination by aas or spectrophotometry

A method ("electrosorption") has been developed for separation of silver from copper by its deposition through internal electrolysis with hydrogen adsorbed on a platinum surface. The silver can then be stripped and determined by atomic-absorption spectrometry or the dithizone method. The activation of the platinum surface with adsorbed hydrogen can be achieved either electrolytically or by passing hydrogen gas through the solution in which the platinum is immersed. The method of electrosorption has been successfully applied to determination of trace levels of silver in copper metal.     

Electrolytic investigations : New electrolytic method for determining silver and separating silver from copper

A new electrolytic method is proposed for determining silver and separating silver from copper. A nitric acid-sodium nitrite medium is used. The deposits are bright and adherent, large and small amounts of silver may be accurately determined, and neither the amperage nor the voltage is critical.     

Needle-type ultra micro silver/silver chloride reference electrode for use in micro-electrochemistry.

A needle-type ultra micro silver/silver chloride reference electrode having a micro capillary with outer and inner diameters of 1.0 microm and 0.5 +/- 0.2 microm, respectively, was constructed. This micro reference electrode can be stuck into a living cell, and is applicable to use in very small environments, such as an electrochemical cell of an electrochemical scanning tunneling microscope or the detection portion of a micro-TAS. Excellent stability and repeatability of the micro reference electrode potential could be obtained by filling the micro capillary with agar gel containing 3.33 mol/L potassium chloride as a salt bridge, by covering the bare part of the silver wire on which silver chloride was deposited, and by electromagnetic shielding of the measurement cell and wire lead from the electromagnetic waves. The electrode showed stable potential for 7 days after its fabrication using 3.3 mol/L potassium chloride aqueous solution containing silver chloride as an internal electrolyte solution. The electrode exhibited constant electrode potential and excellent stability in test solutions of pH 5-9. The electrode potential of a commercial pH glass electrode measured against the micro reference electrode in standard pH buffer solutions was in good accordance with the Nernst equation.     

The electrodeposition of silver composites using deep eutectic solvents

Silver is an important metal for electronic connectors, however, it is extremely soft and wear can be a significant issue. This paper describes how improved wear resistant silver coatings can be obtained from the electrolytic deposition of silver from a solution of AgCl in an ethylene glycol/choline chloride based Deep Eutectic Solvent. An up to 10-fold decrease in the wear volume is observed by the incorporation of SiC or Al(2)O(3) particles. The work also addresses the fundamental aspect of speciation of silver chloride in solution using EXAFS to probe solution structure. The size but not the nature of the composite particles is seen to change the morphology and grain size of the silver deposit. Grain sizes are shown to be consistent with previous nucleation studies. The addition of LiF is found to significantly affect the deposit morphology and improve wear resistance.     

Electrolytic nucleation and growth of silver crystals in silver nitrate melts containing oxidants

Silver crystal nucleation is studied in AgNO₃ melts containing Pb(NO₃)₂ and HNO₃ at 250°C by the galvanostatic method. The maximum nucleation overpotential is higher as compared with pure AgNO₃ and the exchange current of silver deposition-dissolution is lower. It is found that the added substances and the products of their reactions with the melt are strong oxidants, take part in the electrochemical processes, and induce passivation of the cathodic substrate and the surface of growing silver crystals. Substantial changes in the morphology of the cathodic deposit and certain changes in the silver lattice parameter were observed depending on the oxidant content.     

The effect of silver ions electrolytically introduced into colloidal nanodiamond solution on its viscosity and thermal conductivity

Experimental data have been presented on the influence of silver on the viscosity and thermal conductivity of a dispersion of diamond nanoparticles. A stable dispersion (5 wt %) of detonation nanodiamond particles has been used in the experiments. Silver ions have been introduced electrolytically into the dispersion of diamond nanoparticles. Silver concentration was not higher than 0.05 wt %. It has been shown that the introduction of silver ions significantly affects the thermal conductivity and viscosity of the dispersion.     

