Recovery of Silver and Gold From Electronic Waste by Electrodeposition in Ethaline Ionic Liquid

The recycling of metals from electronic equipment waste (e-waste) is of great concern today. The work described in the article focuses on the application of ionic liquids (ILs) to selectively recover of precious metals (Ag and Au) from the anodic slime obtained at the anodic dissolution of cast e-waste. The ingots obtained from molten and cast anodic slime were selectively dissolved in ILs. Silver and gold compositions of the ingots: 39.7 wt.% and respectively 18.9 wt.%. The IL used was an eutectic mixture of choline chloride with ethylene glycol in a 1:2 molar ratio. As catalytic/oxidizing agent, there was used pure iodine in a concentration of 0.1-0.2 moldm-3 at 298-303 K. Cyclic voltammetry was employed for the determination of the electrochemical windows of ILs as well as of the dissolution and electrodeposition potentials of principal metals present in the ingot (anode). For Ag and Au, the deposition potentials determined were 0.074 V and respectively 0.696 V. The XRD and SEM-EDX analyses revealed that the content of precious metals in the cathodic deposits was 99 wt.% for Ag and respectively ]70 wt.% for Au. We demonstrated that ILs electrolytes could be a solution to selective recovery of precious metals from e-waste.

Electroplating of Co-W and Co-Mo Alloys from Na2WO4 Ionic Melts

The cathodic reduction processes of cobalt (II), tungsten (VI) and molybdenum (VI) in Na2WO4 melts are discussed. Electrochemical behavior of cobalt in a tungstate melt, as well as the effect of electrolysis conditions on the composition and structure of Co-W and Co-Mo alloys deposits from tungstate-molybdate melts is also studied. With a decrease in the concentration of cobalt ions and an increase in the concentration of molybdenum (tungsten) ions in the melt, the phase composition of cathodic deposits is shown to change from individual cobalt to individual molybdenum (tungsten) via a series of cobalt-molybdenum (tungsten) compounds of various compositions.

PRODUCTION OF DISPERSED NICKEL POWDER IN ELECTROCHEMICAL PROCESSING OF A RENIUM-CONTAINING HEAT-RESISTANT ALL

The article is devoted to the substantiation of the proposed technological scheme of electrochemical processing of rhenium-containing heat-resistant alloy ZhS32-VI of composition (mass %): Re - 4.0; Co - 9.3; W - 8.6; Y - 0.005; Lа - 0.005; Al - 6.0; Cr - 5.0; Tа - 4.0; Nb - 1.6; Mо - 1.1; С - 0.16; B - 0.15; Cе - 0.025, Ni - 60.05 to obtain nickel-containing cathode deposits. The results of studying the composition, surface morphology and granulometric analysis of cathodic precipitates obtained during the electrochemical processing of the spent heat-resistant alloy ZhS32-VI with the use of acid electrolytes are presented. Anodic dissolution of ZhS32-VI was performed in the galvanostatic mode. The effect of the electrolyte composition on the process parameters (current yield, distribution of alloy components between the electrolysis products, particle size distribution of the cathode product), electrochemical processing of this alloy were established. It is shown that depending on the nature of the electrolyte, cathode deposits of different chemical and phase composition can be obtained. They differ in the size and morphology of the surface. It has been established that the value of the cathode precipitate grains obtained in acid electrolytes is almost the same: 99% of the cathode precipitate grains are in the range from 0.04 to 0.60 μm. The main difference is a slight increase in the amount of fine fraction when sulphosalicylic acid is added to the electrolyte. All the cathodic deposits obtained have a dendritic structure, the development of which depends on the nature of the electrolyte, the precipitates obtained with the use of a nitrate electrolyte having the most developed structure and the smallest particle size.

Effect of the Molybdenum Substrate Shape on Mo2C Coating Electrodeposition

By electrochemical synthesis in the NaCl-KCl-Li2CO3 (1.5 wt.%)-Na2MoO4 (8.0 wt.%) melt on molybdenum, substrates with different configuration Mo2C coatings with the hexagonal lattice were obtained. The influence of the substrate form on the structure of Mo2C cathodic deposits was studied. The molybdenum carbide coatings on a molybdenum substrate (Mo2C/Mo) show a catalytic activity in the water–gas shift (WGS) reaction by at least three orders of magnitude higher than that of the bulk Mo2C phase. The catalytic activity remained constant during 500 h for the water–gas shift reaction.

