Recycling of Platinum Group Metal Alloy Waste: There are many types of platinum group metal alloy waste. In some cases, the waste alloys are collected at designated locations, have consistent composition, and are only contaminated during use or physically damaged, rendering them unusable. In these cases, only the contaminants need to be removed before they can be reprocessed into new devices for reuse. Methods for eliminating physical contamination include high-temperature oxidation to remove oil and carbon deposits, boiling with hydrochloric acid, sulfuric acid, or nitric acid to remove base metals, and dissolving with alkaline solutions or hydrofluoric acid to remove silicon. In most cases, the collected waste alloys have multiple sources and complex compositions, requiring processes such as re-dissolving into a solution, separating impurity elements, separating platinum group metals from each other, and refining to obtain pure metals.
Recycling of Pt-Pd-Rh Waste Catalytic Nets: Pt-Pd-Rh catalytic nets are used in ammonia oxidation towers. The general composition is a ternary alloy Pt-4Rh-3.5Pd or a binary alloy Pt-(5-10)Rh. China uses a quaternary alloy with increased Pd content, Pt-Pd-Rh-M (M being another active metal). Alloys are drawn into fine alloy wires of 0.06-0.09 mm and woven into a mesh. Due to the oxidation and volatilization of Pt and Rh under high-temperature oxidation conditions, a rough “cage-like” structure forms on the surface of the fine wires, reducing their strength and causing them to be damaged. At the same time, they are contaminated by trace amounts of base metals, which reduces their catalytic activity and renders them unusable. They must be recycled and regenerated for use as new meshes.
