Recovery of critical metals from dilute leach solutions – Separation of indium from tin and lead

The strategic metal indium is recovered from solutions containing tin and lead that are typical of those obtained from leach solutions of metal component fractions of electronic waste including the leach solutions from indium tin oxide thin film conductive layers that contain only indium and tin. Almost total recovery of the metals can be achieved from nitric, perchloric and acetic acid leach solutions using a novel cylindrical mesh electrode electrolysis cell under appropriate conditions. The optimum separation of indium from tin and lead is achieved by a novel three-stage process from nitric acid media in the presence of SCN− as a complexing agent. Lead is removed from dilute indium-tin-lead solutions in the first stage from 0.1 mol L−1 nitric acid solution by electrodeposition over an 8 h period in the absence of SCN− to give a residual solution containing a maximum of 2 mg L−1 of lead (97% recovery). Tin is removed in the second stage by electrodeposition over an 8 h period from the solution after addition of 0.02 mol L−1 SCN− to give a maximum residual electrolyte tin concentration of 3 mg L−1 (94% recovery). In the third stage indium is recovered at the anode of the cylindrical mesh electrode cell as an oxy-hydroxide phase by increasing the SCN− concentration to 0.1 mol L−1 and carrying out the electrolysis for a period of 24 h to give a residual solution containing 1 mg L−1 of indium (98% recovery).We acknowledge the support of an EPSRC/LINK WMR3 grant (GR/L03217) with Fluid Dynamics International Limited. We wish to thank Aleppo University for a scholarship to NY and Professor. J. D. Donaldson for all his advice and support

Corrosion of Titanium and Its Alloys in Sulfuric Acid in the Presence of Chlorides

Titanium alloys (ASTM Grades 1, 2, 7, 12, and 18) are employed as the liner and internal components of autoclaves during the high-pressure acid leaching (HPAL) of nickel laterite ores. This paper summarizes the corrosion behavior of these alloys in sulfuric acid and the effect of the addition of chlorides (NaCl). New thermodynamic Eh–pH diagrams for the Ti–H2O, Ti-SO4–H2O, and Ti–Cl–H2O systems are presented. Micrographs are also presented and the corrosion morphology is discussed. Long-term immersion tests were carried out to determine corrosion rates. Electrochemical techniques were used to provide insight into the corrosion chemistry. The shortcomings of accelerated corrosion testing of Ti alloys are addressed. Pd enrichment on the surface of Ti-18 was confirmed by a combination of open-circuit potential measurements and chronoamperometric measurements

Corrosion of Ti-2 and Ti-7 relevant to nickel acid leach chemistry

The corrosion of commercially pure unalloyed titanium (Ti-2) and titanium with 0.15 wt.% palladium (Ti-7) was studied in acid sulphate solutions with and without chlorides. Both immersion testing and electrochemical techniques were used to characterize the corrosion. Corrosion rates calculated from polarization experiments were related to maximum rates observed during immersion testing; the two values generally agreed within an order of magnitude. The palladium alloyed metal showed corrosion resistance superior to Ti-2. The presence of chlorides enhanced the corrosion, especially of the palladium alloy indicating that palladium was dissolving as a chloro-complex. Corrosion was initiated by pitting near the grain boundary. The final corrosion morphology of the two metals differed significantly. Corroded Ti-2 exhibited a rough morphology with preferential dissolution of the grain material while Ti-7 showed a smooth, bubbly surface when corroded with strong acid and chlorides. The samples were thoroughly characterized. (C) 2010 Elsevier B.V. All rights reserved

The effects of gas tungsten arch welding on the corrosion and mechanical properties of AA 6061 T6

Corrosion of welded and un-welded Aluminum Alloy 6061 T6 was investigated by immersing specimens in 3.5% (wt) NaCl solution. Potentiodynamic and open circuit potential measurements were conducted. The mechanical properties were investigated using tensile strength, hardness, and torsion tests. Optical Microscopy and Scanning Electron Microscopy were used to investigate the microstructure evolution and the failure pattern of the specimens. Results revealed that corrosion current of the heat affected zone (HAZ) was higher than the base metal (BM). Corrosion potential for HAZ was more negative than the BM. Significant pitting corrosion was observed on the HAZ compared to the BM. Welding was found to weaken the mechanical properties of the alloy. Welded tensile specimens were failed at the welded area whereas not welded ones were failed at the centre. Welded torsion specimens were failed at the HAZ but not welded ones failed at the centre. The hardness of HAZ was decreased as a result of the heat generated during the welding process. Hardness values were increased as we moved away from the welded region. © 2013 by ESG