Extracting Thorium Oxide from Ore

Scientific concepts / nature phenomena presented

• Thorium in the Earth’s crust

  • Thorium is described as the other major radioactive element present in significant amounts besides uranium.
  • It occurs mainly in minerals such as fluorides and monazite (the subtitle wording includes “monocyte,” but the surrounding context indicates monazite).
  • The video contrasts thorite vs monazite, suggesting naming confusion:
    • Monazite is mined primarily for rare earth elements.
    • Thorium is often treated as a byproduct.

• Thorium radioactivity and radiation types

  • Thorium decays primarily via alpha decay.
  • The detector used cannot measure alpha particles, so the measured radiation mainly comes from:
    • Gamma-emitting daughter nuclei produced during thorium’s decay chain.
    • A small amount of uranium impurity, contributing additional beta/gamma radiation.
  • Radiation measurements described:
    • Natural background: ~10 CPM (beta + gamma only)
    • Raw monazite rocks: up to ~1600 CPM
    • Purified thorium oxide product: ~280 CPM, explained as removal of impurities and many decay daughters

• Radioactive damage in minerals

  • Monazite is described as often metamict, meaning:
    • Alpha radiation damages/crushes the crystal structure, making the mineral amorphous.
  • The video mentions pleochroic halos:
    • Small discoloration halos caused by localized alpha-particle damage around inclusions of radioactive crystals.

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Processes / methodology outlined (chemical extraction & purification)

Starting material and composition

• Uses monazite (“monocyte”) rocks (two specimens).
• Approximate composition mentioned:
  • Thorium dioxide: ~5–20% by mass
  • Remainder: mainly phosphates of lanthanides (e.g., cerium, lanthanum phosphate)

Radiation check

• Measures:
  1. Background radiation
  2. Radiation from the rocks directly on a detector (to estimate beta/gamma from daughters and impurities)

Initial digestion / breakdown of rock

• First attempt:
  • Heat with sodium hydroxide (NaOH) at ~150°C, using about a 75% solution
  • An equipment failure forces changes.
• Alternative preparation:
  • Tries a rock tumbler to powder the material, then instead hammer-smashes.
• Acid digestion / conversion:
  • Uses concentrated sulfuric acid (H₂SO₄) at ~230°C, overnight with stirring.
  • The products become sulfates (conversion to corresponding sulfates).

Thorium precipitation (from sulfuric digestion products)

• After filtration of insolubles / residue:
  • Adjusts pH using ammonia solution (NH₃(aq)) to slightly above pH 1 to precipitate:
    • Thorium as thorium hydroxide
    • plus a small amount of rare earth hydroxides (lanthanides)

Separating thorium from rare earth fractions

• Further pH adjustment with ammonia to pH ~3 precipitates:
  • Rare earth hydroxides
• The rare earth hydroxide “jelly” is stored/discarded and not further processed.

Conversion to thorium nitrate

• Purification step:
  • Converts thorium hydroxide-derived material to thorium nitrate
  • Done by boiling in concentrated nitric acid (HNO₃)

Liquid–liquid extraction using TBP

• Uses a solvent system:
  • Organic phase: long-chain alkane mixture (kerosene-like), described as “Shellsol…” (C11–C12 alkanes; “Shell Sol/… tea” wording)
  • Extracting agent / complexant: tributyl phosphate (TBP)
• The process is described as complex formation / solvation rather than a simple extraction:
  • TBP reacts with thorium nitrate in nitric acid medium.
  • Crust formation is attributed to slow degradation of TBP in nitric acid, and the need to keep nitric acid present (as explained in the video).
• Main steps:
  • Pull thorium into the organic layer as a TBP–thorium nitrate complex
  • Back-extract into water by removing nitric acid (TBP complexes preferentially with water), returning thorium nitrate to the aqueous phase

Concentration and attempted conversion to thorium oxide

• Distills off water to leave a solid.
• Video suggests an “oopsie”:
  • Heating thorium nitrate may produce thorium nitrate oxide and/or thorium dioxide (ThO₂).
• Uses hydrochloric acid (HCl) to convert thorium nitrate to thorium chloride, with NO₂ observed as nitrogen dioxide.
• Further heating/distillation leaves a solid believed to be thorium oxide, inferred from:
  • Insolubility behavior
  • Later acid behavior consistent with ThO₂ dissolving slowly over time in acid

Final product and yield

• Final yield reported:
  • ~4.71 g of presumed thorium oxide
• Estimated thorium content:
  • Thorium dioxide estimated ~12%, noted as higher than typical monazite (~6%)
• Radiation of the final powder:
  • ~280 CPM
  • Explained by reduced uranium impurity and reduced daughter activity; activity would increase over time as daughters regrow.

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Researchers or sources featured

• No specific researchers or external sources are named in the provided subtitles.