Separation of gold from gold ore

Topics: Water, Ammonia, Sulfuric acid Pages: 6 (1170 words) Published: March 7, 2015

What Is Gold?
Gold is a rare metallic element that is found naturally in the Lithosphere of the Earth, normally in veins of quartz and other deposits. It can be found in a free state or in a combination with other metals.

Gold is a transition metal
golden yellow
Atomic weight:
Melting point:
1064.18 oC, 1337.33 K
Boiling point:
2850 oC, 3123 K
Electron shells:
Density @ 20oC:
19.32 g/cm3

Gold is obtained from a variety of ores. Most people think of nuggets and such, but the truth is that very little comes from nuggets - nearly all newly mined gold comes from ores mined from the natural hard rocks that contain gold in tiny, even microscopic particles. Various separation and refinement processes are used to extract the gold for profitable use. Some of the main processes include: Froth Floatation/ Separation floatation

Precipitation reaction

Froth Floatation / separation floatation – Gold extraction

1. The Ore containing small particles of ore are transferred to a mill, where it is ground down to ultra-fine “sand-like” particles. 2. The ground particles are then mixed with a liquid mixture with frothing agents to induce separation of other constituents and the gold. The frothing agents include: a. Amyl alcohol

b. Camphor
c. Phenols
d. Essential oils
3. A collection agent is then added to the frothing mixture. The collection agent bonds with the gold particles by forming an oily film that collects onto air bubbles for frothing. This is known as “floatation”, as gold floats above the liquid 4. Organic chemicals added to the mixture. These chemicals prevent other contaminants adhering to the air bubbles. Carbon is often used which bonds to the contaminants leaving gold to bond to the air bubbles. 5. Liquid solution is aerated then froth is separated from the water bath. The gold concentrate floats on top but in a different cell for easy collection. Water waste is collected from the bottom of the cell and taken to a tailing site 6. Cyanide is added to the gold to remove impurities (sulfides) 7. The gold concentrate is then sent for gold refinement so it can meet the official standard of 99.9% purity before being used for commercial use

Precipitation reaction and fitleration – Gold Refinement
There are actually a few different methods of refining gold. Depending upon the quantity of gold you are working with and the desired level of purity, the two most common methods for refining gold are the use of high temperature flame and the use of chemicals to refine the gold. 1. Unrefined gold is placed in a heavy-gauge plastic buckets or Pyrex Vision Ware pots 2. Nitric acid is added to the gold and allowed to react for 30 minutes. 30 milliliters of Nitric acid is used for every ounce of gold in the container 3. Hydrochloric acid is added to the mixture to assist in the dissolution of the gold. 120 milliliters of hydrochloric acid is required for every 1 gram of gold 4. The mixture is filtered and poured out into another large container. The mixture should have and emerald green colour. 5. A precipitant is added to the mixture while it is boiling to induce the separation of gold into a solid. 1 lbs of a urea and distilled water is added to the mixture which neutralizes the nitric acid but not the hydrochloric acid in the solution 6. The “gold mud” sediment at the bottom of the mixture is separated from the remaining acid and is rinsed multiple times with distilled water and aqua ammonia to clean any other contaminants 7. The “gold mud” is gradually heated on a hot plate until it turns into powder-like consistency. 8. The gold powder is placed into a graphite crucible and smelted at extremely high temperatures, then poured into a mold to be shaped.

Waste from extraction and refinement process
Overburden: Is the...

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