The response of halide ion-selective electrodes to redox systems : A comparison between silver/silver halide electrodes and silver sulphide- based halide ion-selective electrodes

Silver/silver chloride and bromide electrodes, prepared by anodizing ordinary silver electrodes, and the corresponding ion-selective electrodes based on silver sulphide, were tested for their susceptibility towards redox systems. It proved that the latter type of electrode responded significantly to strong oxidants. In contrast, the silver/silver halide types were highly resistant to redox interference provided that the silver halide layer was free from open pores. This could be achieved by generation of sufficiently thick layers and by selection of suitable current densities during electrodeposition (<20 mA cm^-2). The interrelation between the conditions of silver chloride film generation and redox resistance of the resulting electrodes is described in detail.     

Interactions of silver with humates and other species in natural waters

Tracer^110mAg has been used to investigate the speciation of silver in natural waters, which may contain chloride, sulphide or humate ions. Silver chloride or oxide is readily absorbed from waters by many materials, and some may be photochemically reduced to metallic silver. Absorbed silver, silver chloride and silver sulphide may be distinguished by their desorption behaviour. Humates form complexes with silver chloride, silver sulphide and the silver cation, which can be separated from smaller species by gel permeation chromatography.     

Use of half-cell barriers to eliminate junction clogging and thermal hysteresis in silver/silver chloride reference electrodes

The junctions of Ag/AgCl electrodes rapidly become clogged with precipitated silver chloride during use. This causes loss of flow and slow response with thick junctions and may cause offset and stirring error with thin junctions. This problem can be eliminated by using a pure potassium chloride junction electrolyte, together with suitable barriers to impede migration of silver chloride from the half-cell. Diffusional transport through a mechanical barrier is inversely proportional to its electrical resistance when filled with electrolyte. Based on this principle, very effective barriers to half-cell diffusion and flow were fabricated from microporous glass. Alternatively, a cation-selective membrane was used to block soluble silver chloride complexes without a significant increase in electrode resistance. Thermal drift and hysteresis are not inherent features of the Ag/Cl couple and are eliminated by proper design of the half-cell.     

Substoichiometric determination of micro-amounts of silver in platinum

Selectivity of the isotope dilution analysis with substoichiometric separation for silver determination in platinum has been investigated. From dilute sulfuric acid in the presence of hydroxylamine sulfate silver can be extracted with substoichiometric amount of dithizone in chloroform.     

Solubility and equilibria of silver chloride

An hyperbolic cosine method for the study of the solubility equilibria of silver chloride in the presence of sodium chloride is reported in this paper. Various approximations are usually performed in a study of this kind of system in order to carry out single calculations. However, the method proposed considers all solubility data simultaneously, being as a result either more rigorous or simpler than the methods previously used.     

Graft copolymerization onto cellulose-based filter paper and its further development as silver nanoparticles loaded antibacterial food-packaging material

The present work describes ceric ammonium nitrate (CAN) initiated graft copolymerization of acrylamide onto cellulose-based filter paper followed by entrapment of silver nanoparticles. The copolymerization was carried out in aqueous solution, containing 2 M acrylamide monomer and 16 mM N,N’-methylene bisacrylamide (MB) crosslinker. The optimum initiation time and grafting reaction temperature were found to be 15 min and 30 °C, respectively. The silver nanoparticles were loaded into grafted filter paper by equilibration in silver nitrate solution followed by citrate reduction. The formation of silver nanoparticles has been confirmed by TEM and SAED analysis. The novel nano silver loaded filter paper has been investigated for its antimicrobial properties against E.coli. This newly developed material shows strong antibacterial property and thus offers its candidature for possible use as antibacterial food-packaging material.     

A simple hydrothermal route to large-scale synthesis of uniform silver nanowires

This paper describes the preparation of uniform silver nanowires by reducing freshly prepared silver chloride with glucose at 180 degrees C for 18 hours in the absence of any surfactants or polymers. Scanning electron microscopy studies indicated that the silver nanowires are about 100 nm in diameter and up to 500 microm in length. High-resolution transmission electron microscopy analyses showed that the silver nanowires grow perpendicularly to the Ag(200) plane. The silver nanowires are believed to grow through a solid-solution-solid process. Some influential factors on the growth of silver nanowires are also discussed.