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Material World
Element · Cd

Cadmium

A soft metal whose industrial history is largely a record of discovering how toxic it is.

Cadmium plated well, made a brilliant yellow pigment and powered rechargeable batteries. It is also a cumulative poison affecting the kidneys and bones, and the Japanese itai-itai disease outbreak of the mid-twentieth century — caused by cadmium from mine tailings entering rice paddies — established the harm at population scale.

Most of its former uses have been restricted or banned. It survives in cadmium telluride thin-film solar panels, where it is bound in a stable compound.

Uses

Cadmium is in retreat, and deliberately so. It is toxic and accumulates in the body, and regulation has removed it from most consumer applications.

Nickel-cadmium batteries have largely given way to nickel-metal-hydride and lithium-ion. Cadmium pigments — intense yellows, oranges and reds — persist in artists' colours and in plastics needing heat stability. Cadmium telluride remains a commercially significant thin-film solar cell material, and cadmium plating is still used in aerospace fasteners where nothing else performs as well.

Medium confidence Weak evidence

How we know: checked recently · only one source, so there is nothing to cross-check it against · stated directly by the source.

How this connects

Where a connection has been confirmed by an outside reference, that reference is named beside it.

is used as

  • Pigment — application · cadmium yellows and reds, now largely withdrawn on toxicity grounds
  • Photovoltaics — application · as cadmium telluride, the main thin-film technology competing with silicon

is produced by

  • Roasting — process · collected from the flue dust of zinc roasting and refined from it — a by-product of zinc throughout, never mined for itself

is an alternative to

  • Zinc — element · as a sacrificial plating on steel. Cadmium performs better in salt and is banned from most uses for being a cumulative poison, so zinc does the job almost everywhere now

is sourced from

  • Zinc — element · cadmium substitutes for zinc in sphalerite and follows it through roasting; there is no cadmium ore and never has been

is found in

  • Cadmium telluride — compound · half the atoms — and the persistent public objection to the technology, though the compound is far more stable and less bioavailable than the metal Wikidata

Sources

  • Material World
    Our own writing
  • Wikidata
    Wikimedia Foundation · Creative Commons CC0 1.0 Universal (public domain dedication)
  • PubChem
    US National Library of Medicine · Mixed — aggregated third-party content, rights retained by depositors
  • NIST — National Institute of Standards and Technology
    United States Department of Commerce · US Government work — public information, credit requested

Questions this page answers

Where it comes from, and what it becomes

Follow Cadmium back to what it starts as, and forward into what it becomes. Each step is a documented one — a real route material takes, not a chain of inference.

Upstream — what it comes from

  • Cadmium → is sourced from (cadmium substitutes for zinc in sphalerite and follows it through roasting; there is no cadmium ore and never has been) → Zinc → is produced by (as the oxide, which is then reduced — roasting is the step that makes zinc sulfide smeltable) → Roasting → takes as input (a copper sulfide; roasting drives off the sulfur that would otherwise prevent reduction) → Chalcopyrite
  • Cadmium → is produced by (collected from the flue dust of zinc roasting and refined from it — a by-product of zinc throughout, never mined for itself) → Roasting → takes as input (a copper sulfide; roasting drives off the sulfur that would otherwise prevent reduction) → Chalcopyrite
  • Cadmium → is produced by (collected from the flue dust of zinc roasting and refined from it — a by-product of zinc throughout, never mined for itself) → Roasting → takes as input (roasted for its sulfur as much as for its iron) → Pyrite
  • Cadmium → is produced by (collected from the flue dust of zinc roasting and refined from it — a by-product of zinc throughout, never mined for itself) → Roasting → takes as input (roasted to the oxide, the sulfur going to an acid plant rather than the air) → Galena
  • Cadmium → is produced by (collected from the flue dust of zinc roasting and refined from it — a by-product of zinc throughout, never mined for itself) → Roasting → takes as input (roasted to zinc oxide before reduction or electrolytic winning) → Sphalerite
  • Cadmium → is produced by (collected from the flue dust of zinc roasting and refined from it — a by-product of zinc throughout, never mined for itself) → Roasting → takes as input (roasted in air; the mercury leaves as vapour rather than staying behind as an oxide) → Cinnabar

These are the most distinct paths back. Cadmium can be traced through others besides.

Downstream — what it becomes

  • Cadmium → is used as (cadmium yellows and reds, now largely withdrawn on toxicity grounds) → Pigment
  • Cadmium → is used as (as cadmium telluride, the main thin-film technology competing with silicon) → Photovoltaics