Metals can’t hide from X-ray

Imagine this:
You run a sorting plant where the metals are pouring in. Aluminum, copper, stainless steel – mixed together  in a big bulbous mess.

You know there’s money in separating them, but how? Sending a man with a magnifying glass and tweezers through the whole pile is hardly the answer.

This is where X-ray technology comes in. 

With technology that can illuminate materials and sort them by density or chemical composition, you don’t need a magnifying glass or tweezers – in fact, you don’t even have to lift a finger. 

Curious yet?

 

How does it work?
X-ray Transmission (XRT) and X-ray Fluorescence (XRF) may sound like something from a hospital ward, but they are actually key concepts in metal recycling, and they are the ones that make it possible to sort metals with almost surgical precision. 

But what does it mean and what’s the difference?

I’m so glad you asked!

 

XRT (X-ray radiography) – Looks at density/density

Imagine working in customs at an airport and having to examine two different packages without opening them.

You put two packages in an X-ray scanner:

1. The first package contains a heavy, compact lead brick.
2. The second package contains a lighter but larger aluminum block.

When you look at the scan image, you can easily distinguish them:

• The lead brick looks darker because lead has a high density and absorbs more X-rays.
• The aluminum block looks brighter because aluminum has a lower density and absorbs less X-ray radiation.

 

XRT works in the same way: it assesses density and can distinguish between metals with different densities.

So XRT can identify that one package contains a heavy metal (lead) and the other a light metal (aluminum).

 

XRF (X-ray fluorescence) – Analyzes the chemical composition

Now take the same two packages and examine them in a different way:

Instead of scanning them from the outside, you open the packages and look at the “product declaration” of the material.

1. The first package contains pure lead (Pb).
2. The second package contains an aluminum alloy (Al + Mg + Si).

Although XRT already told you that there was a heavy and a light object, XRF now provides precise information about which elements are present.

Here’s the important thing:

• If both packages had exactly the same density, XRT would not be able to tell the difference.
• But XRF would still reveal the difference because it doesn’t look at weight or density – it analyzes the specific elements in the material.

 

XRF can confirm that one package is pure lead while the other is an aluminum alloy – even if they weighed the same.