A Transformative Gold Patterning through Selective Laser Refining of Cyanide

Gold is an essential noble metal for electronics, and its application area is increasing continuously through the introduction of gold nanoparticle ink that enables rapid prototyping and direct writing of gold electrodes on versatile substrates at a low temperature. However, the synthesis of gold nanoparticles has certain limitations involving high cost, long synthesis time, large waste of material, and frequent use of chemicals. In this study, we suggest simultaneous laser refining of gold cyanide and selective fabrication of gold electrodes directly on the substrate without a separate synthesis step. Gold cyanide is commonly the first product of gold from the primitive ore, and the gold can be extracted directly from the rapid photothermal decomposition of gold cyanide by the laser. It was confirmed that laser-induced thermocapillary force plays an important role in creating the continuous gold patterns by aligning the refined gold. The resultant gold electrodes exhibited a low resistivity analogous to the conventional direct writing method using nanoparticles, and the facile repair process of a damaged electrode was demonstrated as the proof-of-concept. The proposed transformative approach for gold patterning, distinguished from the previous top-down and bottom-up approaches, has the potential to replace the well-known techniques and provide a new branch of electrode manufacturing scheme.

Сжимаемость и электронные свойства цианидов металлов

The compressibility and electronic properties of metal cyanides are investigated within the density functional theory taking into account the dispersion van der Waals interaction. It was shown that gold cyanide has a low linear compressibility (less than 0.1% at a pressure of 1 GPa) and a high linear modulus (~ 1200 GPa) along the -Au-CN-Au-CN- chains. Silver cyanide exhibits negative linear compressibility, which correlates with the compressibility of Ag-N coordination bonds. For sodium cyanide, the linear compressibility along the C - N covalent bonds is greater than for gold and silver cyanides, while the elastic anisotropy is less. Unlike sodium cyanide, for gold and silver cyanides, cation-anionic bonds (Au-N, Au-C and Ag-N, Ag-C) are partially covalent in nature, and the upper valence states correspond mainly to the states of cations. The band gap of gold cyanide is smaller than that of silver and sodium cyanides. The band gap widths of gold and silver cyanides significantly decrease with increasing pressure, which indicates the possibility of metallization at sufficiently high pressures.

CIL Gold Loss Characterization within Oxidized Leach Tails: Creating a Synergistic Approach between Mineralogical Characterization, Diagnostic Leach Tests, and Preg-Robbing Tests

A double refractory gold ore contains gold particles locked in sulphides, solid-solution in arsenopyrite, and preg-robbing material such as carbonaceous matter, and so on. The diagnostic leach test (DLT) and preg-robbing (PR) approaches are widely used to investigate the occurrence and the distribution of refractory gold. DLT serves to qualitatively evaluate the gold occurrences within the ore. Preg-robbing, or the ore’s capacity to fix dissolved gold, is evaluated to determine physical surface interactions (preg-borrowing) and chemical interactions (preg-robbing). The objective of this project is to characterize the refractory gold in Agnico Eagle Mine’s Kittilä ore using the DLT and PRT approaches coupled with mineralogical analyses to confirm testing. The studied material was sampled from the metallurgical circuit following carbon in leach (CIL) treatment at the outlet of the autoclave in order to investigate the effect of the autoclave treatment on the occurrence and distribution of gold. Different reagents were used in the DLT procedure: sodium carbonate (Na2CO3), sodium hydroxide (NaOH), hydrochloric acid (HCl), and nitric acid (HNO3). The final residue was roasted at a temperature of around 900 °C. These reagents were selected based on the mineralogical composition of the studied samples. After each leaching test/roasting, cyanide leaching with activated carbon was required to recover gold cyanide. The results show that gold is present in two forms (native and/or refractory): to a small extent in its native form and in its refractory form as association with sulfide minerals (i.e., arsenopyrite and pyrite) and autoclave secondary minerals that have been produced during the oxidation and neutralization processes such as iron oxides, iron sulfates, and calcium sulfate (i.e., hematite and jarosite), along with carbonaceous matter. The results of DLT indicate that 25–35% of the gold in the tails is nonrecoverable, as it is locked in silicates, and 20–40% is autoclave products. A regrind can help to mitigate the gold losses by liberating the Au-bearing sulphide minerals encapsulated within silicates.

Fatality from potassium gold cyanide poisoning

While potassium cyanide poisoning has been well described, the toxicity of potassium gold cyanide is less well understood. This case describes an 84-year-old man who presented after an intentional ingestion of 0.5–1 teaspoons of potassium gold cyanide. Despite antidotal therapy, the patient rapidly developed severe lactic acidosis, multiorgan dysfunction and ultimately expired. While the patient’s clinical findings were consistent with acute cyanide poisoning, a serum cyanide level was below the toxic threshold. Previous reports have suggested that gold toxicity may also contribute to the effects of potassium gold cyanide, and may have played a role in the patient’s rapid decline. In addition to treatment of cyanide toxicity, management of acute gold toxicity should also be considered in potassium gold cyanide ingestion.

Study on Intensification Behavior of Bismuth Ions on Gold Cyanide Leaching

Gold cyanide leaching is inefficient with conventional cyanidation. Bismuth ions can improve the efficiency of gold cyanidation by intensifying gold dissolution. The electrochemical behavior, structure information, and surface product of gold anodic dissolution were studied during the intensification of bismuth ions on gold cyanide leaching. The electrochemical analysis showed that the bismuth ions can not only improve anode current density, but also make gold dissolve at a lower potential, increase the corrosion current and intensify gold anodic dissolution. The microstructure analysis showed that bismuth ions intensified the cyanide corrosion of the gold surface, causing a large number of loose honeycombs, gullies, pits, and large holes on the gold surface. The XPS, FT-IR, and Raman analysis showed that there is weak information of C≡N in the spectrum of Bi intensification contrasting to that of conventional cyanidation. Cyanide compounds may be the insoluble AuCNads, which does not deposit on the surface of gold plate after Bi intensification cyanidation. The insoluble intermediate AuCNads is likely to react promptly with CN- to form soluble Au(CN ) 2 − , making less insoluble AuCNads deposits on the gold surface. Therefore, bismuth ions can promote the dissolution of insoluble AuCNads, prevents its passivation film to cover around the gold plate, keeps cyanide good contact with gold, and finally accelerates the cyanide dissolution of gold.