Friday, November 17, 2017

Iron from Used Toner Cartridges

Students and teachers all do a lot of printing and photocopying.
If your laser printer or photocopier is like ours, it probably has a sign on it that says you should contact admin when it needs a new toner cartridge.

Have you ever wondered what is inside the "toner cartridge"?
The black "ink", the toner, is  actually a mixture of solid carbon and solid iron oxide. A polymer is included to improve the flow. The particles making up the mixture are very small, around 10 micrometers. In general, the smaller the particle size, the better the resolution of the final print.
These small toner particles carry a positive charge which enables them to be deposited electrostatically on a negatively-charged image. Once deposited on the paper, the paper is electrically discharged then heated so that toner particles melt and bind to the fibers of the paper.

So what happens to all the old, used toner cartridges?
It is estimated that about half of all toner cartridges sold each year end up in landfill.
The rest are collected and recycled.
Your "empty" toner cartridge probably contains about 8% of the original mix of carbon, iron oxide and polymer. Generally this left-over toner will have to be cleaned out before the cartridge can be re-filled.

New research has suggested that this left-over toner could be transformed directly into iron. Iron is the main component of steel, one of the most widely used metals in the world.
The researchers heated toner mixture in a furnace to 1550oC, at which temperature iron oxide is reduced to metallic iron by the carbon:
iron oxide + carbon → iron + carbon dioxide
 The reported yield of iron from toner powder was 98%.

Vaibhav Gaikwad, Uttam Kumar, Farshid Pahlevani, Alvin Piadasa, Veena Sahajwalla. Thermal Transformation of Waste Toner Powder into a Value-Added Ferrous Resource. ACS Sustainable Chemistry & Engineering, 2017; DOI: 10.1021/acssuschemeng.7b02875

Suggested Further Reading:
 Percent by Mass (% by mass)
Naming Ionic Compounds
Formula for Ionic Compounds
Name and Formula of Covalent Compounds
Balancing Chemical Equations
Oxidation and Reduction
Oxidation States (oxidation numbers)

Metal Extraction Concepts

Carbon Reduction Method for Extracting Metals from their Ores
Activity Series of Metals

Suggested Study Questions:
  1. Convert 10 micrometers to a diameter in:
    • metres
    • nanometres
    • millimetres
    • centimetres
  2. Write the chemical formula for each of the following substances:
    • iron(II) oxide
    • iron(III) oxide
    • carbon dioxide
    • carbon monoxide
  3. Write a word equation for the reduction of each of the following iron oxides using carbon:
    • iron(II) oxide
    • iron(III) oxide
  4. Write a balanced chemical equation for the reduction of each of the following iron oxides using carbon:
    • iron(II) oxide
    • iron(III) oxide
  5. Give the oxidation state (oxidation number) for iron in each of the following:
    • metallic iron
    • iron(II) oxide
    • iron(III) oxide
  6. Refer to the balanced chemical equations in question 4. In each equation, identify the
    • oxidant (oxidising agent)
    • reductant (reducing agent)
  7. Is the reaction between iron oxide and carbon in the furnace an example of a redox reaction? Justify your answer.
  8. About 40% by mass of the toner cartridge powder is iron oxide. A toner cartridge contains 80 g of toner, what is the mass of iron oxide in the toner cartridge?
  9. At the end of its useful life, a tone cartridge still contains 8% of the original toner. What mass of toner is present in a the toner cartridge at the end of its useful life?
  10. At the end of the toner cartridge's useful life, what mass of iron oxide is present in the cartridge?
  11. Assuming the chemical formula for the iron oxide in the cartridge is Fe3O4, what is the maximum amount of iron in grams that could be obtained from an "empty" toner cartridge?
  12. 350 million "empty" toner cartridges go to landfill each year in the world. If all the available iron could be recovered from each cartridge, what mass of iron would be recovered?

No comments:

Post a Comment