Trends of Technological Development of Platinum Group Metal Recycling: Solubilization and Physical Concentration Processes

A residue containing TiO 2 and PGMs is generated in the hydrometallurgical process used for recycling platinum-group metals (PGMs). In this study, a pyrometallurgical process was considered in which PGMs from the residue generated in the hydrometallurgical process were concentrated in a molten copper phase as a collector metal and TiO 2 was separated into the SiO 2 -CaO-TiO 2 slag phase with SiO 2 and CaO flux. The dissolution of PGMs must be reduced to minimize the loss of PGMs to the slag. Therefore, the distribution ratios of Pt as representative PGMs between the liquid SiO 2 -CaO-Al 2 O 3 -TiO 2 or liquid SiO 2 -CaO-TiO 2 slag and molten copper were measured at 1773 K under an oxygen partial pressure of p O2 ¼ 10 À10 . The experimental results showed that the distribution ratio of Pt increased with TiO 2 concentration in the slag, and the distribution ratio of Pt reached a maximum value at a TiO 2 concentration of approximately 10 mass%, and decreased with a further increase in TiO 2 concentration with the SiO 2 -CaO-Al 2 O 3 -TiO 2 slag. However, as TiO 2 concentration in the slag increased, the distribution ratio of Pt decreased with the SiO 2 -CaO-TiO 2 slag. Additionally, the experimental results showed that the distribution ratio of Pt between the SiO 2 -CaO-Al 2 O 3 -TiO 2 slag and liquid copper increased with the slag basicity B, defined as B = (mass%CaO)/(mass%SiO 2 ) when the TiO 2 concentration in the slag was greater than 10 mass%.

Section: Introductionmentioning

confidence: 99%

“…Although sufficient minable reserves do exist, the ores of these metals are present only in low concentrations. Furthermore, production of PGMs from ores requires a great deal of energy and has a wide environmental impact [1,2].…”

Section: Introductionmentioning

confidence: 99%

Distribution of Platinum between the SiO2–CaO–Al2O3–TiO2 Slag System and Molten Copper

Takahashi,

Murata,

Yamaguchi

2024

“…Thus, an environment-friendly process is required. 9) In addition, treatment of iridium by conventional hydrometallurgical processes using aqua regia is difficult because of its high corrosion resistance. 7) It is often treated using high-temperature chlorine (Cl 2 ) gas flow with sodium chloride (NaCl) to form a water-soluble compound that can be treated by hydrometallurgy.…”

Section: Introductionmentioning

confidence: 99%

Establishment of a Novel Recycling Process for Iridium Using “Dry Aqua Regia”

Yoshimura,

Komatsuda,

Matsuno

2024

Iridium is one of the most refractory platinum group metals (PGMs) used in crucibles, catalysts, and ignition tips for spark plugs. Refining and recycling of iridium are energy-intensive processes with high environmental impacts; therefore, a novel recycling process is desirable to expand the utilization of iridium.Previously, we established a novel process for recycling platinum and palladium using "dry aqua regia", which is a molten salt consisting of iron(III) chloride and potassium chloride. This process can recycle PGMs more easily than conventional recycling processes.In this study, we employed "dry aqua regia" for the recycling of iridium. Iridium was dissolved in molten salt and recovered by precipitation using ammonium chloride as the precipitant and nitric acid or hydrogen peroxide as the oxidant. Consequently, it was dissolved by dry aqua regia treatment at 630-670 K, and the dissolved iridium was recovered by precipitation using ammonium chloride and hydrochloric acid with oxidants. The recovery ratio reached 28.3% and 45.7% using nitric acid and hydrogen peroxide, respectively, as oxidants. Based on these findings, we established the fundamental process of recycling iridium using "dry aqua regia".

“…Rh is one of the platinum group metals (PGMs) and an important element in a wide range of fields owing to its unique catalytic properties, heat resistance, acid resistance, and chemical stability. 1) In particular, Rh is used along with Pt and Pd as a catalyst for automotive exhaust gas purification, accounting for 88% of Rh demand. 1) Rh is necessary for the treatment of NO x emissions from gasoline engines.…”

Section: Introductionmentioning

confidence: 99%

Distribution of Rhodium between SiO2–CaO–CrOx Slag System and Molten Copper

Takahashi,

Murata,

Yamaguchi

2024

In the hydrometallurgical process used for the recycling of platinum group metals (PGMs), a residue containing Cr 2 O 3 and PGMs is generated. In this study, a pyrometallurgical process was applied, in which PGMs from the residue generated in the hydrometallurgical processes were concentrated in a molten Cu phase as a collector metal, and Cr 2 O 3 was separated into a slag phase with SiO 2 and CaO as the flux. To reduce the loss of PGMs into the slag, the dissolution of PGMs into the slag must be reduced. Therefore, the distribution ratio of Rh, as a representative PGM, between the liquid SiO 2 -CaO-Al 2 O 3 -CrO x or the liquid SiO 2 -CaO-CrO x slag and molten Cu were measured at 1773 K under an oxygen partial pressure of p O2 ¼ 10 À10 . The experimental results revealed that the distribution of Rh in the slag increased with increasing CrO x concentration. At a constant Cr 2 O 3 concentration in the slag, the solubility of Rh increased with increasing slag basicity, which is defined as B = (mass%CaO)/(mass%SiO 2 ). Furthermore, compared with the distributions of Rh and Pt between the slag system and molten Cu, Rh was more easily lost to the slag, and the dependence of Rh on basicity was greater than that of Pt.