XRF (XRF)

XRF stands for X-ray fluorescence, an analytical sensor technology that identifies and quantifies the elemental composition of a material by bombarding the sample surface with high-energy X-rays (typically 10-50 keV) and measuring the characteristic secondary X-rays emitted by each element as inner-shell electrons drop to fill vacancies created by the primary beam. Each element has a unique X-ray emission spectrum — copper, iron, nickel, zinc, lead, bromine, chlorine, and many others — making XRF a fast, non-destructive elemental fingerprint.

Application in recycling lines: XRF sensors appear in two roles in modern e-waste plants. As an analytical tool, handheld XRF guns (often called HHXRF or 'XRF gun') let operators identify the metal grade of a single fragment in 2-3 seconds — distinguishing copper-bronze alloys from brass, identifying lead solder content, detecting cadmium plating on connectors, or screening incoming scrap for radioactive contamination. As a real-time sorter sensor, line-mounted XRF heads above conveyor belts scan moving fragments at 1-2 metres per second, identifying metal type by elemental signature and triggering pneumatic air-ejection downstream to separate copper from brass, aluminium from zinc, or stainless from carbon steel.

Why XRF complements NIR: NIR sorting identifies polymer types but cannot see metallic content; XRF sees metals and certain heavier non-metals (bromine, chlorine) but cannot identify polymer chemistry. The two sensors are therefore deployed together in mature recycling lines — NIR for plastic identification, XRF for metal grading and detection of polybrominated flame retardants in plastics and lead or PVC contamination in cable scrap. A combined NIR plus XRF sorting line can produce single-element metal streams at 95-98% purity and flame-retardant-free plastic streams at 99%+ purity.

Limitations: XRF detects only elements heavier than aluminium (or magnesium with helium purge) and cannot speciate (it cannot tell whether copper is metallic Cu or copper oxide). The measurement is also surface-sensitive — a thin oxidation layer can suppress signal, and complex multi-element alloys give convoluted spectra that require trained operators or robust auto-classification software. Capital cost of an industrial XRF sorter runs Rs 1-3 crore. Handheld XRF guns suitable for grade checking are Rs 8-25 lakh per unit and require periodic Atomic Energy Regulatory Board licensing because they contain a low-activity X-ray tube.