Catalytic converters aim to reduce the harmful byproducts of the combustion engine. Some studies show that this part of the exhaust is responsible for reducing carbon monoxide levels by as much as 96% and keeping Americans from living and breathing in what amounts to a giant smoke stack. However, to eliminate these toxins in the air, certain minerals such as rhodium are essential components. Rhodium targets nitrogen oxides (NOx), which in large quantities mask a city’s skyline in permanent smog. Before cars started using catalytic converters, major US cities like Phoenix recorded particulate pollution levels as high as 217 µg/m³ (micrograms per cubic meter) in 1970. PGM of Texas.
Although there are other precious metals in this part of the exhaust system, such as platinum and palladium, rhodium offers some important benefits. A catalyst requires significant amounts of heat to work effectively, so rhodium’s extreme thermal resistance (up to over 3,500 degrees Fahrenheit) is essential. Simply put, rhodium helps change certain molecules of nitrogen compounds, trapping some atoms while releasing oxygen. The amount of rhodium used is minimal, perhaps 0.05 ounces or less per part, which is a good thing considering the price. Still confused? This deep dive into the catalyst explains the topic in more detail for those interested.
Why is rhodium so expensive, and what does it take to extract and recycle it?
However, not only is it rare, but mining it is also difficult and time-consuming because it is created as a by-product of other activities that harvest, for example, nickel and platinum. Initially, rhodium is only part of the ore extracted, and it must undergo a series of processes to be extracted. This consists of cleaning, processing, crushing and metallurgy, resulting in approximately one ounce of rhodium for every 20 tons of ore, per year. Recohub. If that doesn’t sound too complicated, consider that it typically takes about half a year to convert a piece of ore into pure rhodium, according to WHILE.
Fortunately, rhodium can be recycled. Although the process of converting rhodium oxide (which is found in scrap metal) into rhodium is also quite complex. Impurities must be removed through smelting, and much of the process involves refining it to a usable state. Still, recycled catalysts can make significant amounts of money, due to the presence of precious metals. With rhodium hovering around $10,000 per troy ounce (31 grams), the laborious recycling process remains worthwhile. Unfortunately, catalytic converter theft, due to these valuable minerals, is still an expensive problem, but Congress is working on a way to solve it.
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