Application of Ammoniacal Solutions for Leaching and Electrochemical Dissolution of Metals from Alloys Produced from Low-Grade E-Scrap

Paper reports results of the research on the application of ammoniacal solutions (sulfate, chloride, carbonate) for hydrometallurgical treatment of smelted low-grade e-waste. Two Cu-Zn-Sn-Ag-Pb alloys were analyzed in details and discussed. Leaching of copper from the alloys was slow in sulfate solution, but the dissolution rate decreased in chloride and carbonate baths. Anodic alloys dissolution was uniform in sulfate and carbonate electrolytes, but high degradation of the material was observed in chloride bath. Chemical and phase composition of slimes and cathodic deposits produced during electrolysis were characterized. In all cases, separation of copper from other metals was found, but efficiencies of the processes were low.

The Morphology of the Alumina Films Formed tn The Anodization Process of Aluminium in the Orthophosphoric Acid Solution. The Co-Fe Alloys Electrodeposition Into Obtained Alumina Pores

The optimal parameters of the anodic oxidation of aluminium in orthophosphoric acid solution was determined. In the pores of the obtained Al2O3 membranes with the ordered nanometric structure Co-Fe alloys were electrodeposited. The Al2O3 membranes were obtained in the two-stage anodic oxidation of aluminium in the 0.17 M H3PO4 solution in the temperature 1°C and at the electrolysis voltage 180 V. The influence of the anodizing process parameters on the thickness of oxide films and the diameter of pores and the distance between them in the alumina membranes were determined. The electrodeposition of Co-Fe alloys was carried out from sulphate baths containing sulphates (VI) of copper (II) and cobalt (II) of different composition, in potentiostatic conditions. The optimal electrolysis conditions were determined, where the cathodic deposits of the best quality were obtained. The conditions are: the electrolyte composition: 0.3 M Fe; 0.5 M Co; pH = 3, the potential: -0.760 V (vs. SHE1)).

Co-Mo and Co-Mo-C Alloys Deposited in a Magnetic Field of High Intensity and their Electrocatalytic Properties

Co-Mo and Co-Mo-C Alloys Deposited in a Magnetic Field of High Intensity and their Electrocatalytic PropertiesThe article presents results of tests on electrodeposition in a magnetic field of Co-Mo and Co-Mo-C alloys characterised by low overvoltage of hydrogen evolution. Addition of molybdenum and carbon was to lower the values of overvoltage of hydrogen evolution on cobalt. The influence of a magnetic field of high intensity (1 - 12 T) on the deposits composition, structure and morphology was determined. The deposition was conducted in a magnetic field of parallel orientation of the magnetic field forces lines in relation to the working electrode. Electrocatalytic properties of the obtained alloy coatings within the range of hydrogen evolution were tested in a concentrated solution of NaOH. The obtained alloys were analysed with the XRD method, their composition was tested with the WDXRF technique and they underwent observation applying scanning electron microscopy (SEM). The comparison of electrocatalytic properties of Co-Mo alloys with properties of Co-Mo-C ones enabled determining the influence of carbon presence in cathodic deposits on the overvoltage value of hydrogen evolution on them.

FORMATION OF CARBON NANOTUBES IN IRON-CATALYZED LIQUID ARCING METHOD: EFFECT OF IRON-ION CHARGE IN THE AQUEOUS MEDIUM

Carbon nanotubes (CNTs) were synthesized via arc discharge in aqueous solutions containing ferrous and ferric irons to reveal the effect of iron-charge mole ratio, R = [ Fe 2+]/[ Fe 3+], on the purity of CNTs and the process yield. Raman spectroscopy and transmission electron microscopy were used to analyze the cathodic deposits. It is shown that the nucleation of multi-walled CNTs is catalyzed by ferric irons while their growth is affected by ferrous ions. Well-graphitized CNTs with a high-yield are obtained at R = 1 and total iron concentration of 0.05 M. The effect of iron charge is described based on the two-stage formation mechanism.